by Lila Guterman

About the author: Lila Guterman is a reporter for the Chronicle of Higher Education.

If environmentalists were to write down their Ten Commandments, one of the sacred principles would surely be, “Honor thy species.” The green movement takes as a truism that ecosystems are healthier when they contain many species of plants and animals. Ecological scientists have even coined a term for this riot of life: biodiversity.

Though the idea now seems natural to environmentalists, scientists have long wondered whether an abundance of species truly improves the health of ecosystems and the way they work. Experiments to test that link were not completed until the mid-1990’s, when some large-scale, much-heralded studies seemed to provide a positive answer. In 1999, the Ecological Society of America enshrined the...