Proposed Rule2024-28855
Endangered and Threatened Wildlife and Plants; Threatened Species Status With Section 4(d) Rule for Monarch Butterfly and Designation of Critical Habitat
Primary source
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Published
December 12, 2024
Issuing agencies
Interior DepartmentFish and Wildlife Service
Abstract
We, the U.S. Fish and Wildlife Service (Service), propose to list the monarch butterfly (Danaus plexippus), the iconic orange and black butterfly, as a threatened species and designate critical habitat under the Endangered Species Act of 1973, as amended (Act). We propose to list the monarch butterfly as a threatened species with protective regulations under section 4(d) of the Act (a "4(d) rule"). Finalizing this rule as proposed would add this species to the List of Endangered and Threatened Wildlife and extend the Act's protections to the species. We also propose to designate critical habitat for the monarch butterfly under the Act. In total, approximately 4,395 acres (1,778 hectares) in Alameda, Marin, Monterey, San Luis Obispo, Santa Barbara, Santa Cruz, and Ventura Counties, California, fall within the boundaries of the proposed critical habitat designation. We also announce the availability of an economic analysis of the proposed designation of critical habitat for the monarch butterfly. We also are notifying the public that we have scheduled two informational meetings followed by public hearings on the proposed rule.
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[Federal Register Volume 89, Number 239 (Thursday, December 12, 2024)]
[Proposed Rules]
[Pages 100662-100716]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2024-28855]
[[Page 100661]]
Vol. 89
Thursday,
No. 239
December 12, 2024
Part III
Department of the Interior
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Fish and Wildlife Service
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50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Threatened Species
Status With Section 4(d) Rule for Monarch Butterfly and Designation of
Critical Habitat; Proposed Rule
Federal Register / Vol. 89, No. 239 / Thursday, December 12, 2024 /
Proposed Rules
[[Page 100662]]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R3-ES-2024-0137; FXES1111090FEDR-256-FF09E21000]
RIN 1018-BE30
Endangered and Threatened Wildlife and Plants; Threatened Species
Status With Section 4(d) Rule for Monarch Butterfly and Designation of
Critical Habitat
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Proposed rule.
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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to
list the monarch butterfly (Danaus plexippus), the iconic orange and
black butterfly, as a threatened species and designate critical habitat
under the Endangered Species Act of 1973, as amended (Act). We propose
to list the monarch butterfly as a threatened species with protective
regulations under section 4(d) of the Act (a ``4(d) rule''). Finalizing
this rule as proposed would add this species to the List of Endangered
and Threatened Wildlife and extend the Act's protections to the
species. We also propose to designate critical habitat for the monarch
butterfly under the Act. In total, approximately 4,395 acres (1,778
hectares) in Alameda, Marin, Monterey, San Luis Obispo, Santa Barbara,
Santa Cruz, and Ventura Counties, California, fall within the
boundaries of the proposed critical habitat designation. We also
announce the availability of an economic analysis of the proposed
designation of critical habitat for the monarch butterfly. We also are
notifying the public that we have scheduled two informational meetings
followed by public hearings on the proposed rule.
DATES: We will accept comments received or postmarked on or before
March 12, 2025. Comments submitted electronically using the Federal
eRulemaking Portal (see ADDRESSES, below) must be received by 11:59
p.m. eastern time on the closing date.
Public informational meetings and public hearings: We will hold two
public informational meetings followed by public hearings. The first
meeting and hearing will be from 6 p.m. to 8:30 p.m., eastern time, on
January 14, 2025. To accommodate those in western time zones, the
second meeting and hearing will be from 8 p.m. to 10:30 p.m., eastern
time, on January 15, 2025.
ADDRESSES: You may submit comments by one of the following methods:
(1) Electronically: Go to the Federal eRulemaking Portal: <a href="https://www.regulations.gov">https://www.regulations.gov</a>. In the Search box, enter FWS-R3-ES-2024-0137,
which is the docket number for this rulemaking. Then, click on the
Search button. On the resulting page, in the panel on the left side of
the screen, under the Document Type heading, check the Proposed Rule
box to locate this document. You may submit a comment by clicking on
``Comment.''
(2) By hard copy: Submit by U.S. mail to: Public Comments
Processing, Attn: FWS-R3-ES-2024-0137, U.S. Fish and Wildlife Service,
MS: PRB/3W, 5275 Leesburg Pike, Falls Church, VA 22041-3803.
We request that you send comments only by the methods described
above. We will post all comments on <a href="https://www.regulations.gov">https://www.regulations.gov</a>. This
generally means that we will post any personal information you provide
us (see Information Requested, below, for more information).
Availability of supporting materials: Supporting materials, such as
the species status assessment report, are available at <a href="https://www.regulations.gov">https://www.regulations.gov</a> at Docket No. FWS-R3-ES-2024-0137. If we finalize
the critical habitat designation, we will make the coordinates or plot
points or both from which the maps are generated available at <a href="https://www.regulations.gov">https://www.regulations.gov</a> at Docket No. FWS-R3-ES-2024-0137.
Public informational meeting and public hearing: The public
informational meeting and the public hearing will be held virtually
using the Zoom platform. See Public Hearing, below, for more
information.
FOR FURTHER INFORMATION CONTACT: Barbara Hosler, Regional Listing
Coordinator, U.S. Fish and Wildlife Service, Midwest Region
Headquarters, 5600 American Blvd., Bloomington, MN 55437, telephone
517-580-0254, email: <a href="/cdn-cgi/l/email-protection#cba6a4a5aab9a8a38badbcb8e5aca4bd"><span class="__cf_email__" data-cfemail="e18c8e8f80938289a1879692cf868e97">[email protected]</span></a>. Individuals in the United States
who are deaf, deafblind, hard of hearing, or have a speech disability
may dial 711 (TTY, TDD, or TeleBraille) to access telecommunications
relay services. Individuals outside the United States should use the
relay services offered within their country to make international calls
to the point-of-contact in the United States. Please see Docket No.
FWS-R3-ES-2024-0137 on <a href="https://www.regulations.gov">https://www.regulations.gov</a> for a document that
summarizes this proposed rule.
SUPPLEMENTARY INFORMATION:
Executive Summary
Why we need to publish a rule. Under the Act, a species warrants
listing if it meets the definition of an endangered species (in danger
of extinction throughout all or a significant portion of its range) or
a threatened species (likely to become an endangered species within the
foreseeable future throughout all or a significant portion of its
range). If we determine that a species warrants listing, we must list
the species promptly and designate the species' critical habitat to the
maximum extent prudent and determinable. We have determined that the
monarch butterfly meets the Act's definition of a threatened species;
therefore, we are proposing to list it as such and proposing a
designation of its critical habitat. Both listing a species as an
endangered or threatened species and making a critical habitat
designation can be completed only by issuing a rule through the
Administrative Procedure Act rulemaking process (5 U.S.C. 551 et seq.).
What this document does. We propose to add the monarch butterfly as
a threatened species to the List of Endangered and Threatened Wildlife
with protective regulations under section 4(d) of the Act, and we
propose the designation of critical habitat for the species.
The basis for our action. Under the Act, we may determine that a
species is an endangered or threatened species because of any of five
factors: (A) The present or threatened destruction, modification, or
curtailment of its habitat or range; (B) overutilization for
commercial, recreational, scientific, or educational purposes; (C)
disease or predation; (D) the inadequacy of existing regulatory
mechanisms; or (E) other natural or manmade factors affecting its
continued existence. We have determined that the monarch butterfly
meets the definition of a threatened species due to the following
threats: the ongoing impacts from loss and degradation of breeding,
migratory, and overwintering habitat (from past conversion of
grasslands and shrublands to agriculture and widespread use of
herbicides; logging/thinning at overwintering sites in Mexico; urban
development, senescence (i.e., deterioration with age), and
incompatible management of overwintering sites in California; and
drought) (Factor A); exposure to insecticides (Factor E); and effects
of climate change (Factor E).
To improve future conditions so that the monarch migratory
populations stabilize and grow, we need to (1)
[[Page 100663]]
achieve a significant increase in the availability of milkweed and
nectar plants in monarch breeding and migratory areas; (2) protect and
enhance overwintering habitat; (3) avoid and minimize impacts to
monarchs and their habitat from insecticides and herbicides; and (4)
maintain public support for the conservation of monarch butterflies.
Because of the monarch butterfly's general habitat use and wide
distribution, all sectors of society, including the general public,
have an opportunity to participate in a broad range of conservation
efforts throughout the species' range.
Section 4(a)(3) of the Act requires the Secretary of the Interior
(Secretary), to the maximum extent prudent and determinable,
concurrently with listing designate critical habitat for the species.
Section 3(5)(A) of the Act defines critical habitat as (i) the specific
areas within the geographical area occupied by the species, at the time
it is listed, on which are found those physical or biological features
(I) essential to the conservation of the species and (II) which may
require special management considerations or protections; and (ii)
specific areas outside the geographical area occupied by the species at
the time it is listed, upon a determination by the Secretary that such
areas are essential for the conservation of the species. Section
4(b)(2) of the Act states that the Secretary must make the designation
on the basis of the best scientific data available and after taking
into consideration the economic impact, the impact on national
security, and any other relevant impacts of specifying any particular
area as critical habitat.
Information Requested
We intend that any final action resulting from this proposed rule
will be based on the best scientific and commercial data available and
be as accurate and as effective as possible. Therefore, we request
comments or information from other governmental agencies, Native
American Tribes, the scientific community, industry, or any other
interested parties concerning this proposed rule. We particularly seek
comments concerning:
(1) The species' biology, range, and population trends, including:
(a) Biological or ecological requirements of the species, including
habitat requirements for feeding, breeding, and sheltering;
(b) Genetics and taxonomy;
(c) Historical and current range, including distribution patterns,
alternative migratory pathways, and the locations of any additional
populations of this species;
(d) Population dynamics and contributions from the nonmigratory
populations, specifically resident monarchs in southern Florida, the
Gulf Coast, the southern Atlantic Coast, and the southern Pacific
Coast;
(e) Historical and current population levels, and current and
projected trends; and
(f) Past and ongoing conservation measures for the species, its
habitat, or both.
(2) Threats and conservation actions affecting the species,
including:
(a) Factors that may be affecting the continued existence of the
species, which may include habitat modification or destruction,
overutilization, disease, predation, the inadequacy of existing
regulatory mechanisms, or other natural or manmade factors;
(b) Biological, commercial trade, or other relevant data concerning
any threats (or lack thereof) to this species;
(c) Existing regulations or conservation actions that may be
addressing threats to this species; and
(d) Other potential threats that were not identified as key threats
to the species.
(3) Additional information concerning the historical and current
status of this species.
(4) Information to assist us with applying or issuing protective
regulations under section 4(d) of the Act that may be necessary and
advisable to provide for the conservation of the monarch butterfly. In
particular, we seek information concerning:
(a) The extent to which we should include any of the Act's section
9 prohibitions in the 4(d) rule;
(b) Whether we should consider any modifications or additional
exceptions from the prohibitions in the 4(d) rule;
(c) Whether the provisions related to the maintenance, enhancement,
removal, or establishment of milkweed should be revised to include
spatial or temporal restrictions or deferments;
(d) Whether we should include an exception for the use of
pesticides and, if so, what measures are reasonable, feasible, and
adequate to reduce or offset pesticide exposure to monarchs from
agricultural and non-agricultural uses (e.g., rangeland, rights-of-way,
forestry, commercial areas, and mosquito control), including measures
for specific classes of pesticides (e.g., herbicides, insecticides),
pesticide uses, and application methods;
(e) Whether we should include an exception for direct impacts from
transportation and energy infrastructure, including mortality from
collisions with wind turbines; and
(f) Whether we could improve or modify our approach to the 4(d)
rule in any way to provide for greater public participation and
understanding, or to better accommodate public concerns and comments.
(5) Specific information related to critical habitat, such as the
following:
(a) The amount and distribution of monarch butterfly habitat;
(b) Any additional areas occurring within the range of the species
in the United States, especially in breeding, migratory, or
overwintering areas, that should be included in the critical habitat
designation because they (i) are occupied at the time of listing and
contain the physical or biological features that are essential to the
conservation of the species and that may require special management
considerations, or (ii) are unoccupied at the time of listing and are
essential for the conservation of the species; and
(c) Special management considerations or protection that may be
needed in critical habitat areas we are proposing, including managing
for the potential effects of climate change.
(6) Land use designations and current or planned activities in the
subject areas and their possible impacts on proposed critical habitat.
(7) Any probable economic, national security, or other relevant
impacts of designating any area that may be included in the final
designation, and the related benefits of including or excluding
specific areas.
(8) Information on the extent to which the description of probable
economic impacts in the economic analysis is a reasonable estimate of
the likely economic impacts and any additional information regarding
probable economic impacts that we should consider.
(9) Whether any specific areas we are proposing for critical
habitat designation should be considered for exclusion under section
4(b)(2) of the Act, and whether the benefits of potentially excluding
any specific area outweigh the benefits of including that area. If you
think we should exclude any additional areas, please provide
information supporting a benefit of exclusion.
(10) Whether we could improve or modify our approach to designating
critical habitat in any way to provide for greater public participation
and understanding, or to better accommodate public concerns and
comments.
Please include sufficient information with your submission (such as
scientific journal articles or other publications) to
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allow us to verify any scientific or commercial information you
include.
Please note that submissions merely stating support for, or
opposition to, the action under consideration without providing
supporting information, although noted, do not provide substantial
information necessary to support a determination. Section 4(b)(1)(A) of
the Act directs that determinations as to whether any species is an
endangered or a threatened species must be made solely on the basis of
the best scientific and commercial data available, and section 4(b)(2)
of the Act directs that the Secretary shall designate critical habitat
on the basis of the best scientific data available.
You may submit your comments and materials concerning this proposed
rule by one of the methods listed in ADDRESSES. We request that you
send comments only by the methods described in ADDRESSES.
If you submit information via <a href="https://www.regulations.gov">https://www.regulations.gov</a>, your
entire submission--including any personal identifying information--will
be posted on the website. If your submission is made via a hardcopy
that includes personal identifying information, you may request at the
top of your document that we withhold this information from public
review. However, we cannot guarantee that we will be able to do so. We
will post all hardcopy submissions on <a href="https://www.regulations.gov">https://www.regulations.gov</a>.
Comments and materials we receive, as well as supporting
documentation we used in preparing this proposed rule, will be
available for public inspection on <a href="https://www.regulations.gov">https://www.regulations.gov</a>.
Our final determination may differ from this proposal because we
will consider all comments we receive during the comment period as well
as any information that may become available after this proposal. Based
on the new information we receive (and, if relevant, any comments on
that new information), we may conclude that the species is endangered
instead of threatened, or we may conclude that the species does not
warrant listing as either an endangered species or a threatened
species. For critical habitat, our final designation may not include
all areas proposed, may include some additional areas that meet the
definition of critical habitat, or may exclude some areas if we find
the benefits of exclusion outweigh the benefits of inclusion and
exclusion will not result in the extinction of the species. In
addition, we may change the parameters of the prohibitions or the
exceptions to those prohibitions in the protective regulations issued
or applied under section 4(d) of the Act if we conclude it is
appropriate in light of comments and new information received. For
example, we may expand the prohibitions if we conclude that the
protective regulation as a whole, including those additional
prohibitions, is necessary and advisable to provide for the
conservation of the species. Conversely, we may establish additional or
different exceptions to the prohibitions in the final rule if we
conclude that the activities would facilitate or are compatible with
the conservation and recovery of the species. In our final rule, we
will clearly explain our rationale and the basis for our final
decision, including why we made changes, if any, that differ from this
proposal.
Public Hearing
We have scheduled two public informational meetings with public
hearings on this proposed rule for the monarch butterfly. We will hold
the public informational meetings and public hearings on the dates and
times listed above under Public informational meeting and public
hearing in DATES. We are holding the public informational meetings and
public hearings via the Zoom online video platform and via
teleconference so participants can attend remotely. For security
purposes, registration is required. To listen and view a meeting and
hearing via Zoom, listen to a meeting and hearing by telephone, or
provide oral public comments at a public hearing by Zoom or telephone,
you must register. For information on how to register, or if you
encounter problems joining Zoom the day of the meeting, visit <a href="https://www.fws.gov/species/monarch-danaus-plexippus">https://www.fws.gov/species/monarch-danaus-plexippus</a>. Registrants will receive
the Zoom link and the telephone number for the public informational
meeting and public hearing for which they have registered. If
applicable, interested members of the public not familiar with the Zoom
platform should view the Zoom video tutorials (<a href="https://support.zoom.us/hc/en-us/articles/206618765-Zoom-video-tutorials">https://support.zoom.us/hc/en-us/articles/206618765-Zoom-video-tutorials</a>) prior to the public
informational meetings and public hearings.
The public hearings will provide interested parties an opportunity
to present verbal testimony (formal, oral comments) regarding this
proposed rule. While the public informational meetings will be
opportunities for dialogue with the Service, the public hearings are
not: They are forums for accepting formal verbal testimony. In the
event there is a large attendance, the time allotted for oral
statements may be limited. Therefore, anyone wishing to make an oral
statement at a public hearing for the record is encouraged to provide a
prepared written copy of their statement to us through the Federal
eRulemaking Portal, or U.S. mail (see ADDRESSES, above). There are no
limits on the length of written comments submitted to us. Anyone
wishing to make an oral statement at a public hearing must register
before the hearing <a href="https://www.fws.gov/species/monarch-danaus-plexippus">https://www.fws.gov/species/monarch-danaus-plexippus</a>. The use of a virtual public hearing is consistent with our
regulations at 50 CFR 424.16(c)(3).
Previous Federal Actions
On August 26, 2014, we received a petition from the Center for
Biological Diversity, Center for Food Safety, Xerces Society for
Invertebrate Conservation, and Dr. Lincoln Brower, requesting that we
list the monarch butterfly as a threatened species under the Act. On
December 31, 2014, we published a 90-day finding that the petition
presented substantial scientific or commercial information, indicating
that listing the monarch butterfly may be warranted (79 FR 78775). On
December 17, 2020, we published a 12-month finding that listing the
species as an endangered or threatened species is warranted but
precluded by higher priority actions (85 FR 81813). The species
remained so designated in the annual candidate notices of review on May
3, 2022 (87 FR 26152), and June 27, 2023 (88 FR 41560).
Peer Review
A species status assessment (SSA) team prepared an SSA report for
the monarch butterfly. The SSA team was composed of Service biologists,
in consultation with other species experts. The SSA report represents a
compilation of the best scientific and commercial data available
concerning the status of the species, including the impacts of past,
present, and future factors (both negative and beneficial) affecting
the species.
In accordance with our joint policy on peer review published in the
Federal Register on July 1, 1994 (59 FR 34270), and our August 22,
2016, memorandum updating and clarifying the role of peer review in
listing actions under the Act (<a href="https://www.fws.gov/sites/default/files/documents/peer-review-policy-directors-memo-2016-08-22.pdf">https://www.fws.gov/sites/default/files/documents/peer-review-policy-directors-memo-2016-08-22.pdf</a>), we
solicited independent scientific review of the information contained in
the monarch butterfly SSA report. In 2018, we sent the first version
(1.0) of the SSA report to 6 independent peer reviewers and received 5
responses. In 2020, we sent the second version (2.0) of the SSA report
to 3 peer reviewers and received 2 responses. In 2023, we sent the SSA
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report version 2.2 to 13 peer reviewers and received 7 responses. No
individual peer reviewed the SSA report more than once. Results of this
structured peer review process can be found at <a href="https://www.regulations.gov">https://www.regulations.gov</a>. In preparing this proposed rule, we incorporated
the results of these reviews, as appropriate, into the SSA report,
which is the foundation for this proposed rule.
