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The proposed rule, maps, status review report and other materials relating to this proposal can be found on the Alaska Region Web site at:
On March 28, 2008, we initiated status reviews of bearded, ringed (
After reviewing the petition, the literature cited in the petition, and other literature and information available in our files, we found (73 FR 51615; September 4, 2008) that the petition met the requirements of the regulations under 50 CFR 424.14(b)(2), and we determined that the petition presented substantial information indicating that the petitioned action may be warranted. Accordingly, we proceeded with the status reviews of bearded, ringed, and spotted seals and solicited information pertaining to them.
On September 8, 2009, the Center for Biological Diversity filed a lawsuit in the U.S. District Court for the District of Columbia alleging that we failed to make the requisite 12-month finding on its petition to list the three seal species. Subsequently, the Court entered a consent decree under which we agreed to finalize the status review of the bearded seal (and the ringed seal) and submit this 12-month finding to the Office of the Federal Register by December 3, 2010. Our 12-month petition finding for ringed seals is published as a separate notice concurrently with this finding. Spotted seals were also addressed in a separate
The status review report of the bearded seal is a compilation of the best scientific and commercial data available concerning the status of the species, including the past, present, and future threats to this species. The Biological Review Team (BRT) that prepared this report was composed of eight marine mammal biologists, a fishery biologist, a marine chemist, and a climate scientist from NMFS' Alaska and Northeast Fisheries Science Centers, NOAA's Pacific Marine Environmental Lab, and the U.S. Fish and Wildlife Service (USFWS). The status review report underwent independent peer review by five scientists with expertise in bearded
There are two key tasks associated with conducting an ESA status review. The first is to delineate the taxonomic group under consideration; and the second is to conduct an extinction risk assessment to determine whether the petitioned species is threatened or endangered.
To be considered for listing under the ESA, a group of organisms must constitute a “species,” which section 3(16) of the ESA defines as “any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature.” The term “distinct population segment” (DPS) is not commonly used in scientific discourse, so the USFWS and NMFS developed the “Policy Regarding the Recognition of Distinct Vertebrate Population Segments Under the Endangered Species Act” to provide a consistent interpretation of this term for the purposes of listing, delisting, and reclassifying vertebrates under the ESA (61 FR 4722; February 7, 1996). We describe and use this policy below to guide our determination of whether any population segments of this species meet the DPS criteria of the DPS policy.
The ESA defines the term “endangered species” as “any species which is in danger of extinction throughout all or a significant portion of its range.” The term “threatened species” is defined as “any species which is likely to become endangered within the foreseeable future throughout all or a significant portion of its range.” The foreseeability of a species' future status is case specific and depends upon both the foreseeability of threats to the species and foreseeability of the species' response to those threats. When a species is exposed to a variety of threats, each threat may be foreseeable in a different timeframe. For example, threats stemming from well-established, observed trends in a global physical process may be foreseeable on a much longer time horizon than a threat stemming from a potential, though unpredictable, episodic process such as an outbreak of disease that may never have been observed to occur in the species.
In the 2008 status review of the ribbon seal (Boveng
Since that time, NMFS scientists have revised their analytical approach to the foreseeability of threats and responses to those threats, adopting a more threat-specific approach based on the best scientific and commercial data available for each respective threat. For example, because the climate projections in the Intergovernmental Panel on Climate Change's (IPCC's)
A thorough review of the taxonomy, life history, and ecology of the bearded seal is presented in the status review report (Cameron
Bearded seals have a circumpolar distribution south of 85° N. latitude, extending south into the southern Bering Sea in the Pacific and into Hudson Bay and southern Labrador in the Atlantic. Bearded seals also occur in the Sea of Okhotsk south to the northern Sea of Japan (Figure 1). Two subspecies of bearded seals are widely recognized:
Although the validity of the division into subspecies has been questioned (Kosygin and Potelov, 1971), the BRT concluded, and we concur, that the evidence discussed in the status review report for retaining the two subspecies is stronger than any evidence for combining them. The BRT defined geographic boundaries for the divisions between the two subspecies, subject to the strong caveat that distinct boundaries do not appear to exist in the actual populations; and therefore, there is considerable uncertainty about the best locations for the boundaries. The BRT defined 112° W. longitude (
Bearded seals primarily feed on benthic organisms that are more numerous in shallow water where light can reach the sea floor. As such, the bearded seal's effective range is generally restricted to areas where seasonal sea ice occurs over relatively shallow waters, typically less than 200 m in depth (see additional discussion below).
