There is another way in which the landuse of agriculture transforms landcover
and that is working the land harder; that is the intensification of agriculture,
an alternative to the extensification of agriculture dealt with so far.
The size of the human population is related to the size of the area of land
devoted to agricultural landuse. As the human population increases, so also
will the demand on agriculture to feed that population. Agricultural landuse
can respond in two ways: by increasing the area of land under cultivation
(extensification) or by increasing the productivity of existing agricultural
land by the inputs of water, fertiliser, management skill and energy (intensification).
In the Australian context, these pole positions are blurred somewhat. Almost
all extensive agriculture (cereal cropping) uses fertilisers and fossil
fuel as inputs. The most marked agricultural intensification is by irrigation.
In a continent as arid as Australia this option is limited and heavily subsidised
by the public sector.
The history of irrigated agriculture in Australia is long and involved.
I encourage you to explore this issue with the suggested reading. However,
our focus in this book is just the landcover changes associated with the
irrigation areas of this continent.
Let's begin with one of the oldest such areas, the Murrumbidgee Irrigation
Area (MIA) in New South Wales. A subset of the Leeton scene shows the essential
characteristics of all irrigation areas, the small field size and the high
productivity crops.
The Leeton area of the Murrumbidgee Irrigation Area (MIA) in New South Wales.
The essential characteristics of all irrigation areas, small field size
and high productivity crops - are in contrast to the surrounding extensive
cereal growing area. The Difference FCC image shows change during the period
1972 - 1988, but by eyeballing the other FCC images, this change is associated
only with normal agricultural practices. There is little or no expansion,
just activity within established boundaries.
