21 February 2023

Major investment is urgently needed to protect Litchfield National Park from gamba grass.

New research has warned that almost 30% of Litchfield National Park could be infested with the invasive weed gamba grass within a decade.

Infestations in the national park have spread rapidly and already cover about 30,000 hectares of the 144,000-hectare park.

The research, published in the Journal of Environmental Management, called for urgent action and resources to control the weed, which can pose an extreme fire risk to popular visitor areas.

Gamba grass invading along riparian areas in Litchfield National Park. Photo: Natalie Rossiter-Rachor.

Charles Darwin University ecologist and lead author Dr Natalie Rossiter-Rachor of said Litchfield is an iconic national park in northern Australia.

Litchfield National Park contains significant environmental, cultural and social values. It’s referred to as the ‘jewel in the crown’ of Top End parks. However, our research shows this is all at risk unless a major investment is made in weed control.
– Dr Natalie Rossiter-Rachor

The research, funded by the Australian Government’s National Environmental Science Program and the Northern Territory Government, conducted helicopter surveys of the park in 2014 and again in 2021–22. These surveys showed the invasive weed has spread rapidly since 2014, covering 30,000 hectares of the 144,000-hectare park, including near popular sites such as Florence Falls and Buley Rockhole. It is the largest gamba grass infestation in a national park in Australia.

Tackling gamba grass is identified as a priority in the federal government’s Threatened Species Action Plan 2022–2032. New Australian Government funding of $9.8 million is being directed to strategic gamba grass control in locations where it can be eradicated and contained, such as Kakadu National Park and Arnhem Land.

Given the outcomes of this new research, significant investments are also needed to address catastrophic and established infestations in areas managed by states and territories, such as Litchfield National Park.

Researchers examined 3 different future management scenarios for gamba grass in the park and modelled the distribution of gamba grass after 10 years of each scenario. Under the do-nothing scenario, gamba grass will continue to rapidly spread in the park, covering more than 42,000 hectares and impacting all popular visitor sites – degrading habitats for threatened species and posing extreme risks for bushfires fuelled by gamba’s large fuel loads.

The second scenario would see gamba grass removed from the Litchfield’s small existing gamba grass eradication zone on Tabletop Range, predicted to cost $825,000 over 5 years. But under this scenario, sites such as Florence Falls and Tolmer Falls would still become infested and gamba could continue to spread in the rest of the park, covering more than 41,000 hectares of the park over the next decade.

We propose a new scenario where gamba grass is eradicated over a much larger area of the park to better protect the significant values of the park, predicted to cost $6.6 million over 5 years. 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.
– Professor Samantha Setterfield, The University of Western Australia (study co-author)

Dr Rossiter-Rachor emphasised the need for swift action.

Gamba is spreading quickly in Litchfield. The longer we wait to fund intensive management action, the more expensive it will become and the more impacts we’ll see to the park’s incredible biodiversity and stunning natural areas.
– Dr Rossiter-Rachor

Natalie Rossiter-Rachor in a helicopter conducting gamba grass surveys.

Gamba grass invasion in Litchfield National Park. Video: Natalie Rossiter-Rachor.

This animation shows the surveyed and modelled distribution of gamba grass in Litchfield National Park from 2008–32.

Read more about this research in the wrap-up factsheet.