Natural Hazards: Causes and Effects - Disaster Management Center ...

watershed above the Panama Canal is causing increased siltation of a crucial reservoir, thereby
jeopardizing both the canal’s future utility and Panama City’s water supply.
Grazing
In Central and South America large areas of tropical forest have been cleared to create grazing
lands, a transition that is sometimes unsustainable and frequently of dubious social value. The
Brazilian government has granted huge concessions to both domestic and foreign corporations
wanting to raise cattle in the Amazon region. Large tax incentives have attracted investors to
grazing enterprises that would otherwise be uneconomical and will probably be short-lived. 5
Large landowners in Venezuela too are transforming forest into pasture, while in Central
America, virgin forest is giving way to pastures created by ranchers anxious to cash in on the
lucrative beef-export market to the United States. Pointing to massive soil erosion on denuded
slopes and to the widespread deterioration of soil structure, ecologist Joseph Tosi has
estimated that more than half of the pasture land in Costa Rica is not suited to grazing. 6
Firewood Collection
Firewood collection can contribute to the depletion of tree cover, especially in areas that were
only lightly wooded to begin with. Where the balance between tree growth and human numbers
permits, peasants can make do with dead wood and scraps from trees cut for other purposes.
Dense forests can produce a lot of burnable material without any live trees being felled.
The outright destruction of living trees to meet fuel need occurs most commonly around cities
and towns, where commercial markets for firewood and charcoal exist. Well-organized
syndicates bring fuel by truck, camel, and donkey cart into cities like Ouagadougou in Upper
Volta and Niamey in Niger, damaging the landscape in a widening circle.
Firewood scarcity is often most serious in areas far removed from designated forests. The
increase in tree planting required just to meet projected fuel needs, let alone wood for other
uses, is awesome; according to World Bank calculations, the rate of firewood planting (now
perhaps 500,000 hectares a year in the Third World, excluding China) must jump fivefold if
enormous ecological and economic costs are to be avoided.
Logging
Logging in humid tropical forests—much of which has been done by multinational
corporations—usually involves not clear-cutting but the “creaming” of the forest’s small
proportion of commercially valued species. However, the process of cutting and removing
selected trees amid dense foliage and on delicate soils usually causes far more destruction of
vegetation and wildlife than the bare statistics of extracted timber would suggest. One
Indonesian study revealed that logging operations damaged or destroyed about 40 percent of
the trees left behind.
Even when practiced responsibly, logging in many tropical forest areas leads to the permanent
loss of forests. Wherever loggers build roads and settlements, other people follow. With or
without government approval, cultivators move along new logging roads and into cut-over areas,
hoping to put down roots. The clearings and smoke plumes of slash-and-burn cultivation are
normal sights around new roads throughout the humid tropics. When these farms fail, they are
sometimes replaced by cattle pastures or by useless, tenacious grasses.