Wetlands, woodlands or weedlands? 


One of the biggest environmental problems for the Territory is the encroachment of weeds into wetlands and woodlands.

Between 1947 and 1985 a total of 186 grass species were introduced to northern Australia in the hope of providing a feed that would fatten cattle and improve productivity.

According to environmental scientist Dr Michael Douglas, research has now shown that only three of these grasses have been suitable for cattle without becoming weeds.

‘Only 11 species are useful for pasture, but nearly three times as many, 32 species, are now considered weeds,’ he said.

Some of these weedy grasses have moved out of the pastoral land, said Dr Douglas and have brought the Territory's wetlands and woodlands to the edge of disaster.

Many regions in the Territory are infested with weeds that have clogged up waterways, proved a fire hazard, become a threat to wildlife and caused problems for the management of national parks and bushland.

Among the worst of the weeds is the gamba grass that now infests much of Darwin's rural area, with para grass and olive hymenachne heading the list of least-wanted species.

‘It's important to remember, these grasses were introduced for a particular purpose with little knowledge of their impact on the environment,’ Dr Douglas said.

‘Now we are left with the problem of how to control most of them, so the wetlands and woodlands can return to their natural state.’

Dr Douglas said spraying is one solution for many of the weeds, but the encroachment of some of them is so extensive that the task will be enormous.

‘I fear, in the case of olive hymenachne, the situation is on the edge of disaster,’ he said.

‘I'm at a loss to see how we can avoid the loss of most our wetlands to this weed.’

He said governments are moving in the right direction when it comes to tackling the weed menace, but more research needs to be done and many more resources committed to management programs.

Dr Douglas has spent more than a decade researching weed ecology and management, and is currently director of TRaCK, the consortium of research scientists studying rivers and their catchments from the Kimberley to Cape York.

He will give a full account of the weed menace in his Charles Darwin University public lecture Wetlands, Woodlands or Weedlands? at the Museum and Art Gallery of the Northern Territory on May 15 at 6pm.