Fjölrit RALA - 05.12.1999, Blaðsíða 100

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Transformation of desertified land in Northern China
ductive land is being lost annually to desertification in China, mainly in the rangeland-
cropland interlaced regions.
Studies of desertification dynamics and experiments on its reversion in the typical
rangeland-cropland-interlaced belt have been conducted in recent years at two field
stations of the Institute of Desert Research, Chinese Academy of Sciences - Shapotou
Experiment Station of Desert Research in the western part and the Naiman Experi-
ment Station of Desertification in the eastern part of the belt. This paper is intended,
based on the results from these stations, to analyze the features and causes of deserti-
fication in this belt and to suggest reversion strategies and techniques.
General features and analysis of the causes of desertification
Distribution and general featnres of the desertified land
In China, vast areas of sandy deserts and Gobi deserts are mainly located in the arid
zone, between 35-50°N and 74-107°E, where the annual precipitation is less than 250
mm. Desertification in this zone appears only in the oasis regions. Large scale deserti-
fication occurs mainly in the semi-arid and drier sub-humid zones, between 36-50°N
and 107-125°E, where the annual precipitation is 200 to 450 mm. This area includes
200,000 km2 of land affected by desertification along the Great Wall and the Xiliaohe
River, forming a belt about 1,800 km long and 100 to 200 km wide. Its size and fra-
gility is thought to be second only to the Sahel-Sudan belt in the world.
The general features of desertification in this belt are severe land degradation char-
acterized by devegetation, ground surface sand reactivation, soil erosion, the forma-
tion of desert-like landscape, and accompanying process of rapid decline of produc-
tion and poverty. It has been estimated that desertification in this belt is affecting
about 7 million people and leading to a loss of several billion RMB yuan each year. A
single sandstorm disaster on May 5, 1993 resulted in a tremendous economic loss,
amounted to half a billion RMB yuan, and the death of 80 people.
Analysis of the causes of desertification
Although the land subjected to desertification is affected by unfavourable natural fac-
tors, the rangeland in most of the semi-arid zone had not suffered severe desertifica-
tion nor lost its capability of recovering írom light disturbances (Liu Xinmin et al.
1994). Originally, this belt-shaped zone with semi-arid climate and sandy land was
maínly used as rainfed grazing land and dominated by herdsmen. Since around 200
B.C., with the population growth and agriculture development in the middle part of
China, rain-fed cropping moved northwards to this zone and the conflict between
herdsmen and farmers started. In order to keep the newly reclaimed farmland and
avoid conflict or even war, the construction of the Great Wall started under the or-
ganization of the Qin Empire. The Great Wall is considered to have been of great im-
portance, not only as a military demarcation line in the ancient time, but also as an ap-
parent bio-climate dividing line between pasturage and agriculture areas. However, it
did not permanently prevent the intrusion of cropping from the south. It played a bet-
ter role of preventing herdsmen from migrating southwards than of stopping farmers
from moving northwards. The rain-fed agriculture has since crept northwards several
times into excessively dry areas and cropping is now taking place in regions receiving