MINNEAPOLIS / ST. PAUL--An eight-year National Science Foundation-funded study of New Guinean rainforest plants and the insects that feed on them has yielded a new and dramatically lower estimate of the number of species on the planet. The estimate, which lowers the number of species from approximately 31 million to between four and six million, is based on the finding that insects specialize their feeding not on individual species of plants, but on genera and even families of plants. In "bringing some reality" to estimates of world biodiversity, the study allows scientists to get a better handle on how fast species are being lost, said University of Minnesota plant biologist George Weiblen, the principal plant expert on the research team. The work will be published in the April 25 issue of Nature.

It is important to know how fast biodiversity is being lost, but this is hard to gauge without a solid baseline, Weiblen said. Scientists advising governments on policies to curtail species losses must have credible estimates of species numbers if they are to shape appropriate policies. The stakes are high because losses of too many species or certain kinds of species can cripple tropical forest ecosystems, which normally stabilize soil and climate, purify and recycle water, and produce food, medicine, building materials or other useful products, he said.

The current study took a cross-disciplinary approach; besides Weiblen, the principal scientists were insect expert and project coordinator Scott Miller of the Smithsonian Institution and insect community ecologists Yves Basset of the Smithsonian Tropical Research Institute in Panama and Voytech Novotny of the Czech Academy of Sciences.

The team compared insect communities feeding on 51 tropical plant species, most belonging to either the fig family, the mulberry family or the coffee family. While previous work had also based estimates of total species on numbers of insects--the most species-rich
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Contact: Deane Morrison
morri029@umn.edu
612-624-2346
University of Minnesota
24-Apr-2002

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