Forest edges are globally warmer than interiors and exceed optimal temperatures for vegetation productivity.

Forests not only regulate the global climate by absorbing carbon dioxide but also shape local biophysical conditions by creating microclimates that buffer temperature extremes. However, ongoing deforestation and fragmentation are transforming forest interiors into edge environments, which may differ markedly in their microclimatic conditions and undermine local climate-regulating functions. Here, we quantify how proximity to forest edges alters thermal conditions across biomes and seasons using global satellite-derived surface temperature data from nearly 13 million sites. We find that forest edges are consistently warmer on average than interiors, with the magnitude of warming varying with biome type and season. During summer months, surface temperature at edges frequently exceeds the optimal temperature for vegetation productivity, particularly in tropical forests. These results suggest that continued loss of interior forest will reduce the capacity of remnant forests to buffer local climate conditions, potentially hampering ecosystem productivity and resilience.