Forests in mountainous regions are particularly vulnerable to serious losses at the hands of local farmers, logging operations, and charcoal producers. Deforestation most severely disrupts such areas and the ecosystems that depend upon them. The uplands influence precipitation. The state of their soil and vegetation systems influence how this precipitation is released into the streams and rivers and onto the croplands on the plains below. The need for more agricultural land forces villagers to cultivate marginal, unproductive land on steep slopes and hillsides and to denude vast areas of forest cover. Such agricultural techniques and deforestation lead to soil erosion and ultimately to the loss of cultivated land. The problem is aggravated by increasing population pressures and the subsequent developments such as road building. The growing numbers and severity of both floods and droughts have been linked to such deforestation.
Mountainous regions account for a quarter of the earth's land surface and provide a home for a tenth of the world's people, while a further forty percent live in adjacent lowland areas (including some of the great fertile plains of the world) whose future is intimately bound to developments on the slopes above. Environmental deterioration in many mountain regions of the world is proceeding irreversibly, and the widening circle of destruction originating in the mountains is spreading to the plains, river systems and harbours. Damage to basic life support systems is accelerating in practically every mountain area of Asia, Africa and Latin America. There has been a marked increase in the destructive clearance of forests, in flood damage, silting, soil erosion and the spread of pests.
Population pressure in Asia is causing deforestation of the Himalayan foothills in Nepal, India and Pakistan, and a consequent loss of the soil. Demand for agricultural land for farming and wood for firewood and furniture and construction materials, as well as over-grazing by animals, causes the soil loss. The same process is occurring in the Andes in Peru, Colombia and all the other Andean countries. In Africa, the Ethiopian Amhara plateau, and the Kenyan, Tanzanian and Ugandan highlands, are all being deforested. In the Alps, the hill agricultural populations have drastically declined in France, Switzerland, Germany, Austria, Italy and Yugoslavia, while the tourist population increases. Developments have already destroyed much of the land.
Soil erosion is increasing in many hilly sections of both developed and developing countries through the extension of cultivation onto sleep slopes in an inappropriate manner, especially when accompanied by extensive deforestation.