Bearded seals are closely associated with sea ice, particularly during the critical life history periods related to reproduction and molting, and they can be found in a broad range of different ice types. Sea ice provides the bearded seal and its young some protection from predators during the critical life history periods of whelping and nursing. It also allows molting bearded seals a dry platform to raise skin temperature and facilitate epidermal growth, and is important throughout the year as a platform for resting and perhaps thermoregulation. Of the ice-associated seals in the Arctic, bearded seals seem to be the least particular about the type and quality of ice on which they are observed. Bearded seals generally prefer
Being so closely associated with sea ice, particularly pack ice, the seasonal movements and distribution of bearded seals are linked to seasonal changes in ice conditions. To remain associated with their preferred ice habitat, bearded seals generally move north in late-spring and summer as the ice melts and retreats, and then move south in the fall as sea ice forms.
The region that includes the Bering and Chukchi Seas is the largest area of continuous habitat for bearded seals. The Bering-Chukchi Platform is a shallow intercontinental shelf that encompasses about half of the Bering Sea, spans the Bering Strait, and covers nearly all of the Chukchi Sea. Bearded seals can reach the bottom everywhere along the shallow shelf, and so it provides them favorable foraging habitat. The Bering and Chukchi Seas are generally covered by sea ice in late winter and spring, and are mostly ice free in late summer and fall. As the ice retreats in the spring most adult bearded seals in the Bering Sea are thought to move north through the Bering Strait, where they spend the summer and early fall at the southern edge of the Chukchi and Beaufort Sea pack ice and at the wide, fragmented margin of multi-year ice. A smaller number of bearded seals, mostly juveniles, remain near the coasts of the Bering and Chukchi Seas for the summer and early fall. As the ice forms again in the fall and winter, most seals move south with the advancing ice edge through Bering Strait and into the Bering Sea where they spend the winter.
There are fewer accounts of the seasonal movements of bearded seals in other areas. Compared to the dramatic long range seasonal movements of bearded seals in the Chukchi and Bering Seas, bearded seals are considered to be relatively sedentary over much of the rest of their range, undertaking more local movements in response to ice conditions. These differences may simply be the result of the general persistence of ice over shallow waters in the High Arctic. In the Sea of Okhotsk, bearded seals remain in broken ice as the sea ice expands and retreats, inhabiting the southern pack ice edge beyond the fast ice in winter and moving north toward shore in spring and summer. In the White, Barents, and Kara Seas, bearded seals also conduct seasonal migrations following the ice edge, as may bearded seals in Baffin Bay. Excluded by shorefast ice from much of the Canadian Arctic Archipelago during winter, bearded seals are scattered throughout many of the inlets and fjords of this region from July to October, though at least in some years, a portion of the population is known to overwinter in a few isolated open water areas north of Baffin Bay.
Throughout most of their range, adult bearded seals are seldom found on land. However, some adults in the Sea of Okhotsk, and more rarely in a few other regions, use haul-out sites ashore in late summer and early autumn until ice floes begin to appear at the coast. This is most common in the western Sea of Okhotsk and along the coasts of western Kamchatka where bearded seals form numerous shore rookeries that can have tens to hundreds of individuals each.
In general, female and male bearded seals attain sexual maturity around ages 5-6 and 6-7, respectively. Adult female bearded seals ovulate after lactation, and are presumably then receptive to males. Mating is believed to usually take place at the surface of the water, but it is unknown if it also occurs underwater or on land or ice, as observed in some other phocids. The social dynamics of mating in bearded seals are not well known; however, theories regarding their mating system have centered around serial monogamy and promiscuity, and on the nature of competition among breeding males to attract and gain access to females. Bearded seals vocalize during the breeding season, with a peak in calling during and after pup rearing. Male vocalizations are believed to advertise mate quality to females, signal competing males of a claim on a female, or proclaim a territory.
