Geography Reference
In-Depth Information
can be used to gather information about the Earth's surface from
a distant location. EO provides an important source of data
for GIS and working in tandem they have permeated a large
number of now taken-for-granted applications in the real world.
Satellite navigation in cars is one example of everyday use as is
the increasing popularity of Google Earth (the accessible set of
satellite images available on the internet). At more demanding
scientifi c levels, the technology is ideally placed to monitor
environmental change globally, over large areas or in remote
locations. Climatic change, the diminution of glaciers and sea ice
in the polar regions, the spread of desertifi cation in sub-Saharan
Africa, soil degradation in the American Mid-West, and the
clearance of tropical rainforests in the Amazon Basin provide
spectacular and important applications of this type.
Desiccation of the Aral Sea over recent decades provides a
striking example of the use of satellite images in monitoring
environmental change (Figure 25). In 1960, the Aral Sea
was the fourth largest inland water body on Earth, with an
area equal to the combined area of France, Germany, Spain,
and the United Kingdom. It was mismanagement of water
abstraction from the rivers Amudarya and Syrdarya for irrigated
agriculture, the expansion of which was particularly rapid
between 1976 and 1988, that led to this desiccation. Desiccation
of the Aral Sea has led to decline in the groundwater table,
salinization, expansion of halophytic (salt-tolerant) vegetation,
defl ation of the exposed sea-bed and aeolian deposition on
surrounding land surfaces from salt and sand storms. Other
knock-on effects contributing to desertifi cation of large areas of
the Aral Sea drainage basin include waterlogging and secondary
salinization following irrigation, and chemical pollution of soils,
groundwater, rivers, and the Aral Sea itself from toxic chemicals
used in cotton production. The Aral Sea case is a classic example
of a 'creeping environmental problem', induced by human action,
ultimately leading to an 'environmental disaster' and the mass
emigration of people from the affected region. It is only since
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