In their third report from arid Australia, James and Thibaud Aronson discuss some of the serious issues facing conservationists and restorationists.
Concerning the non-native animals in Australia, the general consensus today is that eradication is impossible: the only option that remains is control, in the form of fences or culling, or both. Yet, conflicts of opinion on the ethics of culling abound, even for the armies of feral cats that reportedly kill 75 million native animals every single night. Even fences have their pros and cons, in particular the interruption of the migration of thousands of emus.
Western Australia’s State Barrier Fence, 1170 km long, meant to control dingoes, dogs, foxes and other feral animals, with varying degrees of success.
Both feral cats and foxes are most lethal in areas with relatively little vegetation cover, that is, the massive dry interior of the continent. This is compounded by the monster fires that have plagued Australia since European settlement. A single such fire can burn down hundreds of thousands of hectares, leaving small mammals and other animals with nowhere to hide.
Even this rather small fire, which spared the trees (their dead appearance is deceptive; these trees will resprout), has almost entirely eliminated all low vegetation, leaving small animals vulnerable to cats and foxes. West MacDonnell National Park, Northern Territory.
What’s more, as mentioned in our previous blogpost, most land managers continue to burn on an annual basis without sufficient attention to the impact on animals and indeed many plants. Things are changing though.
In the seasonally dry, tropical Kimberley region, in the northwest, the Australian Wildlife Conservancy, or AWC, is testing new methods, focusing on patchy prescribed burning in the early dry season, and controlling cattle grazing. They are having good results with this approach in preserving more plant cover for small native animals and thereby reducing the lethal impact of feral cats. The AWC has also shown that their fire management techniques are not only beneficial for native animals, but also for pasture quality, and would therefore benefit pastoralists, whom Australians call graziers. Since most landowners in the area are graziers, let’s hope they will follow suit and try new fire management regimes. It is in this region, by the way, that occurs the endemic baobab of Australia, known here as Boab. To our surprise there are thousands of them, in a wide range of habitats. Some are estimated to be well over 1000 years old. Survival of this tree, at least, is clearly not threatened by fire or foxes, even if other problems – such as climate change – do exist. Let’s hope they go on thriving for another 1000 years.
A typical landscape of the Kimberley, dominated by the majestic boabs (Adansonia gregorii). King Leopold Ranges Conservation Park.
Another reason invoked for the proliferation of cats and foxes in Australia is the virtual absence of top predators to control them. This phenomenon, called meso-predator release, is also found in North America, where coyotes have greatly expanded following the extirpation of wolves throughout large portions of the continent. Therefore, some have suggested that allowing dingoes to maintain higher population numbers would have a significant effect on controlling cats and foxes. However, dingoes are still considered pests by pastoralists, and large amounts of money go into controlling them.
And that’s not the last of it. In the last 200 years, people have also introduced many exotic plant species, some of which have become terrible weeds, such as buffel grass (Cenchrus ciliaris) (see our previous blog post), but also Tamarix, Kutch (aka Bermuda grass, Cynodon dactylon), Karroo thorn (Acacia horrida) and others. By 2009, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) estimated that introduced invasive plants were costing the country 4 billion Australian dollars a year in weed control and lost agricultural production, and causing “serious damage to the environment”. With climate change, it seems possible that numerous “lurking” or “sleeper” weeds such as the White weeping broom, Retama raetam, may increase their ranges and their negative impacts.
Buffel grass presents a particularly severe problem – and like the cats, and dingoes, it is controversial. It was one of dozens of African grasses intentionally introduced by Australian agricultural researchers to “improve” pasture for cattle. Indeed cattle do like it, but the problem is that the grass spreads with amazing tenacity and crowds out native grasses, and all other groundstory plants where it invades, and, it carries fire like few other plants. Control is possible, but it is tedious and expensive and is never 100% effective at a large-scale. Furthermore, the ranchers prefer it to the native grasses, and their ideas on when and how to burn are very different from those concerned with conservation. Indeed, only few of the people we met envision stopping prescribed fire altogether.
For example, Peter Latz, a native of the Red Centre, plant ecologist, and author we met in Alice Springs, has been conducting manual removal of buffel and Kutch on his own land. But his main focus has been on excluding fire altogether, and achieving thereby pretty impressive results.
Peter Latz in his garden, next to the hemi-parasitic quandong tree (Santalum acuminatum). Alice Springs.
For more on Peter Latz’s views and lifetime of experience in central Australia, see The Flaming Desert: Arid Australia – a Fire Shaped Landscape.
In our next blog post, we’ll talk about some of the other people and groups in arid and SW Australia undertaking serious steps towards restoration, while fully aware of the obstacles and the complexity of the challenge.
Natural History of Ecological Restoration 