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http://www.theage.com.au/

Icons under threat: Kakadu

Daily spectacle: Magpie geese take flight at sunset above Kakadu's = lush=20 wetlands.
Photo: Simon = O'Dwyer

November 15, 2005 - 12:00AM

The=20 bountiful life in the Northern Territory's famed national park is at = risk,=20 scientists warn, because of rising sea levels. By Melissa Fyfe. =

They call them the supermarkets of Kakadu =97 lush green wetlands = offering a=20 bounty of food for traditional owners such as Violet Lawson. A slight = woman with=20 strength in her face, Lawson is walking across her bit of nature's shop, = picking=20 the pods of lotus lilies =97 the seeds taste nutty =97 and explaining = how the land=20 puts food on her table.

There are turtles. In the dry season they hibernate in the mud. "We = got them=20 out with a stick before. Crowbar now," says Lawson, 50. There are also = bulbs and=20 magpie geese.

Like her ancestors, Lawson is constantly burning the grass, to "get = good=20 hunting back". But no matter how much she cares for the country, there's = something devastating inching its way into her landscape and there's = little she=20 can do about it.

For a half-century, salt water has been creeping into Kakadu's = world-renowned=20 freshwater wetlands. On the East Alligator River alone, tidal creeks = have edged=20 inland four kilometres. By 2000, bare and saline mud flats had grown = ninefold=20 and two-thirds of the melaleuca forest had been killed by salt.

Scientists have speculated about the reason. Natural rising of the = sea,=20 rainfall changes and storm surges probably played their part. Introduced = buffalo, whose hooves carved out channels and eroded land in the world=20 heritage-listed national park, also contributed. But scientists are in = no doubt=20 that the salt will keep coming.

As global warming accelerates the rise in sea levels, the natural = levees=20 acting as a barrier between Kakadu's freshwater and saltwater systems = =97 in=20 places only 20 centimetres high =97 will be breached, leading to a = significant=20 loss of these lily-carpeted waterways that sustain the Aboriginal owners = and=20 attract more than 165,000 annual visitors to the Northern Territory's = most=20 famous park.

"We have to slow it down or try and do something," says Lawson, who = oversaw=20 the building of a barrage in 2003 to halt the salt at Yellow Water, an = iconic=20 wetland that brings in millions of tourism dollars from boat tours. "We = have to=20 do something to save the wetlands and protect them for people hunting = and for=20 people visiting."

THE SCIENCE

CAUGHT IN A RISING TIDE
THE world's oceans are on = the=20 rise. And there is now a clear scientific consensus, says CSIRO's sea = level=20 expert John Church, that planet-warming fossil fuel emissions play a = significant=20 role.=20

As the earth warmed in the last century, sea levels rose between 10 = and 20=20 centimetres, and faster than the earth has seen for 3000 years. This is = not just=20 because of the widespread melting of land ice. When water warms, it = expands and=20 takes up more space.

Global sea levels are creeping up at 1.8 millimetres a year. In = Australia,=20 because the land mass is also rising in response to the last ice age, = the=20 increase has been slightly less, around 1.5 millimetres for Darwin. This = may=20 sound trifling, but it adds up. And the climate change models are = forecasting an=20 accelerated rise over the next 100 years.

Even the very best-case scenario provided by the Intergovernmental = Panel on=20 Climate Change =97 eight centimetres by 2100 =97 will alter Kakadu's = low-lying=20 wetlands. The worst-case scenario, 88 centimetres by century's end, will = turn=20 them into "saline wastelands".

The coastal plains that run down to Van Diemen Gulf are between 20=20 centimetres and 1.2 metres above sea level. In its last report in 2001, = the=20 panel said Kakadu's wetlands could be displaced if predicted sea level = rises of=20 10 to 30 centimetres by 2030 occur.

Even if we turn off the lights now, says Church, sea levels will = continue to=20 rise throughout this century because of the lag between the warming = atmosphere=20 and the warming ocean.

At Kakadu, the gradual inching upwards of the sea will be intensified = by=20 other climate change spin-offs. Tropical storms, predicted to become = more=20 muscular, will create bigger tidal surges, pushing more salt water = inland.

