Biodiversity and ecosystem stability in a decade-long grassland experiment

The idea that greater biodiversity increases ecosystem stability has been around for about 50 years, and has been furiously debated for much of that time. There have been precious few rigorous long-term field experiments to test the theory, but a decade-long biodiversity experiment in grassland at the University of Minnesota's Cedar Creek experimental ecological reserve set out to do that. The results are now in and they show that the presence of greater numbers of plant species increases both stability and productivity. Human-driven ecosystem simplification has highlighted questions about how the number of species in an ecosystem influences its functioning. Although biodiversity is now known to affect ecosystem productivity1,2,3,4,5,6, its effects on stability are debated6,7,8,9,10,11,12,13. Here we present a long-term experimental field test of the diversity–stability hypothesis. During a decade of data collection in an experiment that directly controlled the number of perennial prairie species4, growing-season climate varied considerably, causing year-to-year variation in abundances of plant species and in ecosystem productivity. We found that greater numbers of plant species led to greater temporal stability of ecosystem annual aboveground plant production. In particular, the decadal temporal stability of the ecosystem, whether measured with intervals of two, five or ten years, was significantly greater at higher plant diversity and tended to increase as plots matured. Ecosystem stability was also positively dependent on root mass, which is a measure of perenniating biomass. Temporal stability of the ecosystem increased with diversity, despite a lower temporal stability of individual species, because of both portfolio (statistical averaging) and overyielding effects. However, we found no evidence of a covariance effect. Our results indicate that the reliable, efficient and sustainable supply of some foods (for example, livestock fodder), biofuels and ecosystem services can be enhanced by the use of biodiversity.