Within the last decade both droughts and storms have, for example
in Australia, become consistently more severe. With the accelerated
destruction of the forest, the climatic future of the region looks
grim. Amazonia contains two-thirds of the world's surviving tropi-
cal rainforest, representing about 30% of all the biological material
on the land.^4 You can imagine that when all four tropical rain forests
were intact, they must have contained the greater part of the plant
and animal life on Earth.
The released energy drives the great air masses across the
Amazon basin to the Andes, recycling the rain and evapo-tran-
spiration several times in a leapfrogging process (see Fig. 13.1).
The airflow then splits into three: the southern part is deflected
as far as Patagonia; the central part flows over the Andes into the
Pacific, continuing west as the trade winds; the northern airflow
crosses the Caribbean, and helps to drive the Gulf Stream north-
eastwards to Europe.^6 Rainforests act as thermal engines, rainfall
stimulators and as regulators of atmospheric and oceanic sys-
tems. They moderate the climate of the whole Earth and help to
make it habitable.
The Amazon Basin, which comprises 7 million km^2 of rainfor-
est, is the biggest and most efficient energy transformer on Earth^7 ;
it is self-maintaining when complete, but 25% has already been
lost in the last 35 years. Five million km^2 lie in Brazil which has
recently unveiled an accelerated development plan (see below)
that would result in the loss of a further 20% by 2020 (a total loss
of forest of 45%!). There is a critical size of the Amazonian rain-
forest below which this complex heat engine and rainfall distrib-
utor will fail. Some authorities claim that if it shrinks to much less
than the present 75% of its original area, the forest will not be able
to perform these critical functions effectively, resulting in more
hostile weather patterns and drought across the globe.^8
Areas that have been clear-felled put at risk the remaining forest
for many miles from the edge of the deforested area, rendering the
marginal area more susceptible to die-back due to the local increase
in temperature. In fact, the Amazonian forest through deforestation
is generally losing its ability to withstand the worldwide tempera-
ture increase created by global warming. At some point, perhaps in
the next twenty years (or sooner under present Brazilian plan), a
critical point could be reached, when massive die-back could cause
this vital energy transformer to fail.
- THE ROLE OF THE FOREST