Global Forest Edge Dynamics in the 21st Century

Seventy percent of global forests lie within 1 km of an edge, yet the temporal dynamics of these forest edges remain poorly characterized. Here, we present the first high spatial resolution (0.00025°) global map of forest edges from 2000 to 2020 for the first time, revealing a 24 million km (7%) decline in total forest edge length. The observed decline is primarily driven by the merging of small forest patches in temperate and boreal forests, whereas fragmentation and deforestation in the tropics diminish total forest edge length. In contrast, some countries, including Laos, Liberia, India, and China, exhibit net increases in edge length due to the emergence of new forest patches. These changes often occur episodically, and their distributions are closely linked to policy-driven land management such as logging bans, agricultural expansion, and large-scale reforestation initiatives. Given the critical ecological functions of forest edges ranging from supporting biodiversity and regulating microclimate, our findings highlight the contrasting edge dynamics across biomes and underscore the need for adaptive forest policies that balance biodiversity conservation, carbon storage, and sustainable land use.