Boulders stand bare. Topsoil, having lost its protection, washes away under the assault of heavy rain.

Deforestation in Latin America and the Caribbean is accelerating, a new report shows, and the implications are growing more ominous every year.

Scientists say deforestation, almost always to facilitate planting crops and raising cattle, accounts for about 20 percent of the carbon emissions that contribute to global warming. Environmentalists are pushing to allow countries and companies to offset their emissions by paying to preserve forests elsewhere, such as in Latin America and the Caribbean. The Group of Eight nations, meeting in Germany earlier this month, pledged to help poor countries reduce deforestation to provide "a significant and cost-effective contribution toward mitigating greenhouse gas emissions."

These calls come amid the release of an annual report published last month by the United Nations' Food and Agriculture Organization showing that from 2000 to 2005, the rate of destruction of forest in Latin America and the Caribbean had risen to 0.51 percent of overall land, up from 0.46 percent during the 1990s. Forests accounted for 51 percent of the overall land in Latin America and the Caribbean in 1990, but only 47 percent in 2005.

The amount of forest lost each year from 2000 to 2005 averaged 11,077,734 acres, the study showed -- about the size of Maryland.

Researchers say forest is being increasingly cleared to make way for big cattle ranches and large soybean farms -- especially in Brazil, which accounts for about 60 percent of the forest land in Latin America and the Caribbean.

The culprits in smaller countries such as Peru: poor farmers who clear land to grow food crops, and loggers who cut down trees in areas where it is illegal to do so.

Chile, Uruguay and Costa Rica were the only countries in the region that had more forest land in 2005 compared to 2000, the FAO found.

Peru, like other countries, has taken steps to prevent deforestation. But peasants all too often move into forested areas, cut down trees, set the brush on fire to make way for small plots and plant crops to eke out a living.

"They leave their site in one or two years to move somewhere else, because the soils are not good," said Sandro Rivero, Tarapoto's mayor. "We need enforcement of the law to keep the settlers out."

Peru has only 450 forest rangers in the Peruvian System of Protected Areas, or one per 100,000 acres.

In Brazil, a University of Maryland-led team found through satellite photos that cattle ranches have caused the greatest deforestation, although more and more forest is being cleared for big, mechanized soybean farms.

"Historically, the dominant pattern of forest conversion has begun with small-scale exploration for timber or subsistence agriculture, followed by consolidation into large-scale ranching operations," said the team's report from last year.

"The clearings are huge," Gregory Asner, director of global ecology at the Carnegie Institution, said by telephone from its offices at Stanford University in California. "They are even seen by satellites that miss a lot of detail."

A scientific paper written by Asner and others disclosed that five of the 26 Brazilian states -- Mato Grosso, Amazonas, Pará, Rondonia and Roraima -- account for 90 percent of the deforestation in Brazil.

Asner said the satellites also showed that nearly all logging occurs within 15 miles of dirt and paved roads built through the forests.

That points up the dangers posed by the further extension of the Trans-Amazon Highway, which has been paved through the heart of Brazil's Amazon to the Peru border and is now being paved west to provide an all-weather link to Peru's coast.

The highway -- known as BR-317 on the Brazilian side -- will spur trade between the two countries and create badly needed jobs in Peru.

"But, in general, highways serve as a means to accelerate deforestation," Foster Brown, an environmental scientist at the Federal University of Acre in Brazil, said by telephone. "It's a mechanism by which people enter a region, deforest and occupy land. BR-317 was a vector for a lot of deforestation. Unless mitigating factors are undertaken [in Peru], it will likely have a similar pattern."

Frank Merry, a natural resource economist for the Massachusetts-based Woods Hole Research Center who has worked in Brazil for the past seven years, said efforts to plant new forests and keep out settlers and illegal loggers have had minimal success.

The key to saving forest land, he said, is to make the value of preserving it exceed the value of clearing it.

"That's where carbon credits come in," Merry said by telephone from Mozambique, where he was working on another project. "The forest would be fully valued for logging and provide environmental services as a carbon offset" that companies or countries elsewhere could buy to counteract their own emissions.

The Nature Conservancy, for example, wants to preserve 15,000 acres at Oxapampa, in Peru's central jungle, with funds obtained under this system. The cost: $7 million for a 30-year project. The Arlington, Va.-based conservation group, which operates in all 50 states and more than 30 countries, works to protect ecologically important land and water resources.

"It's very expensive," said Jaime Fernández, the Nature Conservancy's project coordinator in Peru. He noted that the group has already begun preservation efforts in the Oxapampa area with aid from the U.S. Agency for International Development.

Florida Sen. Bill Nelson, on a visit to Tarapoto in February, was dismayed by the deforestation he saw.

Nelson stood with one foot on a boulder, surveyed a field with only a few remaining tree stumps and said he first became interested in the issue in 1986 when, as a member of Congress, he flew in the space shuttle Columbia and could see the destruction of the rain forest as he looked down on Earth.

"We have to stop this process because of the impact on the climate," he said. If not, he added, "We will suffer, and all of us will suffer."