Global effects of biodiversity and eutrophication on the stability of natural grassland ecosystems

Background/Question/Methods

Experimental studies of randomly assembled communities have demonstrated that higher levels of diversity can increase the stability of ecosystem functions through a suite of mechanisms that includes asynchrony in population fluctuations over time where decreases in some species are compensated by increases in others. However, the relevance of these findings to natural ecosystems under realistic, nonrandom changes in biodiversity is still debated. We performed a global study involving 35 grasslands on four continents to evaluate the effect of plant diversity on ecosystem stability and species asynchrony that considered both natural and fertilization-induced variation in diversity.

Results/Conclusions

Observational patterns confirm and generalize results from biodiversity experiments: natural communities with more species had higher asynchrony and stability. However, the stability of fertilized communities was not related to diversity seemingly because fertilization decreased asynchrony in lower diversity communities. Our results demonstrate that the effect of human-induced variations in diversity on stability may be different from that of natural variations in diversity. Impacts of diversity loss on stability therefore need to be integrated with those of other global change drivers through increased understanding of their individual and interactive effects on the underlying biological mechanisms.