Rita Reitano rita.reitano at adelaide.edu.au
Fri Sep 28 04:09:33 CEST 2007

MEDIA Release
Embargoed until 2 October 2007


Many of the 3000 foreign plants species now established as weeds in
Australia could explode into new areas as current climatic limits on them
are lifted, scientists from CSIRO and the Weeds CRC said today.

In a statement issued at the opening of the Greenhouse 2007 conference in
Sydney today, CEO of the Cooperative Research Centre for Australian Weed
Management, Dr Rachel McFadyen, said that climate change was likely to be a
'big win for weeds'.

Not only will increased temperatures allow northern weeds to move south,
such as the frost-intolerant species rubbervine and Siam weed, but lowland
weeds will also do better at higher altitudes where conditions have
previously been too cold for them, Dr McFadyen said. 

'This means we can also expect more weeds to do better in the heritage lands
of the Australian Alps, which will place more pressure on already threatened
alpine ecosystems', Dr McFadyen said. 

Worse still, some plants that are present in Australia but have not yet
behaved as weeds, the so-called 'sleeper weeds', could burst onto the weeds
scene and cost millions to control.

'Weeds already cost the Australian rural economy $4 billion every year', Dr
McFadyen said. 'Loosening the climatic restraints that have kept many
potential weeds well behaved in their gardens is likely to result in a
number of them becoming seriously invasive in farming systems', she said.
She predicted serious economic impacts if ways to control them are not

Dr McFadyen said that climate change will open new windows of opportunity
for weeds to do what they do best - invade. Although most plants will
retreat in the face of changed conditions, the weedier ones will thrive and
rapidly invade any new available space.

'New space for weeds is also made by extreme events such as fire, floods and
storms', Dr McFadyen said. For example, Cyclone Larry in north Queensland in
2006 had opened up gaps for weed invasion in areas of pristine wet tropics

Scientists predict that areas experiencing more intense rainfall events are
also likely to see weeds spread as their seeds are dispersed by large
floods. This is how athel pine suddenly spread in central Australia in the
1970s, and many other weed species can benefit in the same way.

'Most scientists agree that the climate change now underway will bring more
such extreme events - so the weeds win again!', Dr McFadyen said.

In a joint briefing, the CSIRO's Dr Darren Kriticos reported that climate
modelling had progressed sufficiently for weed scientists around the world
to start using these models to predict how known weeds might expand their
range in response to climate change. 

'The big pattern that is emerging in the climate change scenarios is that we
will see weeds currently widespread in northern Australia start to become a
problem further south', Dr Kriticos said.

Using four weeds as examples, namely prickly acacia (Acacia nilotica), Siam
weed (Chromolaena odorata), Scotch broom (Cytisus scoparius) and buddleia
(Buddleja davidii), researchers had mapped the possible extent of the weeds
in the year 2080. Prickly acacia was predicted to expand its range south
into NSW, and Siam weed would also expand south into coastal NSW as well as
further inland in mid-southern Queensland.  

However, the area suitable for buddleia and Scotch broom appeared likely to
contract southwards as temperatures increased, although this would still
bring them into conflict with some of Australia's most productive
agricultural systems. 

According to the researchers, increasing levels of CO2 will also directly
affect plants, apart from any advantage or disadvantage caused by rising

Dr McFadyen explained that there is more than one way that plants generate
energy from sunlight, and that plants with the 'C3' energy system, such as
the northern weed parthenium, will do better under higher CO2 levels.
'Parthenium is one of Australia's 20 worst weeds, and with repeated exposure
causes very unpleasant allergic reactions in most people, Dr McFadyen said.
'It will be even more competitive in the raised CO2 environment.'


Dr McFadyen and CSIRO researcher Dr Darren Kriticos will present their views
and results at a special press briefing as part of Greenhouse 2007. They
will be joined by ecologist and author of the book 'Feral Future', Tim Low.
All will be available for interview.

Time: 12.00 noon 
When: Tuesday 2 October 
Where: Room 2, level 1, Sydney Hilton, 259 Pitt St, Sydney, NSW 2000

Weed images related to this story are at

Further information: Peter Martin 0429 830 366, Rachel McFadyen 0409 263 817
or Rita Reitano 08 8303 6857.


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