Land occupies about 29 per
cent of the earth's surface, the rest 71 per cent is water. Land has soils,
forests, agricultural lands, mountains, human habitations, animals, water
bodies, etc. These components make up the land system, that supports the
biodiversity in a region.
Man has been
exploiting land and its resources. He has been clearing forest lands for
agriculture. However, over the years, the agricultural practices have undergone
a great change. Today, man cultivates genetically modified food crops and cash
crops. These require a change in the techniques of production and support
systems like better irrigation facilities, inputs like fertilizers, and
pesticides. The demand of growing population for shelter, economic activities,
transportation and recreational activities have added pressure on the land-use
pattern. In order to meet the demand for land, natural lands are being
converted to other land- use patterns, resulting in destruction of the land
cover.
The change in
land-use patterns induced by human activities can be judged from the following:
(i)
From 1700 to the mid-1980s, the cropland increased globally from 392% to 466%.
It naturally grew at the expense of forest, grassland and wetlands.
(ii)
The net irrigated cropland has increased, over the last 200 years, from 80,000
sq. km. to 2,000,000 sq. km.
(iii)
The worldwide tree cover has decreased by about 15%. It is estimated that the
annual global loss in forest cover may be as high as 1200,000 sq. km.
(iv)
Land-cover change has led to the loss of 27,000 species annually in tropical
forests.
Land degradation
takes place because of two causes:
(i)
Natural Causes which include different types of weathering and erosion
processes like landslides^ earthquakes, desertification, drought and floods.
(ii)
Man-made Causes which include human activities such as mining, farming,
deforestation, waste disposition, development activities like setting up human
habitations, transport and communication, constructing dams and bridges, etc.
NATURAL CAUSES
In this chapter we
shall have an overview of the natural causes as we shall deal with them in
detail later under the head, Disaster Management
The following are
the natural causes of land degradation:
(a) Earthquakes: The violent earthquakes bring about changes on the surface
of the earth. Earthquakes not only destroy human habitations by damaging
buildings, electric and water supply but also submerge land under the sea. Some
times rivers disappear or change their courses or get flooded.
(b) Desertification: It is a process of sustained land degradation in arid,
semi-arid and dry sub-humid areas. Areas next to deserts are more prone to
desertification because of increasing aridity and wrong use of the resources
like cutting of trees, overgrazing and clearing of the marginal lands. Human
activities also accentuate the rate of desertification of an area. Such
activities include the following:
(i)
Overgrazing of land exposes soil to forces of erosion and transforms land into
barren landscape and finally into a wasteland.
(ii)
Mining activities for extracting natural resources adversely affect the local
landscape due to large scale digging up process using most sophisticated mining
excavators.
These activities
affect the moisture content of the soil leading to desertification. For
example, in Goa, where manganese is found on the ground surface or a few
metres below it, the surface soil is stripped off for the mineral exploitation,
leaving behind a desert like landscape.
(iii)
Unscientific irrigation of arid lands for a considerably long period
contributes to desertification.
(iv) Desertification of an area takes place from uncontrolled exploitation of
groundwater, mismanagement of watersheds, siltation and drying up of rivers.
(c) Landslides: These refer to sudden or gradual movement of rocks or soil
masses down the hill slopes due to the force of gravity. The occurrence of
landslides is more common during the rainy season. Landslides result in the
movement of soil, solid rocks and soil masses. These have a significant
degrading effect on land.
(d) Floods and Drought: Floods
cause loss of life and property. They degrade land by flooding settlements.
They destroy agricultural land through sand deposition and salinisation. They
destroy forests, wildlife, leaching off the soil cover of its nutrients, etc.
Drought refers to
the period of dryness caused by the absence of rainfall or due to rainfall
being lower than the average rainfall of a particular region. Drought causes
following effects— (i) shortage of food due to the decrease in crop production;
(ii) lowers the level of ground water; (iii) lowers the rate of microbial
decomposition in soil; (iv) decreases the rate of mineral formation in the
soil; and (v) leads to increase in the number of forest fires.
