Desertification in the World

Desertification in the World
Desertification is a process by which land that was once productive becomes non-productive. Once productive is not the natural deserts, the climatic desert where rainfall is so low that no productivity can be there. But we are talking of areas where rainfall is 300- 500mm a year. This is enough to produce something. Although now, in some places rainfall is so low that no productivity can occur. The world areas worse affected by desertification are in West Africa, countries like Mauritania, Senegal and Mali, South Africa, South west of North America and many other countries. This is shown on my world map. In my case study area of Africa, the region worst affected is the Sahel in central North Africa. My map of North West Africa shows the countries affected. Desertification is happening mainly in semi- arid areas (average annual rainfall less than 600mm) bordering on deserts. It is happening in the Sahel region where the Sahara deserts margins are near the Sahel. The Sahara desert margins can turn into desert very easily.
The Sahara is sometimes "pictured as a sea of sand dunes washing into the Sahel exposing farmers to waves of sand that roll in from the desert, yearly swallowing large chunks of farming land" (?Desertification? Nick Middleton). But sand only covers 1/7th of the Sahara. In the Sahel (the semi-arid area south of the Sahara desert) the desert moved 100km southwards between 1950 and 1975. [image] Over-grazing is a result of too much live stock being kept on a given area of pasture resulting in the loss of edible species and the consequent encouragement of inedible species. If excessive grazing pressure continues, the loss of vegetation cover can result in soil erosion. Other common way in which human mismanagement causes desertification is over-cultivation, in which soil is exhausted by nutrient loss and erosion, the excessive clearance of vegetation, often for fuel-wood and poor management of irrigation schemes which results in salinization in soils. Over-cultivation occurs due to the shortening of periods when the land is left free from cultivation (fallow), or from the use of techniques which cause widespread loss of soil. This is usually due, as in the Sahel, to increase population pressure which increases the demand for food and so pressure on the farmers to produce more. Forests and wood land is cleared for a variety of purposes, to create agricultural and pasture land for example, but it might be that one of the most serious cause of desertification in this respect is the fuel-wood crises. The collection of fuel-wood form urban hinterlands in the Sahel, the most severely affected region, has resulted in the almost total loss of trees around major cities. We could blame the people in desertification to 3 main groups in Sahel, the nomads, which are people who travel around the Sahel or other places for water and for their cattles, the farmer and the government. The natural ecosystem before desertification was more of a better life for people and for animals. The vegetation had thick forests; it was too thick to cultivate (form). Many trees and shrubs surrounded their fields including edible species. Villages did not need to cut down trees for firewood because enough dead wood was available. There were lots of different types of animals in the village in Burkina Faso; an old man describes it as "the wild animals were too many to count. There were antelope, elephants, buffaloes etc." "Villagers used to hunt many wild animals such antelope, monkey, fox, squirrel, rabbit. And even elephant" says Malam Garba, aged 77 from Dali. Malam Garba and his brother harvested 700 baskets of millet from their field 40 years ago which provided a surplus for both their families. People, especially farmers, were able to crop for a year and leave the land as resting land; they could leave this resting land for 10 or 20 years before coming back to it again. The land at that time was fertile. People could farm the same piece of land for five years, ten years, with no fertilizer. The land was also very deep; people could dig a hole as deep as their body before they could reach hard rock. It was a rainy atmosphere before desertification; it used to have ?tremendous rains?. The rain would start in the morning and the rain until the evening. In that land people used to grow cotton. Rice, sweet potatoes. Today everything is changed, there are no forests left, and land is very open. The only animals that people see are hares, they are adapted to deserts, are other animals but people do not see them. People farm the same fields year after year and each year the field gets smaller and smaller. A piece of land that used to fill two granaries would not even fill one now, this is happening because by digging the land, people could reach rock as deep as their hands, so next year, the rock will rise higher or maybe the soil will get exhausted. Rain only continues for twenty to thirty minutes and then stops, so plants and animals die quickly. These days? rains are lighter and more erratic than before. The daily showers that used to fall during 25 day period in the rainy season have now ceased. Nowadays the wind easily erodes the soil because there is little vegetation, so landscape is broken and desolate for more of the year. Loose sand even moves onto the road. The Sahel is an area of poor savanna grassland with scattered trees and shrubs which stretches 5000km from Senegal and Mauritania on the Atlantic coast to Chad and portions of Sudan and Ethiopia in the east. On a vegetation map of Africa, this zone is marked as savannah grassland, a transition area between the arid desert to