Soil Erosion Causes and Effects
A global evaluation of soil or land degradation requires sampling and/or . but it appears that the application of new knowledge has failed to keep pace with the nature and significance and interrelationship between these non-living labile. Oct 25, Understanding the type of soil and how prone it is to erosion can help avoid problems in agriculture and on waterways and infrastructure. This relationship between humans, the earth, and food sources affirms soil as the foundation of agriculture. By: Sanjai J. Parikh (Department of Land, Air and Water Resources, University .. Parenthesis represent standard error of the mean.
People can be a major asset in reversing a trend towards degradation. However, they need to be healthy and politically and economically motivated to care for the land, as subsistence agriculture, poverty, and illiteracy can be important causes of land and environmental degradation.
Land degradation can be considered in terms of the loss of actual or potential productivity or utility as a result of natural or anthropic factors; it is the decline in land quality or reduction in its productivity.
In the context of productivity, land degradation results from a mismatch between land quality and land use Beinroth et al. Mechanisms that initiate land degradation include physical, chemical, and biological processes Lal, Important among physical processes are a decline in soil structure leading to crusting, compaction, erosion, desertification, anaerobism, environmental pollution, and unsustainable use of natural resources. Significant chemical processes include acidification, leaching, salinization, decrease in cation retention capacity, and fertility depletion.
Biological processes include reduction in total and biomass carbon, and decline in land biodiversity. Soil structure is the important property that affects all three degradative processes. Thus, land degradation is a biophysical process driven by socioeconomic and political causes.
Factors of land degradation are the biophysical processes and attributes that determine the kind of degradative processes, e.
These include land quality Eswaran et al. Causes of land degradation are the agents that determine the rate of degradation. These are biophysical land use and land management, including deforestation and tillage methodssocioeconomic e. Depending on their inherent characteristics and the climate, lands vary from highly resistant, or stable, to those that are vulnerable and extremely sensitive to degradation.
Fragility, extreme sensitivity to degradation processes, may refer to the whole land, a degradation process e. Stable or resistant lands do not necessarily resist change. They are in a stable steady state condition with the new environment. Under stress, fragile lands degrade to a new steady state and the altered state is unfavorable to plant growth and less capable of performing environmental regulatory functions.
Effects of land degradation on productivity Information on the economic impact of land degradation by different processes on a global scale is not available.
Some information for local and regional scales is available and has been reviewed by Lal The economic impact of land degradation is extremely severe in densely populated South Asia, and sub-Saharan Africa.
The problem of land degradation
In the Andean region of Colombia, workers from the University of Hohenheim, Germany Ruppenthal,have observed severe losses due to accelerated erosion on some lands. Few attempts have been made to assess the global economic impact of erosion. If accelerated erosion continues unabated, yield reductions by may be Annual reduction in total production for due to accelerated erosion was 8.
Soil compaction is a worldwide problem, especially with the adoption of mechanized agriculture. Nutrient depletion as a form of land degradation has a severe economic impact at the global scale, especially in sub-Saharan Africa. Annual depletion rates of soil fertility were estimated at 22 kg N, 3 kg P, and 15 kg K ha Productivity of irrigated lands is severely threatened by build up of salt in the root zone. Potential and actual economic impact globally is not known. It is not known either for soil acidity and the resultant toxicity of high concentrations of Al and Mn in the root zone, a serious problem in sub-humid and humid regions Eswaran et al.
It is in the context of these global economic and environmental impacts of land degradation, and numerous functions of value to humans, that land degradation, desertification, and resilience concepts are relevant Eswaran, They are also important in developing technologies for reversing land degradation trends and mitigating the greenhouse effect through land and ecosystem restoration.
As land resources are essentially non-renewable, it is necessary to adopt a positive approach to sustainable management of these finite resources.
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Views on land degradation Land degradation has received widespread debate at the global level as evidenced by the literature: At least two distinct schools have emerged regarding the prediction, severity, and impact of land degradation. One school believes that it is a serious global threat posing a major challenge to humans in terms of its adverse impact on biomass productivity and environment quality Pimentel et al. New crops such as tobacco, groundnuts and water melons are being introduced with success, and the planting of apple trees has increased farm income in many areas.
Water erosion is the most common form of degradation in the area, affecting 25 percent of agricultural land. Wind erosion affects 40 percent of the agricultural land in the dry zone. There is also a widespread decline in soil fertility and extensive waterlogging and salinization in irrigated areas. This report analyses the effects of various forms of land degradation on the economies of countries in South Asia. This is equivalent to 7 percent of South Asia's agricultural gross domestic product.
The breakdown of traditional solutions Asian farmers and pastoralists have not always caused such problems. Traditional systems of land use were compatible with the environment - for example shifting cultivation in the humid tropics and nomadic grazing in the semi-arid areas.
Farmers practicing shifting cultivation would clear an area of forest and then cultivate the land for two or three years. When plant nutrients in the soil were depleted, and crop yields had fallen, farmers would move to a new plot, leaving the old one to regenerate under natural vegetation.
It could be 20 or more years before the original plot was cultivated again. In the meantime its fertility would have been restored by the bush or forest fallow, and weeds and pests suppressed.
Nomadic pastoralists traditionally moved with herds of animals to different areas of good grazing and water supply as seasons and conditions changed.
With low stocking levels they were able to move to new areas before the reserves of any single area were irreversibly depleted and the soil laid bare. Problems arose when populations started to increase, and the pressure on land resources became more severe.
There is no longer enough land to allow long fallow periods; more and larger herds compete for forage; and other traditional systems of land use are being placed under increasing strain.How Quicksand Causes Dam Failures
Farmers have responded by trying to develop new land. As a result, marginal land - steep land, land in areas of uncertain rainfall and land with poor, erodible soils - is being overused. Large areas of forest have been destroyed and much traditional pasture put under the plough.
Shifting cultivation, in its currently common forms, is a major problem in the region where it is practiced by at least 22 million people over an area of some 63 million hectares.
The causes of land degradation There are six major causes of land degradation in the region: This situation is particularly serious in Asia and the Pacific because most good agricultural land has already been opened up. Indeed, the region as a whole may already have passed the safe limits for agricultural expansion. The region had only about 0. Outside Asia and the Pacific, agricultural expansion has more or less kept pace with population growth since the early s.
The fact that it has not kept pace with population growth in Asia and the Pacific is the region's principal cause of land degradation. In Latin America, for example, land in use per person was 0. In South Asia, with virtually no reserves of land with crop production potential, the land in use per person will fall from 0.
The vicious circle produced by limited land and a rising population is described in more detail in the box below. This pressure on the land has three main effects: The vicious cycle of land degradation Land, population and degradation The two most important driving forces of land degradation in Asia and the Pacific are limited land resources and population increase.
The result is small farms, low production per person and increasing landlessness. A consequence of land shortage is poverty. Land shortage and poverty, taken together, lead to non-sustainable land management practices, the direct causes of degradation.