Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition to List the Pacific Walrus as Endangered or Threatened, 7634-7679 [2011-2400]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 76, Number 28 (Thursday, February 10, 2011)]
[Proposed Rules]
[Pages 7634-7679]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-2400]



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Vol. 76

Thursday,

No. 28

February 10, 2011

Part II





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; 12-Month Finding on a 
Petition to List the Pacific Walrus as Endangered or Threatened; 
Proposed Rule

Federal Register / Vol. 76, No. 28 / Thursday, February 10, 2011 / 
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R7-ES-2009-0051; MO 92210-0-0008-B2]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition to List the Pacific Walrus as Endangered or Threatened

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service, announce a 12-month 
finding on a petition to list the Pacific walrus (Odobenus rosmarus 
divergens) as endangered or threatened and to designate critical 
habitat under the Endangered Species Act of 1973, as amended. After 
review of all the available scientific and commercial information, we 
find that listing the Pacific walrus as endangered or threatened is 
warranted. Currently, however, listing the Pacific walrus is precluded 
by higher priority actions to amend the Lists of Endangered and 
Threatened Wildlife and Plants. Upon publication of this 12-month 
petition finding, we will add Pacific walrus to our candidate species 
list. We will develop a proposed rule to list the Pacific walrus as our 
priorities allow. We will make any determination on critical habitat 
during development of the proposed listing rule. Consistent with 
section 4(b)(3)(C)(iii) of the Endangered Species Act, we will review 
the status of the Pacific walrus through our annual Candidate Notice of 
Review.

DATES: The finding announced in this document was made on February 10, 
2011.

ADDRESSES: This finding and supporting documentation are available on 
the Internet at https://www.regulations.gov at Docket Number FWS-R7-ES-
2009-0051. A range map of the three walrus subspecies and a more 
detailed map of the Pacific walrus range are available at the following 
Web site: https://alaska.fws.gov/fisheries/mmm/walrus/wmain.htm. 
Supporting documentation we used in preparing this finding is available 
for public inspection, by appointment, during normal business hours at 
the U.S. Fish and Wildlife Service, Alaska Regional Office, 1011 East 
Tudor Road, Anchorage, AK 99503. Please submit any new information, 
materials, comments, or questions concerning this finding to the above 
address.

FOR FURTHER INFORMATION CONTACT: James MacCracken, Marine Mammals 
Management, Alaska Regional Office (see ADDRESSES); by telephone: 800-
362-5148; or by facsimile: 907-786-3816. If you use a 
telecommunications device for the deaf (TDD), please call the Federal 
Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION: 

Background

    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition 
to revise the Federal Lists of Endangered and Threatened Wildlife and 
Plants that contains substantial scientific or commercial information 
that listing the species may be warranted, we make a finding within 12 
months of the date of receipt of the petition. In this finding, we will 
determine whether the petitioned action is: (a) Not warranted, (b) 
warranted, or (c) warranted, but the immediate proposal of a regulation 
implementing the petitioned action is precluded by other pending 
proposals to determine whether species are endangered or threatened, 
and expeditious progress is being made to add or remove qualified 
species from the Federal Lists of Endangered and Threatened Wildlife 
and Plants. Section 4(b)(3)(C) of the Act requires that we treat a 
petition for which the requested action is found to be warranted but 
precluded as though resubmitted on the date of such finding, that is, 
requiring a subsequent finding to be made within 12 months. We must 
publish these 12-month findings in the Federal Register.

Previous Federal Actions

    On February 8, 2008, we received a petition dated February 7, 2008, 
from the Center for Biological Diversity, requesting that the Pacific 
walrus be listed as endangered or threatened under the Act and that 
critical habitat be designated. The petition included supporting 
information regarding the species' ecology and habitat use patterns, 
and predicted changes in sea-ice habitats and ocean conditions that may 
impact the Pacific walrus. We acknowledged receipt of the petition in a 
letter to the Center for Biological Diversity, dated April 9, 2008. In 
that letter, we stated that an emergency listing was not warranted and 
that all remaining available funds in the listing program for Fiscal 
Year (FY) 2008 had already been allocated to the U.S. Fish and Wildlife 
Service's (Service) highest priority listing actions and that no 
listing funds were available to further evaluate the Pacific walrus 
petition in FY 2008.
    On December 3, 2008, the Center for Biological Diversity filed a 
complaint in U.S. District Court for the District of Alaska for 
declaratory judgment and injunctive relief challenging the failure of 
the Service to make a 90-day finding on their petition to list the 
Pacific walrus, pursuant to section 4(b)(3) of the Endangered Species 
Act, 16 U.S.C. 1533(b)(3), and the Administrative Procedure Act, 5 
U.S.C. 706(1). On May 18, 2009, a settlement agreement was approved in 
the case of Center for Biological Diversity v. U.S. Fish and Wildlife 
Service, et al. (3:08-cv-00265-JWS), requiring us to submit our 90-day 
finding on the petition to the Federal Register by September 10, 2009. 
On September 10, 2009, we made our 90-day finding that the petition 
presented substantial scientific information indicating that listing 
the Pacific walrus may be warranted (74 FR 46548). On August 30, 2010, 
the Court approved an amended settlement agreement requiring us to 
submit our 12-month finding to the Federal Register by January 31, 
2011. This notice constitutes the 12-month finding on the February 7, 
2008, petition to list the Pacific walrus as endangered or threatened.
    This 12-month finding is based on our consideration and evaluation 
of the best scientific and commercial information available. We 
reviewed the information provided in the petition submitted to the 
Service by the Center for Biological Diversity, information available 
in our files, and other available published and unpublished 
information. Additionally, in response to our Federal Register notice 
of September 10, 2009, requesting information from the public, as well 
as our September 10, 2010 press release, and other outreach efforts 
requesting new information from the public, we received roughly 30,000 
submissions, which we have considered in making this finding, including 
information from the U.S. Marine Mammal Commission, the State of 
Alaska, the Alaska North Slope Borough, the Eskimo Walrus Commission, 
the Humane Society of the United States, the Center for Biological 
Diversity, the American Petroleum Institute, and many interested 
citizens. We also consulted with recognized Pacific walrus experts and 
Federal, State, and Tribal agencies.

Species Information

Taxonomy and Species Delineation
    The walrus (Odobenus rosmarus) is the only living representative of 
the family Odobenidae, a group of marine carnivores that was highly 
diversified in

