# Climate and Land‐Use Changes Predicted to Jointly Drive Soil Fungal Diversity Losses in One‐Third of North American Coniferous Forests

## TL;DR

This study predicts that climate and land-use changes will cause significant losses in soil fungal diversity in one-third of North American coniferous forests.

## Contribution

The study introduces a novel approach combining large-scale data and modeling to assess the joint impacts of climate and land-use changes on soil fungal diversity.

## Key findings

- Climate change is projected to cause both diversity losses and gains in coniferous forests and among arbuscular mycorrhizal fungi.
- Land-use change predominantly reduces fungal diversity in broadleaf-mixed forests and for ectomycorrhizal fungi under moderate-emission scenarios.
- Both climate and land-use changes are predicted to cause widespread fungal diversity losses in coniferous forests and grasslands.

## Abstract

Soil fungi underpin key ecosystem functions but face increasing threats from climate and land‐use changes, with their future impacts remaining unclear. This uncertainty is exacerbated by limited large‐scale data and the challenge of quantifying and comparing both factors at comparable spatial scales. By leveraging two continental‐scale sampling networks in North America and applying stacked species distribution models combined with countryside species–area relationship frameworks, we assessed the impacts of climate and land‐use change on soil fungal diversity and identified regions affected by both factors across four biomes. We projected climate and land‐use change by incorporating shared socioeconomic pathways (SSPs) and associated greenhouse gas–induced radiative forcing, focusing on moderate‐ (SSP2–4.5) and high‐emission (SSP5–8.5) scenarios. Climate change typically led to both diversity losses and gains, particularly in coniferous forests and among arbuscular mycorrhizal (AM) fungi. Land‐use change predominantly caused 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 cause widespread diversity losses in coniferous forests (whole‐community, EM fungi, and soil saprotrophs) and grasslands (AM fungi and plant pathogens) while promoting gains in broadleaf‐mixed forests (whole‐community, EM fungi, and saprotrophs) and coniferous forests (AM fungi and pathogens). These results support the need for biome‐ and guild‐specific fungal conservation planning under global change.

This study assessed the potential impacts of climate and land‐use change on soil fungal diversity across four North American biomes. We found that climate change typically caused both diversity losses and gains, particularly in coniferous forests and among arbuscular mycorrhizal fungi, whereas land‐use change mainly reduced diversity, especially in broadleaf‐mixed forests and for ectomycorrhizal fungi. Despite guild‐specific responses, both drivers were projected to cause widespread whole‐community fungal losses in coniferous forests and grasslands, while promoting gains in broadleaf‐mixed and coniferous forests. These results emphasize the need for biome‐ and guild‐specific strategies to conserve fungal diversity under global change.