Karen Chan 6S 22

#3 Soil erosion, demunition of forest and desertification result from land-clearance and over-harvesting. State and explain the undesirable effects of certain agricultural practices in the wise use of our natural resources.

Soil erosion is one form of soil degradation by which the topsoil is removed naturally by the wearing actions of rain and wind. Soil erosion may be a slow process and occur at an unnoticed rate. It may also occur at an alarming rate and cause serious loss of topsoil every year. Soil erosion is one of the major environmental problems faced by people today. It reduces agricultural and forestry production significantly and also degrades the quality of aquatic ecosystems. In the farmland, soil erosion is caused by inappropriate practices such as intensive ploughing and over-grazing.

Soil erosion causes soil loss, leading to the reduction of crop productivity and water pollution problems. The ecological impact of soil erosion by inappropriate practices can be summarized into two major areas: destruction of agricultural farmland and water pollution.

Soil erosion severely affects the stability and texture of soil. When the topsoil is removed, vital plant nutrients such as nitrogen, phosphorus and potassium are lost. The fertility of the soil decreases, leading to a reduced crop production. The breakdown of aggregates of soil particles due to intensive ploughing lowers the water-holding capacity of the soil, making it more susceptible to drought. If soil erosion is severe, the entire layer of topsoil and vegetation may be washed away. No more crops can be cultivated and the farmland may be abandoned.

Soil is washed away by heavy rainfall into streams and water courses below the eroded farmland. It can clog drainage ditches and stream channels, and may form silt in reservoirs and harbors. Pesticides and other agricultural chemicals are carried into aquatic bodies such as streams, rivers and lakes. They may contaminate the fish spawning areas and threaten aquatic life. Also, severe erosion and water runoff on mountain in slopes affect agricultural lands in the valley below. There may be a large quantity of sediment and flooding, which further decrease agricultural productivity and speed up water pollution problems.

Desertification is a process whereby productive farmlands in arid, semi-arid and dry sub-humid areas are degraded into desert. Desertification is caused by two main categories of factors: natural factors and, more importantly, human activities.

Farmlands are important natural resources. Humans rely on them for food. Desertification results in the loss of farmlands, and significantly threatens the living standard and well-being of people inhabiting the areas concerned. This also leads to social problems such as environmental refugees whose lands are too eroded for cultivation or rearing livestock. Desertification also has serious impact on the natural environment. It breaks down the fragile balance that allows plant and animal life to develop in arid, semi-arid and dry sub-humid zones. This breakdown of the equilibrium represents the start of a process that destroys the natural and stable ecosystem. Another problem is that the results of desertification in turn speed up the natural process of desertification. The vulnerability of soil wind and water erosion, the lowering of the water table, the impairment of the natural regeneration of vegetation, and the chemical degeneration of soils are all intensifying desertification.

Deforestation refers to the clearance of forests and the conversion of them for non-forest uses, including agriculture, animal grazing, timbering, and urbanization. Forests may also be destroyed by natural means such as forest fires. The forests can often recover gradually after forest fires. However, deforestation sue to human activities tends to be permanent. Among the different purposes of deforestation, agriculture and animal grazing account for the major destruction of forest.

Forests play a vital role in the biosphere. They act as a climatic buffer by retaining moisture in the air, cooling down the air, and maintaining the balance of carbon dioxide level in the atmosphere. They lock up nutrients and maintain their availability to other organisms. They hold the soil and retain rainwater. These help to prevent soil erosion, flooding, sedimentation and water pollution. Forests are also important as the habitats for a large variety of organisms.

Forest may be cleared for urban and industrial development. New urban and industrial areas are also converted from agricultural lands. This may have dramatic effects on the soil condition. Soil may be washed away from the bare ground during heavy rainfall. This may pollute the aquatic environment and also threaten aquatic lives.

Plants are the main energy sources for us. If we do not do action to reduce soil erosion, demunition of the forest and desertification, I think most of the farm cannot be use anymore. In addition, it will affect our life and also destruct the habitats of other organisms e.g. birds.