Conservation biology. Debate continues over rainforest fate--with a climate twist.

WASHINGTON, D.C.—Depending on whom you talk to, the future of tropical rainforest biodiversity is either "truly catastrophic" or not as bad as feared. The common wisdom tends toward the catastrophic, says tropical ecologist William Laurance of the Smithsonian Tropical Research Institute (STRI), who is based in Brazil. According to some estimates, he notes, tropical forests are vanishing at a rate of 13 million hectares per year. Two prominent conservation biologists have predicted that only 5% to 10% of tropical old-growth forests would survive in 2050, and they gloomily forecast extinctions of up to 75% of the species. But that view was challenged by two papers published in 2006, both by ^^^^ Joseph Wright of STRI and Helene Muller-Landau of the University of Minnesota, Twin Cities. They argued that a trend toward urbanism would mean fewer people living in forests and thus a slowing rate of deforestation. They predicted that more than a third of tropical forests overall would remain in 2030. Moreover, the regrowth of forests on abandoned farms would provide a refuge for tropical species. So in the end, 16% to 35% of species would be threatened with extinction, they estimated. The reaction was fierce. Many biologists felt Wright and Muller-Landau's conclusions would undermine attempts to preserve more rainforest. Laurance, who wrote a high-profile rebuttal in Trends in Ecology and Evolution, says one scientist commented: "Their argument is just plain dangerous. We should hit them hard— and with one voice." As the public faces of the debate, Wright and Laurance decided to host two symposia, one at STRI in Panama last August and another here at the Smithsonian's National Museum of Natural History last week, to evaluate recent evidence on the threat to tropical biodiversity. Their talks, before an audience of 400 at the natural history museum, were illustrated with good-natured caricatures of each other as pro wrestlers, devils, and angels. The bout isn't over: Still unsettled are key points such as the amount of tropical forest that will remain in 2030, the biodiversity contained in degraded and recovering forests, and the effectiveness of nature reserves. But the speakers were united in their concerns that climate change may pose even greater risks of unprecedented disturbance to biodiversity than they realized 3 years ago. Speakers presented evidence that gave cause for both hope and concern. On the negative side, Gregory Asner of the Carnegie Institution of Washington's Department of Global Ecology in Stanford, California, noted that small-scale selective logging affects 28%