Noxious weed consuming tourist icon

A popular national park in northern Australia is under threat from a noxious weed that worsens the effects of climate change when it burns.

New research has estimated almost one-third of Litchfield Park, a tourist icon may be lost to the weed within a decade if urgent action was not taken to eradicate it.

Litchfield Park, covering almost 1500 sq km about 100km south of Darwin, is a popular weekend and holiday destination for Top End tourists and locals, boasting waterfalls, places to swim and stay, 4WD tracks and scenic walks.

Some 260,000 people travel each year to view its iconic waterfalls, which cascade from the sandstone plateau of the Tabletop Range, including familiar beauty spots of Wangi Falls, Florence Falls and Buley Rockhole.

For thousands of years, the area has been home to the Koongurrukun, Mak Mak Marranunggu, Werat and Warray Aboriginal people.

However, all that may be under threat, according to research published in the Journal of

Environmental Management. Modelling by researchers from Charles Darwin University and the universities of Tasmania and Western Australia, reveal that almost one-third of Litchfield National Park would be engulfed by gamba grass within a decade if nothing is done to eradicate it.

Gamba grass habit
Gamba grass as shown on the NT Government’s noxious weed website.

Researchers undertook helicopter surveys of the park in 2014 and again in 2021–22

showing that the invasive weed had spread rapidly and was now covering 30,000 hectares of the 144,000-hectare park to become the largest infestation in a national park in Australia.

Originally from Africa, gamba grass, or Andropogon gayanus, was introduced to the Northern Territory as a pasture species in the 1930s, and spread. It came to Queensland in 1942, but large-scale planting only started around 1983.

Noxious weed declared 2008

The grass was declared a weed by both Queensland and the Northern Territory in 2008, and may be identified using this guide.

The grass grows up to 4m high and threatens the delicate ecosystems of Australia’s north by displacing native grasses, reducing biodiversity, and fuelling hot intense fires that destroy tree canopies.

Gamba grass can also exacerbate the effects of climate change. When it burns, it changes

the amount of greenhouse gases emitted, and reduces the ability of the natural environment to absorb and store greenhouse gases.

Federal Labor last year pledged $9.8 million over four years to help manage the threat but the money is directed to locations where gamba can most readily be eradicated and contained, such as Kakadu National Park and Arnhem Land.

The current research urges that funding be expanded to contain Litchfield. It modelled three scenarios for Litchfield spanning the decade ahead:

  1. Do nothing, in which case gamba spreads to cover 42,000 ha covering all major tourist sites;
  2. Remove the weed from a small existing gamba grass eradication zone on Tabletop Range, predicted to cost $825,000 over five years, and accept that tourist hotspots of Florence Falls and Tolmer Falls would fall to gamba, which would have spread to 41,000 hectares over the decade;
  3. A new and preferred proposal outlined by co-author Professor Samantha Setterfield from The University of Western Australia:

““We propose (that) gamba grass is eradicated over a much larger area … to better protect the significant values of the park, predicted to cost $6.6 million over five years,” the research states.

“Under this scenario, gamba would be kept away from most major visitor attractions.

“This significant investment in intensive gamba grass control and monitoring is needed to protect important habitats and visitor areas in the park.”

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