the north and the more humid wood lands to the south. On a map of Africa annual average rainfall the zone can be taken as the lying between the 100mm and 600mm isohyets. The surface wind circulation and the seasonality of rainfall in this part of the Western Sahara and Sahel is very largely determined by interactions two high pressure systems and the inter-tropical convergence zone (itcz). The pressure systems are known as the Azores high and the Saharan high. The itcz is a frontal zone which marks the meeting place between warm, moist air from the Gulf of Guinea to the south and hot, dry Saharan air to the north. This itcz moves north and south with the seasons. When a town is further away from the itcz the warm air in that town has enough height here to rise, cool and form clouds and rain. But if a town was near the itcz then there would be not enough for air rise and to give rain. In recent years the itcz, pressure belts and wet winds have not been moving so far north. So towns like Burkina Faso in the Sahel have not been receiving much summer rain. This may be because of global warming giving greater strength to the hot air from Sahara, to move further south, than normal. In the winter months the Azores high is close to the African coastline and the Saharan high is strong. While the itcz is at its southern position over the Gulf of Guinea. The circulation from the two pressures systems creates a wind flow that is from the north-east over much of the Western Sahara. These are moisture. During the first six months of the year these hot, dry winds generate fierce dust storms in Mauritania, blowing loose soil, sand and clay particles from the dry unvegetated land surfaces. In the summer months, the Saharan high is replaced by a shallow low pressure system in the central Sahara and the Azores high is strong and further from the coast, giving more northerly winds at most stations. During the period from June to September the itcz is also at its most northerly position, so that the Sahalian areas of the southern Mauritania receive south-westerly monsoon winds that bring the seasonal rainfall to the area. The northward progression of the itcz, bring the boundary of the moist air from the Gulf of Guinea, is reflected in the way that the most southerly parts of Mauritania receive greater annual average rainfalls, beginning slightly earlier in the year, than those parts further north. One important factor of climate change is drought. Droughts are normal events in the climate of dry land areas. They have occurred repeatedly for a long period of time. Drought can badly affect the population including the nomadic herders. As the grass disappears they have to move south with their animals to look for water and fresh grass. Drought also causes problems to farmers they reduce the level of growth in their farm land, but sometimes it can increase it. Drought happens all over the Sahel. The earth?s atmosphere is slowly warming up. The warming is caused by the greenhouse effect. Earths atmosphere is warming up because of an increase in the proportions of greenhouse gases it contains. These are produced both natural processes and by human activities. Without the natural greenhouse gases, the temperature of the Earth would be 33?c colder than it is at the moment. So most living things would not survive without the greenhouse effect. But human activities are causing the concentrations of greenhouse gas in the atmosphere to rise above natural levels, and that is causing a great deal of concern. Greenhouse gases (as mentioned) are another factor of climate change. The increased concentrations of greenhouse gases are causing the temperature of the atmosphere to rise, slowly but surely. The earth is warmed by radiation from the sun. It, in turn, produces infra-red radiation. Greenhouse gases absorb this radiation and re-radiate some of it back to earth. This might has happened in the regions of Sahel, because there are lots of vegetations being grown there. The atmosphere rise will cause changes to climates around the world- some places will become wetter, others drier (like the region of Sahel). The climate changes will change the areas where crops can be grown. This is a natural process. Although seemingly a natural cause, the human release of greenhouse gases could make this another human cause. The direct human cause is worse, people, in the Sahel, have interfered with this balance in two major ways: 1. There has been a massive increase in the combustion of fossil fuels both by industry and by use of motor vehicles. This is increasing the amount of carbon dioxide in the atmosphere, which also increases the temperature; 2. Large areas of forest have been cleared both to produce timber and to clear land for agriculture. When trees are cut down, only the trunk is kept. The branches are burned. This combustion releases carbon dioxide onto the atmosphere. The roots of the trees die, and are decomposed. The first way is in urban cities with factories. The second way is in agricultural places and also when the population increases. The global warming might be responsible for the increased strength of out blowing dry NE trades from the Sahara which hold back the summer progress, the itcz, and so the moist Atlantic air mass over the Sahel which used to bring its full summer wet season(rain). The environment has become an even more fragile eco-system. Where once there were forests too thick to cultivate, has now been very open, the hills are bare in the Yatengá region of North West Burkina Faso. When there is less rain for Toureg nomads, there would be not enough food (grass) for animals; the nomad?s camels produce milk which is essential source of