II. ENVIRONMENTAL IMPLICATIONS OF UNSUSTAINABLE DEVELOPMENT
A. Major green environmental problems and causes
2. Soil erosion
Soil erosion is a natural process, especially in the glaciated valleys of the northern mountains of Pakistan. However, when the land surface on the mountain slopes is left bare of protective vegetation, mainly as a result of human activities, soil erosion is accelerated. That loss of soil results in a serious decline in fertility. The mountainous areas of NWFP are extremely susceptible to water erosion. The highest rate of soil erosion measured by Water and Power Development Authority was recorded in the Indus catchment area between Tarbela and a point 145 km upstream where the estimated loss was 150 to 165 tons of soil per hectare annually. Erosion rates in other watersheds are much lower, totalling approximately 20 tons of soil per hectare annually. The sediment load is higher during the monsoon period (June to September) when rainfall is high, resulting in flash floods. Wind erosion is generally more of a problem in the drier areas of the southern parts of NWFP.