4. Explain the causes of topsoil erosion and desertification.?

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  • 1 decade ago
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    Topsoil erosion is caused principally by loss of root reinforcement from plants followed by non-depositional flooding. Unsustainable farming is not the only problem. If there are not enough plants with deep root systems or that are otherwise better adapted to aridity, a drought can kill the plants and the root reinforcement of the soil decays. With the storms & floods that follow at the break of the drought, the soil is blown and washed away. Insufficient soil permeability to absorb runoff, can lead to tunnel and gully erosion that cuts through the root reinforced layer of the soil, and by undermining this layer, breaks down root reinforcement. Soil permeability is reduced by cementation (precipitation of "calcrete" and evaporites) along with clay formation and loss of humus and mulch.

    This has the potential to make water conservation during a drought pretty pointless if people don't use some of their water reserves to preserve the soil by keeping root reinforcement alive and well in addition to ensuring that the mulching process has just enough water to continue. After all, what is the point of having plenty of water if there is no longer any arable topsoil in which to grow food?

    Desertification is a product of plant die-back. As plant life in a region becomes more sparse, the amount of plant aspiration falls and with it the morning humidity. This has the effect of drying the local or regional climate with the feedback effect of less resources for aspiring plant life.

    Other factors in desertification includes water table poisoning that can occur when salty bore water finds its way into fresh ground water. Excessive irrigation in conjunction with excessive use of chemical fertilisers can also raise ground water salt levels depending on conditions. The first sign is "die-back" where trees with deep roots have large branches and portions that die off at a certain time of year followed by new growth on the largest dying trunks. This continues until conditions improve or the tree dies altogether.

    It doesn't help if a region is too dry to begin with, but it should be remembered that the Sahara was once covered in forest and stripped of it's trees prior to its becoming a desert. Excessive clearance of Australian farmland is continuing to turn arable land into desert at every drought. The Mallee region is one such example, and central South Australia (above goider's Line) once supported sheep & cattle stations serviced by dozens of towns (now abandoned ruins) - before the regional climate shift associated with clearance of the wheat-belt for very minor gains in arable land.

    In Australia's case, it doesn't help when excess water required for soil preservation is instead misappropriated for cash-crops such as cotton, which are notoriously inappropriate for the Australian climate.

    It is vital for agriculture planning to allow for drought and flood as these are essential "super-seasons". It is necessary to both discourage climatically inappropriate crop cultivation and eliminate unsustainable land management practices.

    Sustainability is not the buzzword so often misused by executives in their effort to impress shareholders. Sustainability is a quantifiable attribute of management practices which, in the case of land management, can be measured against the attainment of goals in terms of calculated plant aspiration potentials - just to name one. If such goals legally bind leaseholders and landowners to conducting the anuually reviewed minimum practices necessary to attaining those goals, desertification through unsustainable land management practices may well become a thing of the past.

    Just some thoughts on the subject...

    Source(s): If you want to see the process of desertification first hand, I invite you to take a tour of inland southern and eastern Australia.
  • older
    Lv 7
    1 decade ago

    erosion is caused because there is no ground cover--- a long time ago they farmed in a way that left no ground cover therefore--dust storms--the last dust storm i saw was in 1955 in oklahoma

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