Lands degradation causes a reduction of
economical and biological production, of the complexity of vegetation, of
grazing, of the forest, by soil use, and some processes like water and wind
erosion, soil alteration, destruction of vegetable soil cover.
In Europe degraded areas have increased
of 40% between 1900 and 1970, because of an irrational use of arid or sub arid
lands; bad agricultural practices, overgrazing, deforestation, fires [ES1] and large urbanization have quadruplicated
desertification. Furthermore, human activities increase has produced a reduction
of resilience of arid land’s ecosystem.
Today it
seems that principles causes [E2] [ES1] [ES2] could be:
drought and
desiccation
human activities
overgrazing
deforestation
overcultivation
poor irrigation
practices
soil erosion and
salinisation
Drought and desiccation
[E2] [F1] [F2]
It is protracted rainfall failure. Its duration is
usually short-term, one to two years. In ecological terms, it is a dry period
from which an ecosystem often recovers rapidly after the rains
return.
This kind of ecosystem is called dryland: drylands have limited freshwater supplies.
Precipitation can vary greatly during the year. In addition to this seasonal
variability, wide fluctuations occur over years and decades, frequently leading
to drought. Over the ages, dryland ecology has become attuned to this
variability in moisture; plants and animals can respond to it rapidly. For
example, satellite imagine has shown that the vegetation boundary south of the
Sahara can move by up to 200 km when a wet year is followed by a dry one, and
vice versa.
The biological and economic resources of drylands,
notably soil quality, freshwater supplies [F1] [ES1] [ES2], vegetation, and crops, are easily damaged.
Drought is the most serious physical hazard to agriculture in nearly every part
of the world. People have learned to protect these resources with age-old
strategies such as shifting agriculture and nomadic herding.
However, in recent decades these strategies have become less practical due to
changing economic and political circumstances, population growth, and a trend towards more settled
communities. When land managers cannot or do not respond flexibly to climate
variations, desertification is the result.
Desiccation is a process of aridification resulting
from a dry period lasting in the order of decades. The main difference with
drought is above all its long term.
In many country of the world man continuously combats
drought and desiccation: in Australia, in USA, in Pakistan, in Canada [F1], in France and Sahel, in Tunisia, in Burkina Faso, in Morocco, in Brazil, in China, in Italy, in Senegal, in Nigeria, in Swaziland.
Human activities
The most commonly cited forms of unsustainable land
use are over-cultivation, overgrazing, deforestation, poor irrigation practices and any other
inappropriate land use and human management of
ecosystems.
Perhaps the most important cause of environmental
degradation is the rapidly increasing human and animal population pressure,
leading to overexploitation of and intensified stresses on the natural
resources. The human population in Africa's ASAL (arid and semi arid lands) has
doubled in the past three decades to nearly 400 million and continues to expand
at a rate of three percent a year. This means that the ASAL's natural resources
must feed an additional 12 million people every year, good weather or bad.
Besides, scientists from the Earth Environment
Research Institute, under the Chinese Academy of Sciences, have declared that
human activities have driven the desert in north China [E2] [F1] [F2] [ES] southward by approximately 300 kilometers over the
past 3,000 years.
Today scientists assert the importance of physical
geographical conditions and climatic variation as conditions to cause
desertification, but the desertification process is slow. Human activities have
certainly accelerated and promoted the desertification processes as the leading
factors to cause desertification. Probably international economic forces can
encourage people to overexploit their land.
In fact international trade patterns can lead to
the short-term exploitation of local resources for export, leaving little profit
at the community level for managing or restoring the land. Similarly, the
development of an economy based on cash crops, or the imposition of taxes, can
distort local markets and promote overexploitation of the land. Ignorance,
errors, and natural and man-made disasters can also contribute to land
degradation. Disasters such
as wars and national emergencies also destroy productive land by displacing its
managers or causing heavy concentrations of migrants to overburden an area.
It is important to underline that an expanding human population [E2] is the ultimate driving force behind
desertification. More people in an area inevitably exert a greater pressure on
that area's resources.
But the causes of desertification are complex, and
the relationship between two variables such as population and desertification is
not so clear. For example, a decline in population can result in desertification
since there may no longer be enough people to manage the land adequately. Many
hillside terraces in Yemen have fallen into disrepair with the exodus of labour
to neighbouring oil-rich countries. Examples can also be cited of areas that
support large concentrations of people without much degradation, such as around
the city of Kano in Nigeria.