MAN-MADE CAUSES OF LAND DEGRADATION:
POPULATION GROWTH
Two centuries ago,
R.T. Malthus propounded a theory of the relationship between population growth
and economic development. He wrote an essay in 1978 on The principle of
population' and drew the concept of diminishing returns. He said that
population will grow at geometric rate (i.e., 10, 20, 40, 80...) whereas, at
the same time food supplies increase only at a roughly arithmetic rate (i.e.,
10, 20, 30, 40...) That is to say, that the resources cannot match the
pace of population growth.
Population grows
fast in the developing countries. India's population explosion neutralises the
benefits of its economic progress. Most of the economic activities take place
in cities which offer a hope for a better life. So there is pressure on
available resources in the cities. Expanding cities encroach on surrounding
areas, converting for its use — any kind of land, including fertile fields.
Land is also utilised for infrastructure, such as roads, industries, tourist
facilities, and educational complexes. Better land-use planning, creation of
satellite towns, and other measures are necessary. Population explosion has
also added pressure on food, forests, water supply and energy resources. If
proper steps for population control are not taken, the country will face
serious consequences in the near future. One must remember that man must
control nature and he must also control his numbers.
POPULATION PROBLEMS
The growing
pressure of population on resource base, especially on arable land, has created
many socio-economic and environmental problems. The population problems differ
from region to region.
Most of the world
population lives in the developing countries. China and India have about 20 per
cent and 16 per cent respectively of the total world population. The developing
countries have over three-fourth of the total world population. Rapid growth of
population, unemployment, inadequacy of housing and health, diminishing
resources are the problems affecting the developing countries.
Increased Demand
for Agriculture: Rising population needs more land for farming to meet the
increased demand for food. Demand for land is also enhanced by some external
interests. For example, forests are cleared to convert the land to grasslands
in order to provide fodder for cattle. All this adds pressure on land and
contributes towards land degradation and soil pollution.
Intensive farming
operations exhaust the soil of its nutrients. The fertilisers and pesticides
used to enhance production get washed off the fields and pollute rivers and
lakes and sometimes leach into the sub-surface and lower the quality of the
groundwater. Moreover, both fertiliser production and irrigation require
energy; the harnessing of energy takes toll of the environment.
Unemployment: In
most of the developing countries, the population is largely dependent on
agriculture. There are very limited opportunities for the semi-skilled,
unskilled and highly educated people. The rural areas are the places wherefrom
large number of unskilled workers migrate to cities, thus creating pressure on
the land.
URBANISATION
The great exodus of
rural population into the cities in order to have better earning opportunities
has led to the deterioration in the environment of urban areas. In fact, the
rapid pace of urbanisation has transformed the natural green landscape into a
polluted landmass. Urban sprawl and slums expansion create pressure on
land use and environmental problems. The highly productive agricultural land is
encroached upon by urban houses, roads and industries. Due to uncontrolled
urbanisation rapid environmental degradation has taken place causing shortages
of housing, worsening water quality, excessive air pollution, noise, dust and
heat and the problems of disposal of solid wastes and hazardous wastes.
Urbanisation, 'associated with industrialisation, has created environmental
problems such as:
(i)
growth of slums;
(ii)
industrial pollution (air, water, soil).
The problem of air
pollution is acute in urban areas. One of the reasons is combustion of fossil
fuels and their products. Motor vehicles in urban areas are many and they
produce hydrocarbons, carbon oxide, nitrous oxide and lead particles. Most
noticeable effects of air pollution are reduced visibility, fog formation and
reduced solar radiation.
CONSUMPTION
In the modern
civilisation people consume more than they produce. Therefore, the gross
consumption is rising faster than the production. The US has only 4.7% of the
global population, but consumes 25% of the world's resources. If we compare an
ordinary Indian citizen to a US citizen, the latter uses 50 times more steel;
50 times more energy; 150 times more synthetic rubber; and 250 times more motor
fuel.
The wealthiest
nations in the developed countries consume the most resources, release the most
pollution and also have the greatest capacity to make the necessary changes.
The increased production in wealthy nations no longer serves to satisfy needs,
rather, the creation of needs serves to increase production.
The exploitation of
resources by rich nations has a considerable impact on landscape.
The
impact of land degradation can be summarised as follows:
(a)
removal of trees, vegetation;
(b)
construction of houses,
(c)
construction of septic tanks,
(d)
diversion of nearby streams for public supply,
(e)
accelerated land erosion,
(f)
pollution of streams and wells.
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