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Plants and Animals

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Usually an arid desert environment, the Lake Eyre Basin can, at times, be a watery oases, so we should expect some unexpected features- the highest diversity of frog species in Central Australia, specialised plants and animals in mound springs, the last three populations of the Waddy Tree (Acacia peuce), the last bilbies in Queensland, and the Lake Eyre Dragon (Ctenophorus maculosus), a highly specialised lizard that lives only on the salt at the edge of dry lakes.

Lucasium dameum (beaded gecko) near Birdsville.
Photo: H Cook

The Lake Eyre Basin lies in the arid part of the 70% of Australia that is designated as rangelands i.e. 'land where livestock are grazed extensively on native vegetation, and where rainfall is too low or erratic for agricultural cropping or for improved pastures'. The minimal disturbance helps protect plants and animals.

At the national level, protection and management of natural resources occur within a framework of bioregions, geographic areas characterised by a combination of physical and biological characteristics. The LEB spans many different bioregions, with three almost entirely within the Basin (SSD, STP, CHC), four more with major portions inside the system (MGD DEU MAC FIN), and several with only a small area inside the Basin (see map below).


 

Boom and Bust Conditions

The variety and abundance of plants and animals of the Basin are driven by erratic swings between wet and dry times which result in 'boom and bust' conditions. In boom times microscopic algae multiply in flooded rivers and waterholes, invertebrate, frog and fish eggs hatch and the plentiful food supply brings in

Fait-tailed Dunnart (Sminthopsis crassicaudata).
Photo: A Emmott

thousands of migratory waterbirds to breed. A little later the land responds - grasses and wildflowers bloom and set seed, insect populations increase, and reptiles and mammals respond to the bountiful food resource. Flood waters, connecting up the landscape, magnify the response, and plants, invertebrates, fish and frogs can spread across huge areas. As the plants respond and suitable habitat opens up, the reptiles and mammals spread as well. Not only do waterbirds occur in their thousands, but plague locusts and the long-haired rat (a native species - Rattus villosissimus) occur in abundance, as well as the rare letter-winged kite (Elanus scriptus).

As waters dry up, food and water supplies dwindle, the bust phase has arrived and plant and animal populations decline. Now the characteristics of the Basin become even more important. Deep waterholes and lakes scattered across the landscape, and the richer habitats around them, become refuges for species that will re-colonise the lands and waters when the floods come again. These refugia are of regional and national importance, ensuring the survival of many species of plants and animals during the dry years.

One habitat type comes into its own in the bust - the cracking clays that occur as the floodplains and grasslands dry out. A distinctive group of plants and animals occur here, with some restricted to this environment e.g. some of the grasses; some of the planigales and ningauis (tiny marsupials that weigh less than 10 grams), and the many snake species that feed on them.


 

Terrestrial Plants and Animals

In general, for terrestrial plants and animals of the Basin, the communities are fairly typical of Australian deserts.

Sturt's desert rose (Gossypium sturtianum). Photo A Emmott

However, the relatively undisturbed nature of the Basin means that most of the ecosystems are in very good condition. Relatively few plant species are endangered and very few plant extinctions have occurred. Some animal groups are unusually diverse (e.g. the snakes of western Queensland) and a few species are specialised for the more unusual habitats such as cracking clays (planigales) and stony plains (the Gibber Dragon, Ctenophorus gibba and Gibber Bird, Ashbyia lovensis). We know relatively little about the invertebrates, but many samples have been collected and are being identified, including some species new to science.

 

Aquatic Plants and Animals

When we consider the aquatic plants and animals, the 'desert' of the Lake Eyre Basin comes into its own.

Pelicans on the Thompson River. Photo: A Emmott

There are several unusual aquatic plant communities, especially those associated with ephemeral waters, and the mound springs contain many species found nowhere else. The fish and frog communities are diverse and healthy and contain very few exotic species. The Basin is used by over 80 species of waterbirds, and more than half of those species breed here in huge numbers. Many are nomadic or use national and international flyways and migratory routes that cross the Basin. Again, the aquatic invertebrate fauna is relatively unknown, but recent studies suggest the communities are diverse, abundant and healthy.

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Water Birds

The real stars of the Basin are the birds - millions of them, 2-3 times as many as occur on the wetlands of Kakadu. After major floods, at least 3-4, and probably more like 6 or 7 million waterbirds flock to the area. As many as 53,000 birds have been recorded on just one lake. Mixed groups of breeding birds can contain up to 13 species. The significance of the Basin wetlands to these migratory species is reflected in their national and international recognition - at least 53 major wetlands are recognised as nationally important, and two (Coongie Lakes and Lake Pinaroo) are listed under the international Ramsar Convention.

Fish

The 35 native fish species (including one possible new species collected in the Northern Territory in 2013) found in the Lake Eyre Basin have extraordinary adaptations for desert existence. Some species are able to travel hundreds of kilometres during intermittent flooding to rebuild population levels and recolonise newly inundated habitats. During drier periods many are able to thrive in isolated waterholes with very high temperature, low oxygen and salinity levels often higher than sea water.

