Download Lillian Liem 6S 26

Lillian Liem 6S 26
Date: 23-12-2003
Soil erosion, demunition of forest and desertification result from land-clearance
and over-harvesting. State and explain the undesirable effects of certain
agricultural practices on the ecosystem.
The misuse of agricultural farmlands and inappropriate agricultural
practices such as over-harvesting and land-clearance cause soil erosion,
demunition of forest and desertification.
Agricultural practices on the ecosystem
Over-harvesting increases the impact of soil quality. When crops
are harvested, plant tissues together with large quantities of minerals
are taken away. Thus the nutrients required by the crops are rapidly
depleted from the soil. If fallow periods are not sufficient and fertilizers
are not applied appropriately, the soil will eventually become infertile.
Land-clearance is the general practices to satisfy the demands for
lands for development. It involves the conversion of agricultural lands and
natural areas (such as forests, wetlands and other habitats) into a form
that is suitable for urban ad industrial development.
However, these human activities have been causing undesirable
affects on the natural environment. They destroy natural habitats and
hence threaten biodiversity. Also, they are responsible for degrading
environmental quality, leading to pollution.
Soil erosion
Soil erosion is one form of soil degradation by which the topsoil is
removed naturally by the wearing actions of rain and wind. It reduces
agricultural and forestry production significantly and also degrades the
quality of aquatic ecosystems. It caused by intensive ploughing and
over-grazing. Soil erosion severely affects the stability, structure and
texture of soil. 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. Furthermore, soil is washed away by heavy
rainfall into streams and water courses below the eroded farmland.
Pesticides and other agricultural chemicals are carried into aquatic
bodies such as streams, rivers and lakes. This further decrease
agricultural productivity and speed up water pollution problems.
Demunition of forest
Demunition refers to the conversion of forests for non-forest uses
such as agriculture, animal grazing, timbering and urbanization. Farmers
open up an area by cutting down the trees. The wood are then piled up and
burnt, and crops are grown in such ash areas. They move and clear a new
land after the soil becomes infertile. Moreover, trees are always chopped
down to allow grass to grow, in order to feed livestock such as sheep and
cattle. Animal grazing accounts for nearly 12% of tropical deforestation.
Demunition of forest causes great impact on both the environment and
humans. These include loss of nutrients availability, soil erosion, flooding,
water pollution, hotter and drier weather conditions, global warming, as
well as reduction in biodiversity.
Desertification
Desertification is caused by over-exploitation of woody resources,
over-harvesting and monoculture of cash crops, etc. They usually involve
the removal of nutrient-rich topsoil, leaving coarse, sandy particles with
poor water-retaining ability. As a result, the soil becomes unsuitable for
vegetation growth and is turned eventually into a desert.’
Desertification results in the loss of farmlands, and significantly
threatens the living standard and well-being of people inhabiting the
areas concerned. Also, it breaks down the equilibrium of a process which
destroys the natural and stable ecosystem.