[ASC-media] Media release: Rainforest in "green peril"

JCA Media jcamedia at starclass.com.au
Tue Nov 1 20:14:57 EST 2005

Cooperative Research Centre for Australian Weed Management 

Media Release 05/42

November 2, 2005


Tropical plants from round the world are securing an invasion foothold in one of Australia's most precious ecosystems - the northern rainforest.

In a disturbing development, researchers in the CRC for Australian Weed Management say they are finding invasive alien plants in areas of rainforest previously undisturbed.

"Until now it was thought that weeds only established round the edges and in disturbed areas of rainforest," explain Dr Helen Murphy and CSIRO's Dr Dave Westcott, who are trying to establish the nature, extent and processes involved in the invasion.

"However, certain plants - such as pond apple, guava, coffee and mango trees - can establish in relatively undisturbed areas of forest. And some, like pond apple, are quite capable of dominating surrounding vegetation."

Other invaders include the Central American tree Miconia - responsible for ecological disasters overseas - and the African tree Harangana, which has reinvaded areas of native forest round Mt Bartle Frere where it was once thought to have been eradicated.

The finding adds to concerns over existing pressures on the rainforest caused by fragmentation and human impacts. The invasive shrub lantana has already penetrated many areas of rainforest throughout the wet tropics, and can persist by making its way into the canopy as a climber up other trees.

"The serious aspect of this is that an invading plant can cause changes to the structure of the rainforest - some of these changes may in turn make it easier for other invaders to penetrate," says Dr Murphy.

"At present we have no idea how big the threat is, but in 200 research plots scattered across the wet tropics we have logged around 50 invasive plant species. Individual plots may have as many as 12 or 15 of these environmental weeds."

A further dilemma lies in how invasions of the rainforest can be controlled, Dr Westcott says.  Use of fire and bulldozers are clearly out of the question in rugged terrain and conservation areas.  As yet there is little in the way of biological controls for the invaders, while manual control is costly.

Adding to the problem are Australian native animals and birds, like the cassowary and fruit bat, which are inadvertently helping spread the invaders by eating their fruits and distributing seed in their droppings.

Australia has around 64 birds and animals which disperse rainforest seeds - and around three quarters of the world's tropical forest plants have fleshy fruits capable of being spread in this way.

"Such diversity of species and interactions means that understanding
and managing invasion in rainforest systems will not be easy. Indeed we are at a very early stage," says Dr Murphy.

One answer may depend on the co-operation of landholders and gardeners who live adjacent to rainforest areas in not growing those plants or trees that have a potential to invade the native forest through seed-carriers.

Dr Murphy says her research aims to identify the characteristics of plants or trees which might make them successful as rainforest invaders, so they can be kept in check. She is also seeking to identify the first tell-tale signs that an invasion may be about to occur, so it can be headed off.

Her research involves building an understanding of how an outbreak of invasive plants occurs and trying to predict how serious it will be - whether it will end up dominating the rainforest, or whether the native vegetation will eventually contain and suppress it.

It may also involve a change in attitude on the part of Australians:  "It seems awful to have to regard things like coffee and mangoes as weeds," says Dr Westcott, "but in the wrong place they can do quite a bit of damage to our natural heritage."

More information:
Dr Helen Murphy, CRC Weeds, 07 4091 8828

Peter Martin, Weeds CRC, ph 08 8303 6693 or 0429 830 366

Photos of weeds invading rainforest, close ups and infestations, are available from Jackie Watts at jackie.watts at adelaide.edu.au, 08 8303 6742

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