Forecasting the relative influence of environmental and anthropogenic stressors on polar bears
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Full Publication: https://doi.org/10.1002/ecs2.1370Product Type: Journal Article
Year: 2016
Authors: Atwood, T. C., B. G. Marcot, D. C. Douglas, S. C. Amstrup, K. D. Rode, G. M. Durner, and J. F. Bromaghin
Suggested Citation:
Atwood, T. C., B. G. Marcot, D. C. Douglas, S. C. Amstrup, K. D. Rode, G. M. Durner, and J. F. Bromaghin. 2016. Forecasting the relative influence of environmental and anthropogenic stressors on polar bears. Ecosphere 7(6):e01370. doi:10.1002/ecs2.1370
Abstract
Effective conservation planning requires understanding and ranking threats to wildlife populations. We developed a Bayesian network model to evaluate the relative influence of environmental and anthropogenic stressors, and their mitigation, on the persistence of polar bears (Ursus maritimus). Overall sea ice conditions, affected by rising global temperatures, were the most influential determinant of population outcomes. Accordingly, unabated rise in atmospheric greenhouse gas (GHG) 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 by the latter part of this century. Stabilization of atmospheric GHG concentrations by mid-century delayed the greatly reduced state by ≈25 yr 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, linked closely to sea ice trend, 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 a decreased or greatly decreased population outcome. Minimizing other stressors such as trans-Arctic shipping, oil and gas exploration, and contaminants had a negligible effect on polar bear outcomes, although the model was not well-informed with respect to the potential influence of these stressors. Adverse consequences of loss of sea ice habitat became more pronounced as the summer ice-free period lengthened beyond four months, which could occur in most of the Arctic basin after mid-century if GHG emissions are not promptly reduced. 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.
Keywords: Polar bears, climate change, sea ice, oil and gas exploration, Arctic shipping
Annotation
Sea ice conditions, affected by rising global temperatures, were found to be the most influential determinant on the persistence of polar bear (Ursus maritimus) populations. Using a Bayesian network model, unabated rise in atmospheric greenhouse gas (GHG) concentrations was found to be 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 by the latter part of this century. As sea ice loss increases, polar bears are likely to increasingly utilize terrestrial habitats, increasing the potential impacts of development in these areas. Until further sea ice loss is stopped, management of other stressors such as trans-Arctic shipping, oil and gas exploration, and contaminants may serve to slow the transition of populations to progressively worsened outcomes, and improve the prospects for their long-term persistence.