6.1 - Food webs and the relationship between biodiversity and ecosystem functioning

Abstract

This chapter explores merging biodiversity–ecosystem functioning and food web theories. Multitrophic interactions are expected to make biodiversity–ecosystem functioning relationships more complex and nonlinear, in contrast to the monotonic changes predicted for simplified systems with a single trophic level. Furthermore, these relationships depend strongly on the ecosystem properties considered; total plant biomass, total herbivore biomass, and primary production can show very different patterns as diversity varies. Recent theoretical and experimental work provides clear evidence that biodiversity loss can have profound impacts on the functioning of natural and managed ecosystems and their ability to deliver ecological services to human societies. Work on simplified ecosystems in which the diversity of a single trophic level—mostly plants—is manipulated shows that taxonomic and functional diversity can enhance ecosystem processes such as primary productivity and nutrient retention. Despite the complexity generated by trophic interactions, biodiversity should still act as a biological insurance for ecosystem processes against environmental fluctuations in multitrophic systems, except when consumers are generalists, and generalism has no cost. The relationships between diversity and ecosystem variability also seem to be less dependent on the ecosystem properties considered, because the variability of primary and secondary production shows the same trends as the variability of total plant and herbivore biomass as diversity varies.