Summary of Peer Reviewer Comments
As discussed in Peer Review above, we received comments from 14
total peer reviewers on the draft SSA report. We reviewed all comments
we received from the peer reviewers for substantive issues and new
information regarding the contents of the SSA report. The peer
reviewers provided additional references, clarifications, and
suggestions.
We updated the SSA report based on these peer reviewers' comments,
including restructuring several sections within the report, revising
our description of adaptive capacity, clarifying specific points and
terminology where appropriate, and adding additional details and
suggested references when needed. Additional peer reviewer comments are
addressed in the following summary, as well as throughout the Summary
of Biological Status and Threats, below, and were incorporated into the
SSA report as appropriate (Service 2024a, entire).
Comment 1: Two reviewers asked us to elaborate on whether our
assessment of resilience or the extinction threshold for western
migratory monarchs should change based on a few years of numbers that
have bounced back above 200,000 after the low of less than 2,000
individuals in the winter of 2019-2020.
Our response: It is plausible that migratory monarchs experienced
good weather that resulted in abundant and well-timed milkweed and
nectar resources across their breeding habitat in western North America
in 2021, which provided for a significant increase in the overwintering
count from below 2,000 individuals in 2019-2020. With only a few years
of improved population numbers, we are currently unable to determine
whether the western migratory population's status is improving or if
these data support the continuation of its fluctuation and decline.
While this does not change our current assessment of the population's
resilience, we have added text clarifying this uncertainty to our SSA
report to further address this comment.
We also revisited our extinction thresholds in western North
America. In the model presented in our SSA, we use a range of
extinction thresholds, which are informed by scientific literature
(i.e., Schultz et al. 2017, entire; Wells et al. 1990, p. 124). With
the observed western population rebound, these estimates may be
conservative. While the extinction thresholds we used are currently the
best available, some uncertainty remains about the size of extinction
thresholds and the time lag necessary to confirm assumptions about
population stability or extinction trajectories. Therefore, we could be
either overestimating or underestimating extinction risk depending on
the accuracy of the thresholds.
Comment 2: One reviewer questioned our reliance on overwintering
counts to inform our understanding of eastern North American monarch
butterfly population trends, in contrast to using surveys at other
locations and at other times during the year.
Our response: Monitoring at overwintering sites allows for the most
practical and direct assessment of annual population levels, where the
near-entirety of the migratory population can be evaluated consistently
and comprehensively, reflecting the full range of threats and
population dynamics encountered over the prior annual breeding and
migration cycle. The question about the optimal approach for annual
census of monarch butterfly populations (e.g., overwintering data v.
non-overwintering data) has been addressed in a more recent review of
the methodology, which concluded that the overwintering area of the
eastern North American population is an accurate representation of the
size of the population (Pleasants et al. 2024, p. 62). Our analysis of
this topic based on the preponderance of scientific evidence is
incorporated into the most recent version of the SSA report (Service
2024a, pp. 70-76).
Comment 3: Two reviewers noted that the decline of the eastern
North American monarchs may have slowed or stabilized for the past
decade or more, potentially due to an associated slowing or plateau of
habitat loss. With this potential slowing or stabilization, one of
these reviewers asked if the extinction risk may have thus decreased.
They also noted differences in population decline based on the modeling
assumption of density-dependence or independence.
Our response: The estimates of population viability (and extinction
risk) presented in the SSA report are based on the overall population
trajectory (growth rate), along with the current population size and
the fluctuations exhibited year-to-year. Growth rate and variability
are derived using time series data, which may be influenced by the
number of years being analyzed.
Different analyses have explored the possibility that past declines
in milkweed, or habitat more generally, alongside the expansion of
genetically modified crops and associated herbicides and pesticides,
may have effectively plateaued in recent years. Some evidence has
emerged of a change in trajectory for the eastern population since
2014, but as of 2020, statistical support for such a change was
insufficient (Thogmartin et al. 2020, entire). More recently, an
analysis of overwintering data for the eastern population estimated a
median annual rate of growth of 0.93 (0.67-1.30, 95-percent confidence
interval (CI)). These results indicate that the population is
declining, even when assuming relatively stable land use and landcover
change relative to the conditions that had driven steeper population
declines in previous decades (Thogmartin 2024, entire).
Other published analyses estimate monarch population growth rates
and persistence/extinction risks using alternative models and different
data sets. These include non-overwintering population data, different
time-series of annual population estimates, different modeling
assumptions about density-dependence, and different relationships
between population size and growth (i.e., increased density of monarchs
will result in decreased population growth and decreased density of
monarchs will result in increased population growth). One recent
analysis (Meehan and Crossley 2023, entire) used a variable change
model to characterize the trend in eastern North American monarch
abundance, suggesting that the monarch population has rebounded after a
period of decline, thereby leading to a markedly lower risk of
extinction relative to other assessments (e.g., Semmens et al. 2016,
entire; Schultz et al. 2017, entire; Thogmartin 2024, entire),
including our SSA analyses. Meehan and Crossley (2023, entire) assume
density dependence, which constrains the uncertainty associated with
the predicted abundance estimates (small populations recover faster
under density-dependent assumptions than density-independent
assumptions). Though their density dependent model provides a good fit
for the 10-year dataset they analyzed, the models cannot identify the
mechanism behind the apparent decline in growth rate as populations
increase. The assessment by Meehan and Crossley (2023, entire) did not
incorporate the impacts of changing future conditions.
[[Page 100666]]
Another analysis that also did not incorporate the impacts of
changing future conditions assumes the variability in the population
numbers is now driven by environmental and demographic stochasticity
(Thogmartin 2024, entire). This approach is more conservative because
it results in increased variability at small populations sizes, as
compared to the assumption of density dependence (which assumes
increased per capita growth when populations are small). In this
modeling approach, when population abundance has been reduced to a low
level, demographic and environmental stochasticity alone (and not
necessarily a declining trend) are now the driving factors, resulting
in an increased risk of extinction. After careful examination, our
estimates in the SSA for the annual rate of growth, population
viability, and extinction risk continue to be in line with the best
available information.
Comment 4: One reviewer of a later version of the SSA asked for
additional clarification on why the model for monarch butterfly
extinction was not re-run with updated data that had been collected
since the first version of the SSA.
Our response: Based on our previous sensitivity testing of the
model presented in the SSA, updated values would not significantly
change the output and results, and thus would not change the outcomes
in our report. Therefore, instead of rerunning the model, we instead
prioritized evaluating new literature and information that might have
changed the SSA analyses and conclusions. We provide further
clarification and explanation in the updated SSA report (Service 2024a,
p. 149).
Comment 5: One reviewer commented that nonmigratory monarch
butterflies might persist, even if the migratory monarchs were to
become extirpated. The reviewer also suggested that one potential
reason for the declines in migratory individuals in the West could be
due to a shift to more individuals existing in nonmigratory populations
during winter.
Our response: According to recent research, the resident
(nonmigratory) population in California is not sufficient to make up
for the loss of the migratory population in western North America;
there are still orders of magnitude fewer butterflies now than in the
recent past (Crone and Schultz 2021, p. 1535). Also, the resident
population probably lacks the demographic capacity to expand its range
inland during summer months. Resident populations of monarch
butterflies build up high levels of a protozoan parasite, Ophryocystis
elektroscirrha (OE), at least in part due to the absence of migratory
culling and migratory escape (Satterfield et al. 2015, pp. 4-5). In
California, about 8 percent of migratory monarch butterflies are
infected with OE, compared to about 75 percent of residents
(Satterfield et al. 2016, p. 346). Similarly, for the eastern North
American population, less than 10 percent of migratory monarch
butterflies are infected with OE, compared to 75-100 percent of
nonmigratory monarchs in Florida (Altizer and de Roode 2015, p. 91).
OE-infected monarch butterflies experience lower survival, lower egg-
laying rates, and produce about 0.8 adult daughters per female (Crone
and Schultz 2021, Supplement S4). This rate of increase is enough for
resident monarch butterfly populations to persist in urban areas, but
it does not provide the ability to rapidly colonize the other Western
States (Crone and Schultz 2021, p. 1536). We acknowledge alternative
overwintering strategies, including nonmigratory monarchs, in the
uncertainties section of the SSA report (Service 2024a, pp. 70-76).
I. Proposed Listing Determination
Background
A thorough review of the taxonomy, life history, and ecology of the
monarch butterfly (Danaus plexippus; referred to as ``monarch'' or
``monarch butterfly'' herein) is presented in the SSA report version
2.3 (Service 2024a, entire).
The monarch is a brightly colored butterfly species, native to
North America, with a range that has expanded west via human assistance
to many islands in the Pacific Ocean and to the east to the Iberian
Peninsula to now occupy 90 countries, islands, and island groups.
Despite the expansion, over 90 percent of monarchs worldwide continue
to live and migrate in their native range in North America. The species
requires habitat with milkweed (genus Asclepias or closely related
genera) as a larval host plant and floral nectar sources for adults.
Migratory monarchs in North America also use overwintering habitat,
where the adults cluster on trees.
Adult monarch butterflies are large and conspicuous, with bright-
orange wings surrounded by a black border and covered with black veins.
The black border has a double row of white spots, present on the upper
side and lower side of forewings and hindwings (Bouseman and Sternburg
2001, p. 222). Adult monarchs are sexually dimorphic, with males having
narrower wing venation and scent patches (Commission for Environmental
Cooperation (CEC) 2008, p. 11). The monarch butterfly has bright and
contrasting coloration, which serves as a warning to predators that
eating them can be toxic.
The migratory North American populations are located east and west
of the Rocky Mountains and overwinter primarily at sites with specific
microhabitats in central Mexico and California, respectively. In
central Mexico, the species primarily overwinters in mountainous
regions where the monarchs form dense clusters mainly on oyamel fir
trees (Abies religiosa). Western monarchs spend the fall and winter at
tree groves along the California coast, northern Baja California,
Mexico, and at a few inland sites in the Saline Valley of California.
These groves are populated by a variety of tree species, including blue
gum eucalyptus (Eucalyptus globulus), Monterey pine (Pinus radiata),
Monterey cypress (Cupressus macrocarpa), and others. The overwintering
sites for both the eastern and western North American migratory monarch
populations provide protection from the elements and a microhabitat
conducive for winter survival. In contrast, monarchs in habitats with
suitable winter climates (e.g., some areas in California and Florida)
may breed year-round without migrating.
During the breeding season for monarchs, adults lay their eggs on
milkweed, and larvae emerge after 2 to 5 days (Zalucki 1982, p. 242;
CEC 2008, p. 12). Larvae develop through five larval instars (intervals
between molts) over a period of 9 to 18 days, feeding on milkweed and
sequestering toxic cardenolides as a defense against predators (Parsons
1965, p. 299). The larva then pupates into a chrysalis before eclosing
6 to 14 days later as an adult butterfly. Monarchs produce multiple
generations during the breeding season, with most adult butterflies
living approximately 2 to 5 weeks; however, migrating and overwintering
adults enter into reproductive diapause (suspended reproduction) and
live 6 to 9 months (Cockrell et al. 1993, pp. 245-246; Herman and Tatar
2001, p. 2509).
Regulatory and Analytical Framework
Regulatory Framework
Section 4 of the Act (16 U.S.C. 1533) and the implementing
regulations in title 50 of the Code of Federal Regulations (CFR) set
forth the procedures for determining whether a species is an endangered
species or a threatened species, issuing protective
[[Page 100667]]
regulations for threatened species, and designating critical habitat
for endangered and threatened species.
The Act defines an ``endangered species'' as a species that is in
danger of extinction throughout all or a significant portion of its
range, and a ``threatened species'' as a species that is likely to
become an endangered species within the foreseeable future throughout
all or a significant portion of its range. The Act requires that we
determine whether any species is an endangered species or a threatened
species because of any of the following factors:
(A) The present or threatened destruction, modification, or
curtailment of its habitat or range;
(B) Overutilization for commercial, recreational, scientific, or
educational purposes;
(C) Disease or predation;
(D) The inadequacy of existing regulatory mechanisms; or
(E) Other natural or manmade factors affecting its continued
existence.
These factors represent broad categories of natural or human-caused
actions or conditions that could have an effect on a species' continued
existence. In evaluating these actions and conditions, we look for
those that may have a negative effect on individuals of the species, as
well as other actions or conditions that may ameliorate any negative
effects or may have positive effects.
We use the term ``threat'' to refer in general to actions or
conditions that are known to or are reasonably likely to negatively
affect individuals of a species. The term ``threat'' includes actions
or conditions that have a direct impact on individuals (direct
impacts), as well as those that affect individuals through alteration
of their habitat or required resources (stressors). The term ``threat''
may encompass--either together or separately--the source of the action
or condition or the action or condition itself.
However, the mere identification of any threat(s) does not
necessarily mean that the species meets the statutory definition of an
``endangered species'' or a ``threatened species.'' In determining
whether a species meets either definition, we must evaluate all
identified threats by considering the species' expected response and
the effects of the threats--in light of those actions and conditions
that will ameliorate the threats--on an individual, population, and
species level. We evaluate each threat and its expected effects on the
species, then analyze the cumulative effect of all of the threats on
the species as a whole. We also consider the cumulative effect of the
threats in light of those actions and conditions that will have
positive effects on the species, such as any existing regulatory
mechanisms or conservation efforts. The Secretary determines whether
the species meets the definition of an ``endangered species'' or a
``threatened species'' only after conducting this cumulative analysis
and describing the expected effect on the species.
The Act does not define the term ``foreseeable future,'' which
appears in the statutory definition of ``threatened species.'' Our
implementing regulations at 50 CFR 424.11(d) set forth a framework for
evaluating the foreseeable future on a case-by-case basis, which is
further described in the 2009 Memorandum Opinion on the foreseeable
future from the Department of the Interior, Office of the Solicitor (M-
37021, January 16, 2009; ``M-Opinion,'' available online at <a href="https://www.doi.gov/sites/doi.opengov.ibmcloud.com/files/uploads/M-37021.pdf">https://www.doi.gov/sites/doi.opengov.ibmcloud.com/files/uploads/M-37021.pdf</a>).
The foreseeable future extends as far into the future as the U.S. Fish
and Wildlife Service and National Marine Fisheries Service (hereafter,
the Services) can make reasonably reliable predictions about the
threats to the species and the species' responses to those threats. We
need not identify the foreseeable future in terms of a specific period
of time. We will describe the foreseeable future on a case-by-case
basis, using the best available data and taking into account
considerations such as the species' life-history characteristics,
threat projection timeframes, and environmental variability. In other
words, the foreseeable future is the period of time over which we can
make reasonably reliable predictions. ``Reliable'' does not mean
``certain''; it means sufficient to provide a reasonable degree of
confidence in the prediction, in light of the conservation purposes of
the Act.
Analytical Framework
The SSA report documents the results of our comprehensive
biological review of the best scientific and commercial data regarding
the status of the species, including an assessment of the potential
threats to the species. The SSA report does not represent our decision
on whether the species should be proposed for listing as an endangered
or threatened species under the Act. However, it does provide the
scientific basis that informs our regulatory decisions, which involve
the further application of standards within the Act and its
implementing regulations and policies.
To assess monarch butterfly viability, we used the three
conservation biology principles of resiliency, redundancy, and
representation (Shaffer and Stein 2000, pp. 306-310). Briefly,
resiliency is the ability of the species to withstand environmental and
demographic stochasticity (for example, wet or dry, warm or cold
years); redundancy is the ability of the species to withstand
catastrophic events (for example, droughts, large pollution events);
and representation is the ability of the species to adapt to both near-
term and long-term changes in its physical and biological environment
(for example, climate conditions, pathogens). In general, species
viability will increase with increases in resiliency, redundancy, and
representation (Smith et al. 2018, p. 306). Using these principles, we
identified the species' ecological requirements for survival and
reproduction at the individual, population, and species levels, and
described the beneficial and risk factors influencing the species'
viability.
The SSA process can be categorized into three sequential stages.
During the first stage, we evaluated the individual species' life-
history needs. The next stage involved an assessment of the historical
and current condition of the species' demographics and habitat
characteristics, including an explanation of how the species arrived at
its current condition. The final stage of the SSA involved making
predictions about the species' responses to positive and negative
environmental and anthropogenic influences. Throughout all of these
stages, we used the best available information to characterize
viability as the ability of a species to sustain populations in the
wild over time, which we then used to inform our regulatory decision.
The following is a summary of the key results and conclusions from
the SSA report; the full SSA report can be found at Docket FWS-R3-ES-
2024-0137 on <a href="https://www.regulations.gov">https://www.regulations.gov</a>.
Summary of Biological Status and Threats
In this discussion, we review the biological condition of the
species and its resources, and the threats that influence the species'
current and future condition, in order to assess the species' overall
viability and the risks to that viability.
Species Needs
Individual-Level Ecology
The monarch life cycle varies by geographic location. Migratory
monarchs in North America are the
[[Page 100668]]
ancestral population for all other monarch populations (Pierce et al.
2014, p. 4; Zhan et al. 2014, p. 318; Hemstrom et al. 2022, pp. 4551-
4552), which dispersed from North America via human assistance,
potentially aided through wind dispersal events (Brower 1995, p. 354),
and now occur in Central and South America; Australia; New Zealand;
islands of the Pacific and Caribbean, and elsewhere (Malcolm and
Zalucki 1993, pp. 3-5) where milkweed (their larval host plant) was
already present or introduced. In a few parts of North America (such as
parts of Florida, the Gulf Coast, and California) and in most areas
outside North America, monarchs breed year-round, repeatedly following
the above-referenced life cycle throughout the year. However, monarchs
in temperate climates such as eastern and western North America undergo
long-distance migration, where the migratory generation of adults is in
reproductive diapause and lives for an extended period of time (Herman
and Tatar 2001, p. 2509).
In the fall, in both eastern and western North America, monarchs
begin migrating to their respective overwintering sites. This migration
can take monarchs distances of over 2,000 miles (mi) (3,000 kilometers
(km)) (Urquhart and Urquhart 1978, p. 1760) and last for over 2 months
(Brower 1996, p. 93). The vast majority of migratory individuals in
eastern North America fly south or southwest to mountainous
overwintering grounds in central Mexico, although some minor
alternative migratory routes have also been suggested (Dockx et al.
2023, p. 314). Migratory individuals in western North America generally
fly shorter distances south and west to overwintering groves along the
California coast into northern Baja California (Solensky 2004, p. 79).
Data from monarchs tagged in the southwestern States in the fall
suggest that those in Nevada migrate to California, those in New Mexico
migrate to Mexico, and those in Arizona migrate to either Mexico or
California (Southwest Monarch Study Inc. 2018, unpaginated). In early
spring (February-March), surviving monarchs break diapause and mate at
the overwintering sites before dispersing (Leong et al. 1995, p. 46;
van Hook 1996, pp. 16-17). The same individuals that undertook the
initial southward migration begin flying back through the breeding
grounds, and their offspring start the cycle of generational migration
over again (Malcolm et al. 1993, p. 262).
The spring monarch migrations in eastern and western North America
represent massive annual range expansions. In eastern North America,
monarchs travel north in the spring, from Mexico to Canada, over two to
three successive generations, breeding along the way (Flockhart et al.
