A team of ISU researchers has found evidence suggesting the true effects of deforestation may be far worse than predicted.

Their investigation of long-term global climate patterns has shown that a 20 percent increase in rainfall over the Amazon Basin over the last 40 years has not been taken into account by previous studies.

Relying on the recent, heavy rainfall to make predictions ignores long-term trends, researchers said. Short-term studies can’t show the extent of deforestation, and these study results may have been too optimistic.

The results of the study, “Suppressing Impacts of the Amazonian Deforestation by Global Circulation Change,” were published in the October issue of the Bulletin of the American Meteorological Society. The authors are ISU professors of geological and atmospheric sciences Tsing-Chang “Mike” Chen and Gene Takle and graduate students Jin-ho Yoon and Kathryn St. Croix.

“It was basically a study of global circulation over the past 40 years with an eye towards outside influences to what was going on locally [in the Amazon Basin],” Takle said. “We found that some local indicators, such as rainfall, were going backward, and the area was becoming wetter because of global circulation . and the regrowth of forest species and other ecological factors benefit from precipitation.”

Other studies, such as the Climate Variability and Prediction – an international branch of the World Climate Research Program – look at long-term global circulation patterns to make predictions about climate variability, Yoon said.

But other previous studies conducted in the Amazon Basin have predicted a slower rate of deforestation than that found by the ISU researchers. Yoon said the ISU study is the first to consider changes over the course of several decades.

“This reversal of expected rainfall suppressed the effects of deforestation,” Yoon said.

The research began last year, when St. Croix showed an interest in environmental policy problems while working on her thesis. An analysis of National Centers for Environmental Prediction data from the past 40 years caught their attention, Yoon said.

“We found some interesting anomalies in the data [from the Amazonian Basin], and so I channeled her towards research in interdecadal changes,” Yoon said.

The effects of deforestation would become even more devastating than were previously predicted by models that did not take into consideration the long-term changes, Takle said.

“Forty to 50 years later, the area may become drier,” he said. “Deforestation has a tendency to destroy the whole ecosystem that the forest provides.”

The ecosystem in the Amazon Basin is very fragile, and damaging it even in a small way may have a huge impact, Takle said.

For example, he said, various types of fungi living in the soil of the forest provide minerals to the surrounding trees.

A change in the environment that supports the fungi may eventually damage other parts of the ecosystem as well, Takle said.

“The rainforest is a very complex ecosystem,” he said. “[When] disturbed, the effects are, in many cases, irreversible.”

Many more areas still need to be studied to see if the same results will be consistent around the world, Takle said.

“This raises the question as to if the Amazon is unique,” he said.

“Equatorial Africa, Malaysia and Indonesia all have deforestation problems.”