During the winter and spring, as sea ice begins to break up, perinatal females find broken pack ice over shallow areas on which to whelp, nurse young, and molt. A suitable ice platform is likely a prerequisite to whelping, nursing, and rearing young (Heptner
Females bear a single pup that averages 33.6 kg in mass and 131.3 cm in length. Pups begin shedding their natal (lanugo) coats in utero, and they are born with a layer of subcutaneous fat. These characteristics are thought to be adaptations to entering the water soon after birth as a means of avoiding predation.
Females with pups are generally solitary, tending not to aggregate. Pups enter the water immediately after or within hours of birth. Pups nurse on the ice, and by the time they are a few days old they spend half their time in the water. Recent studies using recorders and telemetry on pups have reported a lactation period of about 24 days, a transition to diving and more efficient swimming, mother-guided movements of greater than 10 km, and foraging while still under maternal care.
Detailed studies on bearded seal mothers show they forage extensively, diving shallowly (less than 10 m), and spending only about 10 percent of their time hauled out with pups and the remainder nearby at the surface or diving. Despite the relative independence of mothers and pups, their bond is described as strong, with females being unusually tolerant of threats in order to remain or reunite with pups. A mixture of crustaceans and milk in the stomachs of pups indicates that independent foraging occurs prior to weaning, at least in some areas.
Adult and juvenile bearded seals molt annually, a process that in mature phocid seals typically begins shortly after mating. Bearded seals haul out of the water more frequently during molting, a behavior that facilitates higher skin temperatures and may accelerate shedding and regrowth of hair and epidermis. Though not studied in bearded seals, molting has been described as diffuse, with individuals potentially shedding hair throughout the year but with a pulse in the spring and summer. This is reflected in the wide range of estimates for the timing of molting, though these estimates are also based on irregular observations.
The need for a platform on which to haul out and molt from late spring to mid-summer, when sea ice is rapidly melting and retreating, may necessitate movement for bearded seals between
Bearded seals are considered to be foraging generalists because they have a diverse diet with a large variety of prey items throughout their circumpolar range. Bearded seals feed primarily on a variety of invertebrates and some fishes found on or near the sea bottom. They are also able to switch their diet to include schooling pelagic fishes when advantageous. The bulk of the diet appears to consist of relatively few prey types, primarily bivalve mollusks and crustaceans like crabs and shrimps. However, fishes like sculpins, Arctic cod (
The BRT reviewed the best scientific and commercial data available on the bearded seal's taxonomy and concluded that there are two widely recognized subspecies of bearded seals:
Under our DPS policy (61 FR 4722; February 7, 1996) two elements are considered when evaluating whether a population segment qualifies as a DPS under the ESA: (1) The discreteness of the population segment in relation to the remainder of the species or subspecies to which it belongs; and (2) the significance of the population segment to the species or subspecies to which it belongs.
A population segment of a vertebrate species may be considered discrete if it satisfies either one of the following conditions: (1) It is markedly separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors. Quantitative measures of genetic or morphological discontinuity may provide evidence of this separation; or (2) it is delimited by international governmental boundaries within which differences in control of exploitation, management of habitat, conservation status, or regulatory mechanisms exist that are significant in light of section 4(a)(1)(D) of the ESA.
If a population segment is considered to be discrete under one or both of the above conditions, its biological and ecological significance to the taxon to which it belongs is evaluated in light of the ESA's legislative history indicating that the authority to list DPSs be used “sparingly,” while encouraging the conservation of genetic diversity (see Senate Report 151, 96th Congress, 1st Session). This consideration may include, but is not limited to, the following: (1) Persistence of the discrete population segment in an ecological setting unusual or unique for the taxon; (2) evidence that loss of the discrete population segment would result in a significant gap in the range of the taxon; (3) evidence that the discrete population segment represents the only surviving natural occurrence of a taxon that may be more abundant elsewhere as an introduced population outside its historic range; or (4) evidence that the discrete population segment differs markedly from other populations of the species in its genetic characteristics.