2013, pp. 4-5). Individual monarchs may disperse as far north as they
can physiologically tolerate based on climatic conditions and available
vegetation; the most specific predictors of the northern distribution
of individual monarchs are monthly mean temperature and precipitation
(Flockhart et al. 2013, p. 4; Flockhart et al. 2017, p. 2570). The
number of generations of monarchs produced in a given year in a
migratory population can vary between three and five and is dependent
upon environmental conditions (Brower 1996, p. 100). While a majority
of the eastern monarchs shift to the more northern reaches of their
range, western monarchs continue to occupy and breed in warmer climates
throughout the summer, while also expanding to include the farther
reaches of their range. In the spring in western North America,
monarchs migrate north and east over multiple generations from coastal
California toward the Rockies and to the Pacific Northwest (Urquhart
and Urquhart 1977, p. 1585; Nagano et al. 1993, entire). In the
southwestern States, migrating monarchs tend to occur more frequently
near water sources such as rivers, creeks, roadside ditches, and
irrigated gardens (Morris et al. 2015, p. 100).
In addition to the monarchs that overwinter by clustering at known
overwintering roost sites, some monarchs in North America also breed
year-round or breed throughout the winter. These individuals require
the breeding habitat and suitable climate (table 1) and are discussed
further in Species-Level Ecology, below.
To facilitate the massive annual spring range expansion, adult
monarch butterflies require a diversity of blooming nectar resources,
which they feed on both throughout their migration routes and in their
breeding grounds (spring through fall). Monarchs also need milkweed
(for both oviposition and larval feeding) embedded within this diverse
nectaring habitat. The correct phenology, or timing, of both monarchs
and nectar plants and milkweed is important for monarch survival. The
position of these resources on the landscape is important as well (see
Population-Level Ecology, below). In western North America, nectar and
milkweed resources are often associated with riparian corridors, and
milkweed may function as the principal nectar source for monarchs in
more arid regions (Dingle et al. 2005, p. 494; Pelton et al. 2018, p.
18; Waterbury and Potter 2018, p. 38; Dilts et al. 2018, p. 8).
Individuals need nectar and milkweed resources year-round in
nonmigratory populations. Additionally, many monarchs use a variety of
roosting trees along the fall migration route (table 1).
Migratory individuals of eastern and western North America require
a specific microclimate at overwintering sites. The eastern population
of monarchs overwinter in Mexico, where this microclimate is provided
by forests primarily composed of oyamel fir trees, on which the
monarchs form dense clusters (Williams and Brower 2015, pp. 109-110).
These cluster formations provide a buffer for individuals against
freezing temperatures, lipid depletion, and desiccation (Brower et al.
2008, p. 186). The sites used for overwintering primarily occur in
mountainous areas west of Mexico City located between elevations of
9,500 feet (ft) (2,900 meters (m)) and 10,800 ft (3,300 m) (Slayback
and Brower 2007, p. 147). The temperature must remain cool enough to
prevent excessive lipid depletion (Alonso-Mej[iacute]a et al. 1997, p.
935), while at the same time staying warm enough to prevent freezing
(Anderson and Brower 1996, pp. 111-113). Exposure to these cooler
temperatures also helps orient the monarchs northward in the spring
(Guerra and Reppert 2013, pp. 421-422). The oyamel fir forest provides
essential protection from the elements, including rain, snow, wind,
hail, and excessive solar radiation (Williams and Brower 2015, p. 109).
Many sites also provide a source of hydration via nectar plants or a
water source (Brower et al. 1977, pp. 237-238). Most of the observed
overwintering sites are located within the Monarch Butterfly Biosphere
Reserve, which covers more than 138,000 acres (ac) (56,000 hectares
(ha)) (Vidal and Rend[oacute]n-Salinas 2014, p. 169; Ram[iacute]rez et
al. 2015, p. 158).
Migratory monarchs in the western population primarily overwinter
in groves along the coast of California and Baja California (Jepsen and
Black 2015, p. 149). The location and structure of these sites provide
the specific microclimate (although different from the Mexico
overwintering microclimate) needed for survival in the western
overwintering areas. Approximately 400 groves have been known to be
occupied, but only a portion of these sites is occupied in any given
year. These sites, typically close to the coast, span approximately 761
mi (1,225 km) of coastline (COSEWIC 2010, p. 10). These groves are
populated by a variety of tree species, including blue gum eucalyptus,
Monterey pine, and Monterey cypress
[[Page 100669]]
(Griffiths and Villablanca 2015, pp. 41, 46-47), all of which act as
roost trees. These groves provide indirect sunlight for the
overwintering monarchs, sources of moisture for hydration, defense
against freezing temperatures, and protection against strong winds
(Tuskes and Brower 1978, p. 149; Leong 1990, pp. 908-910, Leong 1999,
p. 213). The close proximity to the coast (average distance of 1.47 mi
(2.37 km)) also provides a mild winter climate (Leong et al. 2004, p.
180).
Table 1--Individual-Level Requisites for Monarch Survival and Reproduction
----------------------------------------------------------------------------------------------------------------
Life stage Requirements Description
----------------------------------------------------------------------------------------------------------------
Egg, larva, and adult--breeding......... Milkweed resources......... Healthy and abundant milkweed is needed
for oviposition and larval consumption.
Adult--breeding and migration........... Nectar resources........... Sufficient quality and quantity of nectar
from flowers is needed for adult feeding
throughout the breeding and migration
seasons.
Adult--overwintering.................... Suitable habitat for Habitat that provides a specific roosting
overwintering. microclimate for overwintering:
protection from the elements (e.g.,
rain, wind, hail, excessive radiation)
and moderate temperatures that are warm
enough to prevent freezing yet cool
enough to prevent lipid depletion.
Nectar and clean water sources located
near roosting sites.
Adult--migration........................ Connectivity and phenology. Nectar and milkweed resources along the
migration route when butterflies are
present; the size and spatial
arrangement of habitat patches are
generally thought to be important
aspects, but currently unknown. Roosting
sites may also be important for monarchs
along their fall migration route.
----------------------------------------------------------------------------------------------------------------
Population-Level Ecology
Monarchs, like many insects, are sensitive to environmental
conditions (temperature and precipitation) and can experience large
swings in population numbers from year to year in response to these
conditions (Rend[oacute]n-Salinas et al. 2015, p. 3; Schultz et al.
2017, pp. 345-346). During favorable conditions, monarch survival and
reproductive rates are high and population numbers increase;
conversely, when environmental conditions are unfavorable, survival and
reproductive rates are low and population numbers can plummet. Thus, to
successfully recruit over generations and years, they must be capable
of withstanding large swings in population sizes (N). Specifically,
they need a positive population growth rate (lambda, or [lambda]) that
is sufficient for the species to recover from annual stochasticity.
To support a strong growth rate, monarch populations require
sufficiently large population sizes and an adequate quantity and
quality of habitat to support these large population sizes. Large
population sizes also help maintain genetic health and facilitate
thermoregulation during the winter, which is important for good
physical health. A sufficiently large population size may also be
important for finding mates and repelling predators (Malcolm 2018,
pers. comm.). Both migratory and breeding habitat need to be
distributed throughout the landscape to ensure connectivity, allowing
monarchs within a population to reach all portions of their range and
to maximize lifetime fecundity (Zalucki and Lammers 2010, p. 84; Miller
et al. 2012, p. 2).
Species-Level Ecology
The ecological requisites at the species level include having a
sufficient number and distribution of healthy populations to ensure the
species can withstand annual variation in its environment (resiliency),
catastrophes (redundancy), and novel biological and physical changes in
its environment (representation). We describe the monarch's
requirements for resiliency, redundancy, and representation below.
Resiliency
Monarch populations with a robust growth rate, large effective
population size, and suitable quality, quantity, and distribution of
habitat conditions are better able to withstand and recover from
environmental variability and stochastic perturbations (e.g., storms,
dry years) than those populations that are less demographically,
genetically, or physically healthy. Given the monarch's sensitivity to
environmental conditions, which can cause large swings in population
numbers year-to-year (Rend[oacute]n-Salinas et al. 2015, p. 3),
monarchs occupying a diversity of environmental conditions and being
widely distributed helps guard against populations being exposed to
adverse conditions concurrently, and thus, fluctuating in synchrony.
Asynchronous dynamics within and among populations minimizes the
chances of concurrent losses, and thus, provides species resiliency.
Redundancy
Monarch redundancy is best achieved by having a broad geographic
distribution of monarchs relative to the spatial occurrence of
catastrophic events. For the eastern North American migratory
population, potential catastrophic events include extreme storms when
monarchs are densely congregated and widespread drought. For the
western North American migratory population, potential catastrophic
events include widespread drought and co-occurrence of poor
environmental conditions and low population abundance. For dispersed
non-migratory populations, potentially catastrophic events include sea
level rise, which can inundate habitat, and lethal high temperatures.
Migratory North American monarchs are distributed across vast and
diverse habitats across much of North America during their breeding and
migratory seasons. However, while overwintering, most migratory
monarchs are highly concentrated at sites in Mexico and California.
Nonmigratory monarchs in North America are distributed in warmer,
suitable areas throughout the year, including in parts of Florida, the
Gulf Coast, and California. A very small proportion of the species is
also distributed in nonnative or naturalized populations across diverse
habitats throughout 90 countries, islands, and island groups.
Representation
The monarch's ability to withstand novel changes in its environment
is influenced by its adaptive capacity, which is primarily a function
of the species' breadth of variation in biological traits and genetic
diversity. Without such variation, species are less responsive to
change and more prone to extinction (Spielman et al. 2004, p. 15263).
Additionally, as populations with higher genetic diversity can more
quickly adapt to novel changes, species with genetically healthy
populations are better able to adapt (Ofori et al. 2017, p.
[[Page 100670]]
2). Below we describe monarch adaptive capacity by using the best
available data.
Migratory monarchs in North America are the ancestral population
for all other monarch populations around the world (Pierce et al. 2014,
p. 4; Zhan et al. 2014, p. 318; Hemstrom et al. 2022, pp. 4551-4552).
Their unique genetics separate them from nonmigratory monarchs
(Freedman et al. 2021, p. 7). Genetic sampling indicates that the
monarchs from eastern and western North America have continued
interchange between the two populations contributing to low genetic
differentiation (Talla et al. 2020, p. 2573; Freedman et al. 2021, pp.
7-8). During the annual breeding season, the North American migratory
populations use a vast and diverse array of habitats. Following a long-
distance migration through more varied habitats and conditions, the
North American migratory monarchs use sites with a diversity of
physical structures and climatic conditions for overwintering. Having
monarchs occupying areas of unique ecological diversity guards against
losses of adaptive capacity due to stochastic or catastrophic events.
Nonmigratory monarchs represent a life-history strategy that exposes
them to selection pressures that differ from migratory monarchs.
Eastern North American monarchs undergo long-distance migration
every fall, a behavior that differentiates this population from
nonmigratory populations or from migratory populations that fly shorter
distances and to different locations. The migratory phenotype of
monarchs in the eastern migratory population is distinct from monarchs
in other populations that may have latent migratory phenotypes (Tenger-
Trolander et al. 2019, p. 14673). This migratory phenotype consists of
both reproductive diapause and directional flight orientation to the
south, and this migratory behavior of monarchs is remarkably sensitive
to genetic and environmental change (Tenger-Trolander et al. 2019, p.
14673). Monarchs from the eastern North American migratory population
tend to have larger bodies and larger elongated wings compared to
monarchs from most nonmigratory populations (Altizer and Davis 2010,
pp. 1023-1025). Eastern North American migratory monarchs inhabit 70
percent or more of the total area occupied by monarch butterflies in
North America.
Western North American monarchs also migrate long distances,
although their migration is shorter than monarchs in eastern North
America. Whereas eastern monarchs may fly well over 2,000 mi (3,000 km)
to reach the Mexican overwintering sites, western monarchs reach the
California coast by flying approximately 300 mi to 1,000 mi (500 km to
1,600 km) (Yang et al. 2016, p. 1002; Edwards et al. 2023, p. 5).
Western monarchs occupy warmer climates throughout the summer to
include the farther reaches of their range while they continue to breed
in the hotter regions (expand their range). Eastern monarchs, in
contrast, follow more of a stepping-stone path into the northern
States, vacating areas as they warm and recolonizing their range.
Western North American migratory monarchs occupy as much as 30
percent of the total area occupied by monarch butterflies in North
America (Dilts et al. 2019, p. 11). Western monarchs use ecologically
different breeding, migrating, and overwintering habitats (Brower et
al. 1995, p. 542) compared to monarchs in eastern North America.
Differences in breeding habitat include climate (Zalucki and Rochester
2004, pp. 220-221) and availability and abundance of native nectar and
native milkweed plants (Borders and Lee-M[auml]der 2015, entire). The
West is generally hotter and drier than the East, and the milkweed and
nectar resources used by monarchs in the West and East differ (Dilts et
al. 2019, entire). In the fall, western monarchs migrate from Canada
and States west of the Rockies to overwintering groves located
primarily along the California coast south into Baja California, Mexico
(Jepsen and Black 2015, pp. 147-156). Roosting tree species used by
western monarchs for overwintering are different than those used by the
eastern population and include blue gum eucalyptus, Monterey pine, and
Monterey cypress (Griffiths and Villablanca 2015, pp. 43-44). The
western population has fewer monarchs, spread out among hundreds of
overwintering sites compared to fewer than 20 sites in Mexico for the
eastern population (Jepsen and Black 2015, pp. 147-156; Vidal and
Rend[oacute]n-Salinas 2014, entire).
Migratory monarchs in eastern and western North America may also
contribute unique phenotypic variation in wing morphology/coloration,
lipid reserves, and reproductive behavior (Talla et al. 2020, pp. 2572-
2573; Freedman and Dingle 2018, p. 66; Davis 2009, p. 3; Brower et al.
1995, p. 542; Herman et al. 1989, pp. 52-54; 56-57). Compared to
monarchs in western North America and to nonmigratory monarchs in
southern Florida, eastern North American monarchs have lower rates of
infection by the protozoan parasite OE (<10 percent; Altizer et al.
2000, p. 131), which may be due in part to their long-distance
migration (Bartel et al. 2011, p. 348). Migratory monarchs in the West
have OE infection rates (averaging 5-30 percent) that are lower than
most nonmigratory populations but higher than the rates of infection in
migratory monarchs in eastern North America (Altizer and de Roode 2015,
p. 91).
Resident (nonmigratory) monarchs in North America now live in areas
where milkweed availability and climate permit year-round breeding, and
thus are able to reside continually without migrating. These
nonmigratory monarchs in southern Florida are genetically distinct from
the migratory North American monarchs, although the southern Florida
population gets an annual influx of individuals from the eastern
migratory monarch population (Knight and Brower 2009, p. 821; Zhan et
al. 2014, p. 322). Also, some monarchs remain or become reproductively
active and breed throughout the winter along the Gulf Coast, the
southern Atlantic Coast, and the southern Pacific Coast (Howard et al.
2010, p. 3; Satterfield et al. 2016, p. 346). These monarchs are more
likely to be infected with OE (Satterfield et al. 2016, p. 347; 2018,
p. 1676), and there is some question of whether some of the offspring
of these individuals might emerge in diapause and continue to Mexico or
California overwintering sites later in the season (Batalden and
Oberhauser 2015, p. 223). The best available information, including the
quantity and quality of the habitat, indicates that the total number of
resident monarchs appears to be quite small relative to the North
American migratory populations that overwinter in Mexico and
California. Some experts consider the resident monarch populations
demographic sinks (see Crone and Schultz 2021, p. 1536), requiring
continual influxes of monarchs from migratory populations to sustain
them.
Nonmigratory Florida monarchs experience some of the highest
recorded OE infection rates compared to other monarchs worldwide and
particularly high rates compared to migratory eastern and western North
America monarch infection rates (75-100 percent average infection rates
in Florida vs. 5-30 percent infection rates in the western North
American population and less than 10 percent infection rates in the
eastern North American population; Altizer and de Roode 2015, p. 91).
This may be due both to their inability to escape infected habitat, as
well as the nonmigratory behavior not leading to any migratory culling
(the removal of
[[Page 100671]]
less fit individuals from a population due to their inability to
migrate) (Bartel et al. 2011, entire). While we assume most monarchs
found in southern Florida are nonmigratory, it is possible that some
are migratory (Dockx et al. 2023, pp. 314-317).
In the West, the population of migratory monarchs has declined from
several million butterflies in the 1980s (Schultz et al. 2017, p. 345)
to current levels (figure 1b). Concurrently in the West, a portion of
nonmigratory monarch butterflies in urban gardens has been growing
(Crone and Schultz 2021, entire). The increase in numbers of these
nonmigratory monarchs do not seem to make up for the decline of the
migratory population (Crone and Schultz 2021, entire). Additionally,
the nonmigratory portion also probably lacks the demographic capacity
to expand its range inland during summer months. Nonmigratory monarch
butterflies build up high levels of OE, at least in part because of a
lack of migratory culling and migratory escape (Satterfield et al.
2015, pp. 4-5). In California, about 8 percent of migratory monarch
butterflies are infected with OE, compared to about 75 percent of
nonmigratory individuals (Satterfield et al. 2016, p. 346). OE-infected
monarch butterflies have both lower survival and lower egg-laying rates
and produce only about 0.8 adult daughters per female on average (Crone
and Schultz 2021, Supplement S4). While this rate of increase is enough
for nonmigratory monarch butterflies to persist in urban areas, it does
not allow them to expand to other western States (Crone and Schultz
2021, p. 1536). Additional information on the genetic structuring of
monarchs outside of continental North America is available in the SSA
report (Service 2024a, appendix 2).
In order to better understand the population dynamics and
contributions from the nonmigratory populations, we are requesting
additional information on resident monarchs in southern Florida, the
Gulf Coast, the southern Atlantic Coast, and the southern Pacific
Coast. To submit information, see the Information Requested section.
Threats
We have little to no information on positive or negative influences
acting upon monarchs occurring outside of the eastern and western North
American populations. There is limited information on predation,
parasitism, and disease outside of eastern and western North American
populations. Given this limited information, we were unable to
ascertain to what extent predation, parasitism, and disease impact the
monarch populations outside of the eastern and western North American
populations. Similarly, while data suggest global use of insecticides
is increasing, we are unable to estimate the degree of overlap with
monarch populations and thus derive a credible projection of impact on
the monarch populations outside of the eastern and western North
American populations.
The primary drivers affecting the health of the two North American
migratory populations are loss and degradation of breeding, migratory,
and overwintering habitat (from past conversion of grasslands and
shrublands to agriculture and widespread use of herbicides; logging/
thinning at overwintering sites in Mexico; urban development,
senescence, and incompatible management of overwintering sites in
California; and drought); exposure to insecticides; and effects of
climate change. Many other influences to monarchs were evaluated,
including disease, parasitism, captive rearing, collection, impacts of
tourism at overwintering sites, invasive swallow-wort plants, vehicle
mortality, and natural catastrophes. However, these other potential
influences were not determined to be key population drivers (Service
2024a, pp. 109-111).
