| Fires are often set intentionally in a process called "slash-and-burn" agriculture. A farmer clears the land by setting fire to the trees, and is left with a charred patch of open land after the flames subside. Though this may fertilize the soil for a while, it opens up a whole new set of problems, and carbon dioxide is released into the atmosphere, which contributes to the greenhouse effect, providing even more problems. The "haze" in Indonesia and Malaysia during 1997 was the product of huge fires burning in the rainforest, many of which were originally set to clear land and then got out of control. |
Now mostly in tropical regions, fires are set to clear land for agriculture and pastures. Photo by Maya Walters. |
| Effects from the haze will continue to be seen well into the future, as many of the millions of people exposed to the pollution will develop health problems associated with such exposure. The haze was particularly bad because many peat bogs were in the burning areas, and large quantities of carbon particles were being released into the air. These peat fires are particularly dangerous. Peat has been accumulating in lowland areas for thousands of years and the bogs can be 20 feet deep. They are usually moist and excellent at soaking up and storing rainwater, preventing flooding. When it is dry, however, the peat burns easily. Fire moves deep underground in the dry peat bog, where it is almost impossible to put out. Fires that began in 1983 are still burning underground in peat bogs today. One of the major sources of air pollution in the 1997 haze was from a one-million hectare peat bog on the island of Borneo, which the government was draining and it began to burn. |
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An aerial view of a recently deforested and burned tract of land in the Guatemalan rainforest. This land will soon be used for cattle grazing. Photo courtesy of Dana Slaymaker. |
| Forest fires move in varying and often unpredictable ways. Ground fires creep through the duff, and fires may smolder below the surface for long periods of time. Surface fires are another form of forest fire, and move along at up to 1.3 meters in height. Crown fires occur higher in the trees (in the upper branches known as the "crown" of a tree), and can be of several different varieties. These include "dependent crown fires", which use convection* to pre-heat the crown, and most dangerous of all, independent crown fires which leap from tree to tree. |
fire -- page 2 of 4
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