The Role of Vegetative Cover
Land areas covered by plant biomass, living or dead, are more resistant to wind and water soil erosion
and experience relatively little erosion because rain drop and wind energy are dissipated by the biomass
layer and the topsoil is held together by the biomass [17]. For example, in Utah and Montana, as the
amount of ground cover decreased from 100% to less than 1%, erosion rates increased approximately
200-fold [18]. In forested areas, a minimum of 60% forest cover is necessary to prevent serious soil
erosion and landslides [19–21]. The extensive removal of forests for cropland and pasture is followed by
intensive soil erosion.
Loss of vegetative soil cover is especially widespread in developing countries where populations are
large and growing, and agricultural practices are often inadequate to protect topsoils. In addition,
cooking and heating in these countries frequently depend on the use of crop residues for fuel. For
example, in the 1990s about 60% of crop residues in China and 90% in Bangladesh routinely were
removed from the land and burned as fuel [22]. More recent estimates of the amount of crop residues in
Bangladesh that could be harvested for biomass energy conversion without negatively impacting future
crop yields amount to 50% of all rice crop residues and 80% of non-rice crop residues [23]. More
recently crop residues in China are being used less as a domestic fuel source [24] due to the increased
availability of fossil fuels. However China has plans to burn about half of the 600 billion tons of straw
(from grains) crop residues produced annually to generate electricity [25]. In areas where fuelwood and
other biomass are scarce, even the roots of grasses and shrubs are collected and burned [26,27]. All these
practices leave the soil barren and fully exposed to rain and wind erosion forces.
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