Biodiversity and ecosystem functioning: more than meets the eye!

Over the past 25 years, hundreds of empirical studies established that there is generally a positive relationship between the functioning of an ecosystem and the number of species it contains. Ongoing global biodiversity loss by anthropogenic activities therefore poses a major threat to future ecosystem function provisioning. However, recent studies showed that environmental stress, including exposure to chemicals, can alter the biodiversity-ecosystem functioning (BEF) relationship, and hence the consequences of biodiversity loss. In this paper Baert et al. reveal for the first time the mechanisms underlying changes in BEF relationships by environmental stress. By using a simple community model, Baert et al. demonstrate that changes in the BEF relationship in a marine microalgal microcosm experiment could be explained from species stress tolerances and the strength of per-capita species interactions. Together, stress tolerance and species interactions determine how environmental stress will alter species dominance and complementarity, causing the BEF relationship to change. These findings demonstrate how the consequences of biodiversity loss can strongly depend on the environmental conditions. As anthropogenic activities continue to increase stress on ecosystems worldwide, current models may therefore greatly underestimate the consequences of future biodiversity loss.

Scientific abstract

Environmental stress changes the relationship between biodiversity and ecosystem functions, but the underlying mechanisms are poorly understood. Because species interactions shape biodiversity–ecosystem functioning relationships, changes in per capita interactions under stress (as predicted by the stress gradient hypothesis) can be an important driver of stress-induced changes in these relationships. To test this hypothesis, we measure productivity in microalgae communities along a diversity and herbicide gradient. On the basis of additive partitioning and a mechanistic community model, we demonstrate that changes in per capita interactions do not explain effects of herbicide stress on the biodiversity–productivity relationship. Instead, assuming that the per capita interactions remain unaffected by stress, causing species densities to only change through differences in stress tolerance, suffices to predict the stress-induced changes in the biodiversity–productivity relationship and community composition. We discuss how our findings set the stage for developing theory on how environmental stress changes biodiversity effects on ecosystem functions.

Full reference (link)

Baert JM, Janssen CR, Sabbe K, De Laender F. 2016. Per capita interactions and stress tolerance drive stress-induced changes in biodiversity effects on ecosystem functions. Nature Communications 7, Article number 12486