Because the conversion of grasslands to agriculture was a key
driver for past population declines, current and future activities that
may remove milkweed and nectar resources within the breeding and
migratory range, but that do not result in conversion of native or
naturalized grassland, shrubland, or forested habitats and do not
result in significant population-level mortality, are, therefore, not
considered key population drivers. These include habitat restoration
and management activities, livestock grazing and routine ranching
activities, routine agricultural activities and conservation practices,
fire management, silviculture and forest management, management of
habitat on residential and other developed properties, and vegetation
management activities when monarchs are not present. Given that so much
milkweed has been lost historically and that monarchs are impacted by
the ongoing effects of this past habitat loss and degradation, we need
an approach that encourages landowners to add and maintain habitat in
order to achieve a significant increase in the availability of milkweed
and nectar resources. We expect localized removal of milkweed and
nectar plants will be outweighed by an overall addition of these
resources across the landscape, making broadscale public support for
monarch conservation vitally important. For example, landscape-scale
habitat restoration and management activities that provide for the
habitat needs of monarch butterflies (e.g., mowing, haying native
rangeland, prescribed and cultural burning, and control of invasive
plants or noxious weeds) may remove milkweed and could result in loss
of monarchs in the short term but would also increase the overall
quality and quantity of breeding habitat, which is likely to benefit
monarch populations in the long term. We are requesting information on
both our identified key threats as well as other potential threats to
the species, such as collisions with wind turbines (see Information
Requested). The key influences for monarch butterflies are discussed
below.
Availability, Distribution, and Quality of Breeding Habitat and
Migratory Habitat
The availability of milkweed is essential to monarch reproduction
and survival. Reductions in milkweed are cited as a key driver in
monarch declines (Brower et al. 2012, p. 97; Pleasants and Oberhauser
2013, p. 141; Inamine et al. 2016, p. 1081; Thogmartin et al. 2017a, p.
12; Waterbury and Potter 2018, pp. 42-44; Saunders et al. 2019, p.
8612).
A majority of the past milkweed loss has occurred in agricultural
lands, where intensive herbicide usage for weed control has resulted in
widespread milkweed eradication. More than 860 million milkweed stems
were lost in the Midwest between 1999 and 2014, a decline of almost 40
percent (Pleasants 2017, p. 48). Approximately 89 and 94 percent of
corn and soybean crop acreages, respectively, are planted as glyphosate
(herbicide)-tolerant crops (USDA 2018, unpaginated). When glyphosate is
sprayed in or near fields where crops are produced, it kills the
milkweed without harming the glyphosate-tolerant crops. Glyphosate use
in western agricultural lands has also increased dramatically since the
1990s, especially within the Central Valley of California, Snake River
Plain of Idaho, and the Columbia River Basin, which spans the border
between Washington and Oregon (USGS NAWQA 2017, unpaginated; Waterbury
and Potter 2018, p. 42). As weed species develop increasing resistance
to glyphosate, other herbicide (e.g., dicamba)-tolerant crops are
developed, which can lead to a corresponding increase in use of those
herbicides. Accordingly, herbicide impacts to milkweed and nectar
plants will continue to impact monarch resources in agricultural lands.
[[Page 100672]]
Milkweed has also been lost on the landscape through development
and conversion of grasslands (Lark et al. 2015, pp. 3-4). Between 2008
and 2016, a total of 4.9 million acres of grassland were converted to
new cropland, including up to 3 million acres of Conservation Reserve
Program land (Lark et al. 2015, p. 5). Past loss of agricultural
milkweeds in the Midwest has resulted in an estimated 81 percent
decline in monarch production, in part because monarch egg densities
were higher on milkweed in agricultural fields (3.89 times more eggs
than on non-agricultural milkweed; Pleasants and Oberhauser 2013, pp.
139-140). This situation particularly impacts the eastern monarch
population because more Mexico overwintering monarchs originate from
the Midwest crop belt region than any other region (with estimates
ranging from 38 percent to over 85 percent of all overwintering
monarchs originating from the Midwest; Wassenaar and Hobson 1998, pp.
15438-15439; Flockhart et al. 2017, p. 2568). Development and
conversion of grasslands will continue to impact monarch resources in
agricultural lands.
Losses of nectar sources have also been implicated as a potential
key driver in monarch declines (Inamine et al. 2016, p. 1081;
Thogmartin et al. 2017a, p. 12; Saunders et al. 2019, p. 8612). Losses
of nectar resources are due to the same stressors identified above for
milkweed resources. Additionally, with a warming climate, drought
impacts may affect the availability of nectar sources, especially in
the western population and in the migratory bottleneck through Mexico
and into Texas for the eastern population (see Climate Change Effects,
below).
Our future analyses forecast a range of projections for future
nectar and milkweed throughout the monarch butterfly's range. While
these breeding and migratory habitat resources show signs of regional
stabilization or increase, even the best case scenario increases are
less than the amount of milkweed and nectar resources that have been
lost. The reduced amount of breeding and migratory habitat continues to
negatively impact the viability of the migratory North American
monarchs. Monarch conservation needs an approach that encourages and
incentivizes landowners to add milkweeds and nectar resources and
implement actions to maintain this habitat. Unlike with some at-risk
species, the monarch's general habitat usage and wide distribution
allow a broad range of landowners to participate in actions to support
the species. Conservation for the species can occur on land parcels
ranging from quite small to very large, including gardens, parks,
grasslands, agricultural areas, and more.
Availability, Distribution, and Quality of Overwintering Habitat
Both western and eastern monarchs rely on the microclimate provided
by the trees at their overwintering sites (Leong et al. 2004, entire;
Williams and Brower 2015, entire). Loss of trees occurs at
overwintering sites in Mexico primarily through small- and large-scale
logging, storms, and an increasingly unsuitable climate (see Climate
Change Effects below). Most overwintering sites used by eastern
monarchs occur within the Monarch Butterfly Biosphere Reserve
(Reserve), a 139,019-ac (56,259-ha) protected area in Central Mexico.
Within this area, logging is banned within the 33,485-ac (13,551-ha)
core zone (Ram[iacute]rez et al. 2015, p. 158). However, logging has
continued to occur both legally (including salvage logging allowed
after storms) and illegally at multiple colonies within the Reserve
(Vidal et al. 2014, pp. 180-185; Brower et al. 2016, entire).
Logging was estimated in the core zone of the Reserve from 2002
through 2012 (Vidal et al. 2014, p. 180). Within this period, 5,384
acres (2,179 ha) of core zone were either deforested (less than 10
percent canopy cover remained; 3,099 ac (1,254 ha)) or degraded (a
decrease in canopy cover; 2,286 ac (925 ha)). Most of these losses were
attributed to illegal logging (5,083 ac (2,057 ha)), with the remaining
301 acres (122 ha) lost due to floods, drought, strong winds, and fire.
Current estimates of forest loss throughout the Reserve vary from 0-2.4
percent per year (Ram[iacute]rez et al. 2015, p. 163). While anti-
logging and reforestation efforts are underway (L[oacute]pez-
Garc[iacute]a 2022, p. 245), logging is still ongoing within the
Reserve (Brower et al. 2016, entire). Although clearcutting of forests
destroys habitat directly, thinning of the forest also changes the
microclimate needed by overwintering monarchs, making them more
susceptible to winter mortality (Brower et al. 2011, p. 43).
Western monarch overwintering habitat along the Pacific Coast has
been subject to loss through various forms of development, particularly
urban development (Sakai and Calvert 1991, p. 149; Frey and Schaffner
2004, p. 172). Since the 1980s, development has caused the loss of at
least 63 known California overwintering sites (Sakai and Calvert 1991,
pp. 148-49, Meade 1999, p. 97-100, Xerces Society 2024a, unpaginated).
Habitat alteration, such as through natural tree senescence and
improper grove management, can also alter the microclimate of the
western overwintering sites, leading to less suitable habitat
conditions (Jepsen et al. 2015, p. 17). Many other stressors can work
alone or in tandem on the western overwintering sites, including
disease and pests that impact the trees used for overwintering. Fire is
also a threat, both indirectly through habitat loss and directly to
overwintering monarchs (Pelton et al. 2016, pp. 28, 32). Drought in the
West can further exacerbate the stressors on the western overwintering
sites (see Climate Change Effects below).
Insecticide Exposure
Insecticides are pesticides with chemical properties that are
designed to kill insects and most are non-specific and broad-spectrum
in nature. That is, insects exposed to these insecticides are
susceptible to mortality or sublethal effects. Furthermore, the larvae
of many lepidopterans (i.e., insects in the order that includes
butterflies and moths) are considered major pest species, and
insecticides are tested specifically on this taxon to ensure that they
will effectively kill individuals at application rates indicated on
product labels. Even though monarchs are not the target species of
these products, they may be exposed to insecticides where they are
applied and in areas beyond the insecticide application sites due to
drift (Olaya-Arenas and Kaplan 2019, p. 1; Halsch et al. 2020, p. 3).
Insecticide impacts to monarchs are primarily influenced by the
extent to which monarchs are exposed to insecticides throughout their
range. Although insecticide use is most often associated with
agricultural production (e.g., between 2005 and 2012, 60 percent of
insecticides applied occurred on agricultural lands; EPA 2017, p. 11),
any habitat where monarchs are found may be subject to insecticide use.
Insecticides can be used for insect pest control anywhere there is a
pest outbreak or for general pest prevention. Homeowners may treat
yards and gardens to protect plants from pests or purchase plants from
nurseries that sell plants pre-treated or grown from seeds treated with
insecticides as ornamentals. Natural areas, such as forests and parks,
may be treated to control for insects that defoliate, bore into wood,
or otherwise damage trees. Outbreaks of pests, such as spongy moths,
mosquitoes, Mormon crickets, or grasshoppers, may trigger insecticide
treatments over large areas to control populations. Use of insecticides
in vector control, especially pyrethroids and organophosphates, may be
significant in areas of the country where mosquitoes pose a public
health threat
[[Page 100673]]
or reach nuisance levels. The most widely used classes of insecticides
include organophosphates, pyrethroids, and neonicotinoids. Studies
looking specifically at dose-response of monarchs to neonicotinoids,
organophosphates, and pyrethroids have demonstrated monarch toxicity at
product label application rates and field concentration levels (e.g.,
Krischik et al. 2015, entire; James 2019, entire; Krishnan et al. 2020,
entire; Bargar et al. 2020, entire).
Insecticides are a threat to monarchs based on their mode of action
to target insects and their potential exposure to monarchs. Monarchs
can be exposed to liquid insecticides from direct spray at the time of
application, contact with vegetation contaminated with an insecticide,
or ingestion of leaves or nectar contaminated with insecticide
following a spray. This exposure can occur on the site of application
or in adjacent areas as a result of insecticide drift. Biopesticides,
another type of insecticide, generally affect only the target pest and
closely related organisms. These products contrast with broad-spectrum
and conventional insecticides that target all insects. The primary
identified biopesticide exposure threat to monarchs is limited to the
liquid application of certain types of Bacillus thuringiensis (Bt) that
are active against lepidopterans and often used to control caterpillar
pests (such as spongy moth).
Monarchs may also be exposed to insecticides in forms other than
liquids, such as those that have been systemically incorporated into
plant tissues on which monarchs feed (e.g., milkweed leaves, flowers,
pollen, and nectar) or dust that has drifted off treated seeds at the
time of planting. Numerous types of insecticides may be incorporated
into plants systemically or used to treat seeds, including
neonicotinoids. However, there are limited data to suggest that
insecticides used in this manner achieve concentrations likely to
result in negative effects to monarchs. Thus, while monarchs may be
exposed to insecticide residues from these application methods, the
available information indicates that negative effects from insecticide
residues are likely minimal. For insecticides applied in solid forms
such as granules, no exposure is expected to monarchs; thus, negative
effects from application of pesticides in solid forms are unlikely.
Herbicides and fungicides are used within or near areas where
monarchs may be present; however, only a subset of these have data
showing direct negative effects to insects (i.e., as opposed to
insecticides, where all pesticides within this class will cause
negative effects to insects). As such, the information indicates the
negative effects to monarchs from exposure to herbicides and fungicides
is likely minor compared to the direct effects of exposure to
insecticides.
See Appendix 5--Supplementary Information About Pesticides in the
monarch butterfly SSA report (Service 2024a, pp. 123-146) for further
discussion of the risk of pesticides to the monarch, including data,
references, and supporting information.
Climate Change Effects
Climate change can affect monarchs both directly and indirectly
(Nail and Oberhauser 2015, entire) on overwintering, migratory, and
breeding grounds. Increasing storm frequency in the Mexican
overwintering colonies can lead to catastrophic (up to 80 percent)
mortality through the freezing temperatures that accompany these storms
(Anderson and Brower 1996, p. 112; Brower et al. 2004, entire).
Precipitation is predicted to increase during the winter when monarchs
are present in Mexico (Oberhauser and Peterson 2003, p. 14067). Severe
drought can cause tree loss and degradation, decreasing the
availability and quality of overwintering roosting habitat in
California as well (Pelton et al. 2016, p. 29). Eucalyptus trees, the
dominant tree species in many of the groves, are drought sensitive and
become vulnerable to infestation by insect borers when they are
stressed, which can exacerbate tree loss in these groves (Marcar et al.
1995, p. 46; Paine and Millar 2002, p. 148). Eucalyptus loss and
degradation reduces availability of roosting habitat, lessens wind
protection, and eliminates the primary overwintering source of nectar
at many sites. Other dominant trees, such as Monterey pines and
Monterey cypress, are more resistant to drought, but are the primary
species in fewer than 25 percent of overwintering sites. Although
overwintering grounds are widespread, drought could be equally as
widespread, such that it could occur throughout many or most of the
overwintering sites simultaneously. Given the above, extreme drought at
overwintering sites poses a catastrophic risk for the western monarch
population.
Monarchs need a very specific microclimate at their overwintering
sites not just to avoid storm mortality, but also to avoid early fat
depletion. Changing precipitation patterns and temperatures may
influence the microclimate needed by overwintering monarchs (Williams
and Brower 2015, p. 116). For example, current modeling of the
monarch's fundamental niche predicts the loss of 38.6 to 69.8 percent
of current suitable habitat within the Reserve due primarily to
expected temperature changes (Zagorski 2016, p. 17). In western North
America, climate change is predicted to cause a significant change in
the distribution of overwintering monarchs in coastal California
(Fisher et al. 2018, p. 10). While modeling projections suggest an
inland and upslope displacement of suitable overwintering conditions by
the year 2050, the best available evidence does not indicate that
monarchs would move to or use these upslope areas (Fisher et al. 2018,
pp. 10, 13-14).
In addition to the direct impact of climate change on overwintering
monarchs, the Mexico overwintering sites are predicted to be less
suitable for oyamel fir trees, the predominant monarch roosting tree.
The overwintering sites are predicted to become increasingly warm
throughout the year, potentially making 50 percent or more of the sites
unsuitable for oyamel fir trees in 2030 (S[aacute]enz-Romero et al.
2012, p. 102; Ram[iacute]rez et al. 2015, p. 167). Widespread drought
is similarly likely to negatively impact trees in the western
overwintering areas both directly and indirectly due to increased
susceptibility to pests (Paine and Millar 2002, p. 148).
Direct effects of climate change, particularly increasing
temperatures, may impact monarch fecundity (reproductive rate)
(Oberhauser 1997, pp. 168-169), mating success (Solensky and Oberhauser
2009, p. 333), and survival during migration and while overwintering
(Masters et al. 1988, entire; Alonso-Mej[iacute]a et al. 1997, entire).
Laboratory studies indicate optimal temperatures for monarch range
between 81-84 [deg]F (27-29 [deg]C) with sublethal effects beginning
around 86-97 [deg]F (30-36 [deg]C) range and an upper lethal thermal
limit of 108 [deg]F (42 [deg]C) (Zalucki 1982, p. 243; York and
Oberhauser 2002, p. 294; Zalucki and Rochester 2004, p. 225; Nail et
al. 2015, p. 101). Research also indicates that cooler nighttime
temperatures provide respite from elevated daytime temperatures and are
important in allowing monarchs to survive temperature stress (Nail et
al. 2015, p. 104). Temperatures consistently above 91-95 [deg]F (33-35
[deg]C) are unsuitable for monarchs and may account for their general
absence from the southern U.S. after spring (Malcolm et al. 1987, p.
78; Zalucki and Rochester 1999, pp. 155-157).
[[Page 100674]]
High temperatures and drought conditions may be particularly
impactful during the crucial spring migration (Taylor 2020, pers.
comm.). Spring temperatures and precipitation in the southern U.S.
portion of the migratory range have been modeled to have a high
relative importance affecting summer population size of eastern
monarchs (a larger impact than compared to summer weather, summer
herbicide use in cropland, and late-winter population size) (Zylstra et
al. 2021, p. 1443). However, considerable uncertainty remains regarding
the extent, intensity, and biological impacts of climate change during
spring migration (Neupane et al. 2022, pp. 10-14). While increased
temperatures may reduce monarch habitat in some areas, the climatically
suitable niche for monarchs may increase northward, potentially
increasing their summer breeding grounds if both monarchs and milkweed
are able to adapt and track this niche northward (Lemoine 2015, pp. 10-
17).
A warming climate may influence breeding habitat by altering
suitable locations for both monarchs (Batalden et al. 2007, pp. 1369-
1370) and their milkweed host plant (Lemoine 2015, entire). Nectar
resources during migration may be reduced under climate conditions
(decreased precipitation) projected for south-central Texas (Saunders
et al. 2019, p. 8612). Drought may also influence the amount and
availability of nectar needed for migrating butterflies (Brower et al.
2015, entire; Stevens and Frey 2010, p. 740; Espeset et al. 2016, p.
826). Widespread drought caused by climate change is expected to
increase into the future (IPCC 2023, p. 69) negatively impacting
monarchs and their habitat.
Sea level rise is increasing due to climate change. These rising
sea levels are likely to impact monarch populations in coastal areas
(e.g., along the Gulf Coast) and low lying islands through loss of
habitat (TBCSAP 2015, entire; IPCC 2023, p. 69).
Climate change may additionally impact monarchs in ways that are
more difficult to measure. This may include phenological mismatch
(e.g., timing of milkweed and nectar sources not aligning with monarch
migration; Thogmartin et al. 2017a, p. 13) or range mismatch with
associated species. For example, a change in environmental suitability
could cause a range shift for monarch predators and parasitoids,
increasing or decreasing their overlap with the monarch's range
(McCoshum et al. 2016, p. 229-233).
Conservation Efforts and Regulatory Mechanisms
While many factors have been implicated in the decline in monarch
populations, the loss of milkweed and nectar resources (i.e., breeding
and migratory habitat) has been targeted as the threat that can be most
easily addressed through conservation efforts. Because of the monarch
butterfly's general habitat use and wide distribution, all sectors of
society, including the general public, have an opportunity to
participate in a broad range of conservation efforts throughout the
species' range. Protection, restoration, enhancement, and creation of
habitat is a central aspect of recent monarch conservation strategies,
thus highlighting the importance of restoring and enhancing milkweed
and nectar resources (Oberhauser et al. 2017, pp. 56-58; Pleasants
2017, p. 43; Thogmartin et al. 2017a, pp. 2-3; MAFWA 2018, p. 52;
Pelton et al. 2019, pp. 4-5, WAFWA 2019, p. 41). Management at
overwintering sites in California has also been targeted to improve the
status of western North American monarch butterflies (Pelton et al.
2019, p. 4; WAFWA 2019, pp. 37-40). We are not aware of conservation
actions for the populations outside of eastern and western North
America, but conservation measures for the eastern and western North
American populations are described below.
