Lunn Nicholas J, Servanty Sabrina, Regehr Eric V, Converse Sarah J, Richardson Evan, Stirling Ian
Wildlife Research Division, Science & Technology Branch, Environment and Climate Change Canada, CW405 Biological Sciences Centre, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.
Colorado Cooperative Fish and Wildlife Research Unit, Colorado State University, Fort Collins, Colorado, 80523, USA.
Ecol Appl. 2016 Jul;26(5):1302-1320. doi: 10.1890/15-1256.
Changes in the abundance and distribution of wildlife populations are common consequences of historic and contemporary climate change. Some Arctic marine mammals, such as the polar bear (Ursus maritimus), may be particularly vulnerable to such changes due to the loss of Arctic sea ice. We evaluated the impacts of environmental variation on demographic rates for the Western Hudson Bay (WH), polar bear subpopulation from 1984 to 2011 using live-recapture and dead-recovery data in a Bayesian implementation of multistate capture-recapture models. We found that survival of female polar bears was related to the annual timing of sea ice break-up and formation. Using estimated vital rates (e.g., survival and reproduction) in matrix projection models, we calculated the growth rate of the WH subpopulation and projected population responses under different environmental scenarios while accounting for parametric uncertainty, temporal variation, and demographic stochasticity. Our analysis suggested a long-term decline in the number of bears from 1185 (95% Bayesian credible interval [BCI] = 993-1411) in 1987 to 806 (95% BCI = 653-984) in 2011. In the last 10 yr of the study, the number of bears appeared stable due to temporary stability in sea ice conditions (mean population growth rate for the period 2001-2010 = 1.02, 95% BCI = 0.98-1.06). Looking forward, we estimated long-term growth rates for the WH subpopulation of ~1.02 (95% BCI = 1.00-1.05) and 0.97 (95% BCI = 0.92-1.01) under hypothetical high and low sea ice conditions, respectively. Our findings support previous evidence for a demographic linkage between sea ice conditions and polar bear population dynamics. Furthermore, we present a robust framework for sensitivity analysis with respect to continued climate change (e.g., to inform scenario planning) and for evaluating the combined effects of climate change and management actions on the status of wildlife populations.
野生动物种群数量和分布的变化是历史和当代气候变化的常见后果。一些北极海洋哺乳动物，如北极熊（Ursus maritimus），可能因北极海冰的减少而特别容易受到此类变化的影响。我们利用多状态捕获-重捕模型的贝叶斯实现中的活体重捕和死亡回收数据，评估了1984年至2011年环境变化对西哈德逊湾（WH）北极熊亚种群人口统计率的影响。我们发现，雌性北极熊的存活率与海冰破裂和形成的年度时间有关。利用矩阵投影模型中的估计生命率（如存活率和繁殖率），我们计算了WH亚种群的增长率，并在考虑参数不确定性、时间变化和人口统计随机性的情况下，预测了不同环境情景下的种群反应。我们的分析表明，北极熊数量从1987年的1185只（95%贝叶斯可信区间[BCI]=993-1411）长期下降到2011年的806只（95% BCI=653-984）。在研究的最后10年里，由于海冰条件的暂时稳定，北极熊数量似乎保持稳定（2001-2010年期间的平均种群增长率=1.02，95% BCI=0.98-1.06）。展望未来，我们估计在假设的高海冰和低海冰条件下，WH亚种群的长期增长率分别约为1.02（95% BCI=1.00-1.05）和0.97（95% BCI=0.92-1.01）。我们的研究结果支持了先前关于海冰条件与北极熊种群动态之间人口统计学联系的证据。此外，我们提出了一个强大的框架，用于针对持续气候变化的敏感性分析（如为情景规划提供信息），以及评估气候变化和管理行动对野生动物种群状况的综合影响。
