Grassland species loss resulting from reduced niche dimension

Too much of a good thing? What explains biodiversity? One theory holds that in ecosystems in which various resources are limiting, diversity will increase, because the conditions will favour species adapted to cope with the dearth of water, phosphorus, nitrogen and so on. In conditions of abundance, productivity will go up, but the winners will be those few species that can grow fastest and swamp the competition. Although resource limitation is not the only factor that could explain species richness, Harpole and Tilman show that it explains the plant biodiversity in experimental grass plots in Sedgwick, California — and could explain results in the oldest ecological experiment in the world, at Rothamsted in the United Kingdom. These results also provide an alternative explanation for the biodiversity loss caused by human actions that tend to simplify habitats, such as nutrient eutrophication.