Close to eradication of Gamba grass in WA

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At first glance, gamba grass appears to fit right into Australia’s natural landscape, but the tall green tussocks are an insidious threat to native animals, homes and lives.

It was brought to Queensland in 1942, and large-scale planting took place in the 80s as it took hold in Western Australia’s east Kimberley region.

It wasn’t until 2012 that it was recognised as a weed of national significance, competing with native plants and acting as a dangerous accelerant during Australia’s increasingly ferocious bushfires.

Department of Biodiversity, Conservation and Attractions (DBCA) conservation coordinator David Chemello said while native Australian species had adapted to fire, they stood no chance against a gamba grass fire which could increase fire fuel loads by eight times.

As the NT and Queensland continue an uphill battle against the invasive pest, WA is close to eradicating it.

Plant numbers decline

Mr Chemello is committee chair of the Gamba Grass Eradication Program, a partnership project between DBCA, the Department of Primary Industries and Regional Development, El Questro Station and Kimberley Rangelands Biosecurity Association.

He said a control program started in 2011 and by 2018 they were able to count just 3,000 plants.

“By the next year it was down to 300, by 2020 it was down to 23 individual plants and last wet season it was eight plants that were found and controlled,” Mr Chemello said.

A man stands next to a towering formation of green grass
                                                                              Gamba grass can grow up to four metres tall and spreads quickly in dense thickets.(Supplied: CSIRO)

“This is textbook eradication and as close to being finished as we could possibly hope for so it’s pretty exciting stuff.”

But he warned the battle was not over yet with success stories being “very far and few between”.

“We still need to go out for probably another five years in the monitoring phase of the program and that’s just to ensure that any seed that is left in the soil has been exhausted,” he said.

Mr Chemello said DBCA worked collaboratively on a number of projects to reduce or eradicate invasive plants, including a rubber vine program which was on track but still had about a decade before completion.

Like gamba grass, rubber vine was out of control in Queensland and Mr Chemello attributed WA’s success to early intervention.

“We got onto these weeds when we still had a chance, if there were 10 million hectares in WA, eradication wouldn’t even come into the picture but the area was quite small,” he said.

“Even though it is a small area it involves a lot of dedication to these projects year after year.

A different situation across the border

While the project is close to entering the monitoring phase, across the border in the Northern Territory conservationists continue their battle to contain gamba grass.

Pew Charitable Trusts’s Mitch Hart said the global not-for-profit championed conservation efforts in Australia, including a partnership with the Gamba Grass Roots Alliance.

“We focus on Australia’s outback because it’s globally significant. It’s still overall in pretty good nick, but it needs active management,” Mr Hart said.

“That’s why we work on the gamba issue, because we see it as a risk to some of Australia’s most intact tropical savanna.”

A human hand rests on some green wide-blade grass blades with a white stripe in the middle.
                                                                          Gamba grass was originally planted in northern Australia as cattle feed.(Supplied: Gamba Grass Roots)

Mr Hart said gamba grass was a “triple threat” with large infestations from Darwin to Katherine.

“It’s a threat to people’s lives, it’s a threat to the economy of the Northern Territory, and then it has the environmental impacts of reducing and totally destroying Australia’s northern savanna,” he said.

Gamba grass was the only weed listed as a priority threat in the federal government’s Threatened Species Action Plan 2021-2026.

“That’s a real recognition of just how bad gamba can be and the threat it poses to native wildlife,” Mr Hart said.

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