Symposium tackles big question: how many species will survive our generation

Deforestation for rubber plantations in Laos. Photo by Rhett A. Butler
Deforestation for rubber plantations in Laos. Photo by Rhett A. Butler

An overview of the Smithsonian’s Symposium: “Will the rainforests survive? New Threats and Realities in the Tropical Extinction Crisis”

Nine scientists dusted off their crystal balls Monday at the National Museum of Natural History in Washington DC, weighing in on the future of the world’s tropical forest. Despite the most up-to-date statistics, prognosis for the future of tropical forests varied widely.

Debate’s Background
In the last few years a schism has occurred among biologists regarding the future of the tropics. No tropical scientist denies that rainforests and the species which inhabit them face unprecedented threats; neither do they argue that some of these forested regions and species will likely not survive the next fifty years. What has sparked debate, sometimes heated, is how bad will is it really? When the dust settles, what percentage of species will survive and how much forest will remain?

For years scientists have been warning of a mass extinction that could rival the previous five mass extinctions each occurring millions of years ago, including the extinction event that killed off the dinosaurs. Scientists have warned that within our lifetimes 50-75 percent of the world’s species could go extinct. This prediction is largely supported by the continuing destruction of the world’s tropical forest, where the majority of Earth’s biodiversity lives.

Despite decades of conservation awareness, reserve creation, and pressure on policy makers, tropical deforestation has not abated but in fact has steadily risen globally. Some predictions have shown that by 2050 only 5-10 percent of old growth forests will remain. With the loss of these forests, scientists inevitably believe that the world will lose tropical species in startling numbers. This view has been promulgated by a wide variety of prominent and widely-revered biologists, including E.O. Wilson, Norman Myers, Peter Raven, and William Laurance.

Recently however a few notable biologists have begun to push back against this prognosis. Joseph Wright and Helene C. Muller-Landau began the controversy with a series of papers and presentations that argued against the common belief of an impending mass extinction. Wright’s initial study posited that current trends in deforestation would not continue in the future.

Using data from the UN, Wright argued that rural populations in tropical areas, such as those living off subsistence farming, will in the future abandon the rural life and move to cities. This exodus from the tropics by subsistence farmers, who often employ slash-and-burn techniques in rainforest areas for short-term agriculture, would alleviate the pressure of habitat loss on tropical species. Areas that were once agricultural will become secondary forest and capable of supporting high levels of biodiversity, argues Wright, a trend already seen in much of the world as forests take the place of agricultural land that was abandoned in the 1980s and 90s.

In a 2006 paper Wright and Muller-Landau asserted that „large areas of tropical forest cover will remain in 2030 and beyond…. We believe that the area covered by tropical forest will never fall to the exceedingly low levels that are often predicted and that extinction will threaten a smaller proportion of tropical forest species than previously predicted.“

Without widespread loss of habitat there would be no mass extinction, at least not to extent warned about. Wright’s modeling predicted that instead of looking at extinction levels from 50-75 percent, we would see levels of extinction that would be closer to 20-30 percent.

Before the symposium on Monday, this is where the lines had been drawn in the sand. However, the symposium served to expand upon many of the issues impacting the debate—including changing drivers in deforestation, regrowth of tropical forests, new ideas about extinction, and climate change—and even added a few new surprising conclusions about the fate of the global rainforests.

Changes in rainforest destruction trends
At present, deforestation is not slowing down. According to Gregory Asner of the Carnegie Institution, deforestation is still the dominant pattern in tropical forests worldwide. In fact, he told the audience in Baird Auditorium, that if one looks at statistics of global forest loss decade-by-decade than not only is deforestation continuing, but it is on the rise.
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