Anthropogenic climate change may reduce global diazotroph diversity.

Climate change impacts microbial community structure and function, thus altering biogeochemical cycles. Biological nitrogen fixation by diazotrophs is involved in maintaining the balance of the global nitrogen cycle, but the global biogeographic patterns of diazotrophs and their responses to climate change remain unclear. In this study, we use a dataset of 1352 potential diazotrophs by leveraging the co-occurrence of nitrogenase genes (nifHDK) and analyse the global distribution of potential diazotrophs derived from 137,672 samples. Using the random forest model, we construct a global map of diazotroph diversity, revealing spatial variations in diversity across large scales. Feature importance shows that precipitation and temperature may act as drivers of diazotroph diversity, as these factors explain 54.2% of the variation in the global distribution of diazotroph diversity. Using projections of future climate under different shared socioeconomic pathways, we show that overall diazotroph diversity could decline by 1.5%-3.3%, with this decline further exacerbated by development patterns that increase carbon emissions. Our findings highlight the importance of sustainable development in preserving diazotrophs.