Soil Erosion and Desertification

Contents

1. Soil Erosion 3

2. Desertification 8

3. Case Study: Desertification 14

of China

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1. Soil Erosion Soil erosion is a naturally occurring process which involves the loss of the top soil by wind and rain. This is a slow and continuous process which has been taking place for millions of years. The rate of soil erosion is equivalent to the rate of weathering of surface rocks i.e. new soil formation from weathering of surface rocks quickly replaces the soil being lost. Soil erosion is a form of soil degradation along with soil compaction, low organic matter, loss of soil structure, poor internal drainage, sanitization and soil acidity. These types of soil degradation caused by human activities (and in some cases naturally) all contribute to accelerated loss of the topsoil which have far reaching consequences.

Causes:

Soil erosion can either be a product of natural processes or an outcome of human activities. Since this report is giving an overview of the unnatural causes of soil erosion, it is more befitting to state and analyze the human causes of this type of soil degradation. The following are the main human causes of soil erosion:

Clearance of natural of vegetation (deforestation): This creates surfaces bare of vegetation which makes the soil more vulnerable to erosion especially if

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Figure1.2 woodcutters clearing forests

Figure 1.1: A road side view of dramatic erosion in Eritrea, Africa

the trees on slopes are cut down. There are no tree roots to hold soil particles in place, no tree leaves and branches to breakdown the force of the falling rain and no obstacles such as tree stems to restrict the flow of water down slopes.

Overgrazing: When cattle and other livestock are allowed to graze in a pasture beyond the carrying capacity of vegetation, patches of bare soil appear. Overtime, the livestock eat the grass down to the roots and their hooves trample on the soil into a hard layer reducing the ability of the soil to retain water as a result the rain water runs off the surface of the soil without ever penetrating it and carrying the topsoil with it.

Over cultivation: The practice of constantly cultivating and growing crops without letting the soil fallow to recover as consequence the soil quality and productivity is reduced. The worst form of over cultivation can be witnesses in area where monoculture is practiced (growing the same crop on the same land year after year). A reduction is soil fertility can lead to less plant to growth therefore there will be less plant cover and rate of soil erosion further increases.

Bad Farming practices: If the land is ploughed year after year especially in sloped areas natural channels and furrows are created for rainwater to flow down the slope carrying away the soil particles. Also, overuse of fertilizers and leaving the land bare of any vegetation cover will increase the rate at which the soil is eroded.

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Figure 1.3 Overgrazing: see how patches of bare soil have started

to appear.

Figure1. 4 over cultivated farmland

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Figure1.5 shows the many causes of soil erosion and the policy arena which stimulate it

Consequences:

Soil Erosion has adverse effect on the environment which cannot be reversed or fixed. Here is a summary of the series of chain effects soil erosion has on the environment.

Additionally, most of the eroded topsoil is deposited in rivers where it will form excessive amounts of sediments on the riverbeds as result damaging fish breeding areas and causing rivers to overflow thus floods become more frequent.

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Forced Migration

Desertification

Environment suffers from prospects of famine

Excessive soil degradation by Farmers

Farmers income decreases

Crop Yeilds Go down

Soil becomes Infertile

Increased Eutrophication

Overuse of Fertilizers by Farmers

Reduction in soil quality

Methods of Tackling:

Soil Erosion is a natural process which must take place for the benefit of the environment. However, the effects of accelerated soil erosion due to human activities on the environment are often severe and irreversible. Therefore, we cannot inhibit soil erosion nor fix the damaging effects on the environment but we can implement measures to avoid further damage to the environment due to human actions. Here are some of the important and useful measures people particularly farmers can apply into their fields:

Avoiding removal of tress in areas where soil is vulnerable to erosion, and planting trees to aid in stabilizing the land.

Steer livestock away from grazing areas where soil is most likely to erode.

Making terraces on hillsides if crops are to be grown, to restrict the soil from being easily washed away by rain water.

Adding humus e.g. animal dung, peat etc. to the soil to make it more likely to stick together.

Keeping a surface vegetation cover on the soil all year, so that their roots will hold the soil place.

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Figure1.6 the slopes are terraced to reduce the soil erosion by rain

2. DesertificationDesertification is process by which a region exposed to human disturbances such as deforestation; overgrazing or poorly managed agriculture, starts to develop desert like conditions and if theses disturbances escalate; the desert spreads and engulfs area formerly carrying surface vegetation. Desertification is in response to changes in climatic conditions which (are occasionally natural or) are mostly induced by human activities.

