Let's now turn to the great plains of Kansas, USA. The patterns and system
of agricultural landuse in this area have evolved since its occupation by
European settlers early last century. The landcover had for the last several
centuries been grassland, a part of the tallgrass prairies. The first landuse
was a nomadic harvesting by the native peoples who hunted the herds of native
herbivores. This was replaced for a time by sedentary harvesting of the
domestic stock by the early European settlers. This landuse was then largely
displaced by rain-fed agriculture, with the landcover of grasses replaced
by alternating crop and cultivated, bare soil. During a period of frequent
droughts in the 1930s, extensive soil erosion occurred and astronomical
amounts of very productive soil were lost. This was part of the Great Dustbowl.
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The intensification of agricultural landuse and its effects on landuse is the theme of the second international example. This example is from the developed world; Kansas in the USA.
With continuing fluctuation in the prices paid for land and the now necessary
inputs of energy and fertiliser, it has become more profitable to tap groundwater,
the Ogalala Aquifer, and to shift to intensive, irrigated agriculture. The
method of applying the irrigation water is by centre-pivot irrigation, and
the huge circular fields of irrigated crops and pastures are clearly discernible
from 900 km in space. The remnants of all three landcover types can be interpreted
in the image.
The evolution of agricultural landuse, and thus of landcover, has not yet
finished in this region of the USA. The source of the groundwater used for
irrigation, the Ogalala Aquifer, is a fossil source. It is being used at
a much greater rate than it is being recharged. Effectively, the aquifer
is being mined. In a reasonably short time, a matter of decades, most of
the groundwater will be exhausted, the landuse will change and the landcover
will change with it.
