Of all the driving forces of landcover change that are to be examined
in this book, the landuse of agriculture is the most consequential. For
landcover change, agriculture is critical, powerful and influential. It
is critical because it is highly selective. It is powerful because of the
highly sophisticated mechanical and chemical tools at its disposal. Finally,
agriculture is influential because the industry is crucial to the well-being
of Australian society as a whole.
Agriculture involves the most dramatic and irreversible transformations
of landcover; from forests or grasslands to croplands. Agriculture, with
its transformation of landcover and its high use of nutrients, energy and
water, is by far the most effective landuse to support the ever growing
human populations.
There is no avoiding the landcover conversion associated with the indispensable
landuse of agriculture. We cannot live without it. To live in any way other
than nomadic gatherer-hunters or pastoralists, requires the conversion of
some of the original landcover to crops and pastures. The question is not
whether or not, but how much. The questioning of the impacts of agriculture
on landcover can only be ones of balance.
The total area of the landcover of the continent that has been transformed
by agricultural landuse is recorded as (at least) 6%. Satellite images show
the land converted to pastures and crops stretched across the southern part
of the continent and up into central Queensland. The total area of cleared
land looks more like 15%. Unfortunately, this figure that is not accurately
known, which is amazing for a country that shows such great environmental
concern.
Looking back to the agricultural areas, two types of landcover change are
obvious. The first is the expansion of agriculture. The conversion of landcover
to crops and pastures has continued on the fringes of the established cropping
areas in all states examined. This expansion has been driven by market forces,
particularly during the early part of the 1980s. I am convinced that much
of this marginal land cleared for private gain will become a social and
landcare burden on the public purse within a decade, if not now. Within
the core areas or agricultural heartlands, the landcover change was also
of expanding cultivation with vegetation remnants succumbing to the plough.
This loss of even fragments of natural ecosystems has significance for the
relentless biotic impoverishment of the continent.
The second type of landcover change is the good news. We can see from the
changing patterns of cropping observed from 900 km in space that conservation
of the soil resource has grown in importance, and practice over the time
that we can look back. It may be small, but it is an unmistakable start.
I am personally more heartened by these observations than I am disheartened
by the short-sighted expansion of agriculture.
The changing spatial patterns of landcover that we have in Australia by
looking back over the last twenty years, can be found all over the world.
The changes and consequences are the same, even though the driving forces
differ.
In the developing world, the deforestation of places like Rondonia, Brazil
is ultimately driven by the need to support a large and rapidly growing
population. It is thought that 70% of the Brazilian population is under
20 years of age. In the developed world, the landcover of the grasslands
of the Great Plains of Kansas is progressing through a sequence of conversions
as the landuse changes. During the last century, the landuse has changed
from hunter-gatherer through pastoralism, extensive agriculture to intensive
irrigated agriculture. The current landuses in Rondonia and in Kansas are
unsustainable in the long term.
It is a reasonable conclusion that expanding or intensifying agriculture
is not without significant costs. Any rational society concerned about its
long-term well-being would ensure that all those costs are weighed against
the benefits of expanding or intensifying agriculture.
The sting in this argument is that any society whose population continues
to grow at a very high rate, such as ours, has already foreclosed its options.
Such a society must expand or intensify agriculture at the expense of all
else.
