Desert Development: How Does It Relate to Anti Desertification Measures? - Combating Desertification in Asia, Africa and the Middle East - page 418

200

Annual mean precipitation
Mean precipitation of 56 year
Precipitation trend of 56 year

150

100

50

1950 1960 1970 1980 1990 2000

(Year)

Fig. 20.6 Precipitation in Xinjiang, NW China in the 50 C years ending 2005

insufficient water to irrigate it), then just left to the elements and local peasants and
new immigrants, for whom environmental protection was an alien concept.
The recurrent pattern of land use, driven by demands to produce more food,
has consisted of converting (so-called land reclamation) untilled land for crop
production, low levels of input inadequate to sustain acceptable production levels,
abandonment of depleted crop lands after as little as two years, degradation of
abandoned crop lands and search for and conversion of other marginally productive
untilled lands elsewhere. Persistent and extensive poverty consistently and signif-
icantly reinforced this pattern by ensuring that access to much needed irrigation
and cropping technology, improved seed and to fertilizer was unaffordable. Efforts
to change land use policy and to rehabilitate degraded lands commenced most
seriously with land tenure reform about 20 years ago.
Climatic factors obviously played their part (Fig. 20.5 ). An analysis of the rainfall
pattern in representative sites within the four categories of dryland (Lu and Wu
2008 ) shows that there was a period of below-average rainfall for a period of about
20 years that more or less coincided with the efforts by government to undertake
massive land conversion. Ironically, the next 20 years were generally above average
(see Figs. 20.4 , 20.6 and 20.8 ).
Experience elsewhere in the world suggests that most dryland systems have
considerable resilience but that the sequence of rainfall events is as important as
the total amount of precipitation received. For example, a sequence of several years
of rainfall near the long-term average followed by one or two years well below
average will be more devastating to rangeland than a situation where good (above
average) seasons precede drought.
The attempted conversion of large swathes of land, and its subsequent aban-
donment, near the beginning of a long run of drier than average seasons must
have aggravated an already serious ecological situation. Normally in arid land
systems the major perennial plant species are long-lived and recruitment to the