food. With this milk they can also exchange for millet as they do not grow it themselves. Other natural source that is being depleted is the trees, for fuel. They also remove vegetation so by doing this soil is no longer protected by the trees, which then gets washed or blown away by weather which turns it into useless soil. A high population density means soil will be used too intensively in regions. This means the same nitrate nutrients are leached out without rest for soil. It also destroys farmland because farmland will be over-used with the growing of pop; the resources are stretched to the limit. This also makes the water being over-used, this is happening because the water table is dropping mainly because greater water use by the high population density in the region. Growing crops and raising animals put terrific pressure over-using moisture which eventually forms soil-exhaustion. Soil-exhaustion also occurs when intense rainfall can wash top fertile soil away, this also destroys arable land. There are many poor ways that people use to sustain themselves in the savanna. Some are more damaging than other, but all have caused a change in the environment causing more desertification to occur. The effects of reduced rainfall on the erodibility of a soil (the ease with which it is eroded) can also be brought about by human actions. There was a wide spread over use of the environment both during the drought years, themselves and before the drought began. The environmental problems in the Sahel region were due to overgrazing and the excessive cutting of woody vegetation especially for fuel wood. These activities were causing problems before the drought hit. The existing dry conditions of the 1970s had the effect of increasing them. The drought also encouraged nomads to cut woody vegetation to provide fodder and later forced them to concentrate in the southern parts of the country. For example in the south parts of Burkina Faso. Another serious problem is deforestation, which way briefly explained above, as the trees are removed for fuel wood or sustainable technique of slash and burn turns and exposes soil to erosion, this happens by heavy rain which causes soil erosion, gullies and (sometimes) landslide. The use of biomass/wood for fuel is unsustainable and alternatives must be found more efficient. Wood burning stoves would be a start because their use would reduce wood use. Farmers are being forced to intensively cultivate their land due to their high increase of population density and distribution. More and more people are beginning to get settled in small areas and are either depending on animals or crops grown by farmers. More people need to be fed and this means the farmers are not allowing the land to rest and regain its fertility. The same nutrients are being used from the soil and moisture is lost leaving soil useless. The rain water can wash out soil nutrients and the soil can become infertile. People or farmers also cut trees to get space to live in. [image][image] Soil exposed to sun, wind and [image][image]Deforestation rain. Nutrient cycle soil erosion. [image] broken. Soil becomes useless/ exhausted. This diagram shows what would happen if deforestation occurred. Increasing demand for food is probably the most driving force behind over intensive land use. In the Sahel region or the whole African countries has doubled for the past years. More people mean more food. The extra food can either be produced from the same land, by intensifying production, or by agricultural extensification, using more land. Intensification can mean grazing more cattle on an area, or shortening fallow periods for fields. Extensification can mean using land that is not well-suited to agricultural use. Over-cultivation is another form of human action that can lead desertification. It takes a number of forms. It means that pressure for ore food encourages a farmer to cut the length of time a field is left fallow after cultivation. Cultivation can be said as monoculture. It also means the cultivation of soils that are not really suitable for the growing of crop. Over-cultivation reduces soil fertility and plant growth. Fields are often left fallow or used as pasture for several years after a period of continuous cropping. This is to allow the soil to recover its store of nutrients and rebuild its fertility and organic content that have been used by growing crops. When a plot is not allowed to recover its fertility because fallow period are shortened, the soil becomes exhausted, losing nutrients and suffering a breakdown of soil structure. Eventually, this has the effect of reducing crop yields and plant cover, which in turn leaves soils open to the ravages of water and wind erosion, so further depleting nutrient content and soil structure. Monoculture; Allows growing over-used plots [image][image]the same crop [image] Soil exhaustion soil erosion. [image] The same nutrients [image]always taken from nutrients lost from the soil the soil This diagram shows the process of monoculture. [image] This image shows two fields. The top field is forty years ago and the bottom field is now. This field (bottom) is three times larger. But only 1/7th is harvesting. This shows how the soil has eroded. The erosional loss of nutrients from the soils in dry lands is usually greater than in more temperate climates. This is because nutrients in dry land soils tend to be concentrated in the upper layers since there is little rainfall to leach or wash them down through the soil profile. Thus, when soil is lost to blowing wind or flowing water it is the nutrient- rich upper layers which go first.

Desertification in the World 8.3 of 10 on the basis of 1365 Review.