First the rains came, then the birds

Tom Arup The Sydney Morning Herald 24 Jun 11;

ACROSS the great Lake Eyre Basin, an environmental boom not seen in decades is occurring.

This week The Saturday Age travelled to Lake Eyre - to witness the landscape's revival, driven by three consecutive years of heavy rains. Normally a rare event, for the third year running Lake Eyre has filled with water flowing down the basin's rivers from outback Queensland. By comparison, Lake Eyre filled just three times last century.

While much of the water has come to Lake Eyre from the north, it has also been raining in central Australia. Whereas the average yearly rainfall is 120 millimetres, 450 millimetres fell last year alone in the Lake Eyre region.

These rare times are the basin's ''boom cycle'', which can be followed by dry periods lasting decades, and it has spurred an eruption of bird and mammal life. Throughout the basin there is now a plague of native long-haired rats. Confined to the Northern Territory's Barkly Tablelands and western Queensland Channel Country in dry times, in a few short years the rats have spread half a continent to the southern reaches of the 1,200,000-square-kilometre Eyre Basin.

Along the rivers that feed Lake Eyre, birds like the Australian pelican or the rarer Eyrean Grasswren are in abundance.

UNSW's Richard Kingsford, who has spent many years surveying birds in the Eyre Basin, says the region is buzzing. ''The Basin's vast network of lakes and floodplains have all been given this sequence of wet years,'' Professor Kingsford said. ''And what we seem to understand about these systems is that it will tide them over for those really long dry spells.'' Professor Kingsford says when warmer spring weather arrives more invertebrates will emerge, encouraging greater populations of species further up the food chain.

At the Australian Wildlife Conservancy's property Kalamurina, which covers the northern shores of Lake Eyre and a stretch of the Warburton River, Coolibah trees - of Waltzing Matilda fame - are regrowing.

AWC chief executive Atticus Fleming says by removing cattle grazing on the almost 7000-square-kilometre property and managing other feral herbivores - camels, horses, donkeys and pigs - vegetation like the Coolibah will return unimpeded, increasing habitats for threatened species.

Mr Fleming says it is crucial the environmental benefits of the boom are locked in to protect threatened native mammals such as the dusky hopping mouse and the crest-tailed mulgara. ''Australia has the worst mammal extinction record in the world, over 20 mammals have been lost over the last 200 years,'' Mr Fleming said. ''Almost all of those extinctions have been in the centre and the south of Australia, and that extinction wave is being driven by habitat lost, predation by ferals like cat and foxes and competition from feral herbivores. For decades now, as the Warburton floods, the regeneration has been grazed down by feral herbivores.''

''We are going to get to see this country as it was 100-200 years ago, not as it has been in the last 50 years.''

CSIRO's Mark Stafford-Smith says the Lake Eyre Basin's environmental recovery also has lessons for the management of the Murray-Darling. Unlike the Murray-Darling, the Eyre Basin is an unregulated system, perhaps one of world's largest. Dr Stafford-Smith says this has kept the natural variability of water flows into rivers, lakes and wetlands.

''When you have highly variable flows you end up with a whole lot of species, and a whole lot of ecological functions, that don't actually happen in a regular flow,'' he said.

When you change the natural regulation of a river system, Dr Stafford-Smith says, common and introduced species thrive because they are used to regular flows.

''What you lose is the uncommon species … the species that depend on the pulsing effect,'' he says.

The Age stayed at Lake Eyre courtesy of Australian Wildlife Conservancy.