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.

The unexpected canopies of arid Australia

James and Thibaud Aronson report from Australia, where they went to study desert trees and on-going restoration efforts.

Australia’s deserts are like no others, we found. For one thing, they have tree canopies galore and a range of habitat types that one would not expect when looking at the generally flat topography. And they are vast. Australia’s ‘dry country’ occupies 60% of its area, or more, depending on your sources, that is roughly 5 million square km (1.9 million sq mi) or over half the size of the continental US.

Map of Australia’s deserts. From Morton et al. (2011)

These huge regions stand on red or white sands with outcrops of granite, and other subtle but marvelous geomorphological jewels, and hide deep reserves  of iron, copper, bauxite, uranium, and of course, gold.  For two naturalists from the northern hemisphere, it’s like a candy shop: endless skies and landscapes, intriguing animals, and such an array of unique Gondwanan plants.

Very striking indeed was the remarkable diversity of trees in areas with less than 400 mm (12 in) mean annual rainfall, which is our rough and ready cutoff point for the book we are writing on dryland ecosystem restoration, with Edouard Le Floc’h. At present count, we will include at least 400 species of Australian trees, roughly a quarter of the total number of desert trees species, worldwide. But even more striking was the sheer amount of biomass in those trees and the extensive canopies they form, despite the infertile soils and highly unpredictable rainfall.

Eucalypts, the native cypress relative, Callitris sp., and the endemic tree cycad Macrozamia macdonnelii densely packed on rocky ridges. Standley Chasm, West MacDonnell National Park, Northern Territory.

Remarkably dense woodland, away from water, in an area with 286 mm average annual rainfall. Serpentine Gorge, West MacDonnell National Park, Northern Territory.

There are few mountain ranges, perennial rivers, and drainage systems, and yet, regardless of the scale of observation, arid and semi-arid Australia is remarkably heterogeneous. These deserts are also host to a wide array of beautifully adapted animals, including the remarkable “roos”, which come in all shapes and sizes, the blue-tongued lizards, and many more.

Two common wallaroos (Macropus robustus erubescens). Cape Range National Park, Western Australia.

Spinifex pigeon (Geophaps plumifera). Karijini National Park, Western Australia.

Bobtail blue-tongued skink (Tiliqua rugosa). Corackerup Reserve, Western Australia.

Galah (Eolophus roseicapilla). This cockatoo is a nomadic inland species that has greatly increased its range as a result of human land use changes. Fraser Range station, Western Australia.

One of the key areas we visited was where the desert meets the South-Western Floristic Region, which has one of the highest plant diversities on the planet, and is the only biodiversity hotspot in Australia.

This area is characterized by a large number of granite outcrops which act as fire barriers and constitute highly diversified, humid habitats with mosses, ferns and other surprises. Most remarkably, they host a significant number of both terrestrial orchids and sundews, a type of carnivorous plant, two groups we’ve never seen in arid areas anywhere before.

One of the many sundews (Drosera aff. macrantha; fide K. Dixon) found in arid Australia. Kalbarri National Park, Western Australia.

Spider orchid (Caladenia dimidia). Norseman, Western Australia.

This area is what Stephen Hopper – one of the most eminent plant scientists in Australia – calls an OCBIL , an acronym for Old, Climatically Buffered, Infertile Landscapes,  describing the relatively few places on Earth that for a very long time have not been rejuvenated either by orogenesis – mountain formation – or glaciation. This leads to very poor, infertile soils. Southwestern Australia, is one such place, and one that is under threat as well, given the huge pressure from the mining industry, wheat growers, pastoralists, and a government administration that seems to only think short-term.

In our next post, we will discuss a defining, and problematic process of Australian desert ecology, namely fire.

Reference cited:

Morton S., Smith D.S., Dickman C., et al. 2011. A fresh framework for the ecology of arid Australia. J. Arid. Environ. 75:313–329.

Monitoring epiphyte colonization in Costa Rican forest restoration

Leighton Reid and Miguel Chaves are investigating how tropical forest restoration influences plant diversity. Leighton is a postdoctoral fellow in the Center for Conservation and Sustainable Development. Miguel is a doctoral student at University of Missouri Saint Louis.

Epiphytes are plants that live non-parasitically on other plants. That is, they grow on the trunk or branches of another plant (often a tree) without extracting nutrients from it, as mistletoes do. In Missouri, one example is the resurrection fern (Pleopeltis polypodioides), an epiphyte famous for its ability to re-green after lengthy desiccation.

In tropical forests, epiphytes are much more diverse. Science writers commonly use the word “festooned” to describe the profuse growth of aroids, bromeliads, ferns, and especially orchids on tropical trees. In certain places, epiphytes can make up as much as 50% of a forest’s vascular plant species.

We were curious about how ecological restoration influences epiphyte communities, so over the summer Miguel Chaves worked with local conservationist Juan Abel Rosales and botanist Federico Oviedo to survey the vascular epiphyte composition and abundance on 1086 trees growing in thirteen restoration sites in southern Costa Rica. They found about one hundred species, several of which are depicted below.

This fall, we are analyzing these data to learn about how tree planting influences epiphyte community assembly compared to natural forest regeneration. In particular, we hope to shed light on two questions:

(1) To what degree does tree planting facilitate epiphyte recovery?

(2) At what spatial scale does local forest restoration interact with landscape context to influence epiphyte recolonization?

The base of this poro tree (Erythrina poeppigiana) has sufficient ferns to warrant the descriptor “festooned”. Ferns visible in this photograph include: Niphidium crassifolium, Serpocaulon fraxinifolium, Serpocaulon dissimile and Polypodium dulce.

A showy orchid (Dichaea cryptarrhena) hangs from a mossy bed below two bromeliads.

An inflorescence of Drymonia macrantha (Gesneriaceae).

Miguel and Juan Abel at work next to a particularly good-looking bromeliad (Guzmania zahnii). Photo by Karen Holl.

Plants that use other plants for support but also have roots in the ground are called “hemiepiphytes”.

These aroids (Monstera sp and Syngonium hastiferum) are secondary hemiepiphytes, that is, plants that begin life on the forest floor and climb upwards towards the light.

Many of the epiphytes that Miguel and Juan Abel observed were flowerless seedlings, like this Gongora armeniaca (Orchidaceae).