The Conversation recently published an important article about the devastating impact that rabbits have had and continue to exert on Australia plants, wildlife and landscapes. The article summarises the findings of a review paper published in the Journal Restoration Ecology, the lead author of which is Bush Heritage's ecologist Graeme Finlayson.
The review highlights the impact of rabbits on our precious landscapes, as well as the tremendous impact that biological control has had on the invasive rodent, benefiting Australian natives.
Recovering Australia's arid-zone ecosystems: learning from continental-scale rabbit control experiments
Graeme Finlayson, Patrick Taggart & Brian Cooke (2021)
Rabbits are a key threat to 322 species of Australia’s at-risk plants and animals — more than twice the number of species threatened by cats or foxes. They efficiently strip vegetation and prevent regeneration. Being prey to the feral predators they allow them to greatly increase in number.
In arid and semi-arid regions, even very low densities of rabbits are able to eliminate every seedling of species such as she-oaks. Over time, many plant species are eliminated from landscapes, habitats are greatly altered, and animals species such as the Southern Hairy-nosed Wombat decline and are lost.
This has implications for our approach to landscape restoration.
The review assessed the ecological benefits of rabbit bio-control across Australia, and drew on documented cases of species recovery supporting the theory that rabbit control is fundamental to the sustained recovery of species in various landscapes across Australia.
Rabbits form part of an intricate ecological web in many Australian ecosystems. They prevent vegetation recovery, they provide a food source for introduced predators (cats and foxes), and they cause significant damage through their digging to soil nutrients, leading to erosion and the spread of weeds. They also survive the extreme weather by residing in a burrow and can rapidly breed following significant rainfall. In the early 1900s rabbit plagues were a feature of outback Australia and many areas have not recovered completely after these events.
Three main bio-control events were assessed in the review, the release of myxomatosis in 1950, European rabbit fleas that helped spread ‘myxo’ in 1968, and Rabbit Haemorrhagic Disease (RHDV; calicivirus) in 1995. These events alone have led to a broad range of environmental benefits, however they require on-going efforts to continue in a fight against rabbits and to ensure landscape restoration.
It was clear that each bio-control release provided environmental benefits.
For example, just two months after the release of Myxomatosis, sheoak regeneration was able to occur after a long period of having been suppressed. And there was a significant increase in the number of native herbivores, such as Red Kangaroos. The introduction of European Rabbit Fleas aided the spread of myxomatosis in winter when mosquitoes were inactive. One study highlighted the expansion of native species including Southern Hairy-nosed Wombats and Swamp Wallabies following the release.
More recently, with research focussing on environment and conservation and not just agricultural benefits, the spread of rabbit haemorrhagic disease virus has been found to have led to the recovery of a range of native plant species including native pines, needle bush, umbrella wattle, witchetty bush and twin-leaved emu bush. In addition, Dusky Hopping Mice, Spinifex Hopping Mice, Plains Rats and the Crest-tailed Mulgara have been found to benefit, all of which had declined dramatically since rabbits spread to arid Australia.
The review also highlighted that although there is some suggestion that prey-switching occurs when rabbits are removed (i.e. foxes and cats switch from a diet of rabbits to native species), the long-term benefits far outweigh these initial impacts. We can rely on bio-controls to some degree, but traditional methods must also be a priority.
On Boolcoomatta Reserve between 2009 and 2011, 7400 rabbit warrens were mapped and then 6800 were either ripped or fumigated. Very few of these warrens have been re-opened since then. On Bon Bon Reserve prior to 2014, 3252 warrens were mapped and then 863 were ripped and a further 159 fumigated.
We are now a generation of land managers who haven’t experienced rabbits in plague proportions, thanks mainly to these three bio-control methods that have been effective at reducing rabbits across much of Australia. However, even at low densities, rabbits are a key threat to our efforts to restore the country to good health. Effective rabbit control is undeniably essential to arid-zone restoration and must be considered of equal importance to predator control.
Thank you to Rabbit Free Australia for supporting the publication of this research