The region has had a long history of human settlement, and people have left their mark on the landscape. The open rolling grasslands of Thailand, east Java and the Lesser Sunda Islands, which extend from Bali to Timor, are great swathes of once forested land that was cleared for agriculture a long time ago and subsequently abandoned. Traditional peoples living at low densities were once able to practice shifting cultivation in ecological balance with their environment. The Land Dayaks of Borneo, the Muong people of Laos and the hill tribes of Burma all cleared land, grew their crops and then let the land lie fallow for several years before returning to cultivate it again. As human populations have grown and remote areas have been opened up for new settlers, more forest areas have been cleared, often on vulnerable lands with nutrient-poor soils. These fields may provide crops for a year or two, but with regular burning they cannot return to secondary forest.
Eventually these abandoned fields become a sea of alang-alang (cogon) grasslands. These are becoming increasingly common throughout tropical Asia. The tough, tall grass is difficult to supplant, has little value except for new grazing and thrives on burning. Fires sweep through the grasslands, destroying adjacent plantations of newly planted trees and eating into the natural forest.
The demands of agriculture now place tremendous pressures on wilderness areas in the region. Forests are being felled by farmers who cultivate the land and then move on, for plantations, and to satisfy the world's seemingly insatiable appetite for hardwoods. Tropical rainforests are disappearing at an alarming rate. Malaysia, where an estimated 230,000 ha (570,000 acres) are cut down every year, will lose all its remaining forest during the 1990s if this rate continues.
Forests have also been lost as a consequence of war, as in Vietnam where 2 million ha (5 million acres) of forest and mangroves were sprayed with herbicides such as Agent Orange during the conflict with the United States between 1964 and 1975. In Borneo large areas have been lost to forest fires, which consumed 3.6 million ha (8.9 million acres) in Kalimantan, in the center and south of the island, and another million in Sabah in the north during the drought year of 1983. Fires started by farmers practicing shifting cultivation raged out of control and were spread by the underlying coal and peat seams; they swept through forests that had already been logged, and damaged the edges of primary forest. In 1987 east Kalimantan was a sea of fire again until the flames were quenched by the late monsoon rains.
Most countries in Southeast Asia have already lost at least half their forest cover. In densely crowded Java only 9 percent of the island remains forested. Even on Borneo, renowned for its vast tracts of tall dipterocarp and swamp forests, the forest boundaries are being pushed back farther and farther inland and every major river is congested with floating logs. Until people throughout the world become aware of the threat and there is a dramatic reduction in the use of tropical hardwoods, the destructive deforestation of Southeast Asia will continue.
Sometimes the need for conservation is understood only too well by the local people but ignored by governments and business interests, more concerned with short-term profit than the long-term cost of environmental folly. The Penan of Sarawak, hunter-gatherers who harvest wild meat and a few minor forest products for their own use, are now building blockades to halt the timber trucks of the companies that are destroying their traditional lands. Local people, struggling for a livelihood from shifting cultivation, are often blamed for starting the fires that lead to forest losses, but the areas that burn most intensely are those that have already been logged.
Many countries in the region are suffering the environmental consequences that follow the loss of natural landscapes -droughts where there was once rain, floods sweeping down deforested valleys, and erosion of coasts and hillsides. Lowland habitats, particularly on the fertile alluvial lands along river valleys, are the first to disappear. Swamps, mangroves and wetlands are drained for development and agriculture, forests are cleared, limestone hills are quarried for cement, coral reefs are burned for lime and damaged by blasting to kill the fish. As these habitats are lost, so too are the benefits they provide: natural products, fish nurseries, coastline and watershed protection.
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