The breadth of a species' climatic niche is an important ecological trait that allows adaptation to climate change, but human activities often reduce realised niche breadth by impacting species distributions. Some life-history traits, such as dispersal ability and reproductive speed, allow species to cope with both human impact and climate change. But how do these traits interact with human pressure to determine niche change? Here we investigate the patterns and drivers of change in the realised climatic niche of 258 terrestrial mammal species. Our goal is to disentangle the impacts of human land use, climate change and life history. We quantified the past and present climatic niches of each species by considering past climatic conditions (Mid Holocene) within their pre-human impact distributions, and current climatic conditions within the current distributions. Depending on the difference between past and current niche, we defined four categories of change: ‘shrink', ‘shift', ‘stable' and ‘expand'. We found over half of the species in our sample have undergone niche shrink, while only one in six retained a stable niche. Climate change and distribution change were the strongest correlates of species niche change, followed by biogeography, anthropogenic land use and life-history traits. Factors that increased the probability of niche shrink included: overall climatic instability, reduction in distribution range, historical land use, large body mass and long weaning age. Species with these characteristics might require interventions that facilitate natural dispersal or assisted colonisation to survive rapidly changing climates.

中文翻译：

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陆地哺乳动物已实现的气候生态位变化的驱动因素

物种气候生态位的宽度是一个重要的生态特征，可以适应气候变化，但人类活动通常会通过影响物种分布来减少已实现的生态位宽度。一些生活史特征，例如传播能力和繁殖速度，使物种能够应对人类影响和气候变化。但是，这些特征如何与决定利基变化的人类压力相互作用呢？在这里，我们调查了 258 种陆地哺乳动物物种已实现的气候生态位变化的模式和驱动因素。我们的目标是理清人类土地使用、气候变化和生活史的影响。我们通过考虑人类前影响分布中的过去气候条件（全新世中期），量化了每个物种过去和现在的气候生态位，当前分布范围内的当前气候条件。根据过去和当前利基之间的差异，我们定义了四类变化：“缩小”、“转变”、“稳定”和“扩大”。我们发现样本中超过一半的物种经历了生态位缩小，而只有六分之一的物种保持了稳定的生态位。气候变化和分布变化是物种生态位变化的最强相关性，其次是生物地理学、人为土地利用和生活史特征。增加生态位缩小概率的因素包括：整体气候不稳定、分布范围缩小、历史土地利用、体重大和断奶年龄长。