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the late Miocene and early Pliocene (Kohno 2006, pp. 416-419; Harington 
2008, p. 26). Fossil evidence suggests that the genus evolved in the 
North Pacific Ocean and dispersed throughout the Arctic Ocean and North 
Atlantic during interglacial phases of the Pleistocene (Harington and 
Beard 1992, pp. 311-319; Dyke et al. 1999, p. 60; Harington 2008, p. 
27).
    Three modern subspecies of walruses are generally recognized 
(Wozencraft 2005, p. 525; Integrated Taxonomic Information System, 
2010, p. 1): The Atlantic walrus (O. r. rosmarus), which ranges from 
the central Canadian Arctic eastward to the Kara Sea (Reeves 1978, pp. 
2-20); the Pacific walrus (O. r. divergens), which ranges across the 
Bering and Chukchi Seas (Fay 1982, pp. 7-21); and the Laptev walrus (O. 
r. laptevi), which is represented by a small, geographically isolated 
population of walruses in the Laptev Sea (Heptner et al. 1976, p. 34; 
Vishnevskaia and Bychkov 1990, pp. 155-176; Andersen et al. 1998, p. 
1323; Wozencraft 2005, p. 595; Jefferson et al. 2008, p. 376). Atlantic 
and Pacific walruses are genetically and morphologically distinct from 
each other (Cronin et al. 1994, p. 1035), likely as a result of range 
fragmentation and differentiation during glacial phases of extensive 
Arctic sea-ice cover (Harington 2008, p. 27). Although geographically 
isolated and ecologically distinct, walruses from the Laptev Sea appear 
to be more closely related to Pacific walruses (Lindqvist et al. 2009, 
pp. 119-121).
    Pacific walruses are ecologically distinct from other walrus 
populations, primarily because they undergo significant seasonal 
migrations between the Bering and the Chukchi Seas and rely principally 
on broken pack ice habitat to access offshore breeding and feeding 
areas (Fay 1982, p. 279) (see Species Distribution, below). In 
contrast, Atlantic walruses, which are represented by several small 
discrete groups of animals distributed from the central Canadian Arctic 
eastward to the Kara Sea, exhibit smaller seasonal movements and feed 
primarily in coastal areas because the continental shelf is narrow over 
much of their range. The majority of productive feeding areas used by 
Atlantic walruses are accessible from the coast, and all age classes 
and gender groups use terrestrial haulouts during ice-free seasons 
(Born et al. 2003, p. 356; COSEWIC 2006, p. 15; Laidre et al. 2008, pp. 
S104, S115).
    The Pacific walrus is generally considered a single population, 
although some heterogeneity has been documented. Jay et al. (2008, p. 
938) found some differences in the ratio of trace elements in the teeth 
of Pacific walruses sampled in winter from two breeding areas 
(southeast Bering Sea and St. Lawrence Island), suggesting that the 
sampled animals had a history of feeding in different regions. Scribner 
et al. (1997, p. 180), however, found no difference in mitochondrial 
and nuclear DNA among Pacific walruses sampled from different breeding 
areas. Pacific walruses are identified and managed in the United States 
and the Russian Federation (Russia) as a single population (Service 
2010, p. 1).
Species Description
    Walruses are readily distinguished from other Arctic pinnipeds 
(aquatic carnivorous mammals with all four limbs modified into 
flippers, this group includes seals, sea lions, and walruses) by their 
enlarged upper canine teeth, which form prominent tusks. The family 
name Odobenidae (tooth walker), is based on observations of walruses 
using their tusks to pull themselves out of the water. Males, which 
have relatively larger tusks than females, also tend to have broader 
skulls (Fay 1982, pp. 104-108). Walrus tusks are used as offensive and 
defensive weapons (Kastelein 2002, p. 1298). Adult males use their 
tusks in threat displays and fighting to establish dominance during 
mating (Fay et al. 1984, p. 93), and animals of both sexes use threat 
displays to establish and defend positions on land or ice haulouts (Fay 
1982, pp. 134-138). Walruses also use their tusks to anchor themselves 
to ice floes when resting in the water during inclement weather (Fay 
1982, pp. 134-138; Kastelein 2002, p. 1298).
    The Pacific walrus is the largest pinniped species in the Arctic. 
At birth, calves are approximately 65 kilograms (kg) (143 pounds (lb)) 
and 113 centimeters (cm) (44.5 inches (in)) long (Fay 1982, p. 32). 
After the first 7 years of life, the growth rate of female walruses 
declines rapidly, and they reach a maximum body size by approximately 
10 years of age. Adult females can reach lengths of up to 3 meters (m) 
(9.8 feet (ft)) and weigh up to 1,100 kg (2,425 lb). Male walrus tend 
to grow faster and for a longer period of time than females. They 
usually do not reach full adult body size until they are 15 to 16 years 
of age. Adult males can reach lengths of 3.5 m (11.5 ft) and can weigh 
more than 2,000 kg (4,409 lb) (Fay 1982, p. 33).
Behavior
    Walruses are social and gregarious animals. They tend to travel in 
groups and haul out of the water to rest on ice or land in densely 
packed groups. On land or ice, in any season, walruses tend to lie in 
close physical contact with each other. Young animals often lie on top 
of adults. Group size can range from a few individuals up to several 
thousand animals (Gilbert 1999, p. 80; Kastelein 2002, p. 1298; 
Jefferson et al. 2008, p. 378). At any time of the year, when groups 
are disturbed, stampedes from a haulout can result in injuries and 
mortalities. Calves and young animals are particularly vulnerable to 
trampling injuries (Fay 1980, pp. 227-227; Fay and Kelly 1980, p. 226).
    The reaction of walruses to disturbance ranges from no reaction to 
escape into the water, depending on the circumstances (Fay et al. 1984, 
pp. 13-14). Many factors play into the severity of the response, 
including the age and sex of the animals, the size and location of the 
group (on ice, in water, on land), their distance from the disturbance, 
and the nature and intensity of the disturbance (Fay et al. 1984, pp. 
14, 114-119). Females with calves appear to be most sensitive to 
disturbance, and animals on shore are more sensitive than those on ice 
(Fay et al. 1984, p. 114). A fright response caused by disturbance can 
cause stampedes on a haulout, resulting in injuries and mortalities 
(Fay and Kelly 1980, pp. 241-244).
    Mating occurs primarily in January and February in broken pack ice 
habitat in the Bering Sea. Breeding bulls follow herds of females and 
compete for access to groups of females hauled out onto sea ice (Fay 
1982, pp. 193-194). Males perform visual and acoustical displays in the 
water to attract females and defend a breeding territory. Subdominant 
males remain on the periphery of these aggregations and apparently do 
not display. Intruders into display areas are met with threat displays 
and physical attacks. Individual females leave the resting herd to join 
a male in the water where copulation occurs (Fay et al. 1984, pp. 89-
99; Sjare and Stirling 1996, p. 900). Gestation lasts 15 to 16 months 
(Fay 1982, p. 197) and pregnancies are spaced at least 2 years apart 
(Fay 1982, p. 206). Calving occurs on sea ice, most typically in May, 
before the northward spring migration (Fay 1982, pp. 199-200). Mothers 
and newborn calves stay mostly on ice floes during the first few weeks 
of life (Fay et al. 1984, p. 12).
    The social bond between the mother and calf is very strong, and it 
is unusual for a cow to become separated from her calf (Fay 1982, p. 
203). The calf normally remains with its mother for at least 2 years, 
sometimes longer, if not supplanted by a new calf (Fay 1982, pp. 206-
211). After separation from their

