Sunday, February 24, 2013

Are restoration efforts in China halting soil erosion?

Kate Langford in News and Events at World Agroforestry: Immense effort has been put into combating soil erosion in China over recent decades, but how effective have these been? A new study published in Critical Reviews in Environmental Science and Technology found a strong positive relationship between vegetation cover and soil erosion reduction benefit.

Interestingly, the authors discovered that when vegetation cover is below 60 per cent, the soil erosion reduction benefit increases sharply with increasing vegetation cover. But when cover exceeds 60 per cent, the benefits may be diminished. Says co-author, Jianchu Xu from the World Agroforestry Centre, “This implies that vegetation restoration programs should probably aim for only partial vegetation cover”.

Xu warns, however, that because of the variation which occurs in the natural environment, one has to be careful not to universally apply this percentage. “Each location has its own specific characteristics in terms of geographical conditions, vegetation species, forest/grass ratio, age of species and management regime.”

The critical vegetation cover percentage is also determined by factors such as rainfall characteristics, soil type, slope and rainfall intensity. The spatial distribution of vegetation is also significant. In the study, conducted by scientists from the World Agroforestry Centre, National University of Singapore and the Kunming Institute of Botany, a wide range of different sites were analysed to represent the varying climatic zones in China.

Soil erosion is second only to population growth as the biggest environmental and public health problem facing human society; costing an estimated US $400 billion per year globally. In China, top soil is being lost 30 to 40 times faster than the natural replenishment rate as a result of rapid development. Soil erosion is of particular concern in the upper and middle reaches of large river basins such as the Yangtze River, Yellow River and Pearl River...

The eroding edge of the loess plateau just north of Linxia City (near the Wanshou Guan pagoda). Shot by Vmenkov, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

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