Conservation and restoration in arid Australia – an uphill battle.

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.

Australia’s amazing and vulnerable deserts – not as pristine as they look.

In this second report from arid Australia, James and Thibaud Aronson discuss the debated roles of fire, cattle and invasive mammals on the native fauna and flora.

To quote Gary Dinham, director of the Alice Springs Desert Park, “although the average annual rainfall in Alice Springs is just 270 mm, [9 in.], it’s erratic. For example, in 2009 the year’s total rainfall at Desert Park was 64 mm. In 2010, it was 990!”

Imagine, then, a vast region where almost no rain falls for several years, and then one year, a meter falls in two weeks, causing devastating floods. Despite the aridity, and the unpredictability, there are wooded areas in vast parts of inland Australia with annual rainfall comparable to that of Syria or Sudan! In fact,  there is such a remarkable diversity of trees and shrubs, and indeed such extensive savanna or woodland tree cover, that it makes perfect sense to speak of desert canopies occurring there. However, that stunning first impression does not reveal how much the ecosystems and landscapes have been disturbed, especially in the past two centuries. How? Through severely altered fire regimes, overgrazing by domestic and feral herbivores, open-pit mining, and outrageous numbers of intentional and accidental introductions of exotic species of all sorts that really shouldn’t be there.

Open Eucalypt woodland with spinifex grass (Triodia spp.) dominated undergrowth. Karijini National Park, Western Australia.

Because of its inordinately high biomass, the Australian center burns – or gets burned – every year or every other year…. The 70 species of spinifex grasses present throughout the arid and semiarid areas are in fact some of the most flammable plants on the planet. But that’s just part of the story.

500 meters away from where the previous photo was taken, this spot had burned six months earlier. The Eucalypts display here the unusual feature of branches resprouting high in a tree with a completely burnt trunk. What makes this possible in some few trees – including the Mediterranean cork oak – is epicormic buds. Taking advantage of the pulse of nutrients released in the soil, annuals have germinated in profusion, and spinifex will come back too, a little slower.

Because European settlers stubbornly tried to import inappropriate farming and pastoral techniques into Australia’s arid center, with its poor soils and unpredictable rainfall, they overstocked and let their cattle roam essentially freely over vast areas. Under these conditions, certain grasses and shrubs are favored, and vegetation is much more fire-prone. this has led to a large increase in the frequency of monster fires, capable of burning vast areas within days or weeks.

Even today, most landowners with cattle in the outback burn their land every single year. Why? So as to reduce fuel load, as a matter of fact, in efforts – often unsuccessful, as we’ve just said – to reduce the risk of wildfires that might burn down their houses and other infrastructure. But they also are aiming to increase the amount of palatable grasses, including the introduced Buffel grass.

Buffel grass (Pennisetum cenchroides, more commonly known by its old name Cenchrus ciliaris) by a river, showing the worst of its invasive capability, crowding out all native understory species under the canopy of red river gums (Euc. camaldulensis). Hardey River, near Paraburdoo, Western Australia.

There is little doubt that this approach could be improved on, but the truly problematic point is whether or not the desert needs to burn. That debate ultimately is rooted in divergent interpretations of the past 100,000 years of Australia’s history.

It is generally agreed that humans arrived on the island continent approximately 50,000 years ago. What is unclear is what lasting impact the first immigrants had, and on what scale. The suggested date for their arrival roughly coincides with the extinction of all animal species weighing more than 100 kg, similar to what happened later in the Americas and even later in Madagascar. Therefore, some argue that humans must have driven the megafauna to extinction. Others say that Australia had been getting progressively hotter and drier for 20 to 50 thousand years prior to the arrival of humans, and that large animals could not cope with the new climate. If that’s true, at most the earliest Australians hunted out only tiny remnant populations of these large animals (including giant kangaroos, rhinoceros-sized wombats, a lizard twice the size of a Komodo dragon, giant turtles, marsupial lions, and some of the largest birds that ever lived on Earth).

Beaten only by the ostrich, the emu (Dromaius novaehollandiae) is the second largest living bird, standing as tall as an average person. However, it is small compared to the now extinct mihurung or thunder bird (Dromornis stirtoni), that was nearly twice its size and weighed half a ton!

Through the use of ‘fire-stick farming’ (the practice of setting fires in patches to stimulate new tender shoots on grasses and other plants, and thereby attract game), the Aborigines – according to some scholars – gradually transformed most of Australia’s landscapes from fire-sensitive thickets, woodlands, and forests, to spinifex grasslands and Eucalypt woodlands highly tolerant of this kind of fire regime.

Others counter that the earliest humans in Australia in fact stayed at low population densities until the arrival of Europeans and that their nomadic societies could not possibly have transformed landscapes at any meaningful scale. To date, no clear consensus has yet emerged.

What is beyond question is the enormous impact that Europeans have had since 1788, when the first English settlers drove in their tent pegs and set up corrals for their sheep and cattle.  The introduced livestock were the first animals with cloven hooves ever to walk on Australian soil. As a direct result, the biocrust, that is the beneficial communities of lichens, mosses, and bacteria which form on undisturbed soils in many arid lands, and indeed the top profiles of the soils themselves were quickly eliminated.

European settlers also cleared vast areas of land for grazing and crop lands, and introduced rabbits, cats, foxes, rats, mice, donkeys, camels, and other exotic animals  which have had horrific impact on small marsupials, birds, and reptiles of the island, not to mention the complex ecological networks and community dynamics in which those animals occurred. Sad to say, Australia has the worst record of any country for recent animal extinctions.

Unsupervised cattle at a waterhole. Cockatoo Creek, Willare, Western Australia.

Cleared and overgrazed land on a cattle station in Western Australia. The ribbon of woodland in the background provides a reference for what the whole area once looked like.

Of the 60 mammal species that have gone extinct worldwide, in the last 200 years, 30 were Australian – and most inhabited the arid and semi-arid zone. Besides, a further 6 formerly widespread mammals are on the brink of extinction today, surviving only on handkerchief-sized, fenced off reserves or offshore islands inaccessible to feral cats and foxes.

While that is a terribly bleak legacy, promising steps are now being taken to limit the damage going forward, and ensure that the history of massive human-caused extinctions is not repeated. In our third and fourth blog posts from Australia we will discuss the obstacles to restoration, and then some of the encouraging endeavors underway.