If a population segment is discrete and significant (
The range of the bearded seal occurs in cold, seasonally or annually ice-covered Arctic and subarctic waters, without persistent intrusions of warm water or other conditions that would pose potential physiological barriers. Furthermore, the seasonal timings of reproduction and molting vary little throughout the bearded seal's distribution, suggesting that there are no obvious ecological separation factors.
The underwater vocalizations of males during the breeding season recorded in Alaskan, Canadian, and Norwegian waters are often more similar between adjacent geographical regions than between more distant sites, suggesting that bearded seals may have strong fidelity to specific breeding sites. However, these observed differences in vocalizations may be due to other factors such as ecological influences or sexual selection, and not to distance or geographic barriers. Bearded seals are known to make seasonal movements of greater than 1,000 km, and so only very large geographical barriers would have the potential by themselves to maintain discreteness between breeding concentrations. As primarily benthic feeders, bearded seals may be constrained to relatively shallow waters and so expanses of deep water may also pose barriers to movement.
Kosygin and Potelov (1971) conducted a study of craniometric and morphological differences between bearded seals in the White, Barents, and Kara Seas, and bearded seals in the Bering Sea and Sea of Okhotsk. They reported differences in measurements between the three regions, although they suggested that the differences were not significant enough to justify dividing the population into subspecies. Fedoseev (1973, 2000) also suggested that differences in the numbers of lip vibrissae as well as length and weight indicate population structure between the Bering and Okhotsk Seas. Thus, under the first factor for determining discreteness, the BRT concluded, and we concur, that the available evidence indicates the discreteness of two population segments: (1) The Sea of Okhotsk, and (2) the remainder of the range of
The core range of the bearded seal includes the waters of five countries (Russia, United States, Canada, Greenland, and Norway) with management regimes sufficiently similar that considerations of cross-boundary management and regulatory mechanisms do not support a positive discreteness determination. In addition, in all countries in the range of
Having concluded that
Throughout most of their range, adult bearded seals are rarely found on land (Kovacs, 2002). However, some adults in the Sea of Okhotsk, and more rarely in Hudson Bay (COSEWIC, 2007), the White, Laptev, Bering, Chukchi, and Beaufort Seas (Heptner
The Sea of Okhotsk covers a vast area and is home to many thousands of bearded seals. Similarly, the range of the Beringia population segment includes a vast area that provides habitat for many thousands of bearded seals. Loss of either segment of the subspecies' range would result in a substantially large gap in the overall range of the subspecies.
The existence of bearded seals in the unusual or unique ecological setting found in the Sea of Okhotsk, as well as the fact that loss of either the Okhotsk or Beringia segment would result in a significant gap in the range of the taxon, support our conclusion that the Beringia and Okhotsk population segments of
In summary, the Beringia and Okhotsk population segments of
No accurate worldwide abundance estimates exist for bearded seals. Several factors make it difficult to accurately assess the bearded seal's abundance and trends. The remoteness and dynamic nature of their sea ice habitat, time spent below the surface and their broad distribution and seasonal movements make surveying bearded seals expensive and logistically challenging. Additionally, the species' range crosses political boundaries, and there has been limited international cooperation to conduct range-wide surveys. Details of survey methods and data are often limited or have not been published, making it difficult to judge the reliability of the reported numbers. Logistical challenges also make it difficult to collect the necessary behavioral data to make proper adjustments to seal counts. Until very recently, no suitable behavioral data have been available to correct for the proportion of seals in the water at the time of surveys. Research is just beginning to address these limitations, and so current and accurate abundance estimates are not yet available. We make estimates based on the best scientific and commercial data available, combining recent and historical data.
