Anthropogenic impacts on the environment do not affect species consistently across their range. Physiological tolerances to temperature and precipitation, and an individual’s proximity to such tolerance limits, can lead to important variation across a species’ range in responses to global climate change. However, changes in temperature and precipitation regimes are not only occurring at the global scale: land-use changes are also leading to localised climatic changes. In fact, human-altered land uses (such as agriculture) are often drier, and experience hotter and colder extremes of temperature than natural, undisturbed habitats. Human-altered land uses have also been found to be composed of individuals that can tolerate greater extremes of climate compared to those in natural habitats. Yet, the majority of research to date has not considered possible intraspecific variation in responses to land-use change, in particular variation driven by local climatic changes.
The PREDICTS Project database is the largest and most representative, open-source collection of data from studies worldwide comparing ecological assemblages across land uses. We used this database to analyse whether vertebrate species’ abundances within different land uses (natural and secondary vegetation, through to agricultural areas) were affected by the populations’ proximity to temperature and precipitation tolerance limits.
Results/Conclusions
A population’s proximity to their thermal tolerance limits had a strong influence on their abundances across different land uses, with the strength of trends often differing between tropical and temperate latitudes. Human-altered land uses were found to be filtering out populations near their upper maximum thermal tolerance limit and populations near their lower minimum thermal tolerance limit. On the other hand, the influences of proximity to precipitation tolerance limits were more complex: unexpectedly, populations in human-altered land uses further from their dry tolerance limit were more negatively affected than those closer to this climatic limit.
Our results highlight the influence that species’ climatic tolerances and a population’s proximity to these climatic limits have on their ability to occupy human-altered land uses. Importantly, they suggest that land-use change and global climate change may have the most negative impacts on the same populations, specifically those closer to their hot thermal limits, which leads to the potential for synergistic interactions. Understanding spatial variation is important; taking into account differences in responses to drivers of change will enhance our ability to detect and predict which populations may be more vulnerable, ultimately helping us to produce more suitable conservation and land management plans.