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mother, young females tend to remain with groups of adult females, 
whereas young males gradually separate from the females and begin to 
associate with groups of other males. Individual social status appears 
to be based on a combination of body size, tusk size, and 
aggressiveness. Individuals do not necessarily associate with the same 
group of animals and must continually reaffirm their social status in 
each new aggregation (Fay 1982, p. 135; NAMMCO 2004, p. 43).
Species Distribution
    Pacific walruses range across the shallow continental shelf waters 
of the northern Bering Sea and Chukchi Sea, occasionally ranging into 
the East Siberian Sea and Beaufort Sea (Fay 1982, pp. 7-21; Figure 1 in 
Garlich-Miller et al. 2011). Waters deeper than 100 m (328 ft) and the 
extent of the pack ice are factors that limit distribution to the north 
(Fay 1982, p. 23). Walruses are rarely spotted south of the Alaska 
Peninsula and Aleutian archipelago; however, migrant animals (mostly 
males) are occasionally reported in the North Pacific (Service 2010, 
unpublished data).
    Pacific walruses are highly mobile, and their distribution varies 
markedly in response to seasonal and interannual variations in sea-ice 
cover. During the January to March breeding season, walruses congregate 
in the Bering Sea pack ice in areas where open leads (fractures in sea 
ice caused by wind drift or ocean currents), polynyas (enclosed areas 
of unfrozen water surrounded by ice) or thin ice allow access to water 
(Fay 1982, p. 21; Fay et al. 1984, pp. 89-99). The specific location of 
winter breeding aggregations varies annually depending upon the 
distribution and extent of ice. Breeding aggregations have been 
reported southwest of St. Lawrence Island, Alaska; south of Nunivak 
Island, Alaska; and south of the Chukotka Peninsula in the Gulf of 
Anadyr, Russia (Fay 1982, p. 21; Mymrin et al. 1990, pp. 105-113; 
Figure 1 in Garlich-Miller et al. 2011).
    In spring, as the Bering Sea pack ice deteriorates, most of the 
population migrates northward through the Bering Strait to summer 
feeding areas over the continental shelf in the Chukchi Sea. However, 
several thousand animals, primarily adult males, remain in the Bering 
Sea during the summer months, foraging from coastal haulouts in the 
Gulf of Anadyr, Russia, and in Bristol Bay, Alaska (Figure 1 in 
Garlich-Miller et al. 2011).
    Summer distributions (both males and females) in the Chukchi Sea 
vary annually, depending upon the extent of sea ice. When broken sea 
ice is abundant, walruses are typically found in patchy aggregations 
over continental shelf waters. Individual groups may range from less 
than 10 to more than 1,000 animals (Gilbert 1999, pp. 75-84; Ray et al. 
2006, p. 405). Summer concentrations have been reported in loose pack 
ice off the northwestern coast of Alaska, between Icy Cape and Point 
Barrow, and along the coast of Chukotka, Russia, as far west as Wrangel 
Island (Fay 1982, pp. 16-17; Gilbert et al. 1992, pp. 1-33; Belikov et 
al. 1996, pp. 267-269). In years of low ice concentrations in the 
Chukchi Sea, some animals range east of Point Barrow into the Beaufort 
Sea; walruses have also been observed in the Eastern Siberian Sea in 
late summer (Fay 1982, pp. 16-17; Belikov et al. 1996, pp. 267-269). 
The pack ice of the Chukchi Sea usually reaches its minimum extent in 
September. In years when the sea ice retreats north beyond the 
continental shelf, walruses congregate in large numbers (up to several 
tens of thousands of animals in some locations) at terrestrial haulouts 
on Wrangel Island and other sites along the northern coast of the 
Chukotka Peninsula, Russia, and northwestern Alaska (Fay 1982, p. 17; 
Belikov et al. 1996, pp. 267-269; Kochnev 2004, pp. 284-288; Ovsyanikov 
et al. 2007, pp. 1-4; Kavry et al. 2008, pp. 248-251).
    In late September and October, walruses that summered in the 
Chukchi Sea typically begin moving south in advance of the developing 
sea ice. Satellite telemetry data indicate that male walruses that 
summered at coastal haulouts in the Bering Sea also begin to move 
northward towards winter breeding areas in November (Jay and Hills 
2005, p. 197). The male walruses' northward movement appears to be 
driven primarily by the presence of females at that time of year 
(Freitas et al. 2009, pp. 248-260).
Foraging and Prey
    Walruses consume mostly benthic (region at the bottom of a body of 
water) invertebrates and are highly adapted to obtain bivalves (Fay 
1982, p. 139; Bowen and Siniff 1999, p. 457; Born et al. 2003, p. 348; 
Dehn et al. 2007, p. 176; Boveng et al. 2008, pp. 17-19; Sheffield and 
Grebmeier 2009, pp. 766-767). Fish and other vertebrates have 
occasionally been found in their stomachs (Fay 1982, p. 153; Sheffield 
and Grebmeier 2009, p. 767). Walruses root in the bottom sediment with 
their muzzles and use their whiskers to locate prey items. They use 
their fore-flippers, nose, and jets of water to extract prey buried up 
to 32 cm (12.6 in) (Fay 1982, p. 163; Oliver et al. 1983, p. 504; 
Kastelein 2002, p. 1298; Levermann et al. 2003, p. 8). The foraging 
behavior of walruses is thought to have a major impact on benthic 
communities in the Bering and Chukchi Seas (Oliver et al. 1983, pp. 
507-509; Klaus et al. 1990, p. 480). Ray et al. (2006, pp. 411-413) 
estimate that walruses consume approximately 3 million metric tons 
(3,307 tons) of benthic biomass annually, and that the area affected by 
walrus foraging is in the order of thousands of square kilometers (sq 
km) (thousands of square miles (sq mi)) annually. Consequently, 
walruses play a major role in benthic ecosystem structure and function, 
which Ray et al. (2006, p. 415) suggested increased nutrient flux and 
productivity.
    The earliest studies of food habits were based on examination of 
stomachs from walruses killed by hunters. These reports indicated that 
walruses were primarily feeding on bivalves (clams), and that non-
bivalve prey was only incidentally ingested (Fay 1982, p. 145; 
Sheffield et al. 2001, p. 311). However, these early studies did not 
take into account the differential rate of digestion of prey items 
(Sheffield et al. 2001, p. 311). Additional research indicates that 
stomach contents include over 100 taxa of benthic invertebrates from 
all major phyla (Fay 1982, p. 145; Sheffield and Grebmeier 2009, p. 
764), and while bivalves remain the primary component, walruses are not 
adapted to a diet solely of clams. Other prey items have similar 
energetic benefits (Wacasey and Atkinson 1987, pp. 245-247). Based on 
analysis of the contents from fresh stomachs of Pacific walruses 
collected between 1975 and 1985 in the Bering Sea and Chukchi Sea, prey 
consumption likely reflects benthic invertebrate composition (Sheffield 
and Grebmeier 2009, pp. 764-768). Of the large number of different 
types of prey, statistically significant differences between males and 
females from the Bering Sea were found in the occurrence of only two 
prey items, and there were no statistically significant differences in 
results for males and females from the Chukchi Sea (Sheffield and 
Grebmeier 2009, pp. 765). Although these data are for Pacific walrus 
stomachs collected 25-35 years ago, we have no reason to believe there 
has been a change in the general pattern of prey use described here.
    Walruses typically swallow invertebrates without shells in their 
entirety (Fay 1982, p. 165). Walruses remove the soft parts of mollusks 
from their shells by suction, and discard the shells (Fay 1982, pp. 
166-167). Born et al. (2003, p. 348) reported that Atlantic