Major overarching landscape-level conservation plans and efforts
include the Mid-America Monarch Conservation Strategy developed by the
Midwest Association of Fish and Wildlife Agencies (MAFWA) and the
Western Monarch Butterfly Conservation Plan developed by the Western
Association of Fish and Wildlife Agencies (WAFWA). The Mid-America
Monarch Conservation Strategy established a goal of adding 1.3 billion
stems of milkweed on the landscape by 2038 (MAFWA 2018, p. 42). The
1.3-billion-stem goal is an estimated target for adding enough breeding
and migratory habitat to support 14.8 ac (6 ha) of forest occupied by
overwintering monarchs for the eastern North American population
(Thogmartin et al. 2017b, pp. 2-3). Twenty-nine States--including
Arkansas, Connecticut, Delaware, Illinois, Indiana, Iowa, Kansas,
Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota,
Missouri, Nebraska, New Hampshire, New Jersey, New York, North Dakota,
Ohio, Oklahoma, Pennsylvania, Rhode Island, South Dakota, Texas,
Vermont, Virginia, West Virginia, and Wisconsin--have agreed to
participate in the effort to reach the 1.3-billion-stem goal, which
will also need contributions from multiple sectors of society,
including private landowners, agricultural and nongovernmental
organizations, rights-of-way organizations, and Federal, State, and
local governments.
The Western Monarch Butterfly Conservation Plan currently
encompasses the States of Arizona, California, Idaho, Nevada, Oregon,
Utah, and Washington, which comprise the core of the western monarch
range (WAFWA 2019, p. 3). The plan includes short-term goals of: (1)
protecting and managing 50 percent of all currently known and active
monarch overwintering sites, including 90 percent of the most important
overwintering sites by 2029; and (2) providing a minimum of 50,000
additional acres of monarch-friendly habitat in California's Central
Valley and adjacent foothills by 2029. It also includes overwintering
and breeding habitat conservation strategies, education and outreach
strategies, and research and monitoring needs. Many land managers who
oversee overwintering sites in California have developed and
implemented grove management strategies or have included monarch groves
in their general management plans. Conservation efforts in California's
Central Valley currently amount to nearly 9,000 ac (3,600 ha). As of
September 2024, State agencies had implemented milkweed restoration
efforts on over 8,780,404 ac (3,553,303 ha), adding more than an
estimated 546 million milkweed stems to the landscape nationwide.
In early 2020, the Nationwide Candidate Conservation Agreement for
Monarch Butterfly on Energy and Transportation Lands: An Integrated
Candidate Conservation Agreement with Assurances (CCAA) and Candidate
Conservation Agreement (CCA) was finalized and is contributing to MAFWA
Strategy and WAFWA Plan goals. Under this agreement, energy and
transportation entities are providing habitat for the species along
energy and transportation rights-of-way corridors across the country.
Participants carry out conservation measures to reduce or remove
threats to the species and create and maintain habitat annually. In
exchange for implementing voluntary conservation efforts and meeting
specific requirements and criteria, those businesses and organizations
enrolled in this CCAA/CCA receive assurance from the Service that they
will not have to implement additional conservation measures should the
species be listed. The goal of this CCAA/CCA is
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enrollment of up to 26 million acres of land in the agreement,
providing more than 300 million additional stems of milkweed (Rights-
of-Way as Habitat Working Group 2020, p. 3). As of June 2024, this
CCAA/CCA had 57 enrollees with over 981,812 ac (397,325 ha) of enrolled
habitat.
Many conservation efforts implemented under Federal, Tribal, State,
or other programs, such as the Farm Service Agency's Conservation
Reserve Program; the Natural Resource Conservation Service's
Environmental Quality Incentives Program, Agricultural Conservation
Easement Program and Conservation Stewardship Program; and the
Service's Partners for Fish and Wildlife Program, are expected to
contribute to the overarching habitat and population goals of the MAFWA
Strategy and WAFWA Plan. Smaller conservation efforts, such as
pollinator gardens, implemented by local governments, nongovernmental
organizations, private businesses, and interested individuals will also
play an important role in reaching habitat and population goals
established in the MAFWA Strategy and WAFWA Plan.
Many land managers who oversee overwintering sites in California
have developed and implemented grove management strategies or have
included monarch groves in their general management plans. Many others
are in the process of developing grove management plans. As of January
2024, grove management plans are being implemented at no fewer than 24
overwintering sites and are currently being developed for at least a
dozen more. Management and restoration of these sites may include
activities such as replacing dead trees, modifying canopy structure,
planting fall- and winter-blooming shrubs as nectar sources, and
addressing monarch predation issues (Jepsen et al. 2017, entire).
The Service developed the Monarch Conservation Database (MCD) to
capture information about monarch conservation plans and efforts to
inform the listing decision. As of September 2024, the MCD had 145,455
complete monarch conservation effort records that have a status of
completed, implemented, or planned since 2014 and 126 monarch
conservation plans. These efforts constitute a total of 10,457,316 ac
(4,231,926 ha) of land area in the United States (10,246,876 ac
(4,146,764 ha) and 178,920 ac (72,406 ha) in the eastern and western
populations, respectively) enhanced or created for monarchs, with the
most common conservation effort being direct planting of milkweed and
other nectar resources (note that these values include all completed,
implemented, and not yet completed efforts; completed and implemented
efforts to date total 7,415,731 ac (3,001,040 ha) nationally). These
conservation efforts are increasing the amount of milkweed and nectar
resources on the landscape. However, additional milkweed and nectar
resources are required, as initial estimates of the amount of acreage
needed to reach the 1.3-billion-stem goal within the MAFWA Strategy
planning area were around 20 million acres.
In addition to conservation measures for monarch butterflies, there
are also mechanisms that regulate direct and indirect threats to the
species. One such mechanism is the Federal Insecticide, Fungicide, and
Rodenticide Act (FIFRA), which provides for Federal regulation of
pesticide distribution, sale, and use. The term pesticide includes
insecticides, which can directly kill monarchs upon exposure, and
herbicides that can indirectly affect monarchs by impacting their
milkweed and nectar resources. All pesticides distributed or sold in
the United States must be registered (licensed) by the U.S.
Environmental Protection Agency (EPA). Before the EPA registers a
pesticide under FIFRA, the applicant must show, among other things,
that using the pesticide according to specifications ``will not
generally cause unreasonable adverse effects on the environment.''
In 2021, the EPA began developing a comprehensive, long-term
approach to meeting its section 7(a)(2) obligations for FIFRA actions
(EPA 2022, unpaginated). As part of that work, the EPA in August 2024
finalized its first-ever strategy to identify which agricultural uses
of conventional herbicides impact listed species and how to determine
the amount and location of mitigation measures for those herbicides,
hereon referred to as the Herbicide Strategy (EPA 2024a, entire). The
strategy covers listed plants and listed animals whose survival depends
on listed plants, including many insects that depend on plants for
food. The EPA has begun applying the strategy to the registration of
new pesticide registrations (EPA 2024d, unpaginated) and expects to
apply the strategy when the agency reevaluates the registration of
existing pesticides every 15 years.
Similarly, in July 2024 the EPA released its draft Insecticide
Strategy, which proposes a framework to identify which agricultural
uses of conventional insecticides impact listed species and how to
determine the amount and location of mitigation measures for those
insecticides (EPA 2024b, entire). The EPA has agreed to finalize the
Insecticide Strategy by March 31, 2025, and then expects to apply it
when the agency registers a new insecticide or reevaluates an existing
one. The EPA is also pursuing other initiatives to minimize pesticide
impacts on listed species, including through section 7(a)(2)
consultations with FWS on individual pesticide active ingredients and
through its Vulnerable Species Action Plan, which identifies mitigation
measures for listed species particularly vulnerable to pesticides (EPA
2024c, entire).
Under the authority of the Plant Protection Act, the U.S.
Department of Agriculture (USDA) regulates the importation and movement
of plant pests, which covers plant-feeding insects such as the monarch
butterfly. Under this regulation, a permit from USDA-Animal and Plant
Health Inspection Service (APHIS) is required for the importation,
interstate movement, and environmental release of butterflies,
including monarchs. However, multiple States, including Alaska,
Arizona, Connecticut, Hawaii, Montana, and Nevada, plus Puerto Rico,
the Virgin Islands, and Guam, prohibit importation and/or interstate
movement of monarchs for the purpose of environmental release. In
addition, APHIS does not allow the movement of monarchs across the
Continental Divide for environmental release.
Despite these conservation efforts and regulatory mechanisms, the
continued threats facing the monarch butterfly have not been
ameliorated.
Cumulative Effects
We note that, by using the SSA framework to guide our analysis of
the scientific information documented in the SSA report, we have
analyzed the cumulative effects of identified threats and conservation
actions on the species. The best available scientific information
indicates that there are synergistic and cumulative interactions among
the factors influencing monarch butterfly viability. For example,
climate change can impact the monarch directly through increased
temperatures and can also impact other potential threats to the
species, including habitat availability, disease, and predators. We
incorporate the cumulative effects into our SSA analysis when we
characterize the current and future condition of the species. To assess
the current and future condition of the species, we evaluate the
effects of all the relevant factors that may be influencing the
species, including threats and conservation
[[Page 100676]]
efforts. Because the SSA framework considers not just the presence of
the factors, but to what degree they collectively influence risk to the
entire species, our assessment integrates the cumulative effects of the
factors and replaces a standalone cumulative-effects analysis.
Current Condition
Eastern North American Population
Based on the past annual censuses, the eastern North American
population has been generally declining over the last 30 years (figure
1a). Because it is not possible to count individual monarchs at the
overwintering sites in Mexico, the size of the eastern North American
population is measured based on the area occupied by clustered
monarchs. Although the numbers at the overwintering sites have
declined, we did not find a corresponding change in the spatial extent
of the population during the breeding season. We developed a population
model that incorporated the current size, growth rate, and year-to-year
variability of the eastern North American population. The results
indicate that the probability of the population abundance reaching the
point at which extinction is inevitable (``probability of extinction'')
in is less than 10 percent within 10 years (Service 2024a, p. 29). The
probability of extinction does not account for risks from catastrophic
events (discussed below in Future Condition).
Western North American Population
Based on the past annual censuses, the western North American
population has been generally declining over the last 27 years, despite
an increasing number of sites being surveyed (figure 1b). We developed
a similar model for the western North American population as we did for
the eastern population. Under current conditions, the risk of
extinction is predicted to increase sharply over time, between 60 to 68
percent within 10 years (Service 2024a, p. 30). The probability of
extinction does not account for risks from catastrophic events
(discussed below in Future Condition).
[GRAPHIC] [TIFF OMITTED] TP12DE24.000
[[Page 100677]]
[GRAPHIC] [TIFF OMITTED] TP12DE24.001
Figure 1--(a.) Area occupied (in hectares) by eastern North American
monarch butterflies at overwintering sites in Mexico. Year displayed is
the beginning year for the winter (e.g., 2017 represents the number for
the winter of 2017-2018). (Data from Rend[oacute]n-Salinas et al. 2024
(p. 3).)
(b.) Survey counts showing the number of western North American monarch
butterflies observed at overwintering sites (bars). The black line
shows the number of sites monitored (survey effort) for a given year.
(Data from the Xerces Society for Invertebrate Conservation (2024a,
entire).)
Dispersed Nonmigratory Populations
Limited information is available on the status and health of
monarchs outside of the North American migratory populations or
regarding the positive or negative influences acting upon these
populations. Based on observations of the species throughout its range,
69 of the 90 countries, islands, and island groups are currently
extant. Monarch presence within the remaining 21 countries, islands,
and island groups has not been confirmed since 2000, but with no
evidence of extirpation, they are all presumed extant. Furthermore, we
grouped occurrences into 31 populations. Of the 29 populations outside
of North America, 25 are confirmed extant and the remaining 4 are
presumed extant (Service 2024a, pp. 40-42). We were not able to further
assess the level of resiliency of these populations.
Current Resiliency, Redundancy, and Representation
The species' redundancy is evident through its confirmed or
presumed presence in all 90 of the countries, islands, and island
groups where it occurred historically or to where it has dispersed. The
species' adaptive capacity (representation) is evident through its
presence over a large geographical range made up of 31 known
populations (2 North American migratory populations and 29 nonmigratory
or dispersed populations) where the climatic conditions and habitat
vary widely. The species' resiliency varies between populations, with
the estimated probability of extinction for the eastern migratory North
American population at less than 10 percent in 10 years and 60 to 68
percent for the western migratory North American population in 10
years. For monarchs outside of the North American migratory
populations, 69 of the 90 countries, islands, and island groups are
considered currently extant, although we were not able to further
assess the level of resiliency of these populations.
Future Condition
Future Scenarios and Catastrophic Events
North American Migratory Populations
To assess the future condition of monarch populations, we organized
the key factors driving monarch population dynamics into six
categories: (1) milkweed availability, (2) breeding nectar
availability, (3) migration nectar availability, (4) overwintering
habitat availability, (5) climate change effects, and (6) insecticide
exposure. We then forecasted plausible increases and/or decreases, as
appropriate, for each of these influences, using the best available
information, including scientific literature and expert input. We also
included conservation efforts outlined in large-scale monarch
conservation plans, such as the MAFWA Strategy and WAFWA Plan. We did
not evaluate these plans under the Policy for Evaluating Conservation
Efforts (68 FR 15100; March 28, 2003) because these formalized
conservation efforts have been implemented. Next, we combined the upper
plausible limit and the lower plausible limit for each influence
(changes in milkweed, nectar, and overwintering habitat; climate
change; and insecticides) to form composite plausible best case and
plausible worst case scenarios, respectively. Lastly, we incorporated
these scenarios into the population models described in the Current
Condition section, and forecasted population numbers to 60 years to
determine the probability of extinction for both the eastern and
western migratory North American populations to 2080 (Service 2024a,
tables 6.1 and 6.2, pp. 45-47).
We also evaluated several potential events to determine if they
were of sufficient magnitude and severity to cause a population
collapse (i.e., a catastrophic event). We determined that extreme storm
events and widespread
[[Page 100678]]
drought have sufficient potential to pose a catastrophic risk to the
eastern population, and widespread drought and co-occurrence of poor
environmental conditions and low population abundance have sufficient
potential to pose a catastrophic risk to the western population.
Dispersed Nonmigratory Populations
Due to a lack of information on current influences, we were unable
to forecast future scenarios for the populations outside of eastern and
western North America. However, we identified two potential
catastrophic events, both of which are effects of climate change: sea
level rise and lethal high temperatures.
Future Conditions
Eastern North American Population
Under both best and worst case scenarios described above, the
population continues to decline ([lambda] < 1). The greatest impact on
the population occurs during the first 20 years for both scenarios; we
had a slight increase in the growth rate from the current value under
the best case scenario and a decrease of 4.5 percent under the worst
case scenario. As expected under a declining growth rate, the
probability of extinction increases over time (Service 2024a, p. 64).
In 30 years, probability of extinction ranges from 24 to 46 percent. In
60 years, the probability of extinction for the eastern North American
population ranges from 56 to 74 percent.
We were unable to incorporate direct effects from increasing
temperatures and catastrophic risks into the population models, so we
qualitatively discuss the implications of these factors on the future
condition of the population. We evaluated the changes in the spatial
extent and number of days with projected temperatures above lethal and
sublethal thermal thresholds during critical time periods in monarch
migration (Service 2024a, pp. 120-122). We assessed these changes under
two future scenarios, using Representative Concentration Pathways
(RCPs). RCPs reflect different levels of greenhouse gas emissions and
the resulting climate change scenarios (IPCC 2014, p. 57). We used
RCP4.5 and RCP8.5 scenarios projected to 2069 (Service 2024a, p. 122).
Under the RCP4.5 scenario, both the spatial extent and the average
number of days above 38 [deg]C (100 [deg]F) (the threshold for
sublethal effects and moderate reductions in survival) are projected to
markedly increase throughout much of the range, including the southern
and northeastern portions of the eastern North American monarch
breeding range. Although in the northcentral area of the breeding
range, there is a projected decrease in spatial extent and the average
number of days above 38 [deg]C (100 [deg]F). Under the RCP8.5 scenario,
both the spatial extent and the average number of days above 38 [deg]C
(100 [deg]F) have large increases throughout the entirety of the
breeding range. The spatial extent and average number of days above 42
[deg]C (107.6 [deg]F) (the lethal threshold) are projected to increase
dramatically in the southern U.S. during the same period under both
scenarios. Given these results, monarch reproductive success and
survival rates of the first generation of monarchs coming from the
wintering grounds are likely to decline, although the extent to which
these rates will decline is unknown.
Similarly, given the projected population decline described above,
the eastern population will be increasingly vulnerable to catastrophic
losses due to extreme storm events at the overwintering grounds and
widespread droughts during the breeding season and along the migratory
route. Although we cannot quantify this increased risk, the longer the
eastern population remains at low population abundance, the more likely
it is that catastrophic losses will occur and the greater the
extinction risk for the eastern population.
Western North American Population
Under both scenarios, the population continues to decline ([lambda]
< 1). Under the best case scenario, monarchs have a slight increase in
the growth rate from the current value; however, even with an increase,
this was still a declining growth rate. Under the worst case scenario,
the growth rate decreased to a lower rate than the current rate. As
would be expected with a declining growth rate, the probability of
extinction increases over time (Service 2024a, p. 66). In 30 years,
probability of extinction ranges from 92 percent to 95 percent. By year
60, the probability of extinction reaches 99 percent for the western
North American population.
Under the RCP4.5 scenario, increases are projected for the average
numbers of days above 38 [deg]C (100.4 [deg]F) (38 percent) and above
42 [deg]C (107.6 [deg]F) (11 percent). Given this, monarch reproductive
success and survival rates are likely to decline, although the extent
to which these rates will decline is unknown.
Similarly, given the projections of monarch health described above,
the western population is vulnerable to catastrophic losses due to both
widespread drought events and the co-occurrence of poor environmental
conditions and low population abundance. The risk of extinction due to
these events increases the longer the population remains at the current
low abundances.
Dispersed Nonmigratory Populations
We qualitatively assessed the impact due to predicted climate
change effects. Fifteen of the 29 populations are classified as being
``at risk'' due to threats associated with climate change (6 due to sea
level rise and 9 due to unsuitably high temperatures). The populations
susceptible to sea level rise (Johnston Atoll, Kiribati, Marshall
Islands, Nauru, Tokelau, and Tuvalu) are at risk of losing at least
some of their monarch habitat; thus, redundancy could decrease with the
loss of those areas. However, the best available information does not
indicate if populations at risk to high temperatures will lose all or
just a portion of their monarch habitat; thus, they may continue to
contribute to redundancy. Each of the populations at risk due to sea
level rise contains a single country, island, or island group.
Therefore, in the dispersed nonmigratory populations the species will
continue to have redundancy through continued presence in an estimated
84 of the 90 countries, islands, and island groups where it occurred
historically or to where it has dispersed. We anticipate the species
will continue to have adaptive capacity (representation) through its
presence over a large geographical range where the climatic conditions
and habitat vary widely.
Future Resiliency, Redundancy, and Representation
Both the eastern and western migratory North American populations
become more vulnerable to catastrophic events (e.g., extreme storms at
the overwintering habitat) into the future resulting in lower
redundancy for the species. Under plausible climate change scenarios,
monarch butterflies will be exposed to unsuitably high temperatures for
more days each year and over larger areas of their range in North
America. Outside of the two North American migratory populations, 15 of
the 29 nonmigratory or dispersed populations are at risk in the future
due to threats associated with climate change (6 due to sea level rise
and 9 due to unsuitably high temperatures). The populations susceptible
to sea level rise are at risk of losing at least some of their monarch
habitat; thus, redundancy could decrease with the loss of those areas.
Rangewide, the species is likely to maintain considerable redundancy
and adaptive capacity (representation)
[[Page 100679]]
through continued presence in an estimated 84 of the 90 countries,
islands, and island groups where it occurred historically or to where
it has dispersed. Despite uncertainties about resiliency at the
nonmigratory and dispersed populations, the widespread distribution of
monarch populations indicates that the species has low risk of becoming
extirpated from multiple locations should a large-scale catastrophic
event occur; thus, it is unlikely that a single catastrophic event
would affect the entire species across its large range.
