Soil is one of our most precious
resources in this world. Soil erosion is a natural process and has occurred
throughout geological history. The loss of this resource, though land
degradation processes such as wind and water erosion, is one of the most serious
environmental problems.
Types
of Soil Erosion
In general, there are several types of soil erosion
which are rain drop or splash erosion, sheet erosion, rill erosion, gully
erosion and stream bank erosion. The rain drop or splash erosion is the erosion
which preceded by the destruction of the crumb structure due to the impact of
falling raindrop on the surface of soil is termed as splash erosion. The sheet
erosion is the fairly uniform removal of soil in thin layers from the land
surface, often scarcely perceptible, especially when caused by wind. The areas
where loose, shallow topsoil overlies compact soil are most susceptible to
sheet erosion. The rill erosion is a form of water erosion in which numerous
very small and more or less straight channels are produced; the channels get
obliterated by ordinary use. It can be removed by normal tillage operations.
Apart from that, the gully erosion is a form of water erosion in which gullies
are produced by combination of unattended rills. The stream bank erosion
is stream banks are eroded by water either flowing over the sides of a stream
or scouring at the base.
Cause
of Soil Erosion
The main cause of the soil erosion is
due to the human activities. The human activities such as agriculture
activities bring lots of damage to soil and dirt. Many farmers attempt to
restore soil fertility by adding fertilisers or artificial nutrients but some
countries do not have this opportunity due to poverty or lack of
education. In South America soya is a quick-growing and valuable crop.
Despite some artificial fertilisers being added the soil is not allowed enough
time to recover its fertility or structure and is ultimately being eroded by
this human activity. Deforestation also a kind of activities which caused soil
erosion. The removal of trees without sufficient reforestation
has resulted in damage to habitat, biodiversity loss and aridity (drying of
soil). This human activity quickly accelerates natural erosion in two
ways. Firstly the removal of trees is a removal of nutrients and minerals
from the soil as the source of humus is greatly reduced. The natural dead
organic material that supplies the soil with its humus is generally leaves that
have fallen from the trees, animal droppings, tree fruit or decaying trees in
the soil. Secondly, deforestation accelerates soil erosion by leaving
large areas exposed to heavy rainfall (which can cause leaching or flash
floods) or wind erosion. Without the roots of the trees to keep the
soil structure in place the soil is loose and easier to erode. The
tropical rain forests of Brazil are seeing huge areas of forest being cut down
each day. Each year about 13 million hectares of the world’s forests are
lost due to deforestation.
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Figure 1: Deforestation in Brazil 2002 to 2008
Effect of Soil Erosion
The soil erosion will cause the reduction in water
quality. The eroded soil which contain the nutrients, fertilities and
herbicides can be deposited. At the same time it can cause the reduction in the
slope of land. In general, the heavier soil particles will be deposited during
the soil erosion, while finer colloidal clay remain in suspension. The soil
removed by gully erosion may be transported directly to rivers.
Solution of Soil Erosion
However,
there’s some ways to avoid or prevent soil erosion. One of the ways to avoid
the erosion of soil is to reforestation. Reforestation is the deliberate
planting of trees. This may occur in areas of deforestation, mountain
slopes or as a general practise to plant a seedling for each tree cut down. EU
legislation now controls the minimum height and age of tree that can be cut and
also offers incentives to farmers to turn part of their land over for forestry.
In areas like the Apennines in Italy or the mountainous terrain of the West of
Ireland this is seen as a valuable alternative to crop or animal farming. The
EU forestry grant aid is the initiative to attract farmers to grow and maintain
areas of forestry. In the 1900’s only half of one percent of Ireland was
classified as under forests but due to a change in laws and funds this has
risen to over twelve percent. The policy of ‘cut one, plant two’ is hoping to
see an increase in this figure and, in turn, the slowing down of the rate of
soil erosion.
