Deforestation and urbanisation have interrupted the natural rainfall cycle that gives Australia its lush, green east coastline, writes Keith Presnell.
WHEN THE FIRST FLEET arrived in Australia, it was confronted by an environmental pearl. Fertile coastal plains rimmed by the Blue Mountains, all clad with healthy forest.
The south-easterly trade winds brought sufficient advective rain cells onshore to maintain a natural balance that had supported all life flourishing in Paradise, for millennia.
That involved two important mechanisms. The first is a cooling function — liquid to gas, water to water-vapour. In other words, a forest is a natural air conditioner that provides a significant cooling effect on the air masses passing over its canopy. The second is that moisture transpired by forests replenishes rain clouds, enabling them to penetrate further inland.
On the east coast of Australia, that system has been damaged. Not so much by climate destabilisation as by inappropriate land management. In the last two centuries, our coastal forests have been decimated by urbanisation and for short-term profit.
The mechanisms that once maintained a balanced environment have been replaced with a heat mountain that seemingly reaches much higher than the Blue Mountains. Rain events that have been reinforced by increased ocean evaporation are stopped in their tracks when they encounter the strong thermal, causing them to dump their rain near the coast.
That pattern is likely to persist. It also means that during dry spells, inland Australia may be left relying on rainfall from the west, rather than from the east.
All I can say is, don’t mess with the environment.
Keith Presnell, now retired, was director of renewable energy research at Charles Darwin University and Australia's representative on the International Energy Agency (IEA's) photovoltaic subcommittee.
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