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walruses consumed an average of 53.2 bivalves (range 34 to 89) per 
dive. Based on caloric need and observations of captive walruses, 
walruses require approximately 29 to 74 kg (64 to 174 lbs) of food per 
day (Fay 1982, p. 160). Adult males forage little during the breeding 
period (Fay 1982, pp. 142, 159-161; Ray et al. 2006, p. 411), while 
lactating females may eat two to three times that of nonpregant, 
nonlactating females (Fay 1982, p.159). Calves up to 1 year of age 
depend primarily on their mother's milk (Fay 1982, p. 138) and are 
gradually weaned in their second year (Fisher and Stewart 1997, pp. 
1165-1175).
    Although walruses are capable of diving to depths of more than 250 
m (820 ft) (Born et al. 2005, p. 30), they usually forage in waters of 
80 m (262 ft) or less (Fay and Burns 1988, p. 239; Born et al. 2003, p. 
348; Kovacs and Lydersen 2008, p. 138), presumably because of higher 
productivity of their benthic foods in shallow waters (Fay and Burns 
1988, pp. 239-240; Carey 1991, p. 869; Jay et al. 2001, p. 621; 
Grebmeier et al. 2006b, pp. 334-346; Grebmeier et al. 2006a, p. 1461). 
Walruses make foraging trips from land or ice haulouts that range from 
a few hours up to several days and up to 100 kilometers (km) (60 miles 
(mi)) (Jay et al. 2001, p. 626; Born et al. 2003, p. 349; Ray et al. 
2006, p. 406; Udevitz et al. 2009, p. 1122). Walruses tend to make 
shorter and more frequent foraging trips when sea ice is used as a 
foraging platform compared to terrestrial haulouts (Udevitz et al. 
2009, p. 1122). Satellite telemetry data for walruses in the Bering Sea 
in April of 2004, 2005, and 2006 showed they spent an average of 46 
hours in the water between resting bouts on ice, which averaged 9 hours 
(Udevitz et al. 2009, p. 1122). Because females and young travel with 
the retreating pack ice in the spring and summer, they are passively 
transported northward over feeding grounds across the continental 
shelves of the Bering and Chukchi Seas. Male walruses appear to have 
greater endurance than females, with foraging excursions from land 
haulouts that can last up to 142 hours (about 6 days) (Jay et al. 2001, 
p. 630).
Sea-Ice Habitats
    The Pacific walrus is an ice-dependent species that relies on sea 
ice for many aspects of its life history. Unlike other pinnipeds, 
walruses are not adapted for a pelagic existence and must haul out on 
ice or land regularly. Floating pack ice serves as a substrate for 
resting between feeding bouts (Ray et al. 2006, p. 404), breeding 
behavior (Fay et al. 1984, pp. 89-99), giving birth (Fay 1982, p. 199), 
and nursing and care of young (Kelly 2001, pp. 43-55). Sea ice provides 
access to offshore feeding areas over the continental shelf of the 
Bering and Chukchi Seas, passive transportation to new feeding areas 
(Richard 1990, p. 21; Ray et al. 2006, pp. 403-419), and isolation from 
terrestrial predators (Richard 1990, p. 23; Kochnev 2004, p. 286; 
Ovsyanikov et al. 2007, pp. 1-4). Sea ice provides an extensive 
substrate upon which the risk of predation and hunting is greatly 
reduced (Kelly 2001, pp. 43-55; Fay 1982, p. 26).
    Sea ice in the Northern Hemisphere is comprised of first-year sea 
ice that formed in the most recent autumn-winter period, and multi-year 
ice that has survived at least one summer melt season. Sea-ice habitats 
for walruses include openings or leads that provide access to the water 
and to food resources. Walruses generally do not use multi-year ice or 
highly compacted first-year ice in which there is an absence of 
persistent leads or polynyas (Richard 1990, p. 21). Expansive areas of 
heavy ice cover are thought to play a restrictive role in walrus 
distributions across the Arctic and serve as a barrier to the mixing of 
populations (Fay 1982, p. 23; Dyke et al. 1999, pp. 161-163; Harington 
2008, p. 35). Walruses generally do not occur farther south than the 
maximum extent of the winter pack ice, possibly due to their reliance 
on sea ice for breeding and rearing young (Fay et al. 1984, pp. 89-99) 
and isolation from terrestrial predators (Kochnev 2004, p. 286; 
Ovsyanikov et al. 2007, pp. 1-4), or because of the higher densities of 
benthic invertebrates in northern waters (Grebmeier et al. 2006a, pp. 
1461-1463).
    Walruses generally occupy first-year ice that is greater than 20 cm 
(7.9 in) thick and are not found in areas of extensive, unbroken ice 
(Fay 1982, pp. 21, 26; Richard 1990, p. 23). Thus, in winter they 
concentrate in areas of broken pack ice associated with divergent ice 
flow or along the margins of persistent polynyas (Burns et al. 1981, 
pp. 781-797; Fay et al. 1984, pp. 89-99; Richard 1990, p. 23) in areas 
with abundant food resources (Ray et al. 2006, p. 406). Females with 
young generally spend the summer months in pack ice habitats of the 
Chukchi Sea, where they feed intensively between bouts of resting and 
suckling their young. Some authors have suggested that the size and 
topography of individual ice floes are important features in the 
selection of ice haulouts, noting that some animals have been observed 
returning to the same ice floe between feeding bouts (Ray et al. 2006, 
p. 406). However, it has also been noted that walruses can and will 
exploit a fairly broad range of ice types and ice concentrations in 
order to stay in preferred foraging or breeding areas (Freitas et al. 
2009, p. 247; Jay et al. 2010a, p. 300). Walruses tend to make shorter 
foraging excursions when they are using sea ice rather than land 
haulouts (Udevitz et al. 2009, p. 1122), presumably because it is more 
energetically efficient for them to haulout on ice near productive 
feeding areas than forage from shore. Fay (1982, p. 25) notes that 
several authors reported that when walruses had the choice of ice or 
land for a resting place, ice was always selected.
Terrestrial Habitats (Coastal Haulouts)
    When suitable sea ice is not available, walruses haul out on land 
to rest. A wide variety of substrates, ranging from sand to boulders, 
are used. Isolated islands, points, spits, and headlands are occupied 
most frequently. The primary consideration for a terrestrial haulout 
site appears to be isolation from disturbances and predators, although 
social factors, learned behavior, protection from strong winds and 
surf, and proximity to food resources also likely influence the choice 
of terrestrial haulout sites (Richard 1990, p. 23). Walruses tend to 
use established haulout sites repeatedly and exhibit some degree of 
fidelity to these sites (Jay and Hills 2005, pp. 192-202), although the 
use of coastal haulouts appears to fluctuate over time, possibly due to 
localized prey depletion (Garlich-Miller and Jay 2000, pp. 58-65). 
Human disturbance is also thought to influence the choice of haulout 
sites; many historic haulouts in the Bering Sea were abandoned in the 
early 1900s when the Pacific walrus population was subjected to high 
levels of exploitation (Fay 1982, p. 26; Fay et al. 1984, p. 231).
    Adult male walruses use land-based haulouts more than females or 
young, and consequently, have a greater geographical distribution 
through the ice-free season. Many adult males remain in the Bering Sea 
throughout the ice-free season, making foraging trips from coastal 
haulouts in Bristol Bay, Alaska, and the Gulf of Anadyr, Russia (Figure 
1 in Garlich-Miller et al. 2011), while females and juvenile animals 
generally stay with the drifting ice pack throughout the year (Fay 
1982, pp. 8-19). Females with dependent young may prefer sea-ice 
habitats because coastal haulouts pose greater risk from trampling 
injuries and predation (Fay and Kelly 1980, pp. 226-245; Ovsyanikov et 
al. 1994, p. 80; Kochnev

[[Page 7638]]

