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Polar Bear Outlook Favorable Under Certain Scenarios



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A new USGS study, “Forecasting the relative influence of environmental and anthropogenic stressors on polar bears,” finds that aggressive greenhouse gas mitigation could greatly reduce the chance of a substantial decline in the worldwide polar bear population.

Adult female polar bear and her cub photographed near the community of Kaktovik, Alaska, in September 2015.
Above: Adult female polar bear and her cub photographed near the community of Kaktovik, Alaska, in September 2015. [larger version]

The study, an update to the 2015 publication “Evaluating and Ranking Threats to the Long-Term Persistence of Polar Bears,” uses a Bayesian network model to evaluate the relative influence of environmental and anthropogenic stressors and their mitigation on the persistence of polar bears. Overall sea ice conditions, affected by rising global temperatures, were found to be the most influential determinant of population outcomes:

  • An unabated rise in atmospheric greenhouse gas concentrations was the dominant influence leading to worsened population outcomes, with polar bears in three of four ecoregions reaching a dominant probability of decreased or greatly decreased population by the latter part of this century.

  • Stabilization of atmospheric greenhouse gas concentrations by mid-century delayed populations reaching a greatly reduced state by approximately 25 years in two ecoregions.

  • Prompt and aggressive mitigation of emissions reduced the probability of any regional population becoming greatly reduced by up to 25%.

Marine prey availability, which is closely linked to sea ice condition, had slightly less influence on outcome state than sea ice availability itself. Reduced mortality from hunting and defense of life and property interactions resulted in modest declines in the probability of decreased or greatly decreased population outcomes. Minimizing other stressors such as trans-Arctic shipping, oil and gas exploration, and contaminants had a negligible effect on polar bear outcomes.

The study found that long-term conservation of polar bears would be best supported by holding global mean temperature to ≤ 2°C above preindustrial levels. Until further sea ice loss is stopped, management of other stressors may serve to slow the transition of populations to progressively worsened outcomes, and improve the prospects for their long-term persistence.

The full citation for the article is:
Atwood, T. C., Marcot, B. G., Douglas, D. C., Amstrup, S. C., Rode, K. D., Durner, G. M. and Bromaghin, J. F., 2016, Forecasting the relative influence of environmental and anthropogenic stressors on polar bears. Ecosphere, 7:e01370, http://dx.doi.org/10.1002/ecs2.1370.

Related Sound Waves Stories
Polar Bears Forced on Shore by Sea-Ice Loss Are Unlikely to Thrive on Land-Based Foods
July / Sept. 2015
Through the Eyes of a Polar Bear—First "Point of View" Video
May / June 2014
Projected Losses of Arctic Sea Ice and Polar Bear Habitat May Be Reduced if Greenhouse-Gas Emissions are Stabilized
January / February 2011
New Publication on "Predicting 21st-Century Polar Bear Habitat Distribution from Global Climate Models"
April 2009
Coastal and Ocean Researchers Receive DOI Meritorious Service Awards
May 2009

Related Websites
Forecasting the relative influence of environmental and anthropogenic stressors on polar bears
Ecosphere
Evaluating and Ranking Threats to the Long-Term Persistence of Polar Bears
USGS
Polar Bear Outlook Favorable Under Certain Scenarios
USGS News: June 29, 2016
Polar Bears Unlikely to Thrive on Land-based Foods
USGS News: April 1, 2015
The Great Polar Bear Feast
PBS
Predicting 21st-century polar bear habitat distribution from global climate models
Ecological Monographs

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in this issue:

Research
Scientists Bring Wave Action into the Picture

New Map Reuses Decades-Old USGS Data

Website Provides Oceanographic Time-Series Data

New Data Added to USGS Time-Series Data Collection

Fieldwork
Coastal Maps from Unmanned Aerial Systems

Future Fieldwork, August–September 2016

Outreach
USF Oceanography Camp for Girls

Staff
Student Trainee Gains Work Experience at USGS

Publications
Geological Perspective on Conservation of Atlantic Coral Reefs

Polar Bear Outlook Favorable Under Certain Scenarios

June / July Publications

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