[ASC-media] Media release: green tide rising
jcamedia at starclass.com.au
Tue Feb 1 09:07:53 EST 2005
Weeds CRC Media Release 05/06 - WORLD WETLANDS DAY: FEB 2, 2005
Tuesday, 1 February, 2005
GREEN TIDE RISING IN AUSTRALIA'S WATERWAYS
A green tide of invading plants is severely degrading Australia's waterways, wetlands and floodplains, researchers from the Cooperative Research Centre (CRC) for Australian Weed Management say.
On World Wetlands Day, scientists have warned that the nation's wetlands and river systems are especially vulnerable to many kinds of imported plants.
"Three quarters of Australia's plant invaders were deliberately brought here with the best of intentions, but multiplied out of control in our environment," says CSIRO's Dr Tony Grice, a research leader in the Weeds CRC. Some wetland invaders were introduced as pasture, others as garden ornamentals, and others for the aquarium trade.
'Some wetland invaders, such as salvinia, are just as happy in Kakadu as they are in Sydney, said Dr Grice. 'They are immensely successful plants and out-compete native species.'
In doing this they alter the water flow in wetland systems and can completely change the habitat for wetland creatures.
'Population explosions of new plants deplete available nutrients and as they die and rot they also deplete oxygen in the water. Use of these essential resources places serious pressure on native ecosystems. Dr Grice says that wetlands are extremely important and plant invaders are one of the main threats that they face.
'Wetlands are the kidneys of our catchments and ecosystems, just as forests are the lungs', Dr Grice said. 'They are our water purifiers. We just can't afford to let them degrade.
Many deliberately introduced plants are very well suited to take over Australian wetlands. "The meadow grass hymenachne was imported into northern Australia because it grows strongly in well-watered pastures and is very palatable to grazing stock," says Dr Grice.
However, within a mere eight years it became one of the worst wetland invaders, choking billabongs and lagoons, and destroying the habitat of birds, fish and other animals. It is now on the list of Australia's top 20 weeds.
Another example is mimosa, which in its native range in central America is a small shrub that causes no problems.
'But in the NT the same plant grows in thickets to over 5m high, and has taken over more than 100 000 ha of precious floodplain country. It forces out all other species of plants, and the land becomes useless for cattle and many native animals. It even shuts Aboriginal people out of culturally important sites.
Dr Grice says that in many areas invading plants now pose a more serious threat to the environment than better known threats such as land clearing or salinity.
"We're fighting against a green tide of invaders," says Dr Grice. "Many weeds have become so well established in the Australian landscape that the best we can hope for is containment. For most, eradication is probably impossible
Dr Grice says that, although biological control cannot offer a complete solution to the problem of invading plants, there have been some notable successes in the biocontrol of water weeds.
"Good taxonomy is important for good biocontrol," he says. "We have to know which plant species we are dealing with so we can locate its native range overseas. Then we search the native range, eg south eastern Brazil for salvinia, for its natural enemies.
"It was this sort of painstaking research which led to the very successful biological control of salvinia, and substantial control of water hyacinth and aquatic alligator weed. These programs introduced insects that are helping to keep the important weeds in check.
Dr Grice says that protecting our wetlands in future depends on a combination of effective control measures, appropriate legislation, better enforcement, improved practices by commercial interests, and greater public awareness.
The aquarium industry, for example, needs to be more aware of the environmental risks posed by the plants that still circulate in the trade and amongst fish fanciers. It could play a greater role, for instance, in educating their customers not to empty their fish tanks into lakes and streams', Dr Grice said.
"Everyone who interacts with water - whether in a boat as an angler, or as an aquarium keeper - should learn to recognise the most serious invaders and help stem the green tide."
More information from:
Dr Tony Grice, 07 4753 8543
CSIRO Sustainable Ecosystems and Weeds CRC 0419 974 520
Dr Rachel McFadyen, CEO, Weeds CRC 07 3362 9388
0409 263 817
Peter Martin, Weeds CRC 08 8303 6693 0429 830 366
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