Local loss and spatial homogenization of plant diversity reduce ecosystem multifunctionality

Biodiversity is declining in many local communitieswhile also becoming increasingly homogenized across space. Experiments show that local plant species loss reduces ecosystemfunctioning and services, but the role of spatial homogenization of community composition and the potential interaction between diversity at different scales in maintaining ecosystemfunctioning remains unclear, especially when many functions are considered ( ecosystemmultifunctionality). We present an analysis of eight ecosystemfunctions measured in 65 grasslandsworldwide. We find that more diverse grasslands—those with both species-rich local communities(α-diversity) and large compositional differences among localities (β-diversity)—had higher levels of multifunctionality. Moreover, α- and β-diversity synergistically affected multifunctionality, with higher levels of diversity at one scale amplifying the contribution to ecological functions at the other scale. The identity of species influencing ecosystemfunctioning differed among functions and across local communities, explaining why more diverse grasslandsmaintained greater functionality when more functions and localities were considered. These results were robust to variation in environmental drivers. Our findings reveal that plant diversity, at both local and landscape scales, contributes to the maintenance of multiple ecosystemservices provided by grasslands. Preserving ecosystemfunctioning therefore requires conservation of biodiversity both within and among ecological communities.