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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
RESTORATION AND RECOVERY OF ERODED
AND OVERGRAZED ARID GRASS AND
SHRUBLANDS
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).
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).
Overgrazing and erosion
Fenced control sites
0
1
20
40
60
80
100
Vegetation cover, percentage
Distance to the road, kilometres
Source: Nellemann, C.,
et al., Fall of the water
, UNEP, 2004.
2 3 4 5 6 7 8 9
Overgrazing near roads and villages in the
Bayanbulak range, Xinjiang, China