Microbial eco-evolutionary responses amplify global soil carbon loss with climate warming

Abstract Soil microbes respond to warming climates through variation in traits linked to the decomposition of soil organic matter, which impacts global soil carbon emissions. Microbial trait variation is shaped by eco-evolutionary processes; yet soil carbon models largely ignore such processes and their implications for global responses to warming. Here, we apply eco-evolutionary theory to a microbe-enzyme model to optimize a key microbial trait controlling decomposition and re-calculate soil carbon projections. Eco-evolutionary optimization leads microbes subject to warming to allocate more resources to enzyme production, which leads to faster decomposition and larger soil carbon loss, especially in cold regions. As a consequence, microbial optimization significantly amplifies global soil carbon loss by 2100 relative to current models, most strongly at high latitudes. This analysis demonstrates the potential importance of microbial eco-evolutionary dynamics in carbon-cycle feedbacks to climate change.