Ecol Appl. 2014 Jul;24(5):1144-54. doi: 10.1890/13-0829.1.
Climate change vulnerability assessments for species of conservation concern often use species distribution and ecological niche modeling to project changes in habitat. One of many assumptions of these approaches is that food web dependencies are consistent in time and environmental space. Species at higher trophic levels that rely on the availability of species at lower trophic levels as food may be sensitive to extinction cascades initiated by changes in the habitat of key food resources. Here we assess climate change vulnerability for Ursus arctos (grizzly bears) in the southern Canadian Rocky Mountains using projected changes to 17 of the most commonly consumed plant food items. We used presence-absence information from 7088 field plots to estimate ecological niches and to project changes in future distributions of each species. Model projections indicated idiosyncratic responses among food items. Many food items persisted or even increased, although several species were found to be vulnerable based on declines or geographic shifts in suitable habitat. These included Hedysarum alpinum (alpine sweet vetch), a critical spring and autumn root-digging resource when little else is available. Potential habitat loss was also identified for three fruiting species of lower importance to bears: Empetrum nigrum (crowberry), Vaccinium scoparium (grouseberry), and Fragaria virginiana (strawberry). A general trend towards uphill migration of bear foods may result in higher vulnerability to bear populations at low elevations, which are also those that are most likely to have human-bear conflict problems. Regardless, a wide diet breadth of grizzly bears, as well as wide environmental niches of most food items, make climate change a much lower threat to grizzly bears than other bear species such as polar bears and panda bears. We cannot exclude, however, future alterations in human behavior and land use resulting from climate change that may reduce survival rates.
气候变化脆弱性评估通常用于保护关注物种，利用物种分布和生态位模型预测栖息地变化。这些方法中有许多假设，即食物网依赖关系在时间和环境空间上是一致的。依赖于较低营养级物种作为食物的较高营养级物种可能对关键食物资源栖息地变化引发的灭绝级联敏感。在这里，我们使用 17 种最常食用的植物食物项目的预测变化来评估加拿大落基山脉南部的 Ursus arctos（灰熊）的气候变化脆弱性。我们使用来自 7088 个实地调查点的存在-不存在信息来估计生态位，并预测每个物种未来分布的变化。模型预测表明食物项目之间存在特殊反应。尽管根据适宜栖息地的减少或地理转移，发现一些物种易受影响，但许多食物项目仍然存在或甚至增加。其中包括 Hedysarum alpinum（高山甜巢菜），这是一种在其他资源匮乏时春季和秋季重要的根挖掘资源。对于三种对熊来说不太重要的果实物种，也确定了潜在的栖息地丧失：Empetrum nigrum（越桔）， Vaccinium scoparium（越橘）和 Fragaria virginiana（草莓）。熊食物向上迁移的总体趋势可能导致低海拔熊种群更容易受到影响，这些熊种群也最有可能出现人与熊冲突问题。无论如何，灰熊广泛的饮食广度以及大多数食物项目广泛的环境生态位，使得气候变化对灰熊的威胁远低于其他熊种，如北极熊和熊猫。然而，我们不能排除气候变化可能导致人类行为和土地利用发生未来变化，从而降低存活率。
