Synergistic effects of climate change and agricultural land use on mammals

Although climate change and the expansion of agriculture are two of the primary threats to global biodiversity, they are usually considered independently. Here, I show that climate change and agricultural expansion interact synergistically in their impacts on mammals across mega-biodiverse Southeast Asia. Rising temperatures do not directly reduce niche availability for most species but do trigger a major altitudinal expansion in the cultivation zone for oil palm (Elaeis guineensis), a cold-intolerant crop tree that is currently restricted to tropical lowlands. The resulting replacement of native forests would reduce mammal ranges by 47-67% by 2070, given a low- or high-carbon-emissions trajectory, respectively. This reduction is 3-4 times the magnitude of that predicted from land-use change without considering climatic effects. The synergistic interaction between climate change and land-use change greatly outweighs the impact on biodiversity of either factor alone or their additive combination.