Media Release
CRC for Australian Weed Management
28 August 2008


HALF AUSTRALIA’S PLANTS NOW FROM OVERSEAS

The number of plant species now growing in Australia has more than
doubled since European settlement in the 1780s due to new plants
introduced from overseas, according to a new publication from
Australian weed scientists launched today.

And thousands of them are just ‘weeds in waiting’, say the researchers.

Launching the ’Introduced flora of Australia and its weed status’ at
the National Botanic Gardens in Canberra today, Tasmanian Senator
Christine Milne said the 28,000 species brought in from overseas in
merely 200 years was many more than the number of native species.

‘Scientists estimate that the original pre-European rate of plant
introductions was as little as 1-5 species per century, a rate which
the native flora was able to cope with’, Senator Milne said.

‘However, in the last 200 years the average rate of introduction
rocketed to 14,000 per century. In many places this has simply
overwhelmed the adaptive capacity of Australian ecosystems’, Senator
Milne said.

‘If we are to maintain our current level of biodiversity in Australia
and build resilience in ecosystems, then we must have a war on weeds’,
she said.
Compiled by Rod Randall of the WA Department of Agriculture and Food
and the Cooperative Research Centre for Australian Weed Management
(Weeds CRC), the recently completed project set out to list all
introduced plant species now found in Australia as well as their weed
status here or overseas.

Mr Randall said that many weedy plants were introduced for
agriculture, especially for pasture, and later abandoned to go weedy
when they failed to perform.

‘However, most of our worst weeds come from parks and gardens’, Mr
Randall said. Examples include Paterson’s curse, blackberry, willows,
bridal creeper, gorse, lantana and soursob.

The ’Introduced flora of Australia and its weed status’ lists
precisely 2739 foreign species that have become weedy, and a further
5907 that are here, not yet weedy, but have a history of becoming
weeds overseas.

‘Australia has such a diversity of climates we can be sure than many
of these ‘weeds in waiting’ will eventually find their way to a site
that suits them â€" and then they will simply explode in numbers’, Mr
Randall says. ‘We are pretty adept at moving plants and seeds around,
on purpose or by accident, which gives weeds the chance they need to
spread and try their luck in new locations.’

Climate change is also working in their favour, he says, as changes in
local conditions stress existing plants, and open up opportunities for
tougher invaders.

‘Some of these ‘weeds in waiting’ may find that just staying put works
for them’, says Mr Randall, ‘especially if the local changes to
rainfall and temperature suit them. It could be that their time is
coming.’

Gardeners and plant retailers will be able to use the ’Introduced
flora of Australia and its weed status’ to see immediately whether a
plant is known to be weedy outside its native range, and can then
choose to avoid planting or selling it.

‘This is basic ‘weed risk’ information that people have lacked up till
now’, says Mr Randall.

‘If gardeners and sellers over the last 200 years had only known what
we know now about which plants can become highly invasive, we might
have avoided much of the degraded landscapes, lost biodiversity and $4
billion per year agricultural loss now caused by weeds’, he said.

Mr Randall points out that the document lists over 20,000 non-weedy
foreign plants for gardeners to choose from, in addition to the 11,000
native plants now cultivated. The total of over 30,000 species and
cultivars should be a big enough palette for us, he says, and obviate
the need to grow known weeds.
Users will need to know the correct scientific name of plants to
search the system, since common names are too unreliable and vary too
much, Mr Randall says.

Now available free from the Weeds CRC web site, the Flora can also be
searched online via the University of Queensland web site at
http://weeds.cbit.uq.edu.au