High plant diversity is needed to maintain ecosystem services

The more diverse the merrier Biodiversity–ecosystem function experiments have shown the importance of a diverse range of species for the health of ecosystems, but the number of species needed to maintain ecosystem functioning and services remains unclear. A meta-analysis of biodiversity research now shows, surprisingly, that 84% of grassland plant species have promoted ecosystem functioning at least once. Different species were important in different years, in different places and for different functions. These results strongly suggest that most grassland plant species provide ecosystem services. Consequently, even a few extinctions could have a deleterious effect. Biodiversity is rapidly declining worldwide 1 , and there is consensus that this can decrease ecosystem functioning and services 2 , 3 , 4 , 5 , 6 , 7 . It remains unclear, though, whether few 8 or many 9 of the species in an ecosystem are needed to sustain the provisioning of ecosystem services. It has been hypothesized that most species would promote ecosystem services if many times, places, functions and environmental changes were considered 9 ; however, no previous study has considered all of these factors together. Here we show that 84% of the 147 grassland plant species studied in 17 biodiversity experiments promoted ecosystem functioning at least once. Different species promoted ecosystem functioning during different years, at different places, for different functions and under different environmental change scenarios. Furthermore, the species needed to provide one function during multiple years were not the same as those needed to provide multiple functions within one year. Our results indicate that even more species will be needed to maintain ecosystem functioning and services than previously suggested by studies that have either (1) considered only the number of species needed to promote one function under one set of environmental conditions, or (2) separately considered the importance of biodiversity for providing ecosystem functioning across multiple years 10 , 11 , 12 , 13 , 14 , places 15 , 16 , functions 14 , 17 , 18 or environmental change scenarios 12 , 19 , 20 , 21 , 22 . Therefore, although species may appear functionally redundant when one function is considered under one set of environmental conditions 7 , many species are needed to maintain multiple functions at multiple times and places in a changing world.