The problems of our time include climate change, loss of biodiversity, lack of drinking water, poor sanitation and the depletion of fuel wood supplies due to unsustainable rates of use. All of these are significant, but it could be argued that land degradation is the most pressing environmental and social problem facing society today, particularly affecting the world's poor.
It is estimated that an area equal to the size of China and India combined is now classified as having impaired biotic function (damaged ecosystem structure) as a result of poor land management resulting in soil loss. As populations expand, and as social and cultural changes occur, greater and greater demands are being made on larger areas of landscape and soil. In MEDCs where there has been a relatively long tradition of agriculture (agriculture on an industrial scale) there exists, within the agricultural culture, a knowledge of land management that aims for sustained soil fertility and strives to avoid soil erosion. However even in MEDCs there are occasions when climate and intensive agriculture conspire to bring about unprecedented levels of soil erosion.
Two types of processes can give rise to soil degradation:
• Processes that take away the soil (erosion). This mainly occurs when there is no vegetation on the soil. Wind and water can then simply take the soil away.
• Processes that make the soil less suitable for use. In these processes various chemicals end up in the soil and turn the soil useless in the long run.
Examples of human activities that lead to soil degradation are: overgrazing, deforestation and unsustainable agriculture. Overgrazing occurs when too many animals graze in the same area. Overgrazing of grasslands leaves bare patches where roots no longer hold the soil together. When this is combined with the action of rain and wind the bare patches become bigger and soil is removed from the area. This happened on a huge scale in the Sahel area in Africa (just south of the Sahara desert) in the 1970s and 1980s. In many African countries the wealth of a man is measured by the number of cattle he has (quantity not quality is important) — this leads to very high stocking levels and overgrazing becomes a problem. This was then exacerbated in the 705 and 80s when a long dry period strongly reduced the growth of the vegetation which was subsequently eaten by cattle. The soil particles were no longer kept in place by roots and were blown away by the wind. This resulted in the death of most of the cattle and, later on, in a terrible famine. As soil formation is a very slow process, it will take many years for the Sahel region to recover. In wet climates it is often rain water that takes the soil particles away, especially when the rain water is flowing down slopes.
Overcropping depletes soil nutrients and makes the soil friable (dry and susceptible to wind erosion). This reduces soil fertility as no nutrients are being returned to the soil. If the crop fails then the soil surface again becomes susceptible to erosion. This is especially true in dry regions where crop failure can lead to removal of topsoil by wind. During the 1930s, the American Mid West suffered a major period of wind erosion known as the 'Dust Bowl'. Through overuse of the land an area about twice the size of the United Kingdom, from Nebraska through to Texas, was affected by severe wind erosion. The winds moved soil and dust many thousands of kilometres.
Deforestation is the removal of forest. This can be done in different ways, ranging from careful removal of some of the trees to complete removal of all vegetation. Of course, the more vegetation is removed, the more the soil will be prone to erosion. As most forests are in relatively wet areas, the erosion will mainly be due to water. Deforestation can have a massive effect on soil erosion, especially in tropical regions. The leaves of forest trees both deflect and slow down the progress of rain drops. This helps to stop them explosively removing soil particles. The root systems of forests help to bind the soil together and give it stability, while also absorbing large quantities of water from the soil directly. The absorbed water is eventually returned to the atmosphere via transpiration.
Unsustainable agricultural techniques are techniques that cannot be applied over a long period of time without decrease in productivity or increased inputs of chemicals like fertilizers or energy. Urbanization and paving of land in cities for human settlements that result in run-off is also a major factor contributing to soil degradation. The scale of the problem is self evident. Hence, soil conservation methods, sustainable farming techniques and eco-friendly lifestyles are a must to conserve the soil that provides for us and sustains our planet.
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