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Federal Register / Vol. 86, No. 147 / Wednesday, August 4, 2021 / Proposed Rules
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compared to historical sea-ice conditions occur in the nonbreeding season, which has a small influence on emperor penguin population growth rates. Sea-ice conditions during the laying season have the greatest effect on the population growth rates, and those conditions are well addressed in this model Jenouvrier et al. 2020, p. 7. The sea-ice models relied on for the SSA
report represent the best available scientific information.
The demographic parameters for emperor penguin used for all colonies are based on, and extrapolated from, the population at Pointe Geologie in Terre Adelie see figure 1, colony 35
because the vast majority of colonies have not been visited or subject to longterm studies. Sea ice-condition is projected to decrease in Antarctica and emperor penguins will likely need to disperse or attempt to disperse as colonies are disrupted or lost due to seaice instability. The simulations in the latest unpublished models include emperor penguin dispersal behaviors and extreme or catastrophic events, and we find including these additional demographic factors is an improvement because they represent natural and observed parts of the emperor penguins relationship to the sea-ice environment.
See the SSA report for a more thorough discussion of the demographic uncertainties in century-scale projections of climate change as they relate to emperor penguins Service 2021, pp. 5657, 8082.
Low-Emissions Scenario Under the low-emissions scenario, the median global population of emperor penguins is projected to decline by 26
percent under Paris 1.5, and by 27
percent under Paris 2.0 by 2050. At that point, approximately 185,000 breeding pairs would remain. However, the declines would not occur equally around the continent. Colonies in the Ross Sea and Weddell Sea are likely to experience more stable conditions.
Colonies in the Ross Sea are projected to increase from their current size by 2050, as penguins from other areas with less suitable habitat migrate to the Ross Sea. Colonies in the Weddell Sea are projected to increase initially; however, by 2050, the population is projected to be slightly smaller than the current population size in this sector. Colonies in the Indian Ocean, Bellingshausen Sea-Amundsen Sea, and Western Pacific Ocean sectors are projected to decline the most. By 2050, colonies within these three sectors are projected to decline by at least 50 percent, but the vast majority are projected to decline by more than 90
percent.

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Moderate-Emissions Scenarios For simulations under one of the moderate-emissions scenarios, SRES
A1B in CMIP3, the population growth rate is projected to be slightly positive until 2050, while the median global population is projected to decline by 19
to 33 percent by 2100 Jenouvrier et al.
2014a, p. 716; Jenouvrier et al. 2014b, p.
28. We note this projection is at 2100
and we do not have an estimate of the global population or population size within each sector at 2050. Under the other moderate-emissions scenario, RCP
4.5, the global population is projected to decline by 33 percent by 2050 to approximately 167,000 breeding pairs;
Jenouvrier et al. 2021, in litt.. Similar to the projections under the lowemissions scenario, the declines are not equal around the continent. The Ross Sea and Weddell Sea experience the smallest decrease in breeding pairs.
However, even high-latitude colonies in the Ross Sea and Weddell Sea are not immune to changes in sea-ice condition under this scenario Jenouvrier et al.
2014, entire; Schmidt and Ballard 2020, pp. 183184. The vast majority, and possibly all, colonies in the Indian Ocean, Bellingshausen Sea-Amundsen Sea, and Western Pacific Ocean sectors are projected to decline by more than 90
percent. Two important differences in the results of the two moderateemissions scenarios are noteworthy: The projections under SRES A1B were modeled using a different model and method than all the other scenarios, and the projections under RCP 4.5 include demographic factors of dispersal and extreme events while SRES A1B
projections do not. Dispersal behaviors may accelerate, slow down, or reverse the anticipated rate of population decline of emperor penguins, compared to the population projection without dispersal considered, but does not change the overall conclusion that the global population will decline. Extreme events are projected to increase the magnitude of decline throughout the species range.
High-Emissions Scenario Under the high-emissions scenario, RCP 8.5, the global population of emperor penguin is projected to decline 47 percent by 2050 to approximately 132,500 breeding pairs; Jenouvrier et al.
2021, in litt.. Similar to the lowand moderate-emissions scenarios, the declines are not equal around the continent. However, the population decline is greater in magnitude under the high-emissions scenario. The few colonies that are projected to remain occur in the Ross Sea and Weddell Sea.

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The breeding colonies in the Indian Ocean, Bellingshausen Sea-Amundsen Sea, and Western Pacific Ocean sectors are projected to decline by more than 90
percent.
Resiliency, Redundancy, and Representation The two most resilient sectors of Antarctica are first the Ross Sea and then the Weddell Sea under every emissions scenario. The breeding colonies in these sectors are projected to have the highest resiliency because these areas are likely to have the most stable long-term sea-ice conditions. The breeding colonies in the Indian Ocean sector are projected to be the least resilient, and experience the largest population declines and sea-ice decrease and variability under every scenario. The Bellingshausen SeaAmundsen Sea sector is also projected to have low resiliency. Projected declines in the Western Pacific Ocean sector are more complex and vary according to emissions scenario;
however, the colonies in this sector also markedly decline. Under the highemissions scenario RCP 8.5, the vast majority of breeding colonies throughout the range decline significantly by 2050, resulting in the Ross Sea and Weddell Sea serving as the last refuges for the species.
Redundancy is higher under the lowemissions scenario than under the moderateand high-emissions scenarios because more colonies remain extant under the low-emissions scenario.
Under the high-emissions scenario, the colonies in the three least resilient sectors Indian Ocean, Bellingshausen Sea-Amundsen Sea, and the Western Pacific Ocean are predicted to decline substantially, if not disappear entirely, whereas under the other emissions scenarios some colonies are predicted to decline less appreciably in East Antarctica and in West Antarctica depending on the scenario. Including extreme events into the simulations increases the magnitude of declines at breeding colonies throughout the range under every scenario.
Representation is similar to redundancy in that it decreases as the distribution of the species declines. The emperor penguin is predicted to lose genetic diversity under every scenario because the overall population abundance is projected to decline.
Under the low-emissions scenario with projections that do not include dispersal or extreme events, no known metapopulations are lost, although colonies that make up the two metapopulations in East Antarctica are projected to decline. However, when
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