Microbial diversity plays a critical role in maintaining multifunctionality in terrestrial ecosystems. A study using two large-scale datasets—global drylands and Scotland—reveals that soil microbial diversity positively correlates with ecosystem multifunctionality, which encompasses multiple functions such as nutrient cycling, primary production, and climate regulation. This relationship remains significant even when accounting for climate, soil abiotic factors, and spatial variables. The findings suggest that any loss in microbial diversity could reduce the ability of terrestrial ecosystems to provide essential services like climate regulation, soil fertility, and food production. The study highlights that microbial diversity supports ecosystem multifunctionality by facilitating processes like litter decomposition and organic matter mineralization, which link above- and belowground communities. While previous research has focused on plant diversity and its impact on ecosystem functioning, this study provides empirical evidence that microbial diversity is as important as other factors like soil pH, climate, and spatial predictors in driving multifunctionality. The research also shows that microbial diversity is a major predictor of multifunctionality in both the Drylands and Scotland datasets, even after controlling for other variables. Fungal diversity had a slightly higher positive effect on multifunctionality in drylands, likely due to their resilience to dry conditions. The study further demonstrates that microbial diversity supports multifunctionality by enhancing nutrient supply and resource distribution, enabling high rates of material processing in terrestrial ecosystems. The study uses various statistical methods, including Random Forest and Structural Equation Modeling, to assess the relationships between microbial diversity and multifunctionality. These analyses confirm that microbial diversity is a key driver of ecosystem multifunctionality, with significant implications for conservation and management strategies. The findings underscore the importance of protecting soil microbial diversity to maintain ecosystem services in the face of global environmental changes.Microbial diversity plays a critical role in maintaining multifunctionality in terrestrial ecosystems. A study using two large-scale datasets—global drylands and Scotland—reveals that soil microbial diversity positively correlates with ecosystem multifunctionality, which encompasses multiple functions such as nutrient cycling, primary production, and climate regulation. This relationship remains significant even when accounting for climate, soil abiotic factors, and spatial variables. The findings suggest that any loss in microbial diversity could reduce the ability of terrestrial ecosystems to provide essential services like climate regulation, soil fertility, and food production. The study highlights that microbial diversity supports ecosystem multifunctionality by facilitating processes like litter decomposition and organic matter mineralization, which link above- and belowground communities. While previous research has focused on plant diversity and its impact on ecosystem functioning, this study provides empirical evidence that microbial diversity is as important as other factors like soil pH, climate, and spatial predictors in driving multifunctionality. The research also shows that microbial diversity is a major predictor of multifunctionality in both the Drylands and Scotland datasets, even after controlling for other variables. Fungal diversity had a slightly higher positive effect on multifunctionality in drylands, likely due to their resilience to dry conditions. The study further demonstrates that microbial diversity supports multifunctionality by enhancing nutrient supply and resource distribution, enabling high rates of material processing in terrestrial ecosystems. The study uses various statistical methods, including Random Forest and Structural Equation Modeling, to assess the relationships between microbial diversity and multifunctionality. These analyses confirm that microbial diversity is a key driver of ecosystem multifunctionality, with significant implications for conservation and management strategies. The findings underscore the importance of protecting soil microbial diversity to maintain ecosystem services in the face of global environmental changes.