In the future, the resiliency of the eastern and western North
American migratory populations will continue to decline. The estimated
probability of extinction for the eastern migratory North American
population is 56-74 percent in 60 years and greater than 99 percent for
the western migratory North American population in 60 years.
Determination of Monarch Butterfly Status
Section 4 of the Act (16 U.S.C. 1533) and its implementing
regulations (50 CFR part 424) set forth the procedures for determining
whether a species meets the definition of an endangered species or a
threatened species. The Act defines an ``endangered species'' as a
species in danger of extinction throughout all or a significant portion
of its range, and a ``threatened species'' as a species likely to
become an endangered species within the foreseeable future throughout
all or a significant portion of its range. The Act requires that we
determine whether a species meets the definition of an endangered
species or a threatened species because of any of the following
factors: (A) The present or threatened destruction, modification, or
curtailment of its habitat or range; (B) overutilization for
commercial, recreational, scientific, or educational purposes; (C)
disease or predation; (D) the inadequacy of existing regulatory
mechanisms; or (E) other natural or manmade factors affecting its
continued existence.
Status Throughout All of Its Range
After evaluating threats to the species and assessing the
cumulative effect of the threats under the Act's section 4(a)(1)
factors, we determined that the primary threats affecting the monarch
and its habitat are the ongoing impacts from loss and degradation of
breeding, migratory, and overwintering habitat (from past conversion of
grasslands and shrublands to agriculture and widespread use of
herbicides; logging/thinning at overwintering sites in Mexico; urban
development, senescence, and incompatible management of overwintering
sites in California; and drought) (Factor A); exposure to insecticides
(Factor E); and effects of climate change (Factor E).
While the monarch butterfly is historically native to North America
with migratory and nonmigratory populations, monarchs have dispersed
via human assistance from North America in the past two centuries and
their range now includes populations throughout 90 countries, islands,
and island groups where milkweed was already present or introduced.
Populations exist in Central and South America, Australia, New Zealand,
islands of the Pacific and Caribbean, and elsewhere (see Service 2024a,
pp. 41-42). The primary threats have been affecting the resiliency of
the eastern and western North American migratory populations over the
last 20 years, and both populations now have lower abundances and
declining population growth rates. However, in its current condition,
the probability of extinction of the eastern migratory population is
less than 10 percent over the next 10 years. The probability of
extinction of the western migratory population over that same time
period is higher (60-68 percent).
For monarchs outside of the two North American migratory
populations, 69 of the 90 countries, islands, and island groups are
considered currently extant. Monarch presence within the remaining 21
countries, islands, and island groups has not been confirmed since
2000, but the best available information does not indicate they are
extirpated, and thus they are all presumed extant. Of the 29
populations outside of North America, 25 are confirmed extant, and the
remaining 4 are presumed extant (see Service 2024a, pp. 40-42).
Although we were not able to further assess the level of resiliency of
these 29 nonmigratory or dispersed populations, the species' redundancy
is evident through its confirmed or presumed presence in all 90 of the
countries, islands, and island groups where it occurred historically or
to where it has dispersed. The species' adaptive capacity is evident
through its presence over a large geographical range made up of 31
known populations (2 North American migratory populations and 29
nonmigratory or dispersed populations) where the climatic conditions
and habitat vary widely. Despite uncertainties about resiliency at some
of the locations (i.e., the 29 nonmigratory and dispersed populations),
the number and distribution of populations at multiple locations makes
it unlikely that a single catastrophic event would affect the entire
species across its large range. Based on the best scientific and
commercial data available, we conclude that the monarch butterfly is
not currently in danger of extinction throughout all of its range.
While the monarch butterfly is not currently in danger of
extinction, under the Act we must determine whether the species is
likely to become in danger of extinction within the foreseeable future
throughout all of its range (i.e., whether the species warrants listing
as threatened). In the foreseeable future, we anticipate the status of
the eastern and western North American migratory populations will
continue to decline due to the primary threats listed above. The
probability of extinction of the eastern migratory population in the
foreseeable future, which is 60 years, is estimated to be 56-74
percent, and the probability of extinction for the western migratory
population is estimated to be 99 percent. Outside of the two North
American migratory populations, we found that 15 of the 29 nonmigratory
or dispersed populations are at risk in the future due to threats
associated with climate change (6 due to sea level rise and 9 due to
unsuitably high temperatures). The populations susceptible to sea level
rise are at risk of losing at least some of their monarch habitat;
thus, redundancy could decrease with the loss of those areas. However,
the best scientific and commercial data available do not indicate if
populations susceptible to high temperatures are at risk of losing all
or just a portion of their monarch habitat; thus, they may continue to
contribute to redundancy. Therefore, rangewide, we conclude that the
species is likely to maintain considerable redundancy through continued
presence in an estimated 84 of the 90 countries, islands, and island
groups where it occurred historically or to where it has dispersed.
We find that the species will continue to have adaptive capacity
(representation) through its presence over a large geographical range
where the climatic conditions and habitat vary widely. Despite
uncertainties about resiliency at the nonmigratory and dispersed
populations, the widespread distribution of monarch populations
indicates that the species has low risk of becoming extirpated from
multiple locations should a large-scale catastrophic event occur; thus,
it is unlikely that a single catastrophic event would affect the entire
species across its large range. Thus, after assessing the best
available information, we conclude that the monarch butterfly is not
likely
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to become in danger of extinction within the foreseeable future
throughout all of its range.
Status Throughout a Significant Portion of Its Range
Under the Act and our implementing regulations, a species may
warrant listing if it is in danger of extinction or likely to become so
within the foreseeable future throughout all or a significant portion
of its range. The court in Center for Biological Diversity v. Everson,
435 F. Supp. 3d 69 (D.D.C. 2020) (Everson), vacated the provision of
the Final Policy on Interpretation of the Phrase ``Significant Portion
of Its Range'' in the Endangered Species Act's Definitions of
``Endangered Species'' and ``Threatened Species'' (hereafter ``Final
Policy''; 79 FR 37578, July 1, 2014) that provided if the Services
determine that a species is threatened throughout all of its range, the
Services will not analyze whether the species is endangered in a
significant portion of its range.
Therefore, we proceed to evaluating whether the species is
endangered in a significant portion of its range--that is, whether
there is any portion of the species' range for which both (1) the
portion is significant; and (2) the species is in danger of extinction
in that portion. Depending on the case, it might be more efficient for
us to address the ``significance'' question or the ``status'' question
first. We can choose to address either question first. Regardless of
which question we address first, if we reach a negative answer with
respect to the first question that we address, we do not need to
evaluate the other question for that portion of the species' range.
Following the court's holding in Everson, we now consider whether
there are any significant portions of the species' range where the
species is in danger of extinction now (i.e., endangered). In
undertaking this analysis for the monarch butterfly, we choose to
address the significance question first. We assessed whether any
portions of the species' range are biologically significant by
considering them in terms of each portion's contribution to resiliency,
redundancy, or representation of the species as a whole.
The monarch butterfly is historically native to North America, and,
as discussed above, it now occurs in nonnative or naturalized
populations throughout 90 countries, islands, and island groups,
including parts of Central and South America, Australia, New Zealand,
islands of the Pacific and Caribbean, and elsewhere (see Service 2024a,
pp. 41-42). To identify portions for evaluation, we considered these
geographic areas independently and in various combinations to identify
those which are biologically meaningful to the species.
We found that monarch habitat in North America represents a
significant portion of the range. This geographical portion is
significant because it is physically large, representing a large
proportion of the species' range, and has unique habitat features that
support monarch migration. The monarch's North American portion of the
range covers approximately 2.8 billion ac (1.1 billion ha), encompasses
an estimated 62 percent of the species' geographic range, and
represents a vast majority of monarch butterflies worldwide. The
portion is the ancestral source for migratory monarchs in North America
and includes nonmigratory monarchs that have descended from migratory
monarchs. The best available information indicates that the total
number of nonmigratory monarchs in North America appears to be quite
small relative to the North American migratory populations that
overwinter in Mexico and California. The portion contains the entirety
of breeding, migratory, and overwintering habitats used by monarchs in
the eastern and western migratory populations. The monarchs within
eastern and western North America have continued interchange between
the two populations contributing to low genetic differentiation and
forming an admixed population (Lyons et al. 2012, p. 3441; Talla et al.
2020, p. 2573; Freedman et al. 2021, pp. 7-8). These habitats in North
America are unique because they facilitate massive annual range
expansions during the breeding season. Temporary, seasonal resources
allow monarchs to escape habitats as they become more heavily infected
with diseases like OE (Bartel et al. 2011, entire). This seasonal
movement also facilitates migratory culling where smaller and unhealthy
individuals are removed from the breeding population because they are
unable to survive long-distance migration (Bartel et al. 2011, entire;
Majewska et al. 2021, p. 788). Years with favorable conditions across
the broad and spatially diffuse breeding habitat in this portion have
the potential to support rapid migratory monarch population increases
(Yang et al. 2022, p. 20), which is important for population
resiliency.
We also considered eastern and western North America as individual
portions. The portion of North America used by the eastern migratory
population is the largest area used by a single population in terms of
geographic size. It represents roughly 43 percent of the species'
global range. The portion of North America used by the western
migratory population encompasses roughly 18 percent of the species'
global range. Individually, neither portion makes up a large enough
geographic area relative to the remainder of the range. Both migratory
populations require sufficient quality and quantity of milkweed and
nectar resources, suitable habitat for overwintering, and adequate
connectivity and aligned phenology. Both of these portions provide the
resources and space needed to facilitate the massive annual migration
and range expansions necessary to maintain the viability of the
migratory populations, as described above. However, because these
portions individually constitute smaller areas, they were not
determined to be significant individually when compared to the portion
encompassing both North American migratory populations.
Having determined that North America is significant for the
purposes of evaluating a significant portion of the monarch's range, we
then proceeded to address the status question by examining the threats
in that portion to determine if the species is endangered or threatened
in that portion. The statutory difference between an endangered species
and a threatened species is the timeframe in which the species becomes
in danger of extinction; an endangered species is in danger of
extinction while a threatened species is likely to become so (i.e.,
endangered) within the foreseeable future. As discussed under Status
Throughout All of Its Range, above, the primary current threats to the
monarch butterfly are the ongoing impacts from loss and degradation of
breeding, migratory, and overwintering habitat (from past conversion of
grasslands to agriculture; widespread use of herbicides; logging/
thinning at overwintering sites in Mexico; urban development,
senescence, and incompatible management of overwintering sites in
California; and drought), exposure to insecticides, and effects of
climate change. We examined those threats along with the effects from
disease and cumulative effects, and we considered whether conservation
efforts and regulatory mechanisms ameliorated any of the effects.
Many of these factors and threats influence the monarch butterfly
rangewide; however, because we identified the North America portion as
being significant, we considered whether the threats are causing
monarchs in the portion to have a different status than the remainder
of
[[Page 100681]]
the range. As discussed above, this portion contains the eastern and
western North American migratory populations. For the two migratory
populations, we estimated the probability of the population abundance
reaching the point at which extinction is inevitable for each
population. In its current condition, the eastern migratory population
has a probability of extinction of less than 10 percent over the next
10 years. The western migratory population has a higher risk of
extinction due to current threats, with a probability of extinction of
60-68 percent over the next 10 years. The probability of extinction
estimates do not account for risks from catastrophic events; however,
we do not anticipate these effects to significantly increase extinction
risk of North American migratory monarchs in the near term. Based on
the eastern migratory population's level of resiliency in the near term
and because monarchs are distributed across a broad geographic area
contributing to the redundancy and representation of the species in the
portion, we concluded that the monarch butterfly in North America is
not in danger of extinction within this significant portion of its
range and does not meet the definition of an endangered species.
We next considered whether the monarch butterfly is likely to
become an endangered species within the foreseeable future in the North
America portion (i.e., if it meets the Act's definition of a threatened
species). Looking across the range of future conditions for which we
can make reasonably reliable predictions, the probability of extinction
for the eastern migratory population is estimated to be 24-46 percent
in 30 years and 56-74 percent in 60 years. The probability of
extinction for the western migratory population is estimated to be 92-
95 percent in 30 years and reaches 99 percent in 60 years. These
probability of extinction estimates incorporate the primary factors
that influence the populations' resiliency, including the ongoing
impacts of availability of milkweed and nectar resources (losses as
well as gains from conservation efforts), loss and degradation of
overwintering habitat, insecticides, and effects of climate change. In
addition to being affected by these factors, both the eastern and
western migratory populations become more vulnerable to catastrophic
events (e.g., extreme storms at the overwintering habitat) into the
future. Under plausible climate change scenarios, monarch butterflies
will be exposed to unsuitably high temperatures for more days each year
and over larger areas of their range in North America.
The best available scientific and commercial information indicates
nonmigratory monarch populations in North America are very small
compared to the size of the two migratory populations. In our
assessment of the threats, we found that the three nonmigratory
populations in Florida, the Caribbean, and countries in Central America
are at risk due to unsuitably high temperatures associated with climate
change. There is potential for nonmigratory monarch populations in
North America to be demographic sinks (see Crone and Schultz 2021, p.
1536), requiring continual influxes of monarchs from migratory
populations to sustain them. Therefore, the status of nonmigratory
monarchs in the North American portion is also in decline.
After assessing the best scientific and commercial data available,
we found that migratory monarch butterflies in North America, which
represent the vast majority of monarch butterflies worldwide, have a
high likelihood of becoming extirpated in 60 years. Therefore, we
conclude that the monarch butterfly is likely to become in danger of
extinction within the foreseeable future throughout North America.
Therefore, having determined that the North America portion is both (1)
significant; and (2) likely to become in danger of extinction within
the foreseeable future, we conclude that the monarch butterfly is in
danger of extinction within the foreseeable future within a significant
portion of its range. This is consistent with the courts' holdings in
Desert Survivors v. U.S. Department of the Interior, 321 F. Supp. 3d
1011, 1070-74 (N.D. Cal. 2018) and Center for Biological Diversity v.
Jewell, 248 F. Supp. 3d, 946, 959 (D. Ariz. 2017).
Determination of Status
Based on the best scientific and commercial data available, we
determine that the monarch butterfly meets the Act's definition of a
threatened species. Therefore, we propose to add the monarch butterfly
as a threatened species to the List of Endangered and Threatened
Wildlife in 50 CFR 17.11(h) in accordance with sections 3(20) and
4(a)(1) of the Act.
Available Conservation Measures
Conservation measures provided to species listed as endangered or
threatened species under the Act include recognition as a listed
species, planning and implementation of recovery actions, requirements
for Federal protection, and prohibitions against certain practices.
Recognition through listing results in public awareness, and
conservation by Federal, State, Tribal, and local agencies, foreign
governments, private organizations, and individuals. The Act encourages
cooperation with the States and other countries and calls for recovery
actions to be carried out for listed species. The protection required
by Federal agencies, including the Service, and the prohibitions
against certain activities are discussed, in part, below.
The primary purpose of the Act is the conservation of endangered
and threatened species and the ecosystems upon which they depend. The
ultimate goal of such conservation efforts is the recovery of these
listed species, so that they no longer need the protective measures of
the Act. Section 4(f) of the Act calls for the Service to develop and
implement recovery plans for the conservation of endangered and
threatened species. The goal of this process is to restore listed
species to a point where they are secure, self-sustaining, and
functioning components of their ecosystems.
The recovery planning process begins with development of a recovery
outline made available to the public soon after a final listing
determination. The recovery outline guides the immediate implementation
of urgent recovery actions while a recovery plan is being developed.
Recovery teams (composed of species experts, Federal and State
agencies, nongovernmental organizations, and stakeholders) may be
established to develop and implement recovery plans. The recovery
planning process involves the identification of actions that are
necessary to halt and reverse the species' decline by addressing the
threats to its survival and recovery. The recovery plan identifies
recovery criteria for review of when a species may be ready for
reclassification from endangered to threatened (``downlisting'') or
removal from protected status (``delisting''), and methods for
monitoring recovery progress. Recovery plans also establish a framework
for agencies to coordinate their recovery efforts and provide estimates
of the cost of implementing recovery tasks. Revisions of the plan may
be done to address continuing or new threats to the species, as new
substantive information becomes available. The recovery outline, draft
recovery plan, final recovery plan, and any revisions will be available
on our website as they are completed (<a href="https://www.fws.gov/program/endangered-species">https://www.fws.gov/program/endangered-species</a>), or from our Midwest Region
[[Page 100682]]
Headquarters (see FOR FURTHER INFORMATION CONTACT).
Implementation of recovery actions generally requires the
participation of a broad range of partners, including other Federal
agencies, States, Tribes, nongovernmental organizations, businesses,
and private landowners. Examples of recovery actions include habitat
restoration (e.g., restoration of native vegetation), research, captive
propagation and reintroduction, and outreach and education. The
recovery of many listed species cannot be accomplished solely on
Federal lands because their range may occur primarily or solely on non-
Federal lands. To achieve recovery of these species requires
cooperative conservation efforts on private, State, and Tribal lands.
To improve future conditions so that the monarch migratory
populations stabilize and grow, we need to (1) achieve a significant
increase in the availability of milkweed and nectar plants in monarch
breeding and migratory areas; (2) protect and enhance overwintering
habitat; (3) avoid and minimize impacts to monarchs and their habitat
from insecticides and herbicides; and (4) maintain public support for
the conservation of monarch butterflies. Because of the monarch
butterfly's general habitat use and wide distribution, all sectors of
society, including the general public, have an opportunity to
participate in a broad range of conservation efforts throughout the
species' range.
If this species is listed, funding for recovery actions will be
available from a variety of sources, including Federal budgets, State
programs, and cost-share grants for non-Federal landowners, the
academic community, and nongovernmental organizations. In addition,
pursuant to section 6 of the Act, the States of Alabama, Arizona,
Arkansas, California, Colorado, Connecticut, Delaware, Florida,
Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky,
Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota,
Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New
Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio,
Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South
Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West
Virginia, Wisconsin, and Wyoming; the U.S. Commonwealths of the
Northern Mariana Islands and Puerto Rico; and the U.S. Territories of
American Samoa, Guam, and the U.S. Virgin Islands would be eligible for
Federal funds to implement management actions that promote the
protection or recovery of the monarch butterfly. Information on our
grant programs that are available to aid species recovery can be found
at: <a href="https://www.fws.gov/service/financial-assistance">https://www.fws.gov/service/financial-assistance</a>.
Although the monarch butterfly is only proposed for listing under
the Act at this time, please let us know if you are interested in
participating in recovery efforts for this species. Additionally, we
invite you to submit any new information on this species whenever it
becomes available and any information you may have for recovery
planning purposes (see FOR FURTHER INFORMATION CONTACT).
Section 7 of the Act is titled, ``Interagency Cooperation,'' and it
mandates all Federal action agencies to use their existing authorities
to further the conservation purposes of the Act and to ensure that
their actions are not likely to jeopardize the continued existence of
listed species or adversely modify critical habitat. Regulations
implementing section 7 are codified at 50 CFR part 402.
Section 7(a)(1) directs all Federal agencies, in consultation with
the Secretary, to utilize their authorities to carry out ``programs for
the conservation of endangered and threatened species.'' This provision
provides an affirmative and broad mandate to all agencies to take
action to conserve threatened and endangered species. This section
affords broad discretion to agencies on the measures they undertake as
part of their conservation programs within their existing authorities,
and robust section 7(a)(1) programs may assist Federal agencies with
their obligations under section 7(a)(2). Section 7(a)(2) states that
each Federal action agency shall, in consultation with the Secretary,
ensure that any action they authorize, fund, or carry out is not likely
to jeopardize the continued existence of a listed species or result in
the destruction or adverse modification of designated critical habitat.