2004, pp. 285-286; Ovsyanikov et al. 2007, pp. 1-4; Kavry et al. 2008, 
pp. 248-251; Mulcahy et al. 2009, p. 3). Females may also prefer sea-
ice habitats because they may have difficulty nourishing themselves 
while caring for a young calf that has limited swimming range (Cooper 
et al. 2006, p. 101; Jay and Fischbach 2008, p. 1).
    The numbers of male walruses using coastal haulouts in the Bering 
Sea during the summer months, and the relative uses of different 
coastal haulout sites in the Bering Sea have varied over the past 
century. Harvest records indicate that walrus herds were once common at 
coastal haulouts along the Alaska Peninsula and the islands of northern 
Bristol Bay (Fay et al. 1984, pp. 231-376). By the early 1950s, most of 
the traditional haulout areas in the Southern Bering Sea had been 
abandoned, presumably due to hunting pressure. During the 1950s and 
1960s, Round Island was the only regularly used haulout in Bristol Bay, 
Alaska. In 1960, the State of Alaska established the Walrus Islands 
State Game Sanctuary, which closed Round Island to hunting. Peak counts 
of walruses at Round Island increased from 1,000-2,000 animals in the 
late 1950s (Frost et al. 1983, pp. 379) to more than 10,000 animals in 
the early 1980s (Sell and Weiss, p. 12), but subsequently declined to 
2,000-5,000 over the past decade (Sell and Weiss 2010, p. 12). General 
observations indicate that declining walrus counts at Round Island may, 
in part, reflect a redistribution of animals to other coastal sites in 
the Bristol Bay region. For example, walruses have been observed 
increasingly regularly at the Cape Seniavin haulout on the Alaska 
Peninsula since the 1970s, and at Cape Peirce and Cape Newenham in 
northwest Bristol Bay since the early 1980s (Jay and Hills 2005, p. 
193; Figure 1 in Garlich-Miller et al. 2011).
    Traditional male summer haulouts along the Bering Sea coast of 
Russia include sites along the Kamchatka Peninsula, the Gulf of Anadyr 
(most notably Rudder and Meechkin spits), and Arakamchechen Island 
(Garlich-Miller and Jay 2000, pp. 58-65; Figure 1 in Garlich-Miller et 
al. 2011). Several of the southernmost haulouts along the coast of 
Kamchatka have not been occupied in recent years, and the number of 
animals in the Gulf of Anadyr has also declined in recent years 
(Kochnev 2005, p. 4). Factors influencing abundance at Bering Sea 
haulouts are poorly understood, but may include changes in prey 
densities near the haulouts, changes in population size, disturbance 
levels, and changing seasonal distributions (Jay and Hills 2005, p. 
198) (presumably mediated by sea-ice coverage or temperature).
    Historically, coastal haulouts along the Arctic (Chukchi Sea) coast 
have been used less consistently during the summer months than those in 
the Bering Sea because of the presence of pack ice (a preferred 
substrate) for much of the year in the Chukchi Sea. Since the mid-
1990s, reductions of summer sea ice coincided with a marked increase in 
the use of coastal haulouts along the Chukchi sea coast of Russia 
during the summer months (Kochnev 2004, pp. 284-288; Kavry et al. 2008, 
pp. 248-251). Large, mixed (composed of various age and sex groups) 
herds of walruses, up to several tens of thousands of animals, began to 
use coastal haulouts on Wrangel Island, Russia in the early 1990s, and 
several coastal haulouts along the northern Chukotka coastline of 
Russia have emerged in recent years, likely as a result of reductions 
in summer sea ice in the Chukchi Sea (Kochnev 2004, pp. 284-288; 
Ovsyanikov et al. 2007, pp. 1-4; Kavry et al. 2008, p. 248-251; Figure 
1 in Garlich-Miller et al. 2011).
    In 2007, 2009, and 2010, walruses were also observed hauling out in 
large numbers with mixed sex and age groups along the Chukchi Sea coast 
of Alaska in late August, September, and October (Thomas et al. 2009, 
p. 1; Service 2010, unpublished data). Monitoring studies conducted in 
association with oil and gas exploration suggest that the use of 
coastal haulouts along the Arctic coast of Alaska during the summer 
months is dependent upon the availability of sea ice. For example, in 
2006 and 2008, walruses foraging off the Chukchi Sea coast of Alaska 
remained with the ice pack over the continental shelf during the months 
of August, September, and October. However in 2007, 2009, and 2010, the 
pack ice retreated beyond the continental shelf and large numbers of 
walruses hauled out on land at several locations between Point Barrow 
and Cape Lisburne, Alaska (Ireland et al. 2009, p. xvi; Thomas et al. 
2009, p. 1; Service 2010, unpublished data; Figure 1 in Garlich-Miller 
et al. 2011).
    Transitory coastal haulouts have also been reported in late fall 
(October-November) along the southern Chukchi Sea coast, coinciding 
with the southern migration. Mixed herds of walruses frequently come to 
shore to rest for a few days to weeks along the coast before continuing 
on their migration to the Bering Sea. Cape Lisburne, Alaska, and Capes 
Serdtse-Kamen' and Dezhnev, Russia, are the most consistently used 
haulouts in the Chukchi Sea at this time of year (Garlich-Miller and 
Jay 2000, pp. 58-67). Large mixed herds of walruses have also been 
reported in late fall and early winter at coastal haulouts in the 
northern Bering Sea at the Punuk Islands and Saint Lawrence Island, 
Alaska; Big Diomede Island, Russia; and King Island, Alaska, prior to 
the formation of sea ice in offshore breeding and feeding areas (Fay 
and Kelly 1980, p. 226; Garlich-Miller and Jay 2000, pp. 58-67; Figure 
1 in Garlich-Miller et al. 2011).
Vital Rates
    Walruses have the lowest rate of reproduction of any pinniped 
species (Fay 1982, pp. 172-209). Although male walruses reach puberty 
at 6-7 years of age, they are unlikely to successfully compete for 
access to females until they reach full body size at 15 years of age or 
older (Fay 1982, p. 33; Fay et al. 1984, p. 96). Female walruses attain 
sexual maturity at 4-7 years of age (Fay 1982, pp. 172-209), and the 
median age of first birth ranges from approximately 8 to 10 years of 
age (Garlich-Miller et al. 2006, pp. 887-893). Because gestation lasts 
15-16 months, it extends through the following breeding season and 
thus, the minimum interval between successful births is 2 years. 
Ovulation may also be suppressed until the calf is weaned, raising the 
birth interval to 3 years or more (Garlich-Miller and Stewart 1999, p. 
188). The age of sexual maturity and birth rates may be density-
dependent (Fay et al. 1989, pp. 1-16; Fay et al. 1997, pp. 537-565; 
Garlich-Miller et al. 2006, pp. 892-893).
    The low birth rate of walruses is offset in part by considerable 
maternal investment in offspring (Fay et al. 1997, p. 550). Assumed 
survival rates through the first year of life range from 0.5 to 0.9 
(Fay et al. 1997, p. 550). Survival rates for juveniles through adults 
(i.e., 4-20 years old) have been assumed to be as high as 0.96 to 0.99 
per cent (DeMaster 1984, p. 78; Fay et al. 1997, p. 544), declining to 
zero by 40 to 45 years (Chivers 1999, p. 240). Using published 
estimates of survival and reproduction, Chivers (1999, pp. 239-247) 
developed an individual age-based model of the Pacific walrus 
population, which yielded a maximum population growth rate of 8 
percent, but cautioned this should not be considered to be an estimate 
of the maximum growth rate (Chivers 1999, p. 239). Thus, the 8 percent 
figure remains theoretical because age-specific survival rates for 
free-ranging walruses are poorly known.
Abundance
    Based on large sustained harvests in the 18th and 19th centuries, 
Fay (1982, p. 241) speculated that the pre-