Lake Eyre Basin fish can be separated into two groups: those relying on the permanent environments of artesian springs, and those that live in waterholes. A number of species are found nowhere else but within the Basin, with some (eg Elizabeth Springs goby (Chlamydogobius micropterus), red-finned blue-eye (Scaturiginichthys vermeilipinnis) and Dalhousie hardyhead (Craterocephalus dalhousiensis), confined to even smaller ranges such as isolated artesian springs and others, e.g. Cooper catfish (Neosiluroides cooperensis), Finke hardyhead (Craterocephalus centralis) and Finke morgurnda (Mogurnda larapintae), confined to localised catchments.

Fish populations in the basin appear to be remarkably healthy, probably due to the relatively healthy condition of the Lake Eyre Basin landscapes and unregulated nature of Basin rivers. Extensive fish sampling reveals very few exotic species, whereas in the Murray Darling Basin 60-97% of fish are introduced. Of concern, however, is a recent native introduction, Sleepy Cod (Oxyeleotris lineolatus), first surveyed in the Cooper catchment in 2011, and the exotic species gambusia, or Mosquito Fish, which is associated with the decline of endemic fish in artesian springs.

For more information, see the South Australian Arid Lands NRM Board's brochure, Common Native Fish of the Lake Eyre Basin Rivers.

Frogs

Our knowledge of frogs in the Lake Eyre Basin is changing all the time as new species are discovered, and those previously known are re-assessed due to new knowledge. Of the 35 species of frogs known to exist in the Lake Eyre Basin, new science has thrown up the possibility that three, maybe four, species are confined to the Basin.

The huge numbers of frogs that occur after floods are impressive and fall into two major groups - the burrowing frogs, which can store water and take refuge underground in dry times, and the non-burrowing ones, that survive between floods under rocks, leaves or bark.

The invasion of the Cane Toad into the Basin represents a significant threat to the native frogs, as well as to frog-eating species such as snakes and goannas.

RAMSAR WETLANDS IN THE LAKE EYRE BASIN

What is RAMSAR?

The Convention on Wetlands of International Importance (known as the Ramsar Convention) was the first treaty between nations aimed at conserving natural resources. Wetlands that are rare, unique, important for conserving biodiversity or representative of a particular type of wetland can be nominated for the List of Wetlands of International Importance (Ramsar sites).

Many human activities worldwide depend on healthy wetlands and Ramsar listing carries with it an obligation to protect and manage the wetlands. The Convention promotes 'Wise Use' of the wetlands, including conservation actions that prevent changes to their ecology.

RAMSAR in Australia

There are now 65 Ramsar sites in Australia, covering a total of 8.3 million hectares, with many of the waterbirds found in these areas covered under Australia's migratory bird agreements with Japan (JAMBA), China (CAMBA) and the Republic of Korea (ROKAMBA).

There are two Ramsar wetlands in the Lake Eyre Basin - Coongie Lakes and Lake Pinaroo. The international rarity of desert wetlands makes these especially valuable.

Coongie Lakes- 2,178,952 hectares; near Innamincka in far north-east of SA.

The 'desert wetlands' of Coongie Lakes are an extensive, complex network of ephemeral or semi-permanent channels, waterholes, lakes, internal deltas, floodout plains, interdune corridors and swamps.

 M Turner 

Coongie Lake in flood. Photo: M Turner

Fed mostly by natural flows from the Cooper Creek, the many aquatic ecosystems are basically undisturbed and unaltered. Water reaches the northern part of the system most years, and up to 20,000 water birds (some rare or threatened) can breed here, but during major floods the system fills and hundreds of thousands of waterbirds use the region. Endemic fish species include the Lake Eyre Callop and Cooper Catfish. The abundance and variety of the bird and fish fauna across such a massive area of temporally variable and diverse wetlands in the driest part of Australia, give rise to a boom-and-bust phenomenon rarely seen in the rest of the world. Used extensively for cattle grazing, the area also supports oil and gas production. The natural features, as well as the many cultural and historical sites of significance to Aboriginal and non-Aboriginal people, mean that tourism and recreation are increasing. Monitoring of all development in the area will be essential to ensure the 'Wise Use' tenets of Ramsar listing apply.

Lake Pinaroo (Fort Grey Basin) - 800 hectares; 80 km north-west of Tibooburra in Sturt National Park, NSW.

Lake Pinaroo is a very large terminal lake that only fills on the rare occasions when Frome Swamp overflows after intense local rainfall events. However, once full, it can take up to 6 years to dry out again, and therefore plays an important role in the survival of the native fauna of this arid region. An open lake with very little surrounding vegetation, it can support up to 40 waterbird species and for some of these, it provides a reliable breeding area. It is a refuge for those that have bred in inter-dune swamps, which only hold water for 4-6 months, and an important stop-over site for migratory wading birds moving between other areas such as Coongie Lakes, Caryapundy Swamp and the Paroo Wetlands. The surrounding National Park contains many Aboriginal sites, and Charles Sturt built a stockade next to Lake Pinnaroo and named it Fort Grey, his base camp for exploration of the Simpson Desert.

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