加拿大科研人员在新一期《自然—通信》（Nature Communications）杂志上报告说，由于气候变暖导致北极海冰面积逐渐缩减，生活在加拿大哈得孙湾的北极熊生育率正在下降。
哈得孙湾是位于加拿大东北部的一个大型海湾，位于北冰洋边缘，是北极熊的重要栖息地。加拿大艾伯塔大学的科研人员分析了哈得孙湾上世纪90年代以来冰层缩减的情况，并将所获得的数据与北极熊的数量进行对比。
海冰是北极熊觅食和生活的重要平台，也是雌性北极熊怀孕时的休养生息之地。研究发现，海冰如果融化过早，北极熊捕食海豹的难度就会增加，导致能量积蓄不足，难以生育。
模拟推算显示，如果哈得孙湾海冰每年融化的时间比上世纪90年代提前1个月，就会有40%至73%的怀孕雌性北极熊无法成功生育；如果海冰融化时间提前两个月，这一比例会达到55%到100%。
在过去10年里，哈得孙湾北极熊的数量已由1200头下降至目前的约900头。研究人员指出，如果北极海冰面积缩减的趋势持续下去，不仅哈得孙湾的北极熊将减少，整个北极地区的北极熊也将面临一场生存危机。（生物谷Bioon.com）
生物谷推荐原文出处：
Nature Communications doi:10.1038/ncomms1183
Predicting climate change impacts on polar bear litter size
Péter K. Molnár,1, 2, 4 Andrew E. Derocher,2 Tin Klanjscek3 & Mark A. Lewis1, 2
Predicting the ecological impacts of climate warming is critical for species conservation. Incorporating future warming into population models, however, is challenging because reproduction and survival cannot be measured for yet unobserved environmental conditions. In this study, we use mechanistic energy budget models and data obtainable under current conditions to predict polar bear litter size under future conditions. In western Hudson Bay, we predict climate warming-induced litter size declines that jeopardize population viability: ~28% of pregnant females failed to reproduce for energetic reasons during the early 1990s, but 40–73% could fail if spring sea ice break-up occurs 1 month earlier than during the 1990s, and 55–100% if break-up occurs 2 months earlier. Simultaneously, mean litter size would decrease by 22–67% and 44–100%, respectively. The expected timeline for these declines varies with climate-model-specific sea ice predictions. Similar litter size declines may occur in over one-third of the global polar bear population.