Causes:

Desertification is a product of a number of factors involving human activities, natural processes and population rise. Its causes can be closely linked to that of soil erosion since soil erosion inevitably leads to desertification. The following are the causes of desertification which are under two sub-headings:

Natural Causes;

Climatic Shift - Climatic shifts such as a decline in rainfall leads to drought which initiates a regression in vegetation cover. As a result the soil is vulnerable and its structure is destroyed by the various types of soil degradation. Eventually the sand become dry as well as sandy and is blown away by the wind or washed away by rain leaving the infertile lower soils layers exposed which then bake in the sun and become unproductive hot pans. Desertification then takes place.

Human Activities;

Overgrazing- Increase in demands for food due to an increasing human population forces pastoralists to graze more cattle and other

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Figure 2.1 Desertification of an area previously covered with vegetation.

livestock in pastures where the livestock exceeds the carrying capacity of vegetation thus patches of bare soil appear. Overtime, the livestock eat the grass down to the roots and their hooves trample on the soil into a hard layer reducing the ability of the soil to retain water as a result the rain water runs off the surface of the soil without ever penetrating it and carrying the topsoil with it. Ultimately, the infertile lower soils layers are exposed which then bake in the sun and become unproductive hot pans. Desertification then takes place.

Over cultivation- The rising demands for food due to the ever-growing population force farmers to put pressures on the environment. Farmers respond by constantly cultivating and growing crops without letting the soil to recover. As a consequence the soil quality and productivity is reduced. A reduction is soil fertility can lead to less plant growth therefore there will be less plant cover as a result the soil is vulnerable and its structure is destroyed by the various types of soil degradation. Farmers further react by overusing fertilizers. This causes more adverse effects and any hope for soil recovery is diminished as all the nutrients leach out of the soil by rain. Finally, the sand become dry as well as sandy and is blown away by the wind or washed away by rain leaving the infertile lower soils layers exposed which then bake in the sun and become unproductive hot pans. Desertification then takes place.

Employment of inappropriate irrigation methods- Any water used for Irrigation contains dissolved salts to some extent therefore soil salinisation ( the process by which top soil becomes concentrated with salt) is inevitable. However, salinisation is increased by poor water drainage and the use of salt water for irrigation. The increase in soil salinity reduces the ability of plants to absorb water from the soil as a result impending plant growth as well as a leading reduced to vegetation cover therefore land

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Figure 2.2 Overgrazing is one of the principal causes of desertification. When the herds are too numerous compared to the available vegetation, the vegetation is

unable to regenerate

productivity is reduced. The farmers react by using more irrigation water on the plants. This causes minerals to leach out of the soil and to some degree contributes to the erosion of the top soil. The land is left behind and eventually, the topsoil become dry as well as sandy and is blown away by the wind or washed away by rain leaving the infertile lower soils layers exposed which then bake in the sun and become unproductive hot pans. Desertification then takes place.

Deforestation- The demand for fuel and fire wood is one of the main causes of desertification in tropical arid areas. In order to sustain the increasing population trees are cut down to provide space as well as wood for domestic purposes. However, the soil in tropical rainforest quickly become infertile if the vegetation is removed; the soil becomes exposed to erosion. The top soil is then blown or washed away leaving the infertile lower soils layers exposed which then bake in the sun and become unproductive hot pans. Desertification then takes place.

Consequences: Desertification arises from rigorous erosion of the soil. Desertification’s effects are akin to those of soil erosion as it has a series of chain effects. The following diagram illustrates the severe effects of desertification.

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Figure 2.4 Katiola in the Côte d’Ivoire: diamond mines or precious metal open quarries are a cause of desertification.

Large surfaces are cleared and turned upside down hundreds of meters into the ground. When the mines are then

disaffected the environment is totally destroyed rendering land rehabilitation almost impossible.