[[Page 7639]]

exploitation population was represented by a minimum of 200,000 
animals. Since that time, population size is believed to have 
fluctuated in response to varying levels of human exploitation. Large-
scale commercial harvests are believed to have reduced the population 
to 50,000-100,000 animals in the mid-1950s (Fay et al. 1997, p. 539). 
The population apparently increased rapidly in size during the 1960s 
and 1970s in response to harvest regulations that limited the take of 
females (Fay et al. 1989, p. 4). Between 1975 and 1990, visual aerial 
surveys jointly conducted by the United States and Russia at 5-year 
intervals produced population estimates ranging from 201,039 to 
290,000. Efforts to survey the Pacific walrus population were suspended 
by both countries after 1990, due to unresolved problems with survey 
methods that produced population estimates with unknown bias and 
unknown--but presumably large--variances that severely limited their 
utility (Speckman et al. 2010, p. 3).
    In 2006, a joint U.S.-Russian survey was conducted in the pack ice 
of the Bering Sea, using thermal imaging systems to detect walruses 
hauled out on sea ice and satellite transmitters to account for 
walruses in the water (Speckman et al. 2010, p. 4). The number of 
walruses within the surveyed area was estimated at 129,000, with 95-
percent confidence intervals of 55,000 to 507,000 individuals. This is 
a minimum estimate, as weather conditions forced termination of the 
survey before much of the southwest Bering Sea was surveyed; animals 
were observed in that region as the surveyors returned to Anchorage, 
Alaska. Table 1 provides a summary of survey results.

                                            Table 1--Estimates of Pacific Walrus Population Size, 1975-2006.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                          Population size (with range
                  Year                    or confidence interval) \a\                                      Reference
--------------------------------------------------------------------------------------------------------------------------------------------------------
1975...................................                       214,687  (Udevitz et al. 2001, p. 614).
1980...................................               250,000-290,000  (Johnson et al. 1982, p. 3; Fedoseev 1984, p. 58).
1985...................................                       242,366  (Udevitz et al. 2001, p. 614).
1990...................................                       201,039  (Gilbert et al. 1992, p. 28).
2006...................................      129,000 (50,000-500,000)  (Speckman et al. 2010).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\Due to differences in methods, comparisons of estimates across years (population trends) are not possible. Most estimates did not provide a range or
  confidence interval.

    We acknowledge that these survey results suggest to some that the 
walrus population may be declining; however, we do not believe the 
survey methodologies support such a definitive conclusion. Resource 
managers in Russia have concluded that the population has declined, and 
accordingly, have reduced harvest quotas in recent years (Kochnev 2004, 
p. 284; Kochnev 2005, p. 4; Kochnev, 2010, pers. comm.), based in part 
on the lower abundance estimate generated from the 2006 survey results. 
However, past survey results are not directly comparable among years 
due to differences in survey methods, timing of surveys, segments of 
the population surveyed, and incomplete coverage of areas where 
walruses may have been present (Fay et al. 1997, p. 537); thus, these 
results do not provide a basis for determining trends in population 
size (Hills and Gilbert 1994, p. 203; Gilbert 1999, pp. 75-84). Whether 
prior estimates are biased low or high is unknown, because of problems 
with detecting individual animals on ice or land, and in open water, 
and difficulties counting animals in large, dense groups (Speckman et 
al. 2010, p. 33). In addition, no survey has ever been completed within 
a timeframe that could account for the redistribution of individuals 
(leading to double counting or undercounting), or before weather 
conditions either delayed the effort or completely terminated the 
survey before the entire area of potentially occupied habitat had been 
covered (Speckman et al. 2010). Due to these general problems, as well 
as seasonal differences among surveys (fall or spring) and 
technological advancements that correct for some problems, we do not 
believe the survey results provide a reliable basis for estimating a 
population trend.
    Changes in the walrus population have also been investigated by 
examining changes in biological parameters over time. Based on evidence 
of changes in abundance, distributions, condition indices, and life-
history parameters, Fay et al. (1989, pp.1-16) and Fay et al. (1997, 
pp. 537-565) concluded that the Pacific walrus population increased 
greatly in size during the 1960s and 1970s, and postulated that the 
population was approaching, or had exceeded, the carrying capacity of 
its environment by the early 1980s. Harvest increased in the 1980s: 
changes in the size, composition, and productivity of the sampled 
walrus harvest in the Bering Strait Region of Alaska over this time 
frame are consistent with this hypothesis (Garlich-Miller et al. 2006, 
p. 892). Harvest levels declined sharply in the early 1990s, and 
increased reproductive rates and earlier maturation in females 
occurred, suggesting that density-dependent regulatory mechanisms had 
been relaxed and the population was likely below carrying capacity 
(Garlich-Miller et al. 2006, p. 893). However, Garlich-Miller et al. 
(2006, pp. 892-893) also noted that there are no data concerning the 
trend in abundance of the walrus population or the status of its prey 
to verify this hypothesis, and that whether density-dependent changes 
in life-history parameters might have been mediated by changes in 
population abundance or changes in the carrying capacity of the 
environment is unknown.

Summary of Information Pertaining to the Five Factors

    Section 4 of the Act (16 U.S.C. 1533) and implementing regulations 
(50 CFR part 424) set forth the procedures for adding species to, 
removing species from, or reclassifying species on the Federal Lists of 
Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of 
the Act, a species may be determined to be endangered or threatened 
based on any of the following 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.
    In making this 12-month finding, we considered and evaluated the 
best available scientific and commercial information. Information 
pertaining to the Pacific walrus in relation to the five

[[Page 7640]]

factors provided in section 4(a)(1) of the Act is discussed below.
    In considering what factors might constitute threats to a species, 
we must look beyond the exposure of the species to a particular 
stressor to evaluate whether the species may respond to that stressor 
in a way that causes actual impacts to the species. If there is 
exposure to a stressor and the species responds negatively, the 
stressor may be a threat and we attempt to determine how significant a 
threat it is. The threat is significant if it drives, or contributes 
to, the risk of extinction of the species such that the species 
warrants listing as endangered or threatened as those terms are defined 
in the Act. However, the identification of stressors that could impact 
a species negatively may not be sufficient to compel a finding that the 
species warrants listing. The information must include evidence 
sufficient to suggest that these stressors are operative threats that 
act on the species to the point that the species meets the definition 
of endangered or threatened under the Act. Also, because an individual 
stressor may not be a threat by itself, but could be in conjunction 
with one or more other stressors, our process includes considering the 
combined effects of stressors.
    To inform our analysis of threats to the Pacific walrus, we also 
took into consideration the results of two Bayesian network modeling 
efforts; one conducted by the Service (Garlich-Miller et al. 2011), and 
the other conducted by the U.S. Geological Survey (USGS) (Jay et al. 
2010b). Although quantitative, empirical data can be used in Bayesian 
networks, when primarily qualitative data are available, such as for 
the Pacific walrus, the models are well suited to formalizing and 
quantifying the opinions of experts (Marcot et al. 2006, p. 3063). 
Bayesian network models (also known as Bayesian belief networks, 
reflecting the importance of expert opinion) graphically display the 
relevant stressors, the interactions among stressors, and the 
cumulative impact of those stressors as they are integrated through the 
network. In general terms, the network is composed of input variables 
that represent key environmental correlates (e.g., sea-ice loss, 
harvest, shipping) and response variables, (e.g., population status). 
Although we did not rely on the results of the Bayesian models as the 
sole basis for our conclusions in this finding, the models corroborated 
the results of our threats analysis. Results of the models are 
presented in the five-factor analysis below, where pertinent.

Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range

    The following potential stressors that may affect the habitat or 
range of the Pacific walrus are discussed in this section: (1) Loss of 
sea ice due to climate change; and (2) effects on prey species due to 
ocean warming and ocean acidification.
Effects of Global Climate Change on Sea-Ice Habitats
    The Pacific walrus depends on sea ice for several aspects of its 
life history. This section describes recent observations and future 
projections of sea-ice conditions in the Bering and Chukchi Seas 
through the end of the 21st century. Following this presentation on the 
changing ice dynamics, we examine how these changing ice conditions may 
affect the Pacific walrus population.
    The Arctic Ocean is covered primarily by a mix of multi-year sea 
ice, whereas more southerly regions, such as the Bering Sea, are 
seasonal ice zones where first-year ice is renewed every winter. The 
observed and projected effects of global warming vary in different 
parts of the world, and the Arctic and Antarctic regions are 
increasingly recognized as being extremely vulnerable to current and 
projected effects. For several decades, the surface air temperatures in 
the Arctic have warmed at approximately twice the global rate 
(Christensen et al. 2007, p. 904). The observed and projected effects 
of climate change are most extreme during summer in northern high-
latitude regions, in large part due to the ice-albedo (reflective 
property) feedback mechanism, in which melting of snow and sea ice 
lowers surface reflectivity, thereby further increasing surface warming 
from absorption of solar radiation.
    Since 1979 (the beginning of the satellite record of sea-ice 
conditions), there has been an overall reduction in the extent of 
Arctic sea ice (Parkinson et al. 1999, p. 20837; Comiso 2002, p. 1956; 
Stroeve et al. 2005, pp. 1-4; Comiso 2006, pp. 1-3; Meier et al. 2007, 
p. 428; Stroeve et al. 2007, p. 1; Comiso et al. 2008, p. 1; Stroeve et 
al. 2008, p. 13). Although the decline is a year-round trend, far 
greater reductions have been noted in summer sea ice than in winter sea 
ice. For example, from 1979 to 2009, the extent of September sea ice 
seen Arctic wide has declined 11 percent per decade (Polyak et al. 
2010, p. 1797). In recent years, the trend in Arctic sea-ice loss has 
accelerated (Comiso et al. 2008, p. 1). In September 2007, the extent 
of Arctic Ocean sea ice reached a record low, approximately 50 percent 
lower than conditions in the 1950s through the 1970s, and 23 percent 
below the previous record set in 2005 (Stroeve et al. 2008, p. 13). 
Minimum sea-ice extent in 2010 was the third lowest in the satellite 
record, behind 2007 and 2008 (second lowest), and most of this loss 
occurred on the Pacific side of the Arctic Ocean.
    Of long-term significance is the loss of over 40 percent of Arctic 
multi-year sea ice over the last 5 years (Kwok et al. 2009, p. 1). 
Since 2004, there has been a reversal in the volumetric and areal 
contributions between first-year ice and multi-year ice in regards to 
the total volume and area of the Arctic Ocean that they cover, with 
first-year ice now predominating (Kwok et al. 2009, p. 16). Export of 
ice through Fram Strait, together with the decline in multi-year ice 
coverage, suggests that recently there has been near-zero replenishment 
of multi-year ice (Kwok et al. 2009, p. 16). The area of the Arctic 
Ocean covered by ice predominantly older than 5 years decreased by 56 
percent between 1982 and 2007 (Polyak et al. 2010, p. 1759). Within the 
central Arctic Ocean, old ice has declined by 88 percent, and ice that 
is at least 9 years old has essentially disappeared (Markus et al. 
2009, p. 13: Polyak et al. 2010, p. 1759). In addition, from 2005 to 
2008 there was a thinning of 0.6 m (1.9 ft) in multi-year ice 
thickness. It is likely that the rapid decline of sea ice in 2007 was 
in part the result of thinner and lower coverage, of the multi-year ice 
(Comiso et al. 2008, p. 6). It would take many years to restore the ice 
thickness through annual growth, and the loss of multi-year ice makes 
it unlikely that the age and thickness composition of the ice pack will 
return to previous climatological conditions with continued global 
warming. Further loss of sea ice will be a major driver of changes 
across the Arctic over the next decades, especially in late summer and 
autumn (NOAA 2010, p. 77503).
    Due to asymmetric geography of the Arctic and the scale of weather 
patterns, there is considerable regional variability in sea-ice cover 
(Meier et al. 2007, p. 430), and although the early loss of summer sea 
ice and volumetric ice loss in the Arctic applies directly to the 
Chukchi Sea, it cannot be directly extrapolated to the seasonal ice 
zone of the Bering Sea (NOAA 2010, p. 77503). The contrasts between the 
two are dramatic: The Bering Sea is one of the most stable in terms of 
sea ice, especially in the winter, and the Chukchi Sea has had some of 
the most dramatic losses of summer sea ice

[[Page 7641]]