Each Federal agency shall review its action at the earliest possible
time to determine whether it may affect listed species or critical
habitat. If a determination is made that the action may affect listed
species or critical habitat, formal consultation is required (50 CFR
402.14(a)), unless the Service concurs in writing that the action is
not likely to adversely affect listed species or critical habitat. At
the end of a formal consultation, the Service issues a biological
opinion, containing its determination of whether the Federal action is
likely to result in jeopardy or adverse modification.
In contrast, section 7(a)(4) of the Act requires Federal agencies
to confer with the Service on any action which is likely to jeopardize
the continued existence of any species proposed to be listed under the
Act or result in the destruction or adverse modification of critical
habitat proposed to be designated for such species. Although the
conference procedures are required only when an action is likely to
result in jeopardy or adverse modification, action agencies may
voluntarily confer with the Service on actions that may affect species
proposed for listing or critical habitat proposed to be designated. In
the event that the subject species is listed or the relevant critical
habitat is designated, a conference opinion may be adopted as a
biological opinion and serve as compliance with section 7(a)(2) of the
Act.
Examples of discretionary actions for the monarch butterfly that
may be subject to conference and consultation procedures under section
7 are management of Federal lands administered by the Army Corps of
Engineers, Bureau of Land Management, Department of Defense (DoD),
National Park Service, Office of Surface Mining, and U.S. Forest
Service as well as actions that require a Federal permit (such as a
permit from the U.S. Army Corps of Engineers under section 404 of the
Clean Water Act (33 U.S.C. 1251 et seq.)) or actions funded by Federal
agencies such as the Federal Highway Administration, Federal Aviation
Administration, U.S. Department of Agriculture, or the Federal
Emergency Management Agency. We also anticipate conferencing or
consultation by the EPA as part of their pesticide registration actions
under FIFRA. Federal actions not affecting listed species or critical
habitat--and actions on State, Tribal, local, or private lands that are
not federally funded, authorized, or carried out by a Federal agency--
do not require section 7 consultation. Federal agencies should
coordinate with the local Service Field Office or Midwest Region
Headquarters (see FOR FURTHER INFORMATION CONTACT) with any specific
questions on section 7 consultation and conference requirements.
II. Protective Regulations Under Section 4(d) of the Act
Background
Section 4(d) of the Act contains two sentences. The first sentence
states that the Secretary shall issue such regulations as she deems
necessary and advisable to provide for the conservation of species
listed as threatened species. Conservation is defined in the Act to
mean the use of all methods and procedures which are
[[Page 100683]]
necessary to bring any endangered species or threatened species to the
point at which the measures provided pursuant to the Act are no longer
necessary. Additionally, the second sentence of section 4(d) of the Act
states that the Secretary may by regulation prohibit with respect to
any threatened species any act prohibited under section 9(a)(1), in the
case of fish or wildlife, or section 9(a)(2), in the case of plants.
With these two sentences in section 4(d), Congress delegated broad
authority to the Secretary to determine what protections would be
necessary and advisable to provide for the conservation of threatened
species, and even broader authority to put in place any of the section
9 prohibitions, for a given species.
The courts have recognized the extent of the Secretary's discretion
under this standard to develop rules that are appropriate for the
conservation of a species. For example, courts have upheld, as a valid
exercise of agency authority, rules developed under section 4(d) that
included limited prohibitions against takings (see Alsea Valley
Alliance v. Lautenbacher, 2007 WL 2344927 (D. Or. 2007); Washington
Environmental Council v. National Marine Fisheries Service, 2002 WL
511479 (W.D. Wash. 2002)). Courts have also upheld 4(d) rules that do
not address all of the threats a species faces (see State of Louisiana
v. Verity, 853 F.2d 322 (5th Cir. 1988)). As noted in the legislative
history when the Act was initially enacted, ``once an animal is on the
threatened list, the Secretary has an almost infinite number of options
available to [her] with regard to the permitted activities for those
species. [She] may, for example, permit taking, but not importation of
such species, or [she] may choose to forbid both taking and importation
but allow the transportation of such species'' (H.R. Rep. No. 412, 93rd
Cong., 1st Sess. 1973).
The provisions of this species' proposed protective regulations
under section 4(d) of the Act are one of many tools that we would use
to promote conservation of the monarch butterfly by encouraging
creation and management of habitat in ways that address threats to the
species and maintain public support for its conservation. To achieve a
significant increase in the availability of milkweed and nectar plants
in monarch breeding areas, we need to incentivize return of milkweed to
large portions of the landscape where it is now nonexistent or where
what remains is highly fragmented. Given that so much milkweed has been
lost historically and that monarchs are impacted by the ongoing effects
of this past habitat loss and degradation, we need an approach that
encourages landowners to add milkweeds and nectar plants and implement
actions to maintain them. Creation, enhancement, and maintenance of
higher quality habitat by the public may lead to the temporary
destruction of milkweed and nectar plants and incidental take of
monarchs. Private landowner and general public support are crucial
because the species is wide-ranging and needs broad conservation
action, from small- to large-scale efforts, throughout its range.
Conservation for the species can occur on land parcels ranging from
quite small to very large, including gardens, parks, grasslands,
agricultural areas, and more. Because of the monarch butterfly's
general habitat use and wide distribution, all sectors of society,
including the general public, have an opportunity to participate in a
broad range of conservation efforts throughout the species' range. The
proposed 4(d) rule allows for the general public to take action to
participate in the recovery of monarchs without fear of unintentional
violation for the Act. Public action is necessary for the conservation
of the species.
The proposed protective regulations would apply only if and when we
make final the listing of the monarch butterfly as a threatened
species. Nothing in 4(d) rules changes in any way the recovery planning
provisions of section 4(f) of the Act, the consultation requirements
under section 7 of the Act, or the ability of the Service to enter into
partnerships for the management and protection of the monarch
butterfly.
As mentioned previously in Available Conservation Measures, section
7(a)(2) of the Act requires Federal agencies, including the Service, to
ensure that any action they authorize, fund, or carry out is not likely
to jeopardize the continued existence of any endangered species or
threatened species or result in the destruction or adverse modification
of designated critical habitat of such species. In addition, even
before the listing of any species or the designation of its critical
habitat is finalized, section 7(a)(4) of the Act requires Federal
agencies to confer with the Service on any agency action which is
likely to jeopardize the continued existence of any species proposed to
be listed under the Act or result in the destruction or adverse
modification of critical habitat proposed to be designated for such
species. These requirements are the same for a threatened species
regardless of what is included in its 4(d) rule.
Section 7 consultation is required for Federal actions that ``may
affect'' a listed species regardless of whether take caused by the
activity is prohibited or excepted by a 4(d) rule (under application of
a ``blanket rule'' (for more information, see 89 FR 23919, April 5,
2024) or a species-specific 4(d) rule). A 4(d) rule does not change the
process and criteria for informal or formal consultations and does not
alter the analytical process used for biological opinions or
concurrence letters. For example, as with an endangered species, if a
Federal agency determines that an action is ``not likely to adversely
affect'' a threatened species, this will require the Service's written
concurrence (50 CFR 402.13(c)). Similarly, if a Federal agency
determinates that an action is ``likely to adversely affect'' a
threatened species, the action will require formal consultation with
the Service and the formulation of a biological opinion (50 CFR
402.14(a)). Because consultation obligations and processes are
unaffected by 4(d) rules, we may consider developing tools to
streamline future intra-Service and interagency consultations for
actions that result in forms of take that are not prohibited by the
4(d) rule (but that still require consultation). These tools may
include consultation guidance; streamlined, online consultation
processes via the Service's digital project planning tool (Information
for Planning and Consultation; <a href="https://ipac.ecosphere.fws.gov/">https://ipac.ecosphere.fws.gov/</a>);
template language for biological opinions; or programmatic
consultations. Nonetheless, section 7(a)(1) authority provides a great
deal of unrealized potential in achieving recovery goals, and this 4(d)
rule incentivizes agencies to fully utilize their authorities to design
and implement conservation programs that meaningfully benefit monarch
butterflies.
Provisions of the Proposed 4(d) Rule
Exercising the Secretary's authority under section 4(d) of the Act,
we have developed a proposed rule that is designed to address the
monarch butterfly's conservation needs. As discussed previously in
Summary of Biological Status and Threats, we have concluded that the
monarch butterfly is likely to become in danger of extinction within
the foreseeable future primarily due to the ongoing impacts of loss and
degradation of breeding, migratory, and overwintering habitat (from
past conversion of grasslands and shrublands to agriculture and
widespread use of herbicides; logging/thinning at overwintering sites
in Mexico; urban development, senescence, and
[[Page 100684]]
incompatible management of overwintering sites in California; and
drought), exposure to insecticides, and effects of climate change.
Section 4(d) requires the Secretary to issue such regulations as she
deems necessary and advisable to provide for the conservation of each
threatened species and authorizes the Secretary to include among those
protective regulations any of the prohibitions that section 9(a)(1) of
the Act prescribes for endangered species. We are not required to make
a ``necessary and advisable'' determination when we apply or do not
apply specific section 9 prohibitions to a threatened species (In re:
Polar Bear Endangered Species Act Listing and 4(d) Rule Litigation, 818
F. Supp. 2d 214, 228 (D.D.C. 2011) (citing Sweet Home Chapter of
Communities for a Great Oregon v. Babbitt, 1 F.3d 1, 8 (D.C. Cir.
1993), rev'd on other grounds, 515 U.S. 687 (1995))). Nevertheless,
even though we are not required to make such a determination, we have
chosen to be as transparent as possible and explain below why we find
that, if finalized, the protections, prohibitions, and exceptions in
this proposed rule as a whole satisfy the requirement in section 4(d)
of the Act to issue regulations deemed necessary and advisable to
provide for the conservation of the monarch butterfly.
The protective regulations we are proposing for the monarch
butterfly incorporate prohibitions from section 9(a)(1) to address the
threats to the species. The prohibitions of section 9(a)(1), and the
implementing regulations codified at 50 CFR 17.21, make it illegal for
any person subject to the jurisdiction of the United States to commit,
to attempt to commit, to solicit another to commit or to cause to be
committed any of the following acts with regard to any endangered
wildlife: (1) import into or export from, the United States; (2) take
(which includes harass, harm, pursue, hunt, shoot, wound, kill, trap,
capture, or collect, or to attempt to engage in any such conduct)
within the United States, within the territorial sea of the United
States, or on the high seas; (3) possess, sell, deliver, carry,
transport, or ship, by any means whatsoever, any such wildlife that has
been taken illegally; (4) deliver, receive, carry, transport, or ship
in interstate or foreign commerce, by any means whatsoever and in the
course of commercial activity; or (5) sell or offer for sale in
interstate or foreign commerce. This protective regulation includes all
these prohibitions because the eastern and western North America
monarch populations are at risk of extinction within the foreseeable
future and putting these prohibitions in place will help to prevent
further declines, slow the rate of decline, and decrease negative
effects from other ongoing or future threats.
In particular, this proposed 4(d) rule would provide for the
conservation of the monarch butterfly by prohibiting the following
activities, unless they fall within specific exceptions or are
otherwise authorized or permitted: importing or exporting; take;
possession and other acts with unlawfully taken specimens; delivering,
receiving, carrying, transporting, or shipping in interstate or foreign
commerce in the course of commercial activity; or selling or offering
for sale in interstate or foreign commerce. We are proposing to
prohibit these activities in the contiguous United States, Puerto Rico,
and the U.S. Virgin Islands. We are not proposing to prohibit these
activities in Hawaii or other U.S. Territories because these areas are
outside the historical range of the species and monarchs in these areas
will not contribute to recovery of the species in North America. We are
also not proposing to prohibit these activities in Alaska because the
species does not occur there. Further, import and interstate movement
of monarch butterflies is regulated by the U.S. Department of
Agriculture, and monarchs may not be transported to Hawaii, Alaska, or
any of the U.S. Territories under existing regulations in 7 CFR part
330.
Under the Act, ``take'' means to harass, harm, pursue, hunt, shoot,
wound, kill, trap, capture, or collect, or to attempt to engage in any
such conduct. Some of these provisions have been further defined in
regulations at 50 CFR 17.3. Take can result knowingly or otherwise, by
direct and indirect impacts, intentionally or incidentally. Regulating
take would help to preserve the species' migratory populations, slow
their rates of decline, and decrease synergistic, negative effects from
other ongoing or future threats. Therefore, we propose to prohibit take
of the monarch butterfly, except for take resulting from those actions
and activities specifically excepted by the 4(d) rule.
Exceptions to the prohibition on take would include all the general
exceptions to the prohibition on take of endangered wildlife, as set
forth in 50 CFR 17.21 and additional exceptions, as described below.
Despite these prohibitions regarding threatened species, we may
under certain circumstances issue permits to carry out one or more
otherwise-prohibited activities, including those described above. The
regulations that govern permits for threatened wildlife state that the
Director may issue a permit authorizing any activity otherwise
prohibited with regard to threatened species. These include permits
issued for the following purposes: for scientific purposes, to enhance
propagation or survival, for economic hardship, for zoological
exhibition, for educational purposes, for incidental taking, or for
special purposes consistent with the purposes of the Act (50 CFR
17.32). The statute also contains certain exemptions from the
prohibitions, which are found in sections 9 and 10 of the Act.
In addition, to further the conservation of the species, any
employee or agent of the Service, any other Federal land management
agency, the National Marine Fisheries Service, a State conservation
agency, or a federally recognized Tribe, who is designated by their
agency or Tribe for such purposes, may, when acting in the course of
their official duties, take threatened wildlife without a permit if
such action is necessary to: (i) Aid a sick, injured, or orphaned
specimen; or (ii) dispose of a dead specimen; or (iii) salvage a dead
specimen that may be useful for scientific study; or (iv) remove
specimens that constitute a demonstrable but nonimmediate threat to
human safety, provided that the taking is done in a humane manner. Such
taking may involve killing or injuring only if it has not been
reasonably possible to eliminate such threat by live-capturing and
releasing the specimen unharmed, in an appropriate area.
We recognize the special and unique relationship that we have with
our State natural resource agency partners in contributing to
conservation of listed species. State agencies often possess scientific
data and valuable expertise on the status and distribution of
endangered, threatened, and candidate species of wildlife and plants.
State agencies, because of their authorities and their close working
relationships with local governments and landowners, are in a unique
position to assist us in implementing all aspects of the Act. In this
regard, section 6 of the Act provides that we must cooperate to the
maximum extent practicable with the States in carrying out programs
authorized by the Act. Therefore, any qualified employee or agent of a
State conservation agency that is a party to a cooperative agreement
with us in accordance with section 6(c) of the Act, who is designated
by his or her agency for such purposes, would be able to conduct
activities designed to conserve monarch butterflies that may result in
[[Page 100685]]
otherwise prohibited take without additional authorization.
The main threats affecting the two North American migratory
populations of monarch butterflies are the ongoing impacts from loss
and degradation of breeding, migratory, and overwintering habitat (from
past conversion of grasslands and shrublands to agriculture and
widespread use of herbicides; logging/thinning at overwintering sites
in Mexico; urban development, senescence; and incompatible management
of overwintering sites in California; and drought), exposure to
insecticides, and effects of climate change. To improve future
conditions so that the monarch migratory populations stabilize and
grow, we need to (1) achieve a significant increase in the availability
of milkweed and nectar plants in monarch breeding and migratory areas;
(2) protect and enhance overwintering habitat; (3) avoid and minimize
impacts to monarchs and their habitat from insecticides and herbicides;
and (4) maintain public support for the conservation of monarch
butterflies.
The proposed 4(d) rule would also provide for the conservation of
the species by allowing exceptions that incentivize conservation
actions or that, while they may have some minimal level of take of the
monarch butterfly, are not expected to rise to the level that would
have a negative impact (i.e., would have only de minimis impacts) on
the species' conservation. The proposed exceptions to these
prohibitions include take resulting from activities conducted for the
benefit of monarch butterflies or with only de minimis impacts that may
maintain, enhance, remove, or establish milkweed and nectar plants
within the breeding and migratory range; implementation of a
comprehensive conservation plan developed by or in coordination with a
State agency or implementation of a conservation program developed by a
Federal agency; maintenance or improvement of monarch overwintering
habitat in the United States consistent with a site-specific Service-
approved Overwintering Site Land Management Plan; monarch mortality due
to vehicle strikes; small-scale (250 or fewer butterflies) collection,
possession, captive-rearing, and release of monarchs; scientific
research; educational activities; possession of dead monarchs; and sale
of captively reared monarchs.
In this proposed rule, the range of the monarch where these
exceptions would apply include all areas under the jurisdiction of the
U.S. Government where the monarch occurred historically and were not
aided by human dispersal (i.e., the contiguous United States, Puerto
Rico, and the U.S. Virgin Islands). These exceptions would not apply to
States that are not part of the contiguous United States (e.g., Hawaii)
or territories that are outside the historical range of the species
(e.g., American Samoa) because, as noted above, these activities would
not be prohibited there.
(1) Activities that may maintain, enhance, remove, or establish
milkweed and nectar plants within the breeding and migratory range that
do not result in conversion of native or naturalized grassland,
shrubland, or forested habitats.
These activities include the following:
(a) Habitat restoration and management activities, such as mowing
and haying native rangeland, that sustain monarch butterfly habitat,
including activities to eliminate plant communities that contain
invasive plants or noxious weeds as part of site preparations or
habitat enhancement activities.
(b) Livestock grazing and routine ranching activities, including
rotational grazing, patch-burn grazing, vegetation and invasive species
management, other grazing practices implemented to make pasture and
rangelands productive, construction and maintenance of fences, the
gathering and management of livestock, and the development and
maintenance of watering facilities for livestock.
(c) Routine agricultural activities, including plowing, drilling,
disking, mowing, and other mechanical manipulation and management of
lands already in use for agricultural production (e.g., conventional
row crops, pasture, hay fields, orchards, and vineyards). This also
includes other mechanical manipulation and land management activities
in direct support of cultivated agriculture, such as replacement,
upgrades, maintenance, and operation of existing infrastructure (e.g.,
buildings, irrigation conveyance structures, fences, and roads), and
routine implementation and maintenance of agricultural conservation
practices, such as terraces, dikes, grassed waterways, and conservation
tillage.
(d) Fire management actions (e.g., prescribed burns, cultural
burns, hazardous fuel reduction activities, vegetation management,
maintenance of fuel breaks and minimum clearance requirements, and
other fuels reduction activities).
(e) Silviculture practices and forest management activities that
use State-approved best management practices.
(f) Maintenance, enhancement, removal, and establishment of
milkweed and nectar plants on residential and other developed
properties.
(g) Vegetation management activities, such as mowing, ground
disturbance, and other management activities, that remove milkweed and/
or nectar plants when conducted at times of year when monarchs are not
likely present.
We intend for this proposed exception to encourage numerous small-
and large-scale projects that will increase the quality and quantity of
breeding habitat on the landscape in the long term. We expect localized
removal of milkweed and nectar plants will be outweighed by an overall
addition of these resources across the landscape, making broadscale
public support for monarch conservation vitally important. For example,
landscape-scale habitat restoration and management activities that
provide for the habitat needs of monarch butterflies (e.g., mowing,
haying native rangeland, prescribed and cultural burning, and control
of invasive plants or noxious weeds) may remove milkweed and could
result in take of monarchs in the short term but would also increase
the overall quality and quantity of breeding habitat, which is likely
to benefit monarch populations in the long term. Similarly, forest,
fuels and wildland management activities, and rangeland management may
have some minimal level of take of monarch butterflies but are not
expected to rise to the level that would have a negative impact (i.e.,
would have only de minimis impacts) on the species' conservation. These
activities can help maintain and manage native, naturalized, and
restored grassland, shrubland, and forested habitats, which is a
conservation benefit to the species.
