Widespread Effects of Climate Change on Local Plant Diversity

Human activity has sent many measures of biodiversity into long-term decline, and there are suggestions that the sheer scale of this impact is sufficient to consider the modern era as a geological epoch of its own, known as ‘‘The Anthropocene’’. However, recent meta-analyses show that local alpha diversity is often stable or slightly increasing. Here, we show that the local alpha diversity (species richness) of plants found in quadrats and transects has increased the most in cooler regions of the world that have experienced the highest absolute changes (i.e., changes in either direction) in climate. The greatest statistical support is for the effects of precipitation change. On average, alpha diversity declined slightly (4.2% per decade) in the third of sites that experienced the lowest precipitation change but increased (+10.8% per decade) in the third of sites with the highest precipitation change. These results suggest that the ‘‘perturbation’’ of local communities during climatic transitions increases the average number of species, at least temporarily, an effect likely to remain important as climate change continues.