Climate-driven changes in the composition of New World plant communities

Climate change is altering the distributions of species, which in turn causes shifts in the composition of plant communities. Specifically, rising temperatures should cause increasing relative abundances of heat-loving or heat-tolerant species (that is, ‘thermophilization’) and changes in precipitation should cause altered abundances of water-demanding species. We analysed millions of records of thousands of species and found that the plant communities in most ecoregions in North, Central and South America have experienced thermophilization over the past four decades (1970–2011). Thermophilization was fastest in ecoregions with intermediate temperatures and was positively correlated with warming rates within many biomes. Changes in the relative abundances of water-demanding species were less consistent and were not correlated with changes in precipitation, meaning that the drought sensitivity of some ecoregions may be increasing despite decreasing rainfall and increasing probabilities of drought. Climate-driven changes in plant community composition will affect the function and stability of New World ecoregions. Climate change is driving changes in the species composition of plant communities. Analyses of the collection records of thousands of New World plant species reveal widespread increases in the relative abundances of heat-loving species but less consistent responses to changes in precipitation.