The origins of this book were in the cooperative efforts that were the International
Space Year, 1992. I wanted this book to be a voyage of discovery. I wrote
this book in a way that would make you better appreciate your home continent,
and to make you realise that you are responsible for its well being, no
matter where you live or what you do.
What did we find on our voyage of discovery? What did we find when we
looked back?
Our first discovery was that satellite images are unique and extremely powerful
in conveying information about our environment. The view provided is new
and challenging; it is a new truth and a
new history. The management of the Earth has never had such a powerful
tool at its disposal.
Our focus was landcover, a familiar subject matter but an unfamiliar word.
Landcover is a convenient label for that part of the biosphere that is critical
to the continued existence of terrestrial life, and which shapes the flow
of energy and mass that are the Climate System and the Biogeochemical Cycles
of planet Earth.
Satellite images indisputably demonstrated that landcover changes. Some
of these changes are driven by the seasons: these changes are diffuse in
space and reversible in time. It also changes because of human use: these
changes are usually irreversible in time and sharp-edged in space.
Both types of landcover change are of interest to us. The first indicates
how the terrestrial biosphere is functioning. The second is a measure of
our cumulative impact on the terrestrial Biosphere.
We set aside as unimportant the changes in landcover activity to concentrate
on the more substantial and permanent changes in structure and composition.
For convenience, we divided the study into eight landuses and considered
each in turn.