Data analyzed from aerial surveys conducted in April and May 2007 produced an abundance estimate of 63,200 bearded seals in an area of 81,600 sq km in the eastern Bering Sea (Ver Hoef
Aerial surveys flown along the coast from Shishmaref to Barrow during May-June 1999 and 2000 provided average annual bearded seal density estimates. A crude abundance estimate based on these densities, and without any correction for seals in the water, is 13,600 bearded seals. These surveys covered only a portion (U.S. coastal) of the Chukchi Sea. Assuming that the waters along the Chukchi Peninsula on the Russian side of the Chukchi Sea contain similar numbers of bearded seals, the combined total would be about 27,000 individuals.
Aerial surveys of the eastern Beaufort Sea conducted in June during 1974-1979, provided estimates that averaged 2,100 bearded seals, uncorrected for seals in the water. The ice-covered continental shelf of the western Beaufort Sea is roughly half the area surveyed, suggesting a crude estimate for the entire Beaufort Sea in June of about 3,150, uncorrected for seals in the water. For such a large area in which the subsistence use of bearded seals is important to Alaska Native and Inuvialuit communities, this number is likely to be a substantial underestimate. A possible explanation is that many of the subsistence harvests of bearded seals in this region may occur after a rapid seasonal influx of seals from the Bering and Chukchi Seas in the early summer, later than the period in which the surveys were flown.
In the East Siberian Sea, Obukhov (1974) described bearded seals as rare, but present during July-September, based on year-round observations (1959-1965) of a region extending about 350 km east from the mouth of the Kolyma River. Typically, one bearded seal was seen during 200-250 km of travel. Geller (1957) described the zone between the Kola Peninsula and Chukotka as comparatively poor in marine mammals relative to the more western and eastern portions of the northern Russian coasts. We are not aware of any other information about bearded seal abundance in the East Siberian Sea.
Although the present population size of the Beringia DPS is very uncertain, based on these reported abundance estimates, the current population size is estimated at 155,000 individuals.
Fedoseev (2000) presented multiple years of unpublished seal survey data from 1968 to 1990; however, specific methodologies were not provided for any of the surveys or analyses. Most of these surveys were designed primarily for ringed and ribbon seals, as they were more abundant and of higher commercial value. Recognizing the sparse documentation of the survey methods and data, as well as the 20 years or more that have elapsed since the last survey, the BRT recommends considering the 1990 estimate of 95,000 individuals to be the current estimated population size of the Okhotsk DPS.
Cleator (1996) suggested that a minimum of 190,000 bearded seals inhabit Canadian waters based on summing the different available indices for bearded seal abundance. The BRT recommends considering the current bearded seal population in Hudson Bay, the Canadian Archipelago, and western Baffin Bay to be 188,000 individuals. This value was chosen based on the estimate for Canadian waters of 190,000, minus 2,000 to account for the average number estimated to occur in the Canadian portion of the Beaufort Sea (which is part of the
Section 4(a)(1) of the ESA and the listing regulations (50 CFR part 424) set forth procedures for listing species. We must determine, through the regulatory process, if a species is endangered or threatened because of any one or a combination of the following factors: (1) The present or threatened destruction, modification, or curtailment of its habitat or range; (2) overutilization for commercial, recreational, scientific, or educational purposes; (3) disease or predation; (4) inadequacy of existing regulatory mechanisms; or (5) other natural or human-made factors affecting its continued existence. These factors are discussed below, with the Beringia DPS, the Okhotsk DPS, and
The main concern about the conservation status of bearded seals stems from the likelihood that their sea ice habitat has been modified by the warming climate and, more so, that the scientific consensus projections are for continued and perhaps accelerated warming in the foreseeable future. A second concern, related by the common driver of carbon dioxide (CO
The threats (analyzed below) associated with impacts of the warming climate on the habitat of bearded seals, to the extent that they may pose risks to these seals, are expected to manifest throughout the current breeding and molting range (for sea ice related threats) or throughout the entire range (for ocean warming and acidification) of each of the population units, since the spatial resolution of data pertaining to these threats is currently limited.
