Beat the invaders: Five ways we're tackling pest species in SA
Are you a fan of ABC TV’s recent show ‘Eat the Invaders’? Even if it did not make your mouth water, or appeal to your culinary instincts, it may have made you more curious about what is being done to manage the invasive species which threaten South Australia's native biodiversity.
In South Australia, invasive feral species such as rabbits, carp, cats, goats, horses, donkeys, deer, foxes, pigs and camels pose significant challenges to the environment. These species disrupt ecosystems, have few natural predators, outcompete native animals and cause extensive environmental degradation. Whilst the problem is widespread, the good news is that a range of pest management strategies and programs exist to mitigate the worst harms caused by these pests.
Rabbits
Rabbits are notorious for their rapid reproduction and voracious appetite, leading to overgrazing, soil erosion and destruction of crops worth millions of dollars. They prevent plant regeneration by consuming seedlings, thereby hindering the growth of native vegetation. To address this, South Australia employs biological control methods, such as the release of the calicivirus, effectively reducing their populations, sometimes by up to 90%. However, rabbits are very good at developing resistance over time, so new strains and new viruses must be developed in future to prevent population numbers increasing again. Local management methods include fumigation, warren ripping, baiting and commercial harvesting, all working towards conserving important native flora that provides habitat and resources to our native animals.
Feral cats
Feral cats are formidable predators, killing over 1.5 billion native mammals, birds, reptiles and frogs, and 1.1 billion invertebrates in Australia each year. Their impact is profound, especially on species already vulnerable due to low population numbers. South Australia's pest management strategies include fencing, trapping and baiting programs aimed at controlling feral cat populations to safeguard native wildlife. Additionally, the Department for Environment and Water is currently developing a Cat Management Strategy which will provide a framework for the state-wide management of owned and unowned cats.
Carp
Introduced from Europe over a century ago, Carp have become the dominant fish in the Murray-Darling Basin, constituting up to 90% of the fish biomass in some areas. Their feeding habits degrade water quality and disrupt aquatic ecosystems, at the expense of native fish species.
Following years of testing, Australian scientists have determined that using the naturally occurring carp herpesvirus as a biological control agent could help reduce the number of carp in our freshwater systems. Considerable work, research and consultation has occurred and continues to help determine the viability of releasing the herpesvirus, as part of the Federal Government’s National Carp Control Plan. In the meantime, a range of activities are being implemented to manage carp, such as the installation of carp exclusion screens at numerous wetlands in the Murray-Darling Basin.
Also, a carp separation cage is in use at Lock 1 at Blanchetown that exploits the innate jumping behaviour of carp, as distinct from the movement of similar-sized native fish, allowing carp to be trapped and removed from the River Murray.
Other 4-legged pests
With population numbers in the millions, deer, goats, camels, horses, pigs and donkeys trample native vegetation, foul waterways and compete with native herbivores for resources. Deer and goats in particular, prevent plant regeneration by eating seedlings. Control measures include population monitoring, trapping and culling to mitigate their environmental impact.
Pest control across South Australia is a huge undertaking, made possible by everyone playing their part. The Department for Environment and Water (DEW) works with a variety of agencies to deliver control programs on and off the land it manages. Primarily, DEW works with Landscape Boards, government agencies including the Department for Primary Industry and Regions (PIRSA), neighbouring landholders, volunteers and commercial operators.
PIRSA is the lead biosecurity agency for South Australia and has lots of additional information about control measures for pest animals.
Key island projects in South Australia
When it comes to managing invasive species, the remoteness of some of South Australia's islands provides both a challenge and an opportunity. Whilst remote locations can create logistical difficulties for pest control projects, the advantage of a contained land area, bordered by seawater helps to ensure that invasive species are less likely to return once a project is completed.
Kangaroo Island
Such is the case on Kangaroo Island, where deer and goats were eradicated in 2018, after a 12-year campaign. The eradication of feral pigs on Kangaroo Island is now in its final stages, through a program which was possible due to a significant reduction in the population following the 2019/20 bushfires. The Island also remains fox and rabbit free, thanks to strict biosecurity measures. The main invasive animal species left on Kangaroo Island is the feral cat. The KI Feral Cat Eradication Program is currently in place, with an initial focus on the eastern end of the Island.
Flinders Island Safe Haven
About 30km offshore from Elliston on the state’s west coast, lies Flinders Island, a privately owned 4000-hectare island refuge for at risk native animals. However, to protect the native animal inhabitants, an eradication program is required to rid the island of its feral cats, rats and mice. Targeted baiting operations will run until December 2025 and will take place outside of shorebird and seabird breeding seasons. Strict biosecurity measures for future Island visitors will help to maintain Flinders Island as a safe haven for threatened native species, like the banded hare-wallaby and the southern brown bandicoot.
So... can we eat the invaders?
TV programs like 'Eat the Invaders' help raise awareness about the need to address ecological challenges, and also encourage innovative solutions, such as considering invasive species as alternative food sources. Whilst 'Eat the Invaders' highlighted some of the legal and logistical issues affecting our access to invasive species as menu items, it is possible to find some butchers, market vendors or restaurants who sell or serve venison (deer), goat and rabbit meat. Who would have thought that helping to address an environmental problem could involve a tasty casserole or curry?
Like this article? Read more about Creating an island safe haven for threatened species or learn more about feral rabbits in South Australia or feral pigs on Kangaroo Island.
Main image credit: Fisheries Research and Development Corporation/ National Carp Control Plan - Department of Agriculture, Fisheries and Forestry.