(Meier et al., p. 431). Below, we describe the sea-ice conditions in 
the Bering and Chukchi Seas as they occur presently, as well as recent 
trends and projections for the future.
    In March and April, at maximal sea-ice extent, the Chukchi Sea is 
typically completely frozen, and ice cover in the Bering Sea extends 
southward to a latitude of approximately 58-60 degrees north (Boveng et 
al. 2008, pp. 33-52). The Bering Sea spans the marginal sea-ice zone, 
where ice gives way to water at the southern edge, and around the 
peripheries of persistent polynyas. Sea ice in the Bering Sea is highly 
dynamic and largely a wind-driven system (Sasaki and Minobe 2005, pp. 
1-2). Ice cover is comprised of a variety of first-year ice 
thicknesses, from young, very thin ice to first-year floes that may be 
upwards of 1.0-m (3.3-ft) thick (Burns et al. 1980, p. 100; Zhang et 
al. 2010, p. 1729). Depending on wind patterns, a variable (but 
relatively minor) fraction of ice that drifts south through the Bering 
Strait could be comprised of some thicker ice floes that originated in 
the Chukchi and Beaufort Seas (Kozo et al. 1987, pp. 193-195).
    Ice melt in the Bering Sea usually begins in late April and 
accelerates in May, with the edge of the ice moving northward until it 
passes through the Bering Strait, typically in June. The Bering Sea 
remains ice free for the duration of the summer. Ice continues to 
retreat northward through the Chukchi Sea until September, when minimal 
sea-ice extent is reached.
    Freeze-up begins in October, with the ice edge progressing 
southward across the Chukchi Sea. The ice edge usually reaches the 
Bering Strait in November and advances through the Strait in December. 
The ice edge continues to move southward across the Bering Sea until 
its maximal extent is reached in March. There is considerable year-to-
year variation in the timing and extent of ice retreat and formation 
(Boveng et al. 2008, p. 37; Douglas 2010, p. 19).
    Within various regions of the Arctic, there is substantial 
variation in the monthly trends of sea ice (Meier et al. 2007, p. 431). 
In the Bering Sea, statistically significant monthly reductions in the 
extent of sea ice over the period 1979-2005 were documented for March 
(-4.8 percent), October (-42.9 percent), and November (-20.3 percent), 
although the overall annual decline (-1.9 percent) is not statistically 
significant (Meier et al. 2007, p. 431). The Bering Sea declines were 
greatest in October and November, the period of early freeze-up. In the 
Chukchi Sea, statistically significant monthly reductions were also 
documented for 1979 to 2005 for May (-0.19 percent), June (-4.3 
percent), July (-6.7 percent), August (-15.4 percent), September (-26.3 
percent), October (-18.6 percent), and November (-8.0 percent): The 
overall annual reduction (-4.9 percent) is statistically significant 
(Meier et al. 2007, p. 431). In essence, the Chukchi Sea has shown 
declines in all months when it is not completely ice-covered, with 
greatest declines in months of maximal melt and early freeze-up 
(August, September, and October).
    During the period 1979-2006, the September sea-ice extent in the 
Chukchi Sea decreased by 26 percent per decade (Douglas 2010, p. 2). In 
recent years, sea ice typically has retreated from continental shelf 
regions of the Chukchi Sea in August or September, with open water 
conditions persisting over much of the continental shelf through late 
October. In contrast, during the preceding 20 years (1979-1998), broken 
sea-ice habitat persisted over continental shelf areas of the Chukchi 
Sea through the entire summer (Jay and Fischbach 2008, p. 1).
    From 1979 to 2007, there was a general trend toward earlier onset 
of ice melt and later onset of freeze-up in 9 of 10 Arctic regions 
analyzed by Markus et al. (2009, pp. 1-14), the exception being the Sea 
of Okhotsk. For the entire Arctic, the melt season length has increased 
by about 20 days over the last 30 years, due to the combined earlier 
melt and later freeze-up. The largest increases, of over 10 days per 
decade, have been seen for Hudson Bay, the East Greenland Sea, and the 
Laptev/East Siberian Seas. From 1979 to 2007, there was a general trend 
toward earlier onset of ice melt and later onset of freeze-up in both 
the Bering and Chukchi Seas: For the Bering Sea, the onset of ice melt 
occurred 1.0 day earlier per decade, while in the Chukchi/Beaufort Seas 
ice melt occurred 3.5 days earlier per decade. The onset of freeze-up 
in the Bering Sea occurred 1.0 day later per decade, while freeze-up in 
the Chukchi/Beaufort Seas occurred 6.9 days later per decade (Markus et 
al. 2009, p. 11).
    Later freeze-up in the Arctic does not necessarily mean that less 
seasonal sea ice forms by winter's end in the peripheral seas, such as 
the Bering and Chukchi Seas (Boveng et al. 2008, p. 35). For example, 
in 2007 (the year when the record minimal Arctic summer sea-ice extent 
was recorded), the Chukchi Sea did not freeze until early December and 
the Bering Sea remained largely ice-free until the middle of December 
(Boveng et al. 2008, p. 35). However, rapid cooling and advancing of 
sea ice in late December and early January resulted in most of the 
eastern Bering Sea shelf being ice-covered by mid-January, an advance 
of 900 km (559 mi), or 30 km per day (19 mi per day). Maximum ice 
extent occurred in late March, with ice covering much of the shelf, 
resulting in a near record maximum ice extent. Ice then slowly 
retreated, and the Bering Sea was not ice-free until almost July. 
Therefore, winter ice conditions are not necessarily related to the 
summer-fall ice conditions of the previous year.
Model Projections of Future Sea Ice
    The analysis and synthesis of information presented by the 
Intergovernmental Panel on Climate Change (IPCC) in its Fourth 
Assessment Report (AR4) in 2007 represents the scientific consensus 
view on the causes and future of climate change. The IPCC AR4 used 
state-of-the-art Atmosphere-Ocean General Circulation Models (GCMs) and 
a range of possible future greenhouse gas (GHG) emission scenarios to 
project plausible outcomes globally and regionally, including 
projections of temperature and Arctic sea-ice conditions through the 
21st century.
    The GCMs use the laws of physics to simulate the main components of 
the climate system (the atmosphere, ocean, land surface, and sea ice) 
and to make projections as to the response of these components to 
future emissions of GHGs. The IPCC used simulations from about 2 dozen 
GCMs developed by 17 international modeling centers as the basis for 
the AR4 (Randall et al. 2007, pp. 596-599). The GCM results are 
archived as part of the Coupled Model Intercomparison Project-Phase 3 
(CMIP3) at the Program for Climate Model Diagnosis and Intercomparison 
(PCMDI). The CMIP3 GCMs provide projections of future effects that 
could result from climate change, because they are built on well-known 
dynamical and physical principles, and they plausibly simulate many 
large-scale aspects of present-day conditions. However, the coarse 
resolution of most current climate models dictates careful application 
on smaller spatial scales in heterogeneous regions.
    The IPCC AR4 used six ``marker'' scenarios from the Special Report 
on Emissions Scenarios (SRES) (Carter et al. 2007, p. 160) to develop 
climate projections spanning a broad range of GHG emissions through the 
end of the 21st century under clearly stated assumptions about 
socioeconomic factors that could influence the emissions. The six 
``marker'' scenarios are classified according to their emissions as 
``high'' (A1F1, A2),

[[Page 7642]]

``medium'' (A1B and B2) and ``low'' (A1T, B1). The SRES made no 
judgment as to which of the scenarios were more likely to occur, and 
the scenarios were not assigned probabilities of occurrence (Carter et 
al. 2007, p. 160). The IPCC focused on three of the marker scenarios--
B1, A1B, and A2--for its synthesis of the climate modeling efforts, 
because they represented ``low,'' ``medium,'' and ``high,'' scenarios; 
this choice stemmed from the constraints of available computer 
resources that precluded realizations of all six scenarios by all 
modeling centers (Meehl et al. 2007, p. 753). With regard to these 
three emissions scenarios, the IPCC Working Group I report noted: 
``Qualitative conclusions derived from these three scenarios are in 
most cases also valid for other SRES scenarios'' (Meehl et al. 2007, p. 
761). It is important to note that the SRES scenarios do not contain 
additional climate initiatives (e.g., implementation of the United 
Nations Framework Convention on Climate Change or the emissions targets 
of the Kyoto Protocol) beyond current mitigation policies (IPCC 2007, 
p. 22). The SRES scenarios do, however, have built-in emissions 
reductions that are substantial, based on assumptions that a certain 
amount of technological change and reduction of emissions would occur 
in the absence of climate policies; recent analysis shows that two-
thirds or more of all the energy efficiency improvements and 
decarbonization of energy supply needed to stabilize GHGs is built into 
the IPCC reference scenarios (Pielke et al. 2008, p. 531).
    There are three main contributors to divergence in GCM climate 
projections: Large natural variations, across-model differences, and 
the range-in-emissions scenarios (Hawkins and Sutton 2009, p. 1096). 
The first of these, variability from natural variation, can be 
incorporated by averaging the projections over decades, or, preferably, 
by forming ensemble averages from several runs of the same model.
    The second source of variation is model to model differences in the 
way that physical processes are incorporated into the various GCMs. 
Because of these differences, projections of future climate conditions 
depend, to a certain extent, on the choice of GCMs used. Uncertainty in 
the amount of warming out to mid-century is primarily a function of 
these model-to-model differences. The most common approach to address 
the uncertainty and biases inherent in individual models is to use the 
median or mean outcome of several predictive models (a multi-model 
ensemble) for inference. Excluding models that poorly simulate 
observational data is also a common approach to reducing the spread of 
uncertainty among projections from multi-model ensembles.
    The third source of variation arises from the range in plausible 
GHG emissions scenarios. Conditions such as surface air temperature and 
sea-ice area are linked in the IPCC climate models to GHG emissions by 
the physics of radiation processes. When CO2 is added to the 
atmosphere, it has a long residence time and is only slowly removed by 
ocean absorption and other processes. Based on IPCC AR4 climate models, 
expected global warming--defined as the change in global mean surface 
air temperature (SAT)--by the year 2