Wilson Ryan R, Andersen Erik M
U.S. Fish and Wildlife Service, Marine Mammals Management, Anchorage, AK, USA.
Sci Rep. 2025 Feb 10;15(1):4975. doi: 10.1038/s41598-025-89218-3.
Greenhouse gas emissions continue to increase and negatively affect sea ice conditions that polar bears rely on. It is therefore important to better understand how specific emissions levels affect polar bear demography. A recent study proposed a framework to address this issue, but sensitivity to decisions rules of the approach may limit its utility. We tested how sensitive the approach is to decisions rules related to sea ice concentration, choice of subpopulation boundaries, and modeling choices for bears in the Chukchi Sea and Southern Beaufort Sea subpopulations. We found that the number of ice-free days, number of fasting days, and when 10% of reproductive females exhibited recruitment failure varied considerably depending on equally-valid decisions rules versus those used in the existing study. Whereas the previous study suggested that both subpopulations surpassed the critical number of ice-free days that negatively affect recruitment, we found this threshold was never reached by the Southern Beaufort Sea subpopulation and only once for the Chukchi Sea subpopulation for the decision rules we considered. Our results suggest that the previously published approach is too sensitive to modeling assumptions and choice of decision rules to accurately evaluate the impacts of GHG emissions on polar bear demographic rates.
温室气体排放持续增加，并对北极熊赖以生存的海冰状况产生负面影响。因此，更好地了解特定排放水平如何影响北极熊种群动态至关重要。最近的一项研究提出了一个框架来解决这个问题，但该方法对决策规则的敏感性可能会限制其效用。我们测试了该方法对与海冰浓度、亚种群边界选择以及楚科奇海和波弗特海西南部亚种群中北极熊建模选择相关的决策规则的敏感程度。我们发现，无冰天数、禁食天数以及10%的繁殖雌性出现繁殖失败的时间，在同等有效的决策规则与现有研究中使用的规则之间存在很大差异。尽管之前的研究表明，两个亚种群都超过了对繁殖产生负面影响的关键无冰天数，但我们发现，对于我们考虑的决策规则，波弗特海西南部亚种群从未达到这个阈值，楚科奇海亚种群仅出现过一次。我们的结果表明，先前发表的方法对建模假设和决策规则的选择过于敏感，无法准确评估温室气体排放对北极熊种群动态率的影响。
