Changes in temperature alter the relationship between biodiversity and ecosystem functioning

Significance Empirical evidence for the response of ecosystem functioning to the combined effects of warming and biodiversity loss is scarce. We show that warming and biodiversity loss interact synergistically, impairing the functioning of microbial communities. We found that as temperatures departed from ambient conditions more species were required to maintain ecosystem functioning. Our results suggest interspecific complementarity increased under thermal stress and high-diversity communities that seemed functionally redundant at ambient temperature became more functionally unique as temperatures changed. Biodiversity may therefore be even more important than previously anticipated when considering the impacts of multiple facets of environmental change.