Biodiversity Helps Keep Ecosystems Healthy

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For years, prominent biologists and conservationists have campaigned for the preservation of biological diversity, despite little proof of their assertion that reducing the number of plant and animal species upsets nature's balance. Now, two experimental studies illustrate the detrimental effects of species loss.

More than 10 years ago, ecologist David Tilman of the University of Minnesota in St. Paul and his colleagues began investigating how as many as 250 kinds of plants could thrive in midwestern grasslands, even though the flora competed for limited resources. They did not expect to address the question of the value of biodiversity, Tilman says.

For this experiment, the researchers …