Deforestation is the loss of forestlands through encroachment by agriculture, industrial development, nonsustainable commercial forestry, or other human as well as natural activity.
Concerns about deforestation, particularly in tropical regions, have risen as the role that tropical forests play in moderating global climate has become better understood.
Environmental activists decried the apparent accelerating pace of deforestation in the twentieth century because of the potential loss of wildlife and plant habitat and the negative effects on biodiversity.
By the 1990’s research by mainstream scientists had confirmed that deforestation was indeed occurring on a global scale and that it posed a serious threat to global ecology.
Deforestation as a result of expansion of agricultural lands or nonsustainable timber harvesting has occurred in many regions of the world at different periods in history. The Bible, for example, refers to the cedars of Lebanon.
Lebanon, like many of the countries bordering the Mediterranean Sea, was thickly forested several thousand years ago. A growing human population, over harvesting, and the introduction of grazing animals such as sheep and goats decimated the forests, which never recovered.
Countries in Latin America, Asia, and Africa have also lostwoodlands. While some of this deforestation is caused by a demand for tropical hard-woods for lumber or pulp, the leading cause of deforestation in the twentieth century, as it was several hundred years ago, was the expansion of agriculture.
|nonsustainable timber harvesting|
The growing demand by the industrialized world for agricultural products such as beef has led to millions of acres of forestland being bulldozed or burned to create pastures for cattle.
Researchers in Central America have watched with dismay as large beef-raising operations have expanded into fragile ecosystems in countries such as Costa Rica, Guatemala, and Mexico.
A tragic irony in this expansion of agriculture into tropical rain forests is that the soil underlying the trees is often unsuited for pastureland or raising other crops. Exposed to sunlight, the soil is quickly depleted of nutrients and often hardens.
The once verdant land becomes an arid deserts, prone to erosion, that may never return to forest. As the soil becomes less fertile, hardy weeds begin to choke out the desirable forage plants, and the cattle ranchers move on to clear a fresh tract.
|Percentage of annual deforestation|
Beef industry representatives often argue that their ranching practices are simply a form of slash-and-burn agriculture and do no permanent harm. It is true that many indigenous peoples in tropical regions have practiced slash-and-burn agriculture for millennia, with only a minimal impact on the environment. These farmers burn shrubs and trees to clear small plots of land.
Anthropological studies have shown that the small plots these peasant farmers clear can usually be measured in square feet, not hectares as cattle ranches are, and are used for five to ten years. As fertility declines, the farmer clears a plot next to the depleted one.
The farmer’s family or village will gradually rotate through the forest, clearing small plots and using them for a few years, and then shifting to new ground, until they eventually come back to where their ancestors began one hundred or more years before.
As long as the size of the plots cleared by farmers remains small in proportion to the forest overall, slash-and-burn agriculture does not contribute significantly to deforestation.
If the population of farmers grows, however, more land must be cleared with each succeeding generation. In many tropical countries, traditional slash-and-burn agriculture can then be as ecologically devastating as the more mechanized cattle ranching operations.
Although logging is not the leading cause of deforestation, it is a significant factor. Tropical forests are rarely clear-cut by loggers, as they typically contain hundreds of different species of trees, many of which have no commercial value. Loggers may select trees for harvesting from each stand. Selective harvesting is a standard practice in sustainable forestry.
However, just as loggers engaged in the disreputable practice of high-grading across North America in the nineteenth century, so are loggers high-grading in the early twenty-first century in Malaysia, Indonesia, and other nations with tropical forests.
High-grading is a practice in which loggers cut over a tract to remove the most valuable timber while ignoring the damage being done to the residual stand. The assumption is that, having logged over the tract once, the timber company will not be coming back.
This practice stopped in North America, not because the timber companies voluntarily recognized the ecological damage they were doing but because they ran out of easily accessible, old-growth timber to cut. Fear of a timber famine caused logging companies to begin forest plantations and to practice sustainable forestry.
While global satellite photos indicate significant deforestation has occurred in tropical areas, enough easily harvested old-growth forest remains in some areas that there is no economic incentive for timber companies to switch to sustainable forestry.
Logging may also contribute to deforestation by making it easier for agriculture to encroach on forestlands. The logging company builds roads for use while harvesting trees. Those roads are then used by farmers and ranchers to move into the logged tracts, where they clear whatever trees the loggers have left.
Despite clear evidence that deforestation is accelerating, the extent of the problem remains debatable. The United Nations Food and Agriculture Organization (FAO), which monitors deforestation worldwide, bases its statistics on measurements taken from satellite images. These data indicate that between 1980 and 1990, at least 159 million hectares (392 acres) of land became deforested.
Environmental activists are particularly concerned about forest losses in Indonesia and Malaysia, two countries where timber companies have been accused of abusing or exploiting native peoples in addition to engaging in environmentally damaging harvesting methods.
Researchers outside the United Nations have challenged the FAO’s data. Some scientists claim the numbers are much too high, while others provide convincing evidence that the FAO numbers are too low. Few researchers, however, have tried to claim that deforestation on a global scale is not happening.
In the 1990’s the reforestation of the Northern Hemisphere, while providing an encouraging example that it is possible to reverse deforestation, was not enough to offset the depletion of forestland in tropical areas. The debate among forestry experts centers on whether deforestation has slowed, and, if so, by how much.
Deforestation affects the environment in a multitude of ways. The most obvious effect is a loss of biodiversity. When an ecosystem is radically altered through deforestation, the trees are not the only thing to disappear. Wildlife species decrease in number and in variety.
As forest habitat shrinks through deforestation, many plants and animals become vulnerable to extinction. Many biologists believe that numerous animals and plants native to tropical forests will become extinct from deforestation before humans have a chance to even catalog their existence.
Other effects of deforestation may be less obvious. Deforestation can lead to increased flooding during rainy seasons. Rainwater that once would have been slowed or absorbed by trees instead runs off denuded hillsides, pushing rivers over their banks and causing devastating floods downstream. The role of forests in regulating water has long been recognized by engineers and foresters.
Flood control was, in fact, one of the motivations behind the creation of the federal forest reserves in the United States during the nineteenth century. More recently, disastrous floods in Bangladesh have been blamed on logging tropical hardwoods in the mountains of Nepal and India.
Conversely, trees can also help mitigate against drought. Like all plants, trees release water into the atmosphere through the process of transpiration. As the world’s forests shrink in total acreage, fewer greenhouse gases such as carbon dioxide will be removed from the atmosphere, less oxygen and water will be released into it, and the world will become a hotter, dryer place.
Scientists and policy analysts alike agree that deforestation is a major threat to the environment. The question is whether effective policies can be developed to reverse it or if short-term economic greed will win out over long-term global survival.