Copyright 2001 Los Angeles Times
October 19, 2001
By Gary Polakovic

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

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 Niño or global warming.

But the latest findings — published today in the journal Science — indicate that as trees on Costa Rican 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 is home to more than 800 species of orchids and birds, as well as jaguars, ocelots and resplendent quetzals, plumed birds favored by the Mayans. It is also a watershed that supplies farms, towns and power plants in the lowlands.

The findings are consistent with similar localized weather changes seen in deforested parts of the Amazon region. Scientists say 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," the scientists conclude, "and they will thus decrease in area and become increasingly fragmented and in many low mountains may disappear altogether."

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 Hartshorn, president of the Organization for Tropical Studies, a consortium of rainforest 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, the scientists examined how forest clearing along the Caribbean coastline — more than 80 percent of lowland forests there have been cleared for farms and towns — influences weather downwind in the Cordillera de Tilarán, a range in northern Costa Rica. 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 land clearing began. 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, the study says, clouds were more abundant over lowlands just across the border in Nicaragua, where forests still blanket much of the coastal plain.

"Deforestation has effects that may be much broader than the immediate deforested areas," said Robert Lawton, tropical-rainforest ecologist at the University of Alabama. "Mountain forests that are protected may be affected by what's happening some distance away."

Each year, 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 constitute just 1.4 percent of the Earth's land mass, yet they are believed to harbor about 60 percent of the world's plant and animal species. Washington-based Conservation International, a nonprofit group leading the campaign, says protecting those lands could cost $24 billion.

However, the study in Science suggests that even protected lands seemingly removed from human encroachment are vulnerable to localized climatic shifts. Error: Unable to read footer file.