RESTORATION AND RECOVERY OF ERODED AND OVERGRAZED ARID GRASS AND SHRUBLANDS
Overgrazing, deforestation or cutting of shrubs for firewood are primary causes of land and wind erosion in drylands, such in the Sahel, Eastern and Southern Africa, Central Asia, Chi- na, ranges of Argentina and Chile, the Mediterranean and in southern and southwestern US (UNEP, 2006; Ibanez et al., 2007; Hoshino et al., 2009). In some areas, like in the Medi- terranean and in Australia, where wildfires are common, not only aboveground biomass, but also root biomass, is extremely important, and restoration must carefully select or copy natu- ral local vegetation to ensure that restoration efforts are not short-lived (De Baets et al., 2009). Shrubs, so crucial in dry- lands, dominating the largest share of the modest 15–30% total vegetation cover (Li Xr et al., 2009), must be a crucial compo- nent in restoration processes. In addition, it is often necessary to establish purely physical “dead” wind erosion networks to hinder erosion and establish a first barrier for creating viable conditions for plant growth. Where terrain with gullies and slope shave been overgrazed or cleared of vegetation, run-off and subsequent erosion (Descroix et al., 2008) or even flash- floods can have detrimental effects on both people, livestock, infrastructure and wildlife (UNEP, 2004, 2006). Restoring vegetation must also carefully address the initial causes of land degradation, such as overgrazing (Su et al., 2005, Zhang et al, 2005). Restoration is a particular valuable tool in drylands for restoring livable conditions for plants, wildlife and people, as
natural regeneration may take at least 50–300 years, and full restoration of ecosystem services as much as 3000 years (Lov- ich and Bainbridge, 1999).
Overgrazing near roads and villages in the Bayanbulak range, Xinjiang, China
100 Vegetation cover, percentage
Fenced control sites
20 40 60 80
Overgrazing and erosion
Source: Nellemann, C., et al., Fall of the water, UNEP, 2004.
234 56 789
01 Distance to the road, kilometres
Figure 17: Overgrazing by domestic animals concentrates along road corridors and new settlements, with resultant drop in grass coverage and increase in erosion on plains and slopes close to roads. Each black dot represents a randomly selected site (with five vegetation plots each) on the Bayanbulak range, East Tian Shan, Xinjiang, China. Fenced control areas protected against grazing across a 20 year period are shown as open circles. Ar- eas impacted can however in some instances be up to 30 km from major settlements as those people that still retain more traditional lifestyles are forced to use more marginal lands in dry seasons 15–30 km away from their traditional now-occupied ranges close to new settlements (Source: UNEP, 2005).
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