Ecosystem function of biodiversityRegarding ideal levels of species richness, the data are few and unclear

tionists that biodiversity is crucial to the earth's "life-support system": as we lose species, we also alter the integrity of processes that maintain soil fertility and water quality, provide natural checks on pest outbreaks, convert carbon dioxide into plant tissue, and support the complex food webs upon which we and other creatures depend. Until recently, however, ecologists have made few attempts to find out just how changes in the number of species or even the diversity of ecosystems across a landscape might affect these processes. Earlier this year, 50 ecologists from around the world gathered at Asilomar on California's Monterey Peninsula to try to do just that. The goal of the workshop, sponsored by the Scientific Committee on Problems of the Environment (SCOPE), was to pull together what is known about the impact of biodiversity on ecosystem functions and identify major gaps in our knowledge. The gaps were evident right outside the meeting rooms. One side of the problem-the relentless human pressure on biodiversity-was easy to spot. Crowds of sunbathers encroached on the territory of harbor seals, and signs warned beachcombers away from trampled dunes where tiny, endangered wallflowers clung to life in protective cages. But how the loss of seals or wallflowers or any other species might alter ecosystem processes-especially those crucial to human life-turns out to be much harder to predict. Participants in the SCOPE project