Abstract

A large number of studies have now explicitly examined the relationship between species loss and ecosystem functions. The results from such “biodiversity experiments” have previously been collated and analyzed by two independent groups of authors. Both data sets show that reductions in species diversity generally result in reduced ecosystem functioning, even though the studies cover a wide range of ecosystems, diversity manipulations, and response variables. In this chapter, we analyze the two data sets in parallel to explain variation in the observed functional effects of biodiversity. The main conclusions are: 1) the functional effects of biodiversity differ among ecosystem types (but not between terrestrial and aquatic systems), 2) increases in species richness enhance community responses but negatively affect population responses, 3) stocks are more responsive than rates to biodiversity manipulations, 4) when diversity reductions at one trophic level affect a function at an adjacent trophic level (higher or lower), the function is often reduced 5) increased biodiversity results in increased invasion resistance. We also analyze the shape of the relationship between biodiversity and response variables, and discuss some consequences of different relationships.