Australia’s Lake Eyre is perhaps best known as the continent’s largest lake, and for the rare floods that bring the desert to life.
But Lake Eyre is much more than a lake. Taking into account the rivers that drain into it and where they come from, the Lake Eyre Basin is one of largest inland draining systems in the world, the size of Germany, France and Italy combined. It is home to many natural wonders, such as Uluru, and many species of threatened wildlife.
It is also threatened by invasive animals and plants, and climate change. How can we best protect the basin, given finite funds?
In two studies (published this week in Global Change Biology and the Journal of Applied Ecology) and in two CSIRO reports we show that managing feral pigs is one of the most effective ways to ensure the basin remains healthy in the future.
Introducing Lake Eyre (Kati Thanda)
Ecosystems in the Lake Eyre Basin are intimately connected when rainfall is high and water is flowing through three major river systems. Decisions within the four states that manage the basin - Northern Territory, Queensland, South Australia and New South Wales - will impact neighbouring habitats.
Australia’s Lake Eyre Basin covers 120 million hectares. This huge area of the outback has a rich and thriving Indigenous culture stretching back tens of thousands of years, with Indigenous people making up 40-90% of the population.
The basin contains natural and cultural assets such as Kati Thanda-Lake Eyre, Uluru, Coongie Lakes and other internationally important wetlands.
There are threatened “mound springs” (EPBC Act 1999, which are permanent wetlands in arid ecosystems fed by the water from the Great Artesian Basin that provide refuge for at least 13 plant species and 65 animal species that occur nowhere else on earth.
The basin is also home to many other unique, rare, threatened species such as the greater bilby, yellow-footed rock wallaby, night parrot, grey falcon and letter-winged kite.
Threats to the basin
Invasive species and climate change are two things scientists are most concerned about in the Lake Eyre Basin.
The basin is already characterised by a highly variable climate and climate change impacts are predicted to increase this variability.
Significant pressures are threatening the natural systems of the Lake Eyre basin, with exotic animals’ and plants’ establishment and spread being major concerns.
Climate change is also a major concern as it is altering the habitat suitability for many native species and may increase the severity of other threats, such as invasive species.
Invasive animals can reproduce and spread quickly, as they are highly adaptable to changing weather and biotic conditions. This combined pressure from climate change and invasive animals will impact on threatened native species already disadvantaged by habitat and environmental conditions.
We estimated that 29 species (including the greater bilby) would be at risk of extinction thanks to climate change, unless we manage other threats.
Getting our priorities right
Management across such a large area like the basin is expensive, so smart decisions are necessary to make sure resources are used as efficiently as possible.
So we want to know managing which invasive species will give us the most bang for our buck. And we want to know that it will continue to pay off under a changing climate.
We combined local knowledge, scientific data and analyses to develop an efficient and rational set of strategies for managing the negative impacts of invasive species – the priority threat management approach.
After comparing 11 different strategies for managing invasive species (including dogs, cats, camels and rabbits) we found managing feral pigs proved the most cost-effective strategy overall.
Pigs impact many different native species (including flora and fauna). Experts estimated that pig control would have the highest uptake, a moderate cost and one of the highest benefits for threatened species.
The benefit for threatened native wildlife of controlling pigs was estimated to decrease when the climate change scenario was considered.
While managing pigs overall was the best strategy, if we focus on threatened mammals we find, perhaps unsurprisingly, that managing feral predators such as cats, dogs, and foxes is the best option.
Invasive animals also impact on agriculture so managing them for biodiversity increases agricultural productivity. We found that managing predators (cats, dogs and foxes), goats and rabbits, would potentially increase agricultural productivity by 10% or more.
We also found we would need to reduce invasive plants by 30% to reduce their impact, particularly parkinsonia, chinee apple and mesquite.
We have limited funds for protecting Australia’s environment. Prioritising what action we take can help preserve our unique biodiversity now and into the future.