Overgrazing is the exhaustion of land and pasture resources by
continuous grazing [E2] of animals. It results in weakened forage plants
with reduced root system and lower forage yield, increased soil erosion, water
runoff and weeds. Consequently to the growing of population, the extension of subsistence
farming and marginal grazing activities are going to cover
larger proportions of the region. Besides there is an increase of fuel wood
collection by the population and consequently an increase in deforestation.
Overgrazing has made the Rio Puerco Basin of central
New Mexico one of the most eroded river basins of the American West and has
increased the high sediment content of the river.
Deforestation [E1] [E2] [F1] is the permanent destruction of indigenous forests [F1] and woodlands. One of the primary causes of deforestation in Africa is that population growth has rendered traditional patterns of
agriculture unsustainable. These include the practice in parts of Southern and
Central Africa of shifting cultivation to newly cleared land after several
seasons, increasing the need for cleared land and putting excessive strain on
Africa's forest resources. In Madagascar and parts of Central Africa,
slash-and-burn agricultural practices are also contributing to the problem of
deforestation
Unless stewardship practices are changed, Africa's
food and fuel security will be threatened, and erosion, land degradation and
desertification will become even more pressing realities.
Today many environmental organizations think that
with the actual deforestation there won’t be more
indigenous forest in Africa
from 5 to 10 years.
Poor irrigation practices and overcultivation
Water [E2] [ES1] [ES2] [F1] [F2] is a scarce resource and best
management practices must be applied when irrigating crops, to conserve water and sustain the
environment.
Really, we can
say that it is not completely true that Africa hasn’t water: Africa hasn’t
enough clean, safe, drinkable water.
What would cause this? How could a regional area with
enough water be having a shortage, not with water, but clean drinkable water?
There are several main reasons why North Africa is
having a shortage of drinkable water: agriculture, that leads to salinisation of the soil, pollution, caused by waste
management and industrial waste, water management [E2], it contributes to there being a shortage and the
improper use of the little water that these countries have left. The water
management is unorganized and inefficient.
The use of agricultural fertilizers, pesticides,
contaminates groundwater, aquifers, and surface waters.
Finally there’s another important cause of the
inability of african water: the pollution caused by the presence of too many
sediments coming from mountains, that are today more erodible consequently of
the soil erosion.
Soil erosion
Drought, desertification, overcultivation,
overgrazing and human activities lead to the soil erosion [E2] [E3] [E4] [E5] [ES1] this is a key problem because soil
is a non-renewable resource. For nature to form a layer of top-soil thick enough
to support plant life takes thousands of years. Through human misuse, the layer
can be destroyed in a few decades, or in a few years. Once eroded, its loss is
permanent.
Some arid and semi-arid lands can support crops, but
additional pressure from greater populations or decreases in rainfall can lead
to the few plants present disappearing. The soil becomes exposed to wind,
causing soil particles to be deposited elsewhere. The top layer becomes eroded.
With the removal of shade, rates of evaporation increase and salts become drawn
up to the surface. This is salinisation, and inhibits plant growth. The loss of
plants causes less moisture to be retained in the area, which may change the
climate pattern leading to lower rainfall.
Fragile soils are being degraded through improper
cultivation practices, fuel wood cutting leading to deforestation, and
overgrazing destroying the ground cover over large areas.
Soil can be eroded away by wind and water. High winds
can blow away loose soils from flat or hilly terrain.
Water erosion generally occurs only on slopes, and
its severity increases with the severity of the slope. In many parts of the
world much of the wind erosion occurs in winter when the ground is frozen, but
the upper most soil layer is dry and loose. Water erosion occurs during the
spring with the thawing and melting action of the snow.
Activity Two: Exploring Causes
-
Make a discussion on the question: “What are the causes of desertification?”
Natural
causes:
Drought
Wind
Human
activities:
Deforestation
Reclamation
-
Make with the class a chart of the
causes
-
Discuss and give oral
answers
-
Continue with activity
one:
have each group member choose
an area the group has identified and research and evaluate possible causes for
desertification, such as degradation of natural resources, global climate
changes, effects of economic development, and other possible factors.
Challenge students to create
model action plans that could combat desertification or promote rehabilitation
in an at-risk area they choose. Before the groups begin their plans, remind
students that because ecological processes such as desertification override
boundaries between nations, a high degree of international cooperation is
necessary to combat the problem.
