A Dry Horizon for the Amazon

Climate changes are pushing rain forests to the point of no return.

By Kristin Elise Phillips
posted June 27th, 2007.

A spider monkey in the Amazon. [CREDIT: ANTHONY DI FIORE]

It is stunning to think that the Amazon � a humid land of frogs, anacondas and parasitic strangler figs � could disappear in this century. 

Environmentalists have been predicting dire consequences for the rain forest for years, but a new report from the United Nation�s Intergovernmental Panel on Climate Change finds that the Amazon could be on an irreversible course to extinction. Some researchers add to the report�s predictions saying the conservative climate models used in the IPCC�s projections underestimate regional drying.

Two big scenarios threaten the Amazon and the life it contains, and both have human activity at the root. One is forest die-back caused by human land use, including logging and smoke released by fires, says Daniel Nepstad, an ecologist at the Woods Hole Research Center in Massachusetts. The other is an overall warming of the Amazon climate, which most researchers attribute to human activity.

�By the time we get to 2025, 2030, at least half of the Amazon Basin will be cleared, compromised because of severe drought and associated fire, or logged,� Nepstad adds.

The IPCC�s report predicts that by 2050, parts of the Amazon will be completely decimated. The report also emphasizes a high likelihood of extinctions and significant biodiversity loss associated with the change of landscape. In fact, according to the IPCC�s projections, global warming alone could lead to the extinction of between 20 and 30 percent of the world�s plants and animals�many of which reside in the Amazon�by the end of this century.

The IPCC used a combination of several different computer models to make predictions about the fate of the Amazon. But a number of researchers claim that the report underestimates the speed with which the rain forest will be destroyed and argue that the panel should have relied more on a specific model, the Hadley Centre Climate Model, for making projections about the Amazon Basin.

�Not all models are equal,� says Philip Fearnside of the National Institute for Research in the Amazon. �If you�re talking about the Amazon, you need to look at the Hadley model.�

The Hadley Model focuses on what ecologists already see happening across the Amazon: droughts. The most recent drought was in 2005, and this model predicts that global warming will increase drought frequency as the current pattern of ocean circulation in the North Atlantic weakens and warmer sea-surface temperatures move southward. In short, the Hadley projections have �climate locking into a permanent El Ni�o,� explains Fearnside. Under those conditions, �the Amazon becomes much dryer and the temperature goes way up, and Amazon forest is basically wiped out by 2080.�

The situation is likely to be even more dire, because climate models don�t account for the impact of other human activities on the rain forest. Each year, the Amazon is being further sliced and fragmented by new roads and cleared for large-scale cattle and soy production, which is eliminating the habitats of hundreds of thousands of plants and animals. Both commercial and illegal logging further exacerbate the drying process, because removing trees reduces the amount of moisture released into the air, which reduces rainfall. And the fires used to clear forest for agriculture inhibit normal cloud formation, creating a feedback loop that results in further climatic change.

�Deforestation is not only destroying the forest directly, it is also contributing to climate change,� says ecologist Fearnside.

Decimation of the Amazon basin isn�t a local problem; the global population will be affected. �Climate changes poses risks to human society as well because we and the biological systems that we depend upon are so tightly adapted to our current climate,� says Paul Higgins, a senior policy fellow at the American Meteorological Society. Some think that the solution is also global: wealthy nations could purchase carbon shares from Brazil or pay countries like Ecuador to halt oil development. But these plans require immediate action. Once the Amazon rainforest and the plant and animal species that call it home are gone, there�s no going back. The drying out process, just like species extinction, is irreversible.