Desertification: causes, consequences and solutions - Climatic Change in Deserts - page 492

loess is now becoming eroded through excess clearing and overcultivation, a familiar
practice in the history of land degradation that is worse in times of drought and was
responsible for dynastic change in the past. Despite some substantial achievements in
desertification control, rates of soil and nutrient loss from the Loess Plateau remain
very high (Douglas, 1989 ;Liu, 1999 ;Fuetal., 2000 ).
Equally important is the clearing of once vegetated and stable dunes in northern
China; what is known as sandy desertification in that region increased very rapidly
from 176,000 km 2 in the mid-1970s to 197,000 km 2 in the mid-1980s, a mean yearly
increase of 2,100 km 2 (Wang, 1993b ). Of the major human causes of sandy deserti-
fication in northern China in the early 1990s, Wang ( 1993a ) estimated that in terms
of total area affected, over-collection of wood for fuel accounted for 31.8 per cent,
overgrazing on the steppes for 28.3 per cent, overcultivation on the steppes for 25.4 per
cent and misuse of water resources 8.3 per cent, with other factors responsible for the
balance of 6.2 per cent. However, there is a clear need to re-evaluate earlier estimates
of the extent and severity of desertification in northern China (Williams, 2000 a).
One region of particular concern at present is the Inner Mongolian Autonomous
Region, especially the Alashan Plateau in the north-west of the region, where there is
an accelerating influx of wind-blown sand from once stable dunes into the Huanghe
(Yellow) River. The Alashan region of Inner Mongolia is one of the driest and poorest
regions in China. It covers an area of roughly 270,000 km 2 , with rainfall declining
from 300 mm in the east of the region to less than 50 mm in the west (Yang, 1991 ).
Mountains occupy about 10,000 km 2 and are flanked by gently sloping sand and
gravel alluvial plains, or gobi , which cover 91,000 km 2 of the Alashan. In the north-
east, west and south-east of the Alashan, there are three major active dune fields that
occupy an area of about 81,000 km 2 . Fixed and semi-active dune fields cover roughly
90,000 km 2 and are the places most vulnerable to desertification.
Until the 1950s, many of these low dune fields and sand sheets were covered in a
relatively dense cover of shrubs, trees and grasses. Since that time, the human popula-
tion has doubled and livestock numbers have tripled, mainly as a result of an influx of
immigrants from Gansu Province and the Ningxia Autonomous Region to the south
(Williams, 2000 a). In addition, there have been a number of severe droughts, includ-
ing the exceptionally severe 1989 drought (during an El Ni no year). Local Mongolian
farmers considered the unusually heavy rains of 5 and 6 August 1999 (a La Ni na
year) to be the best rains of the previous decade, bringing the preceding three-year
drought to an end (Williams, 2000 a).
The combination of sporadic but severe droughts much increased stock numbers,
and the influx of economic refugees from the south has led to widespread and locally
severe overgrazing, the destruction of localised patches of forest and severe deser-
tification. Local estimates in July 1999 suggested that 30,000 km 2 were severely
degraded, with the rate of desertification increasing by about 1,000 km 2 each year