Temperatures at global forest edges exceed vegetation productivity optima

Ongoing fragmentation puts increasing parts of the world’s forests in proximity to edges. Forest edges are known to differ from interiors for many ecosystem variables like biomass and species diversity, but also microclimate. While it is documented that temperatures change with presence and absence of forests, our knowledge of edge effects in temperatures (temperature change with distance to forest edge) is largely restricted to local studies and shorter timeframes. Here, we use satellite data to investigate edge effects in surface temperature of forests across the globe and across seasons. We find that edge effects indeed exist, with the forest interior generally being cooler, though effect sizes differ with biome and season. Worryingly, summer temperatures at forest edges lie above the optimal temperature for ecosystem level vegetation productivity across the globe, especially in the tropics. Our analyses suggest that the creation of forest edges through fragmentation reduces the ability of remnant forest patches to regulate their local temperatures, leading to hotter edges, which may hamper ecosystem productivity.