Climate and land-use changes predicted to jointly drive soil fungal diversity losses across one-third of North American coniferous forests

Soil fungi underpin key ecosystem functions but face increasing threats from climate and land-use changes, with their future impacts remain unclear. We assessed the impact of climate and land-use changes on soil fungal diversity across four North American biomes by incorporating Shared Socioeconomic Pathways (SSPs) and their associated greenhouse gas-induced radiative forcing, focusing on moderate- (SSP2–4.5) and high-emission (SSP5–8.5) scenarios. Climate change typically drove both diversity losses and gains, particularly in coniferous forests and for arbuscular mycorrhizal (AM) fungi. Land-use change predominantly drove diversity losses under SSP2–4.5, especially in broadleaf-mixed forests and for ectomycorrhizal (EM) fungi, with these effects diminished under SSP5–8.5 due to minimal land-use changes. Across emission scenarios, both factors were predicted to drive widespread diversity losses in coniferous forests (whole-community, EM fungi, and soil saprotrophs) and grasslands (AM fungi and plant pathogens), while promoting diversity gains in broadleaf-mixed forests (whole-community, EM fungi, and soil saprotrophs) and coniferous forests (AM fungi and plant pathogens). This study supports biome- and guild-specific fungal conservation planning under global change.