Prickly acacia disaster looms in aftermath of North Queensland floods

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North Queensland graziers warn an environmental disaster looms as February’s floods spread invasive prickly acacia seeds into previously untouched areas, including Lake Eyre.

Acacia Key points

Key points:

Cattle grazier Alan Davison has been trying to eradicate prickly acacia (Acacia nilotica) on his 3,200-hectare property near Hughenden for 25 years.

Introduced from India in the late 1800s as fodder and a shade tree for livestock, the thorny weed quickly spread along water courses and through cattle and sheep movements.

“We started eradicating as soon as we got here, trying to, and we’ve been through highs and lows and I think it will always be here, but we’ll get it to a manageable level.”

The former school teacher said the weed killed the Mitchell and Flinders grass that grew on his property.

“When prickly acacia becomes thick it covers the ground and a lot of grass can’t grow underneath it,” he said.

“The seed is easily spread and so when cattle eat it they spread it all around the place.

Hughenden grazier Alan Davison fears February’s North Queensland floods has spread the weed.

“It’s very hard to kill it and the seed remains dormant for so long that it can come back years and years later.”

Since flooding rains swept across the state’s north in February, Mr Davison had noticed a new wave of acacia weeds had emerged.

“There’s been another batch of young trees coming through,” he said.

Pest once planted for fodder

Many North Queensland graziers spread acacia seeds across their properties in the 1960s to provide fodder for their stock during dry periods.

Flinders Shire Mayor Jane McNamara said flooding in the mid 1970s then spread the acacia seeds across vast areas of Queensland’s north west.

Prickly acacia distribution in North Queensland.

“Since 1974 we’ve probably had half of the Flinders Shire infested with some degree of prickly acacia, so that would be about 21,000 square kilometres,” she said.

“We are at the watershed of the Lake Eyre Basin and the Gulf of Carpentaria, so it’s very important to be able to nip this in the bud at the head of the waterways.

“If you can’t control it at the top of the watershed then whatever happens downstream keeps being eroded, because the seeds keep going through.”

The Federal Member for Kennedy, Bob Katter, said prickly acacia has the potential to become an environmental apocalypse.

“You could have an argument whether the rabbits were worse or the prickly trees, but it’s most certainly neck and neck between the two.”

Flinders Shire Mayor Jane McNamara says 21,000 acres of the region is infested with invasive prickly acacia.

Mr Katter said if the problem was not tackled soon it would reduce the carrying capacity of cattle in Australia.

“A reduction of 30 per cent,” he said.

“To turn that into figures, that’s about $5 billion a year.”

Last week Prime Minister Scott Morrison visited North Queensland and committed $5 million to fight prickly acacia.

Alan Davison believed prickly acacia would never be fully eradicated and warned graziers and councils to act if the pest arrived on their land.

“There will certainly be an explosion somewhere, I would almost guarantee,” he said.

“Get rid of them when you find a few, because it won’t take long to go from a few, to a few thousand, to a few million.”