Deforestation Far Away Hurts Rain Forests, Study Says

Weather itself is changing in the lush cloud forests of Costa Rica because of deforestation many miles away, scientists say in a new study published today in the journal Science

The changes threaten diverse plant and animal communities as well as assumptions behind an effort to save the world’s best remaining rain forests. Up to now, the changes have been blamed on El Nino or global warming. But the latest findings indicate that as trees on Costa Rica’s coastal plains are removed and replaced by farms, roads and settlements, less moisture evaporates from soil and plants, in turn reducing clouds around forested peaks 65 miles away.

At risk is an ecosystem atop a Central American mountain spine that provides valuable services to people and nature. It is home to the Monteverde Cloud Forest Reserve, one of the world’s most famous cloud forests and a linchpin of the nation’s tourist economy. A realm of moss and mist, the woodland in the clouds--a type of rain forest--is home to more than 800 species of orchids and birds, as well as jaguar, ocelot and the Resplendent Quetzal, a plumed bird sacred to the Mayans. It is also a watershed that supplies farms, towns and hydropower plants in the lowlands.

The findings are consistent with similar localized weather changes seen in deforested parts of the Amazon region. Scientists say that cloud forests in Madagascar, the Andes and New Guinea are also at risk. Those environments account for a small portion of the Earth, but they harbor a disproportionate share of the planet’s plant and animal species.

“These results suggest that current trends in tropical land use will force cloud forests upward and they will thus decrease in area and become increasingly fragmented and in many low mountains may disappear altogether,” the scientists conclude.

The findings are the work of a team of researchers at the University of Alabama and Colorado State University.

“It’s incredibly ominous that over such a distance deforestation can alter clouds in mountains. This is a very serious concern,” said Gary S. Hartshorn, president of the Organization for Tropical Studies, a consortium of rain forest researchers at Duke University.

“This is confirmation of what we have predicted for a long time,” said Stanford University ecologist Gretchen Daily. “The implications are very serious for the tropics and other parts of the world.”

Using data collected from satellites and computer models, scientists examined how forest clearing along the Caribbean coastline--more than 80% of lowland forests there have been cleared for farms and towns--influences weather downwind in the Cordillera de Tilaran mountain range. Evaporation from lowland vegetation is a principal source of moisture for the 4,000-to-5,000-foot mountains during the dry season of January to mid-May.

The researchers found that the moisture content of the clouds over the mountains has declined by about half since intensive land clearing began in the 1950s. Also, the cleared land is warmer, pushing the base of clouds nearly a quarter of a mile higher on some days, meaning they pass over the mountain range dropping little moisture. In contrast, clouds were more abundant over forested lowlands just across the border in Nicaragua, where forest still blankets much of the coastal plain, the study says.

“Deforestation has effects which may be much broader than the immediate deforested areas. Mountain forests that are protected may be affected by what’s happening some distance away,” said Robert Lawton, tropical rain forest ecologist at the University of Alabama.

Each year about 81,000 square miles of tropical forests are cleared, Hartshorn said.

The findings in the study complicate a worldwide effort to save the most biologically diverse and most threatened remaining tropical forests. Many scientists have endorsed a plan to save 25 of the world’s biodiversity “hot spots.” Those regions, which include parts of Southern California, Africa, the Amazon and Asia, constitute just 1.4% of the Earth’s land mass. Yet they are believed to harbor about 60% of the world’s plant and animal species. Washington-based Conservation International, a nonprofit group leading the campaign, says protecting those lands will cost an estimated $24 billion.

However, the study in Science suggests that even protected lands seemingly removed from human encroachment are vulnerable to localized climatic shifts. The problem is also compounded by global warming, which many scientists agree is being caused in part by fossil fuel burning.

“This is going to be a big problem,” said Gustavo Fonseca, vice president of science for Conservation International. “We can’t only hold these tiny pockets of native habitat and hope they will survive. We have to look at these areas planned for protection and realize that unless we change our use of the landscape we could still lose them.”

More research is planned in Costa Rica. In the next phase, scientists using a $480,000 grant from NASA plan to fund a three-year follow-up study, which will include installing instruments to measure rainfall, inventorying plants and animals in the cloud forest and studying the impacts on the Pacific side of the mountain range.