As more and more species have either become extinct or are threatened with extinction, ecologists are increasingly interested in understanding what a loss in species diversity means for communities and the way in which they function. Let’s next consider research designed to understand how species diversity affects communities as well as agricultural crops.

Community function describes the way a community works and can be measured using metrics such as plant productivity, soil fertility, or water availability. Another measure of how well a community functions is its resistance to (or recovery from) disturbance, known as its stability. Ecologists have hypothesized that communities with more species function better than communities with fewer species. The argument is that no two species in a community uses resources in exactly the same way such that a community with more species will show more complete and efficient resource use. Also, should environmental conditions change, a species-rich community is more likely to contain some species that can persist under the new conditions. Thus a species-rich community should be more stable—that is, less likely to change over time in either productivity or species composition—than a species poor community. Let’s examine these assumptions with some experiments.