Geoscience Reference
In-Depth Information
further demands on already overstretched irrigation systems. A related issue is water
quality, which requires basin-wide biological and chemical monitoring programmes
to be implemented, as in the exemplary scientific study of the Ganga River in northern
India (Krishna Murti et al.,
1991
).
Menon et al. (
2002
) have modelled the present-day consequences of the increase in
atmospheric carbon particles over China (and, possibly, India), concluding that they
will lead to an increase in floods in the south of China and an increase in drought and
desertification in the north (Menon et al.,
2002
; IPCC,
2007a
). However, this must
remain conjectural until all other factors are considered.
The following two regional examples of desertification in Asia are given in some
detail because they illustrate how human activities can aggravate the effects of an
already dry climate, with the rider that increasing evaporation and less reliable rainfall
or river flow postulated for the future (see
Chapter 25
) will exacerbate desertification
processes.
24.9.1 Central Asia: drying up of the Aral Sea
The drying up of the Aral Sea has been variously described as 'the world's largest man-
made disaster' (Tanton and Heaven,
1999
) and 'perhaps the most notorious ecological
catastrophe of human making' (Stone,
1999
). The volume edited by Glantz (
1999
)
avoids such hyperbole and provides a comprehensive overview of previously relatively
inaccessible hydrological, ecological and human health investigations within the Aral
Sea Basin, and it complements earlier studies of environmental degradation within
the basin (Babaev,
1996
; Micklin and Williams,
1996
).
Two major rivers flow into the Aral Sea from the east: the Amu Darya and the Syr
Darya. The present Aral Sea is the remnant of a once extensive early Holocene lake
(Glazirin and Trofimov,
1999
; Boomer et al.,
2000
). Very gradually, over the previous
half-century, the environmental problems in the basin worsened. Glantz (
1999
)terms
this phenomenon 'creeping environmental change' and defines it as the result of 'long-
term, low-grade, incremental but cumulative environmental problems'. The origin of
the crisis began early last century with the search for self-sufficiency in cotton from
Central Asia, and it was aggravated by the construction of the 1,400-km long Karakum
Canal, which deprived the Aral Sea of 15 km
3
of water each year. The outcome was
stark, with what was once the fourth largest lake in the world shrunk to less than half
its former size and its volume reduced by more than two-thirds.
The consequences for the surrounding region (
Priaraliye
in Russian) have been
analysed in a number of perceptive studies (Saiko,
1998
; Spoor,
1998
;Glantz,
1999
;
Saiko and Zonn,
2000
). They include exposure of saline ground, contamination of
water and soils with salts and pesticides, accelerated soil loss in dust storms, collapse
of the regional fishing industry, and a rapid and widespread decline in human health.