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Polar bears (Ursus maritimus) require the relative warmth and stability afforded by snow dens for successful reproduction. Pregnant bears must travel from foraging habitats on the sea ice to land in autumn to establish winter dens. Data of sea ice extent and composition from satellite-acquired passive microwave (PMW) imagery show a reduction in summer sea ice extent throughout the Arctic from 1979-2006. Additionally, General Circulation Models (GCM) predict that Arctic sea ice extent will continue to diminish throughout the 21st century. Greater energetic demands will be placed on pregnant polar bears in the future if they travel greater distances from summer forage habitats to traditional denning habitats on land....
Categories: Publication; Types: Citation; Tags: Administrative Report
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This is a demographic analysis of the southern Beaufort (SB) polar bear population. The analysis uses a female-dominant stage-classified matrix population model in which individuals are classified by age and breeding status. Parameters were estimated from capture-recapture data collected between 2001 and 2006. We focused on measures of long-term population growth rate and on projections of population size over the next 100 years. We obtained these results from both deterministic and stochastic demographic models. Demographic results were related to a measure of sea ice condition, ice(t), defined as the number of ice-free days, in year t, in the region of preferred polar bear habitat. Larger values of ice correspond...
Categories: Publication; Types: Citation; Tags: Administrative Report
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The Southern Hudson Bay (SH) population of polar bears (Ursus maritimus) resides in a seasonal sea ice environment and is the most southerly population in the species’ range. Therefore, SH polar bears may be among the first to show negative effects associated with climate warming and consequent loss of sea ice. Polar bears in the neighboring Western Hudson Bay (WH) population have declined significantly in body condition since the mid-1980s, and a recent study indicated that the size of the WH population declined by about 22% between 1987 and 2004. Similarly, SH bears have shown a significant decline in body condition since the mid-1980s, and an assessment of the current status of the SH population was therefore...
Categories: Publication; Types: Citation; Tags: Administrative Report
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To inform the U.S. Fish and Wildlife Service decision, whether or not to list polar bears as threatened under the Endangered Species Act (ESA), we forecast the status of the world's polar bear (Urslls maritimus) populations 45, 75 and 100 years into the future. We applied the best available information about predicted changes in sea ice in the 21 st century to current knowledge of polar bear populations and their ecological relationships to the sea ice to understand how the range-wide population of polar bears might change. We combined the world's 19 polar bear subpopulations into 4 ecological regions based on current and projected sea ice conditions. These "ecoregions" are the (1) Seasonal Ice Ecoregion which includes...
Categories: Publication; Types: Citation; Tags: Administrative Report
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The U.S. Geological Survey (USGS) Southeast Asia Seismic Hazard Project originated in response to the 26 December 2004 Sumatra earthquake (M9.2) and the resulting tsunami that caused significant casualties and economic losses in Indonesia, Thailand, Malaysia, India, Sri Lanka, and the Maldives. During the course of this project, several great earthquakes ruptured subduction zones along the southern coast of Indonesia (fig. 1) causing additional structural damage and casualties in nearby communities. Future structural damage and societal losses from large earthquakes can be mitigated by providing an advance warning of tsunamis and introducing seismic hazard provisions in building codes that allow buildings and structures...
Categories: Publication; Types: Citation; Tags: Administrative Report
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This report describes uncertainties in climate model simulations of Arctic sea ice decline, and proposes a selection criterion for models to be used in projecting polar bear (Ursus maritimus) habitat loss. Uncertainties in model construction are discussed first, both for climate models in general and for their sea ice component models. A key point in the discussion is that the inherent climate sensitivity of sea ice leads inevitably to uncertainty in simulations of sea ice decline. The ability of climate models to simulate gross properties of Arctic ice cover, including the annual mean, seasonal cycle, and recent trends, is then assessed, followed by a review of model projections of 21st Century decline. The proposed...
Categories: Publication; Types: Citation; Tags: Administrative Report
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Changes in individual stature and body mass can affect reproduction and survival and have been shown to be early indicators of changes in status and trends of polar bear populations. We recorded body length, skull size, and mass of polar bears (Ursus maritimus) during capture/recapture studies conducted in the southern Beaufort Sea of Alaska (SB) between 1982 and 2006. We calculated a body condition index (BCI) which reflects trends in mass relative to length. We also recorded the number of dependent young accompanying females in the spring and fall as an indicator of cub recruitment. Previous work suggested stature of some sex and age classes of bears in the SB had changed between early and latter portions of this...
Categories: Publication; Types: Citation; Tags: Administrative Report
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Predictions of polar bear (Ursus maritimus) habitat distribution in the Arctic polar basin during the 21st century were developed to help understand the likely consequences of anticipated sea ice reductions on polar bear populations. We used location data from satellite-collared polar bears and environmental data (e.g., bathymetry, coastlines, and sea ice) collected between 1985–1995 to build habitat use models called Resource Selection Functions (RSF). The RSFs described habitats polar bears preferred in each of four seasons: summer (ice minimum), autumn (growth), winter (ice maximum) and spring (melt). When applied to the model source data and to independent data (1996–2006), the RSFs consistently identified habitats...
Categories: Publication; Types: Citation; Tags: Administrative Report


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