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Federal Register / Vol. 86, No. 147 / Wednesday, August 4, 2021 / Proposed Rules
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As of 2020, 61 emperor penguin breeding colonies are extant. Of the 66
total known colonies, four were not extant or not visible in the 2019 satellite imaging, 1 colony is extirpated, and 11
of the colonies were newly discovered or rediscovered in 2019. The global population comprises approximately 270,000280,000 breeding pairs or 625,000650,000 individual birds. The Ross Sea and Weddell Sea sectors contain the highest abundance of birds relative to the other three sectors.
In the Southern Ocean, sea-ice extent undergoes considerable inter-annual variability, although with much greater inter-annual variability regionally than for the Southern Ocean as a whole Parkinson 2019, p. 14414. Sea-ice extent in the Southern Ocean is currently within its natural range of variability. Over the 40 years from 1979
to 2018, the yearly sea-ice extent in the Southern Ocean has a small, but statistically insignificant, positive trend.
However, this overall increase masks larger and sometimes opposing regional differences in trends Turner et al. 2015, pp. 12; Parkinson 2019, p. 14419. The greatest increase in sea ice extent has been in the Ross Sea sector, with smaller increases in the Weddell Sea and along the coast of East Antarctica, and a decrease in the Bellingshausen Sea and Amundsen Sea in West Antarctica Turner et al. 2015, p. 9;
Holland 2014, in Meredith et al. 2019, p. 214; Parkinson 2019, entire. The satellite record reveals that the gradual, decades-long overall increase in Antarctic sea-ice extent reversed in 2014, with subsequent rates of decrease in 20142018. All sectors, except the Ross Sea, have experienced at least one period since 1999 when the yearly average sea-ice extent decreased for 3 or more consecutive years only to rebound again, and eventually reach levels exceeding the sea-ice extent preceding the 3 years of decreases. Therefore, recent decreases in sea ice may not indicate a long-term negative trend Parkinson 2019, p. 14420.
Emperor penguins may have difficulties finding food in years of low sea ice, which may increase adult mortality and reduce breeding success.
Currently, prey abundance appears not to be a limiting factor for emperor penguins.
The emperor penguin currently has high resiliency, redundancy, and representation. Sixty-one breeding colonies are distributed around the coastline of Antarctica with no indication that their distribution has decreased or is presently decreasing.
The number of known breeding colonies
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has increased over time, because the use of satellite imagery has improved the ability to locate colonies and roughly estimate population sizes at colonies.
Catastrophic events may include iceberg calving, ice-shelf disintegration, and storm events. However, if a catastrophic event occurs, it only affects a small proportion of the total breeding colonies at any one time, and the displaced penguins try to return to that same breeding location or relocate to another nearby colony. Breeding colonies within the four known metapopulations have some degree of connectivity among metapopulations and very high connectivity between breeding colonies within each of the metapopulations.
Two of the four metapopulations are in East Antarctica Mawson Coast and Amanda Bay/Point Geologie metapopulations while the other two are the Weddell Sea metapopulation and the Ross Sea metapopulation Younger et al. 2017, p. 3892. There has been no loss of the known metapopulations.
Future Condition The interaction of demographic processes of reproduction and survival drives the population dynamics of the emperor penguin, which are all related to the sea-ice environment. Therefore, to project the long-term viability of emperor penguin, the sea-ice extent and/or concentration and how it relates to the emperor penguins long-term demographics has been modeled under different climate change scenarios Ainley et al. 2010, entire; Jenouvrier et al. 2009, 2012, 2014, 2017, 2020. The research into emperor penguin populations and their habitat conditions uses an ensemble of climate models based on changes in sea ice into the future that is founded on standard climate modeling efforts e.g., Ainley et al. 2010; Jenouvrier et al. 2009, 2012, 2014, 2017, 2020; Melillo et al. 2014.
The future scenarios for population projections of emperor penguins are based on climate change model projections following available IPCC
scenarios using Global Circulation Models driven by Special Report on Emissions Scenarios SRES and by Representative Concentration Pathways RCP scenarios Hayhoe et al. 2017, p.
142.
Modeling efforts projected sea-ice conditions and the emperor penguins response under low-, moderate-, and high-emissions scenarios. The Paris Agreement set a goal to limit global warming to below 2 C and preferably to 1.5 C, compared to pre-industrial levels United Nations 2021, unpaginated.
The Paris Agreement goals low-

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emissions scenario do not represent or equate to any RCP scenario; they are uniquely designed to meet the global temperature change targets set in the Paris Agreement Sanderson and Knutti 2016, in Jenouvrier et al. 2020, p. 1;
Sanderson et al. 2017, p. 828. The global temperature is likely to increase 0.31.7 C under RCP 2.6, and 1.02.6 C
under RCP 4.5 IPCCb 2019, p. 46.
Therefore, based strictly on the projected increase in global temperature, the Paris Agreement goals would fall within the projected range of RCP 2.6 and RCP 4.5 projections. Thus, we view the two projections aligned with the Paris goals collectively as one low-emissions scenario. We also evaluated two moderate-emissions scenarios: One in which the global temperature is projected to increase up to 2.6 C under RCP 4.5, and a second in which the global temperature is projected to increase up to 3.2 C by the end of the century SRES A1B. Finally, we used a high-emissions scenario RCP
8.5 with the greatest warming where global temperature is projected to increase up to 4.8 C IPCC 2019b, p.
46.
Given the complexities of Global Circulation Models and advancements in technology, models typically build upon previous modeling efforts. The modeling for the global population of emperor penguins and sea-ice conditions was initially run under scenario SRES A1B in CMIP3 using the best available information of the population and demographics at the time. SRES A1B in CMIP3 is consistent with RCP 6.0 in CMIP5 Melillo et al.
2014, p. 755. As newer models were developed, and experts learned more about emperor penguin dispersal capabilities and behavior and discovered more colonies that increased the global population size, the modeling efforts were refined to account for additional colonies and inter-colony dispersal behaviors. Additionally, the most recent projections for the emperor penguin include simulations that account for extreme or catastrophic events occurring in Antarctica Jenouvrier et al. 2021, in litt..
The Community Earth System Model Large Ensemble project was used in the most recent modeling efforts to simulate the sea-ice conditions, building upon the initial efforts of the moderateemissions scenario SRES A1B, which used models that contributed to CMIP3.
The Community Earth System Model contributed to CMIP5 and was included in the IPCC fifth assessment report Jenouvrier et al. 2020, pp. 34. The largest differences between the Community Earth System Model
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