Deforestation is the permanent destruction of indigenous forests and woodlands. The term does not include the removal of industrial forests such as plantations of gums or pines. Deforestation has resulted in the reduction of indigenous forests to four-fifths of their pre-agricultural area. Indigenous forests now cover 21% of the earth's land surface.
WHAT ARE FORESTS AND WOODLANDS?
In a forest the crowns of individual trees touch to form a single canopy. In a woodland, trees grow far apart, so that the canopy is open.
GOING, GOING GONE!
Of great concern is the rate at which deforestation is occurring. Currently, 12 million hectares of forests are cleared annually - an area 1,3 times the size of KwaZulu/Natal! Almost all of this deforestation occurs in the moist forests and open woodlands of the tropics. At this rate all moist tropical forest could be lost by the year 2050, except for isolated areas in Amazonia, the Zaire basin, as well as a few protected areas within reserves and parks. Some countries such as Ivory Coast, Nigeria, Costa Rica, and Sri Lanka are likely to lose all their tropical forests by the year 2010 if no conservation steps are taken.
HOW DOES IT HAPPEN?
Deforestation is brought about by the following:
* conversion of forests and woodlands to agricultural land to feed growing numbers of people;
* development of cash crops and cattle ranching, both of which earn money for tropical countries;
* commercial logging (which supplies the world market with woods such as meranti, teak, mahogany and ebony) destroys trees as well as opening up forests for agriculture;
* felling of trees for firewood and building material; the heavy lopping of foliage for fodder; and heavy browsing of saplings by domestic animals like goats.
To compound the problem, the poor soils of the humid tropics do not support agriculture for long. Thus people are often forced to move on and clear more forests in order to maintain production.
CONSEQUENCES OF DEFORESTATION
* Alteration of local and global climates through disruption of:
a) The carbon cycle. Forests act as a major carbon store because carbon dioxide (CO2) is taken up from the atmosphere and used to produce the carbohydrates, fats, and proteins that make up the tree. When forests are cleared, and the trees are either burnt or rot, this carbon is released as CO2. This leads to an increase in the atmospheric CO2 concentration. CO2 is the major contributor to the greenhouse effect. It is estimated that deforestation contributes one-third of all CO2 releases caused by people.
b) The water cycle. Trees draw ground water up through their roots and release it into the atmosphere (transpiration). In Amazonia over half of all the water circulating through the region's ecosystem remains within the plants. With removal of part of the forest, the region cannot hold as much water. The effect of this could be a drier climate.
* Soil erosion With the loss of a protective cover of vegetation more soil is lost.
* Silting of water courses, lakes and dams This occurs as a result of soil erosion.
* Extinction of species which depend on the forest for survival. Forests contain more than half of all species on our planet - as the habitat of these species is destroyed, so the number of species declines (see Enviro Facts "Biodiversity").
* Desertification The causes of desertification are complex, but deforestation is one of the contributing factors (see Enviro Facts "Desertification")