Sea ice in the Northern Hemisphere can be divided into first-year sea ice that formed in the most recent autumn-winter period, and multi-year sea ice that has survived at least one summer melt season. The Arctic Ocean is covered by a mix of multi-year sea ice. More southerly regions, such as the Bering Sea, Barents Sea, Baffin Bay, Hudson Bay, and the Sea of Okhotsk are known as seasonal ice zones, where first year sea ice is renewed every winter. Both the observed and the projected effects of a warming global climate are most extreme in northern high-latitude regions, in large part due to the ice-albedo feedback mechanism in which melting of snow and sea ice lowers reflectivity and thereby further increases surface warming by absorption of solar radiation.
Sea ice extent at the end of summer (September) 2007 in the Arctic Ocean was a record low (4.3 million sq km), nearly 40 percent below the long-term average and 23 percent below the previous record set in 2005 (5.6 million sq km) (Stroeve
Sea ice and other climatic conditions that influence bearded seal habitats are quite different between the Arctic and seasonal ice zones. In the Arctic, sea ice loss is a summer feature with a delay in freeze up occurring into the following fall. Sea ice persists in the Arctic from late fall through mid-summer due to cold and dark winter conditions. Sea ice variability is primarily determined by radiation and melting processes during the summer season. In contrast, the seasonal ice zones are free of sea ice during summer. The variability in extent, thickness, and other sea ice characteristics important to marine mammals is determined primarily by changes in the number, intensity, and track of winter and spring storms in the sub-Arctic. Although there are connections between sea ice conditions in the Arctic and the seasonal ice zones, the early loss of summer sea ice in the Arctic cannot be extrapolated to the seasonal ice zones, which are behaving differently than the Arctic. For example, the Bering Sea has had 4 years of colder than normal winter and spring conditions from 2007 to 2010, with near record sea ice extents, rivaling the sea ice maximum in the mid-1970s, despite record retreats in summer.
The analysis and synthesis of information presented by the IPCC in its
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 CO
Comprehensive Atmosphere-Ocean General Circulation Models (AOGCMs) are the major objective tools that scientists use to understand the complex interaction of processes that determine future climate change. The IPCC used the simulations from about two dozen AOGCMs developed by 17 international modeling centers as the basis for the AR4 (IPCC, 2007). The AOGCM 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 AOGCMs provide reliable projections, because they are built on well-known dynamical and physical principles, and they simulate quite well many large scale aspects of present-day conditions. However, the coarse resolution of most current climate models dictates careful application on small scales in heterogeneous regions.
There are three main contributors to divergence in AOGCM climate projections: Large natural variations, the range in emissions scenarios, and across-model differences. 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 arises from the range in plausible emissions scenarios. As discussed above, the impacts of the scenarios are rather similar before mid-21st century. For the second half of the 21st century, however, and especially by 2100, the choice of the emission scenario becomes the major source of variation among climate projections and dominates over natural variability and model-to-model differences (IPCC, 2007). Because the current consensus is to treat all SRES emissions scenarios as equally likely, one option for representing the full range of variability in potential outcomes would be to project from any model under all of the six “marker” scenarios. This can be impractical in many situations, so the typical procedure for projecting impacts is to use an intermediate scenario, such as A1B or B2 to predict trends, or one intermediate and one extreme scenario (
There is no universal method for combining AOGCMs for climate projections, and there is no one best model. The approach taken by the BRT for selecting the models used to project future sea ice conditions is summarized below.
NMFS scientists have recognized that the physical basis for some of the primary threats faced by the species had been projected, under certain assumptions, through the end of the 21st century, and that these projections currently form the most widely accepted version of the best available data about future conditions. In our risk assessment for bearded seals, we therefore considered the full 21st century projections to analyze the threats stemming from climate change.
The CMIP3 (IPCC) model simulations used in the BRT analyses were obtained from PCMDI on-line (PCMDI, 2010). The
Climate models generally perform better on continental or larger scales, but because habitat changes are not uniform throughout the hemisphere, the six IPCC models used to project sea ice conditions in the Northern Hemisphere were further evaluated independently on their performance at reproducing the magnitude of the observed seasonal cycle of sea ice extent in 12 different regions throughout the bearded seal's range, including five regions for the Beringia DPS, one region for the Okhotsk DPS, and six regions for
While our inferences about future regional ice conditions are based upon the best available scientific and commercial data, we recognize that there are uncertainties associated with predictions based on hemispheric projections or indirect means. We also note that judging the timing of onset of potential impacts to bearded seals is complicated by the coarse resolution of the IPCC models.
