The finding has major implications for the care and management of the worlds remaining rainforests and tropical river systems, as well as global water security.
It is giving the upland rainforests a whole new environmental significance in the landscape, as cloud harvesters which add billions of litres of extra flow into tropical river systems, says CSIROs Dr Paul Reddell.
Dr Reddell and Dr David McJannet lead a team in the Rainforest Co-operative Research Centre, involving scientists from CSIRO and James Cook University.
From our early work, it looks as though rainforests may pull up to 40 per cent more water out of the clouds than is measured as rainfall in a standard rain gauge, they say.
In high, wet tropical regions above 900 metres, low cloud, mist and fog blow constantly through the forest, condensing on trees and running or dripping down them to the ground.
This condensation is additional to normal precipitation and does not occur where the forest has been cleared.
The role of rainforests in the water cycle is poorly understood. We know forests are important in regulating the flow of water through the landscape and we know that, by holding back water, they contribute to the dry-season flow of coastal rivers said team member Dr David McJannet.
Now we have clear evidence of another role, cloud-stripping, in which the forest actually harvests large volumes of moisture additional to the rainfall.
A serious issue is that, when rainforests are cleared, the amount of moisture reaching the soil decreases significantly due to the removal of the cloud-stripping effect.
Also, because these upland rainforests transpire very little, they contribute a disproportionately large volume of water to their catchment. This contribution is greatly r
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Contact: Margaret Bryant
margaret.bryant@per.clw.csiro.au
61-8-9333-6215
CSIRO Australia
31-Jan-2002