Routine agricultural activities on lands already in use for
agricultural production, not including conversion of native or
naturalized grassland, shrubland, and forested habitats, would result
in loss of milkweed and nectar plants that we consider inconsequential
to the conservation of the species. Monarchs are impacted by the
ongoing effects of past habitat loss and degradation; therefore,
routine agricultural activities on lands already in use for
agricultural production will not result in significant additional
habitat loss and degradation. This is also true for maintenance,
enhancement, removal, or establishment of milkweed and nectar plants on
residential and other developed properties. Vegetation management
activities that remove milkweed and/or nectar plants when conducted at
times of year when monarchs are not likely present and that
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do not result in conversion of native or naturalized grassland,
shrubland, or forested habitats would also result in a level of take
considered inconsequential to the conservation of the species. In
addition, some activities may provide both conservation benefits to the
species while also contributing to an inconsequential level of take
(e.g., livestock grazing).
While the goal of substantially increasing the breeding habitat
available to monarchs and reducing fragmentation of their habitat will
require working with people in many different sectors, a high priority
needs to be placed on working with farmers as well as the Natural
Resources Conservation Service, Farm Service Agency, and other partners
who work with private landowners. We will especially focus on the key
monarch breeding and migratory areas to encourage support for voluntary
efforts to create suitable habitat and improve connectivity of these
habitat patches to increase the productivity of monarchs and increase
the carrying capacity of monarch habitat on the landscape in important
parts of the species' range.
Under this proposed 4(d) rule, incidental take caused by activities
that may maintain, enhance, remove, or establish milkweed and nectar
plants within the breeding and migratory range that do not result in
conversion of native or naturalized grassland, shrubland, or forested
habitats will not be prohibited. These exceptions to the prohibitions
are intended to encourage widespread adoption of voluntary milkweed and
nectar restoration and maintenance as well as reduce the regulatory
requirements for the public on forms of take that are considered
inconsequential to the conservation of the species.
(2) Implementation of comprehensive conservation plans and
programs.
When making a determination as to whether incidental take from
implementation of a conservation plan or program would be excepted
pursuant to this 4(d) rule, we would consider the following:
<bullet> Whether the plan comprehensively addresses the threats
affecting the monarch within the plan area;
<bullet> Whether the plan establishes objective, measurable
biological goals and objectives for population and habitat necessary to
ensure a net conservation benefit, and provides the mechanisms by which
those goals and objectives will be achieved;
<bullet> Whether the plan administrators demonstrate the capability
and funding mechanisms for effectively implementing all elements of the
plan, including enrollment of participating landowners, monitoring of
activities, and enforcement of plan requirements, as applicable;
<bullet> Whether the plan employs an adaptive management strategy
to ensure future program adaptation as necessary and appropriate; and
<bullet> Whether the plan includes appropriate monitoring of
effectiveness and compliance.
To achieve a significant increase in the availability of monarch
breeding areas that is required for improvement in the status of the
species, breeding habitat needs to be returned to large portions of the
landscape where it is now nonexistent or where what remains is highly
fragmented. Given that so much milkweed has been lost historically and
that monarchs are impacted by the ongoing effects of this past habitat
loss and degradation, we need an approach that encourages landowners to
add milkweeds and nectar plants and implement actions to maintain them,
and comprehensive plans and projects to conserve the monarch butterfly
could be important sources of that conservation across the broader
landscape. State-wide plans developed by or in coordination with States
and implemented by State agents and enrolled participants (e.g.,
private landowners, local governments) are opportunities for large-
scale conservation. Likewise, programs developed by Federal agencies in
fulfillment of their section 7(a)(1) responsibilities are also
opportunities for large-scale conservation. Therefore, we intend for
this proposed exception to encourage implementation of conservation
plans and programs that comprehensively address threats affecting the
monarch within the plan area.
(3) Maintenance or improvement of overwintering habitat.
Overwintering habitat is defined as habitat that provides
overwintering monarch butterflies with the abiotic and biotic
conditions necessary for clustering, aggregating, and feeding
(nectaring). An overwintering site is defined as an area where
migratory monarch butterflies cluster on trees during the fall and/or
winter. Unlike breeding habitat, which is widely dispersed across the
continental United States and can be quickly created in a variety of
locations, overwintering habitat in Mexico (for the eastern migratory
population) and California (for the western migratory population) is
usually restricted to specific areas and consists of tree groves that
are not easily created in new locations. Migratory monarchs require a
very specific microclimate at overwintering sites. Maintenance and
improvement of overwintering habitat will aid conservation and recovery
of the species by maintaining and enhancing those specific conditions
at existing groves. We do not regulate take in foreign countries;
therefore, we do not prohibit incidental take resulting from
management, including logging, of monarch overwintering habitat in
Mexico. Our proposed 4(d) exceptions apply only to incidental take
resulting from maintenance or improvement of monarch overwintering
habitat in California or elsewhere in the United States. Under this
proposed 4(d) rule, incidental take resulting from maintenance or
improvement of monarch overwintering habitat in the United States that
is consistent with the goals and objectives of a site-specific Service-
approved overwintering site land management plan at the site would not
be prohibited. Our current Overwintering Site Land Management Plan
template and an example plan are available on <a href="https://www.regulations.gov">https://www.regulations.gov</a> under Docket No. FWS-R3-ES-2024-0137.
(4) Vehicle strikes.
It is common for monarchs to be struck by vehicles and killed in
the course of normal driving activities. Research suggests there may be
roadkill hotspots where monarch vehicle mortality is particularly high,
especially during periods of migration (Kantola et al. 2019, pp. 153
and 158). The best available information shows that mortality due to
vehicle strikes is not one of the primary drivers of changes in monarch
populations, and it was not identified as a primary driver by monarch
experts (Service 2024a, p. 39). At this time the impacts from monarch
deaths due to vehicle strikes are considered minimal and not affecting
the monarch butterfly at a population or species level. Furthermore,
research suggests that roadside monarch habitat can still provide a net
benefit to the species, despite losses due to collisions, through
strategic improvements to roadside vegetation management (Kasten et al.
2016, entire; Phillips et al. 2019, entire). Habitat along roadsides
may provide milkweed and nectar resources in otherwise heavily
developed and agricultural regions, as well as provide needed habitat
connectivity across the landscape (Wu-Smart & Schacht 2019, entire;
Ding & Eldridge 2022, entire).
We conclude that the overall impact of vehicle strikes is not
expected to negatively affect conservation and recovery efforts for the
monarch butterfly. Therefore, we propose that
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take due to vehicle strikes not be prohibited under this 4(d) rule.
(5) Non-lethal collection, possession, captive-rearing, and release
of a limited number of monarchs.
Monarch butterflies are collected non-lethally, held in captivity
(and in some cases sold), and released for a variety of purposes,
including educational purposes. Collecting (defined in this rulemaking
as the non-lethal capture and holding of live monarchs at any life
stage), captively rearing (defined in this rulemaking as the holding of
caterpillars, pupae, or adults and raising them in captivity long
enough for them to move to the next life stage or to reproduce), and
releasing monarchs has inspirational and educational value and can
foster lifelong connections to nature. Collection of monarchs at any
life stage from the wild has the potential to pose a risk to population
numbers. After evaluating the threat of collection, we determined there
is no evidence that the current rate of collection, in combination with
the current rate of release, is affecting monarch populations (Service
2024a, p. 109). However, we assume that the collection of clustering
monarchs could have greater impacts to the populations and species'
viability, as the migratory populations are at their smallest when
monarchs are clustering and overwintering clusters contain concentrated
numbers of individuals; thus, wild clustering monarchs may not be
collected as part of this exception.
Captive-rearing can also pose risks to wild monarch populations,
such as through the spread of diseases and loss of genetic diversity
(Altizer et al. 2015, p. 1), and potential negative effects to the
fitness of individuals and their migratory capabilities (Altizer et al.
2015, p. 2). The negative effects can greatly impact wild monarch
populations when rearing is conducted on a large scale (Altizer et al.
2015, pp. 1-3). However, captive-rearing on a small scale can achieve
all the inspirational and educational benefits while reducing the risk
of negatively affecting populations, particularly if protocols are
followed to minimize disease and genetic impacts. For the purposes of
this proposed rule, we describe small-scale captive-rearing as
collection, raising, and releasing 250 or fewer monarchs in a given
year. We consider the collection, raising, and releasing of more than
250 monarchs per year to be a large-scale endeavor, for which a permit
would be required through section 10(a)(1)(A) of the Act.
We conclude that the overall impact of collecting, possessing,
captively rearing, and releasing 250 or fewer individual monarchs at
one location or facility (e.g., home, botanical garden, school, or
business) is not expected to negatively affect conservation and
recovery efforts for the monarch butterfly. Therefore, take due to
these activities would not be prohibited under this proposed 4(d) rule.
However, collection of clustered monarchs would be prohibited.
Clustered monarchs are typically the individuals that will produce the
next year's first migratory generation. The migratory populations are
at their smallest during the overwintering time period when monarchs
cluster (typically September through March), and it is especially
important that these individuals survive the winter to breed in the
spring. Therefore, our proposed exception does not include take
resulting from handling or collection of clustered monarchs; a permit
to do so would be required through section 10(a)(1)(A) of the Act.
(6) Non-lethal scientific research and educational activities
involving a limited number of monarchs.
Future scientific research on monarch butterflies and their use in
educational activities in the contiguous United States will aid
conservation and recovery by leading to a better understanding and
appreciation of the biology and ecology of the species. Activities
associated with scientific research and education may include non-
lethal collection for purposes of handling, netting, sampling for
disease, tagging of monarchs, and conducting life cycle and specimen
observations of captive monarchs. The same restrictions related to
possession and release of monarchs (i.e., limiting activities to 250 or
fewer monarchs per year) would apply to scientific research and
educational activities. To encourage continued and further scientific
research and educational activities, we are proposing to include
exceptions in the 4(d) rule that allow these activities without
requiring additional permits; however, we do not include take of
clustered monarchs in the exception. As discussed in the previous
section, it is especially important that clustered overwintering
monarchs survive the winter to breed in the spring. Therefore, we do
not include handling or collection of clustered monarchs for scientific
research from this exception; a permit to do so would be required
through section 10(a)(1)(A) of the Act.
(7) Possession of dead monarchs.
Though overwintering monarchs can live longer, the average life
expectancy of monarchs during the breeding season is 2 to 5 weeks. It
is common for people to find and collect dead adult monarchs or pieces
of wing. Collection and possession of this type is not currently a
threat to the species. In some cases, with other species, we might be
concerned about collection becoming a threat due to collectors
capturing live butterflies and preserving them because the species is
listed and likely to become more rare. However, the monarch has
historically occurred in such large numbers and across such a large
range that the species is already a common specimen in butterfly
collections. The potential impacts from collection and possession of
dead monarchs are considered minimal and not likely to affect the
monarch butterfly at a population or species level. Collection of live
wild adult monarchs and intentionally killing them for preservation
purposes would be prohibited. We are proposing in this 4(d) rule that
possession of dead monarchs collected in a lawful manner would not be
prohibited.
(8) Sale of captively reared monarchs.
We propose to limit the sale of captively reared monarchs to 250 or
fewer individuals per year from a single location or facility. It is
common for individuals and organizations such as garden groups,
schools, and small businesses to sell captively reared monarchs during
the breeding season. These activities provide inspirational and
educational value for the public but have the same risks as discussed
above. We find that if these activities are conducted on a small scale
(limited to 250 or fewer monarchs in a given year), the potential for
negative impacts would be minimal.
We conclude that the overall impact of selling 250 or fewer
individual monarchs at one location or facility (e.g., home, botanical
garden, school, or business) is not expected to negatively affect
conservation and recovery efforts for the monarch butterfly. Therefore,
take due to these activities would not be prohibited under this
proposed 4(d) rule.
Public Comment Requested on Exception for Pesticide Use
We seek public comment on how to address pesticide use under a 4(d)
rule for the monarch. We recognize that certain types of pesticide use
can have direct or indirect negative effects on monarchs, including
aerial broadcast application of insecticides, use of herbicides that
remove milkweeds, and use of some biopesticides. However, not all uses
and application methods will impact monarchs. For example, insecticide
application using hand-held sprayers, soil injection, in furrow sprays,
tree trunk drenching, or tree injection, are unlikely to result in
[[Page 100688]]
pesticide exposure to monarchs. We seek comment on which pesticide uses
and application methods result in exposure and adverse effects to
monarchs, whether to except take from those uses in a 4(d) rule, and
whether the exceptions for those uses should include measures to
mitigate the effects of pesticides on monarchs. We also seek comment on
whether we should tailor any measures according to the areas and times
of the year when monarchs are present and, if so, what is the most
feasible method to convey this information to pesticide users. Further,
any measures should focus on minimizing impacts to monarchs by reducing
exposure to the species, but we also seek comment on whether it is
appropriate to offset unavoidable impacts such as through habitat
restoration and, if so, how to accomplish this in a 4(d) rule.
If we include mitigation measures for excepted uses and application
methods in a 4(d) rule, we also seek comment on how to align those
measures with the EPA's work under FIFRA to minimize the effects of
pesticides on listed species and to ensure that FIFRA registration and
registration review decisions comply with section 7(a)(2) (see
Conservation Efforts and Regulatory Mechanisms, above). FIFRA, not the
ESA, is the primary Federal law that determines the conditions under
which pesticides may be used. Given all the EPA's ongoing work to
address pesticide impacts on listed species (e.g., Herbicide Strategy,
Insecticide Strategy, Vulnerable Species Action Plan), we seek to
minimize confusion and regulatory burdens for pesticide users as a
result of any mitigation measures we may include in a 4(d) rule for any
excepted pesticide uses. Rather than include specific pesticide
mitigation measures in the proposed 4(d) rule, we seek comment on how
best to identify those measures in a manner that aligns with the EPA's
ongoing work on this issue.
To inform public comments, we provide additional information on
certain pesticide uses that impact monarchs. Many insecticides are a
threat to monarchs based on their mode of action to target insects and
their potential exposure to monarchs. Conventional insecticides have
active ingredients used to control insects by killing or otherwise
preventing them from engaging in behaviors that are undesirable or
destructive. Insecticides are used in areas where monarchs occur and
can drift off intended use sites with certain methods of application.
They are likely to cause lethal and sublethal effects to nontarget
lepidopterans (i.e., the order of insects that includes butterflies and
moths) that are exposed (Service 2024a, appendix 5). Even though
monarchs are not typically the target of insecticides, they can be
killed by these chemicals if they are incidentally exposed. Many
conventional insecticides have nonspecific modes of action and are
expected to result in mortality to most or all insect species when
exposure exceeds a certain threshold.
In contrast, biopesticides are typically less toxic than
conventional pesticides and generally affect only the specific target
insect pest and closely related organisms. Biopesticides include
naturally occurring substances that control pests by nontoxic
mechanisms (e.g., biochemical pesticides), microorganisms that control
pests (e.g., microbial pesticides), and pesticidal substances produced
by plants containing added genetic material (e.g., plant-incorporated
protectants). While application of most biopesticides is not expected
to affect monarchs, certain forms of the microbial pesticide Bacillus
thuringiensis (Bt) are active against lepidopterans. Lepidoptera-active
Bt strains produce a specific mix of insecticidal proteins that are
active against caterpillars due to taxa-specific biological properties
and are used to control pests such as the spongy moth. At present,
Lepidoptera-active strains include Bacillus thuringiensis kurstaki
(Btk) and Bacillus thuringiensis azawai (Bta), though additional
Lepidoptera-active Bt products may be registered in the future. Other
currently registered Bt products, such as Bacillus thuringienses
israelensis (Bti), are not active against Lepidoptera and thus are not
expected to cause negative effects to monarchs. Products incorporated
with Bt, such as Bt-corn, are also not expected to cause negative
effects to monarchs because the toxin expression in Bt-corn is limited
to pollen, where it occurs at such low concentrations that exposure
presents a low risk to monarchs. In addition to direct exposure to
insecticide residues from spray application, monarchs may be exposed
via diet to systemic insecticides that are absorbed by nectar and
milkweed plants from the soil and become incorporated into tissues
(e.g., leaves, flowers, pollen, and nectar). While numerous types of
insecticides may be incorporated into plants systemically,
neonicotinoids are a class of insecticides that is particularly known
to distribute throughout plant tissues in this manner. Laboratory
studies demonstrate that exposure to neonicotinoids can negatively
affect adult, larval, and pupal survival of monarchs. However,
concentrations of neonicotinoids in the environment from systemic
incorporation have not been found to reach levels known to elicit the
negative effects seen in laboratory studies.
Another application of systemic insecticides is the direct
application or coating of seeds with insecticides prior to planting to
control or repel disease organisms, insects, and pests that attack
crops or desirable plants. Because seeds are broadly treated and often
used prophylactically (i.e., not in response to a documented pest
outbreak), their use is widespread for certain crops. Insecticide
applications by wet or liquid seed-coatings and slurry seed treatment
create limited exposure pathways to the monarch. Dust-treated seed
applications incur a potential for the dust to drift at the time of
planting. Treated seed dust could drift off the field, exposing
monarchs by direct contact with the insecticide or from systemic
incorporation into nearby milkweed or nectar plants. However, the
exposure potential to the monarch from treated seeds is orders of
magnitude lower compared to exposure potential from aerial broadcast
applications, and concentrations of insecticides detected in pollen and
nectar following seed treatments are below known thresholds for
negative effects in monarchs (Beedle and Harbin 2011, p. 8; EPA 2016,
pp. 14-22; EPA 2020, pp. 87-88).
Other pesticide formulation types, in contrast to liquid forms that
can result in direct exposure, are less likely to lead to exposure of
monarchs through contact or dietary routes and are therefore not
expected to negatively affect monarchs. For example, solid forms of
pesticides, such as granules or baits, are applied directly to the soil
or turf grass typically by hand or a spreader specifically designed for
the size of the carrier particle and provide little opportunity for
contact with monarch adults or larvae. In addition, solid formulations
are not expected to result in drift.
For other pesticide classes, such as herbicides and fungicides, our
review of the scientific information available indicates a limited
number of individual monarchs will experience negative effects from
direct exposure to these pesticides. We do not expect the low number of
individuals affected from direct exposure to other classes of
pesticides to impact the monarch butterfly at a population or species
level. Certain herbicide uses, however, have resulted in the loss of
milkweed and nectar, which is discussed in the Activities that may
maintain, enhance, remove, or establish milkweed and
[[Page 100689]]
nectar plants within the breeding and migratory range that do not
result in conversion of native or naturalized grassland, shrubland, or
forested habitats section. As a result, we are considering what
mitigation measures, if any, from the EPA's Herbicide Strategy (EPA
2024a, entire) and the agency's other ESA work (EPA 2024b, entire; EPA
2024c, entire), should inform any exceptions for herbicide use in a
4(d) rule for the monarch. Further, the EPA is considering how habitat
restoration and other forms of compensatory mitigation may address
unavoidable pesticide impacts to listed species. We thus seek comment
on whether and how we should consider habitat restoration or creation
as an offset for unavoidable pesticide impacts to the monarch under a
4(d) rule.
Summary
To promote conse
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