Projections of Northern Hemisphere sea ice extent for November indicate a major delay in fall freeze-up by 2050 north of Alaska and in the Barents Sea. By 2090, the average sea ice concentration is below 50 percent in the Russian Arctic and some models show a nearly ice free Arctic, except for the region of the Canadian Arctic Archipelago. In March and April, winter type conditions persist out to 2090. There is some reduction of sea ice by 2050 in the outer portions of the seasonal ice zones, but the sea ice south of Bering Strait, eastern Barents Sea, Baffin Bay, and the Kara and Laptev Seas remains substantial. May shows diminishing sea ice cover at 2050 and 2090 in the Barents and Bering Seas and Sea of Okhotsk. The month of June begins to show substantial changes as the century progresses. Current conditions occasionally exhibit a lack of sea ice near the Bering Strait by June. By 2050, however, this sea ice loss becomes a major feature, with open water continuing along the northern Alaskan coast in most models. Open water in June spreads to the East Siberian Shelf by 2090. The eastern Barents Sea experiences a reduction in sea ice between 2030 and 2050. The models indicate that sea ice in Baffin Bay will be affected very little until the end of the century.
In July, the Arctic Ocean shows a marked effect of global warming, with the sea ice retreating to a central core as the century progresses. The loss of multi-year sea ice over the last 5 years has provided independent evidence for this conclusion. By 2050, the continental shelves of the Beaufort, Chukchi, and East Siberian Seas are nearly ice free in July, with ice concentrations less than 20 percent in the ensemble mean projections. The Kara and Laptev Seas also show a reduction of sea ice in coastal regions by mid-century in most but not all models. The Canadian Arctic Archipelago and the adjacent Arctic Ocean north of Canada and Greenland, however, are predicted to become a refuge for sea ice through the end of the century. This conclusion is supported by typical Arctic wind patterns, which tend to blow onshore in this region. Indeed, this refuge region is why sea ice scientists use the phrase: A nearly sea ice free summer Arctic by mid-century.
In order to feed on the seafloor, bearded seals are known to nearly always occupy shallow waters (Fedoseev, 2000; Kovacs, 2002). The preferred depth range is often described as less than 200 m (Kosygin, 1971; Heptner
An assessment of the risks to bearded seals posed by climate change must consider the species' life-history functions, how they are linked with sea ice, and how altering that link will affect the vital rates of reproduction and survival. The main functions of sea ice relating to the species' life-history are: (1) A dry and stable platform for whelping and nursing of pups in April and May (Kovacs
Bearded seal mothers feed throughout the lactation period, continuously replenishing fat reserves lost while nursing pups (Holsvik, 1998; Krafft
For any of these life history events, a greater tendency of bearded seals to aggregate while hauled out on land or in reduced ice could increase intra- and inter-specific competition for resources, the potential for disease transmission, and predation; all of which could affect annual survival rates. In particular, a reduction in suitable sea ice habitat would likely increase the overlap in the distribution of bearded seals and walrus (
For a long-lived and abundant animal with a large range, the mechanisms identified above (
Potential mechanisms for resilience on relatively short time scales include adjustments to the timing of breeding in response to shorter periods of ice cover, and adjustments of the breeding range in response to reduced ice extent. The extent to which bearded seals might adapt to more frequent years with early ice melt by shifting the timing of reproduction is uncertain. There are many examples of shifts in timing of reproduction by pinnipeds and terrestrial mammals in response to body condition and food availability. In most of these cases, sub-optimal conditions led to reproduction later in the season, a response that would not likely be beneficial to bearded seals. A shift to an earlier melt date may, however, over the longer term provide selection pressure for an evolutionary response over many generations toward earlier reproduction.
It is impossible to predict whether bearded seals would be more likely to occupy ice habitats over the deep waters of the Arctic Ocean basin or more terrestrial habitats if sea ice fai