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Shred but not dead.

Maps made from roving-satellite snapshots of Latin America, especially of the verdant mantle of the Amazon rainforest, show large tracts of land that are still covered in forest. The maps often depict these areas in black. In contrast, white areas on the map appear entirely denuded. But a closer look at the region portrayed on the map reveals that things are not as black and white as they seem, says John Schelhas, a Cornell University expert on land use in Central America.

Scattered across areas that look cleared, says Schelhas, are tufts of leftover forest. These fragments are too sparse to show up on current maps, but more research on them may brighten, to some extent, the gloomy picture we have been seeing of rapid forest destruction in Latin America, Africa, and Southeast Asia.

The biological richness of such fragments may vary, but a number of biologists, sobered by the rate of deforestation in tropical countries, have concluded that pieces of forest - whatever their ecological assets - are far better than no forest at all. This view represents a painful pragmatism, since many experts concede that large-scale clearing of tropical forests is inevitable. They estimate that only 5 to 10 percent of the world's primary forests will make it safely into protected reserves. Given this bleak outlook, conservationists who concentrate only on rescuing large tracts of primary tropical forest are "setting standards that are too high," say Judith Gradwohl and Russell Greenberg of the Smithsonian Institution.

Until recently, forest fragments suffered from a kind of arboreal discrimination, or "image" problem. Viewed as crippled ecosystems, they failed to entrance biologists or inspire the efforts of conservationists as much as did the dense mystery of untouched, primary forests. But newer studies of these relict forests, which range in size from small stands to thousands of acres, have revealed that they are serendipitous refuges for various migrating birds, primates, frogs, and plants. While some fragments have lost much of their original biological wealth, others shelter vibrant ecosystems.

Remnant forests offer a variety of uses to Third World populations, and so are often spared from further clearing. In Latin America, for example, many farmers leave clumps of trees on their land to provide fruit and to give shade to homesteads that would otherwise swelter in the sun. On other settlements, a fringe of soaring trees follows the riverside, and trees are left clinging to the sides of steep gullies. In Mexico, farmers keep trees to provide shade over rustic coffee plantations, which require practically no labor for upkeep. In parts of Latin America and Asia, indigenous tribes preserve and tend forest groves. Both white colonists and indigenous people believe that allowing trees to remain alongside the river keeps the water pure and that saving trees ensures regular rainfall, says Janis Alcorn, an ethnobotanist and senior program officer with the Biodiversity Support Program at the World Wildlife Fund.

As a result, land that seems denuded when seen through the cameras mounted on satellites comes into view as a mosaic of fields and forest fragments when seen from the seat of an airplane. No reliable estimate of how much remnant forest remains in the world yet exists, but "a good portion of the world's moist and dry tropical forest is already fragmented," according to Richard Bierregaard, director of the Biological Dynamics of Forest Fragments Project at the Smithsonian Institution in Washington, D.C.

Left isolated in cattle pastures, or strung out along the peaks of a chain of mountains, some patches of tropical forest quickly unravel. Biologists understand only a few of the causes of this internal collapse, but the sheer size of the fragment appears to be an important factor. Smaller patches, for example, have a smaller area relative to their boundaries. Areas close to the edges are often sunnier, drier, hotter, and more likely to be buffeted by winds. "Anything smaller than 100 hectares [250 acres] is completely dominated by edge effects," says Bierregaard, "and absolutely useless to preserving resident flora and fauna."

Another factor is the availability of food. Large carnivores typically hunt across wide swaths of land. And some species require several different habitats, so they may go extinct when one of these habitats vanishes. When animals vanish, the remaining plants can be drastically affected. For example, some 75 percent of tropical tree species in Central and South America and the Caribbean rely on seed-eating vertebrates to disperse their seeds.

But even when forest patches are no longer full-fledged forest ecosystems, they can still serve as stepping stones and temporary shelters for species migrating to deep forest. They can also encircle and protect large reserves of primary forest. By providing resources to rural peasants or indigenous tribes, relict forests help alleviate pressure on remaining intact forests.

Janis Alcorn describes the role of people like the Huastec of northeastern Mexico and the Bora of Peru and Columbia, in protecting such fragments. Both groups grow a variety of crops, including maize, manioc, fruit, and beans, and both allow forest to stand on their farming sites. Alcorn estimates that the Huastec set aside at least 25 percent of their land in tree groves, often along streams or on hillsides. Many plots contain more than 300 species of plants, some of which, like coffee, are planted by the Huastec. Others grow up naturally in the original forest, dispersed by bats and birds. "Total removal of the forest makes no sense to those who have tried for generations to make a living in areas of tropical moist forest," says Alcorn. She believes that people like the Huastec and the Bora are model conservers of remnant forests, and should receive collective, legal rights to the lands they manage.

It is non-native settlers who are responsible for most of the recent deforestation the tropics, but these settlers have few incentives to preserve forest fragments. In fact, a policy that has the opposite effect, says John Schelhas, is one that allows settlers to make a legitimate claim to land by clearing it for pasture, widely regarded as a land "improvement." Elimination of this and other policies that encourage land speculation - the driving force behind rain forest conversion in Brazil in the 1980s - would remove some of the temptations to clear away even the fragments.

It is less clear what sorts of policies might provide positive encouragement to colonists to keep forest patches on their land. Schelhas suggests imposing taxes that increase as landowners remove forest. But if social scientists and policymakers could only figure out what makes farmers keep fragments initially (sometimes only to sacrifice them later), they might have a better handle on how to save them without flying in the face of powerful interests and desperate colonists:

The prerequisite to any new policy, though, is the need to give full recognition to the conservation potential of forest fragments - something that the best maps of the world's forest do not yet do. Whether or not conservationists fully appreciate the value of a remnant forest - even a damaged remnant - as the biodiversity reservoir it is depends on whether they view the fragment as a glass half full or half empty, says Alcorn. She adds, "The judgment of a glass half empty does not reflect the views of local people."
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Title Annotation:remnants of forests
Author:Misch, Ann
Publication:World Watch
Date:Jul 1, 1993
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