Dr Reddell also warns of the consequences for water security in the event of global warming: if the cloud banks which currently contribute water to the forest via cloud stripping rise in altitude - as they are forecast to do - there could be a major loss in water gathering by the forest and its catchment, with consequences for communities downstream that rely on these resources.
To work out how much moisture falls as rain and how much is harvested by the forest, the team set up rain gauges in open areas at Longlands Gap and Mt Lewis in North Queensland, and throughfall troughs and collar gauges round trees in the forest. The throughfall troughs measure water which directly reaches the forest floor, dripping through the canopy. The collars measure stemflow, or water running down the tree trunks.
The difference between whats in the rain gauge and throughfall plus stemflow is the amount of extra water stripped by the forest.
The team are now looking at developing gauges that can be used to estimate cloud stripping at a much wider range of sites and so build a fuller picture of the wet North Queensland rainforests contribution to the wet tropics hydrological cycle.
Dr Reddell says that the information will be valuable in several ways:
it will contribute to more accurate water balances, and so to the development of sustainable water allocation policy
it will make the public more keenly aware of the value of rainforests and the services they provide to the environment and people
it will alert the world to a new aspect of the losses sustained when upland rainforests are cleared, and contribute to better management of tropical catchments and rivers
it may encourage people to replant trees in cleared areas of the wet tropical uplands
it could even generate income from sale of the extra water harvested from a replanted forest.
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Contact: Margaret Bryant
margaret.bryant@per.clw.csiro.au
61-8-9333-6215
CSIRO Australia
31-Jan-2002