Climate change and other human-driven (anthropogenic) environmental changes will continue to cause biodiversity loss in the coming decades (Sala et al. 2000), in addition to the high rates of species extinctions already occurring worldwide (Stork 2010). Biodiversity is a term that can be used to describe biological diversity at a variety of different scales, but in this context we will focus on the description of species diversity. Species play essential roles in ecosystems, so local and global species losses could threaten the stability of the ecosystem services on which humans depend (McCann 2000). For example, plant species harness the energy of the sun to fix carbon through photosynthesis, and this essential biological process provides the base of the food chain for myriad animal consumers. At the ecosystem level, the total growth of all plant species is termed primary production, and — as we'll see in this article — communities composed of different numbers and combinations of plant species can have very different rates of primary production. This fundamental metric of ecosystem function has relevance for global food supply and for rates of climate change because primary production reflects the rate at which carbon dioxide (a greenhouse gas) is removed from the atmosphere. There is currently great concern about the stability of both natural and human-managed ecosystems, particularly given the myriad global changes already occurring. Stability can be defined in several ways, but the most intuitive definition of a stable system is one having low variability (i.e., little deviation from its average state) despite shifting environmental conditions. This is often termed the resistance of a system. Resilience is a somewhat different aspect of stability indicating the ability of an ecosystem to return to its original state following a disturbance or other perturbation.