Figure 2.3 Mato Grosso in Brazil: extensive deforestation to the north of Cacères

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Migration

Conflicts for resources

Increase in food security

Famine

Poverty

Decline in cash crop for exports

Reduced food output

Loss of Biodiversity

Formation of Sand Dunes

Reduced crop yield

Soil becomes infertile

Increase in soil Salinity

Increase in Irrigation

Drought

Reduction in river flow and underground water level

Reduced Rainfall

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Figure 2.5 Summary of the causes, consequences and effects of desertification

Methods of Tackling:

Desertification occurs naturally over a period of time. Nevertheless, human influences on the environment have aided in speeding up this process. Therefore methods of tackling these causes, postponing and even reversing desertification have been discovered and developed. The following table is mentioning them:

Cause Method Of TacklingOver cultivation Use Good Farming practices

Use Higher yielding, drought resistant seeds

Use Crop rotation year after year Use Manure instead of Fertilizers

Overgrazing Fence off young Trees to prevent grazing by animals

Control amount of cattle grazing in grazing land

Rotate grazing land Reduce number of cattle by using

higher-yielding breedsDeforestation Implement Afforestation and

replant tree especially in shelter belts

Alternatives to fuel wood, for example , biogas plants

Poor Irrigation Use good irrigation practices Make sure not to pump out to

much underground water

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3. Case Study: Desertification in ChinaChina is a developing country with a large population. The country has to bear the responsibility of feeding 22% of the world’s population with only 7% of the world’s arable land. Population pressures have forced the government to clear more forests and marginal lands for cultivation. Farmers are compelled to over cultivate lands and herders are forced to allow their livestock to overgraze pastures in order to feed the rising population. Increasing demands for water has instigated the government to order the massive withdrawal of underground water for agricultural,

industrial and domestic purposes. All of these activities have lead to an increase in soil salinity, a decrease in soil fertility which has brought severe drought hence the expansion of old deserts and the formation of new ones.

Desertification is a pressing environmental issue in China which has been suffering from desert related problem for these past few decades. The expansion of deserts

and desertified land had destroyed villages, buried railways and roads, engulfed croplands together with grasslands and is a threat to the people along with the livestock.

Desertification occurs mostly in western part of north eastern China, north part of northern china, most parts of northwest China, in areas near shelter belts and places bordering deserts.

Desertification in China is severe and the rate of desert formation is faster in China than anywhere else in the world with old deserts constantly expanding and new ones being continually created.

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Figure 2.6 An area of Inner Mongolia before desertification

Figure 2.7 An area of Inner Mongolia after desertification

Land desertification by wind erosion totals 1533 million kilometres square and that by rain erosion totals 1794 million kilometres square and is concentrated on the Loess Plateau (which is the most severely eroded area in China and probably the whole world) located in the middle and upper reaches of the Yangtze River.

The annual expansion of desertification of land increased from 1600 kilometres square in 1970s to 2100 kilometres square during the 1980s. Furthermore, about an area of 3,600 square kilometres was lost per year in the 1990s and due to numerous successful model projects the rate has slowed down to 300 kilometres square in 2002.

Among all the deserts in China, the Gobi desert expanded the most by covering an area of 52400 kilometres square between 1994 and 1999. Nowadays, it expands at a rate of 3,600 kilometres per year. Additionally, the huge Takilmakan and Kumtag deserts in western China are expanding at such a rate that, these deserts are expected to merge in the near future.

Desertification in China has left the land in a critical condition. It has impacted about 27% of China’s total land territory and has affected about 400 million people in the past few decades. Moreover, desertification has created powerful sand storms with its intensity increasing every year. Added to that, farmers have been forced to abandon their fields and the levels of rural poverty have been escalating. What's more is that the desertification of China is also affecting neighbouring countries such as Japan, North Korea, and South Korea.

The hardest areas in China, are poor and dry provinces such as Ningxia and Qinghai where populations shrank from 6.3 million to 5.63 million. Chengdu plain, one of China’s primary grain growing areas is threatened by sands from the defamed Ruoergoi grasslands. Warnings about the development of dustbowls have been issued due to the overgrazing of the plain. Wells have already dried up and emergency grains supplies have to be brought in to prevent starvation and death due to malnutrition. The conditions became so grave that people were encouraged to move to more hospitable places.

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Future prospects :

China’s administration spends billons every year combating deforestation. In 1978, the government launched the largest ecological project called ‘The Green Wall of China’ which aims to increase the human-made tree cover from 5% to 15% of the country’s landmass. Additionally China aims to restore 40,000 and 70,000 kilometres square of desertified land through planting new trees and rejuvenating old forests. Finally, efforts to support poor farmers, train them and educate them on good agricultural practices have been put into effect in the recent years.

The government envisioned that by 2050 these projects would spawn forests that would stretch four million kilometres square of the country’s north.

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