Soil erosion and land degradation

Soil erosion and land degradation is one of the most critical problems affecting the future economic development in Sri Lanka. The demands of a rapidly expanding population in turn has resulted in a high level of environmental degradation. The more important manifestations are heavy soil losses; high sediment yields; soil fertility decline and reduction in crop yields; marginalization of agricultural land; salinization; land slides and deforestation and forest degradation.

(a) Heavy Soil Losses
It has been estimated that nearly one third of the land in Sri Lanka is subjected to soil erosion, the erodible proportion ranging from less than 10.0% in some districts to over 50.0% in others. Severe erosion takes place in the hill country on sloping lands under market gardens (vegetables and potatoes) tobacco, poorly managed seedling tea and chena cultivation. Soil erosion is also considered a threat to agricultural production in the rainfed farming areas in the Dry Zone.

(b) High Sediment Yields
A part of the soil that is removed is transported by rivers and streams leading to sedimentation of reservoirs, downstream floods etc., commonly referred to as the off-site effects of soil erosion. Some recent studies undertaken within the Upper Mahaweli catchment have shown high rates of sediment yield in some rivers. Sedimentation is also taking place in small village tanks in the Dry Zone.

(c) Soil Fertility Decline and Reduction in Crop Yields
It is commonly believed that the depletion of soil fertility has led to a loss of productivity of agricultural lands in the country. The decline in yields of major food crops as well as plantation crops over the past several decades has been attributed to the loss of valuable top soil due to erosion. It is widely accepted that agriculture on sloping lands in many areas is generally maintained by the artificial replacement of nutrients removed by erosion.

Land Resources of Sri Lanka