Lillian
Liem 6S 26
Date:
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.