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Desert and Forests

Throughout history, people have increasingly used the land on which they live, tailoring it to their purposes. In Europe and North America, forests were cleared over the centuries to make room for agriculture, Today, machinery can change the face of the landscape, deliberately or accidentally, at an alarming rate. Increasing populations in the developing world are putting natural ecosystems under extreme pressure. Changes in land use can be felt outside the territory in which they occur, even globally. This globe shows changes in forest and desert areas during this century. In the tropics, it is estimated that only half of the original rain-forest cover remains. Most of the remaining forest is in the Amazon basin in South America. In 1990, satellite surveys showed that the rate of destruction in the Amazon was almost double that of 1980. Brazil has now ended its policy of encouraging city dwellers to settle the forest areas and enforces a licensing arrangement to control the cutting of forests. Other countries in Africa and Southeast Asia, eager for export earnings often to pay off loans frome the developed world, are continuing with large-scale logging and the clearing of forest lands for agriculture.

Forest land is not suitable for sustained agriculture. Once clearnd of trees, the topsoil is quickly washed away and cultivation must move to fresh areas. Meanwhile, the increased sediment load of rivers can cause siltation and flooding downstream. In addition to the suffering caused by such side effects, the development of forest lands can be tragic for native populations who have exploited the forest in a sustainable way for centuries.

Trees absorb carbon dioxde from the atmosphere, using sunlight to turn it into oxygen and carbohydrates. The tropical rain forests are the lungs ot the planet. When they did, trees release the stored carbon back into the atmosphere as carbon dioxide, which can lead to warming by enhancing the "greenhouse effect." Seventeen percent of extra carbon dioxide in the atmosphere today has come from burning forests.

In sub-Saharan Africa, the "carrying capacity" of the land is under severe strain. Increasing population has led to destruction of treea and shrubs for fuel. The reduction of fallow periods on poor soils has been made wores by several years of drought. When rain or wind comes, the depleted vegetation cover an no longer hold the soil in place, leading to severe erosion.

In the developed world, intensive cutivation of marginal land, often reliant on large-scale irrigation, can lead to long-term decline. Salt can build up if irrigted land is not drained porperly, resulting in soil unable to support crops. Countries of the former Soviet Union, as well as the southwestern Uintd States, suffer in this way.

Another problem associated with the industrialized countries is "Waldsterben," or "forest death" in German. The remaining forests in Europe, North America and China are declining for a number of reasons. Originally mixed forests, they are now ofen harvested and restocked with the same species, reducing ecological diversity and increasing vulnerability to insects, fungi and stresses.

One of the largest contributors is "acid rain," sulfates and nitrates from the burning of fossil fuels, carried by the winds and washed out by rain or snow. Airborne pollutants do not respect national boundries, with forests in Sweden, Germany and Canada afflicted by pollution from the United Kingdom, Eastern Europe and the northeastern United States. Acid rain also leads to the acidification of lakes and rivers, affecting the health of fish stocks and reducing nutrients in the soil.

Copyright 1996 Planetary Visions Ltd.

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