Should this plant be declared one of the worst weeds in Australia?
- Written by Ellen Ryan-Colton, Senior Research Officer, Australian National University
You might not have heard of buffel grass, a robust and invasive grass that has spread across tens of thousands of square kilometres of inland Australia. But you might know its effects.
Most people remember the deadly 2023 fires in Maui, Hawaii, which killed more than 100 people. Many will know of the worsening bushfires in Australia’s centre. In both cases, buffel grass, (including Cenchrus ciliaris), played a role by adding fuel in dry environments.
Right now, the federal government is weighing up whether to declare buffel grass one of the worst weeds in the country – a “Weed of National Significance”.
Our new study shows buffel grass does real damage to native animals, and we can now predict the types of animals most at risk. Building on previous work, we show buffel grass affects at least three major groups – birds, reptiles and ants – in multiple habitats and regions.
What is buffel grass?
Buffel is a tussock grass, bulkier than most Australian native grasses. Native to Africa, the Middle East and Asia, buffel grass first arrived in Australia via imported camel saddles in the 1870s. It was later planted for dryland pasture as its deep roots allow it to thrive in dry climates.
Buffel grass was first planted in the 1920s and became well established by the 1960s. It enabled significant returns to the pastoral industry, including economic returns in dry years.
But now buffel grass has spread much further and is smothering Aboriginal land, conservation reserves, public places and regional and remote towns. More summer rainfall in central Australia, as part of climate change, is fuelling the growth, seeding and spread of buffel grass.
The issue is complex: although valued by many graziers, buffel grass is now spreading so rapidly and widely its severe negative impacts can no longer be ignored.
It has significant impacts on biodiversity, people’s health and safety and on cultural sites and practices, especially for Aboriginal people in central Australia. The case for recognising it as an invasive weed of national significance is compelling.
What our research found
We surveyed birds, reptiles and ants in the Aṉangu Pitjantjatjara Yankunytjatjara Lands of inland South Australia in two regions, 300 kilometres apart. Survey sites included rocky hills, fertile plains, spinifex grasslands and wooded sites. We wanted to see whether buffel grass invasion changes the mix of animals species in an area, and if we could predict which types of animals would be most affected.
We found reptile, bird and ant communities had all changed where buffel grass had taken over these habitats. Certain groups of animals were consistently less common in areas affected by buffel grass.
Buffel grass changes the whole ground layer of a site; thick grass replaces open native grasses and shrubs. As we expected, animals that use the ground and need open space, such as small reptiles, ants and ground-feeding birds, were less common in buffel grass. These findings are consistent with earlier local studies of reptiles, and birds in central Australia.
Dusky grasswren lives on rocky hillsides in central Australia and specialises on eating insects. We found grasswrens on hills with spiky native spinifex grass, but not on hills where buffel had displaced spinifex.
Tom Hunt, CC BY-ND
Once buffel grass invades, it dominates plant communities, reducing the diversity of native plants. We predicted this would make it harder for animals with specialised diets to find food compared to animals that eat more broadly. As expected, specialist eaters were most affected, such as seed-eating ants and birds.
Birds that feed on insects were also consistently worse off. For example, the dusky grasswren is a stout wren that only lives on rocky hillsides in central Australia and specialises on eating insects. We found grasswrens on hills with spiky native spinifex grass, but not on hills where buffel had displaced spinifex. Likewise, the rufous whistler – another insectivore that prefers Acacia woodlands – was less prevalent where buffel grass had invaded.
Whole groups of animals at risk
Because these trends were mostly predictable and consistent across animal groups, habitats and regions, we expect the same thing is happening in other areas. Considering how widespread buffel grass is, whole groups of fauna across inland Australia are at risk if its invasion progresses unchecked.
Loss of major animal groups is often only evident after it is too late. With mounting evidence available, we must act now.
Buffel grass was declared a weed in South Australia in 2019, and the Northern Territory in 2024. Weed recognition can lead to more strategic research and management.
A national listing of buffel grass as a “Weed of National Significance” would be critical recognition of its impact at a continental scale. It would also mean a nationally coordinated response, which is the only way to protect whole groups of species, ecosystems and livelihoods of arid Australia. Without national policy, the spread and impacts of buffel grass will continue unchecked.
Authors: Ellen Ryan-Colton, Senior Research Officer, Australian National University
Read more https://theconversation.com/should-this-plant-be-declared-one-of-the-worst-weeds-in-australia-279109