THE CLIMATE

WHAT HAS CHANGED
THE rocks of Kakadu =97 the = canvas for one=20 of the world's greatest rock art displays, dating back 22,000 years =97 = have great=20 antiquity, but the area's wetlands are a comparatively modern = phenomenon.=20

During the past 100,000 years, the sea level fluctuated greatly as = the Earth=20 shifted in and out of ice ages. The northern coast of Australia was at = times 400=20 kilometres north of where it lies today. At the end of the last ice age, = around=20 15,000 years ago, temperatures increased and the sea level rose. It = stabilised=20 6000 years ago, and Kakadu's freshwater flood plains formed about 2000 = years=20 later. These events were recorded in the rock art of the Arnhem Land=20 escarpment.

No scientist could blame global warming for the salt water intrusion = seen in=20 the past 50 years at Kakadu and throughout the Top End. The timescales = are just=20 not long enough. But the same cannot be said for the next 50 years. In = the=20 meantime, scientists have found that climate change has left its mark on = the=20 park in other ways.

Work by Professor David Bowman and his students at Charles Darwin = University=20 has found that woody vegetation in the park is thickening, possibly = because of=20 the carbon dioxide we have pumped into the atmosphere (it makes plants = more=20 efficient). Bowman, who has a rather evocative turn of phrase, says the = trees=20 are "rampaging paperbarks" and "like Triffids". Kakadu's small pockets = of=20 rainforest are also expanding, although changed fire regimes and higher = rainfall=20 may also be factors.

ENVIRONMENT

WHAT LIES AHEAD
VICTOR Cooper is pointing on a = map to the=20 land of his clan group, Limilngan. It's the area around Wildman River. = "In 20 to=20 30 years' time," he says, "all of this will be gone, this flood plain, = it will=20 all be mangrove."

In the 1980s, says Cooper, a boundary fence was built near the = Wildman=20 River's mangroves. The mangroves have since marched a kilometre past the = fence.=20 Cooper, one of the park's many indigenous rangers, has witnessed what = several=20 Top End environmental scientists say is a taste of the future.

The Kakadu flood plain is a very flat, dynamic system. The wet season = brings=20 large floods pushing out to sea; the dry season dries out the = billabongs. The=20 push and pull of fresh versus salt is constantly eroding, depositing, = eking out,=20 flushing down, surging in.

Max Finlayson, a wetland specialist, and Ian Eliot, a coastal = scientist, have=20 studied what will happen to Kakadu's wetlands as sea levels rise. Part = of the=20 freshwater wetlands may become salty mudflats, the trees salt-scalded = and=20 freshwater plants such as lotus lilies, wild rice and native water = chestnuts=20 lost. This has already been seen at some places hit hard by buffalo = erosion.

As the system transforms to a salt environment, the animals that live = there=20 will go. Of biggest concern are the birds, which gather in spectacular = numbers=20 around the vast but shrinking pools of water in the late dry season. The = wetlands support more than 60 species of water bird, including herons, = egrets,=20 ibises, spoonbills and cormorants. Up to 3 million waterbirds have been=20 estimated to congregate at Kakadu during the dry season between August = and=20 October.

These coastal wetlands are also important nursery areas for=20 commerciallycaught fish such as barramundi, prawns and mudcrabs. They = are=20 breeding places for crocodiles and support turtles, cherabin crayfish, = water=20 snakes and frogs.

Although they have written papers together on the topic, Eliot and = Finlayson=20 have different points of view on what will be lost and how much it = matters.=20 Finlayson, a wetland ecologist, fears that the change will be dramatic, = and that=20 tourists and Aboriginal people will grieve over it "partly because they = cannot=20 do anything about it". Eliot believes the impact may be patchy. The = much-loved=20 Yellow Water wetland might go, but others will form.

Kakadu is unlikely to turn into a great swamp, he says, unless the = sea level=20 rises by several metres. "Some of the freshwater wetlands will disappear = and=20 some will grow," he says.

THE PEOPLE

WHAT LIES AHEAD
AT THE dry season's end, Kakadu's = savannah=20 is a worn-out desert. But on the flood plain, life teems =97 lilies, = crocodiles=20 and thousands of birds on long lakes of still water. This, and the rock = art, is=20 what tourists come to see.

If these wetlands are degraded, tourists' expectations will have to = change.=20 "Kakadu is in the arid part of Australia. Wildlife is thin on the = ground," says=20 Bowman. "But there's the one giant exception of the freshwater flood = plain.=20 There you see the ebullience of life, the waterfowl, the fish, the = crocodile,=20 even at the height of the dry season."

Their loss would be a national tragedy, he says. "There's something=20 archetypal about how fecund nature is, the deep green, the enormous = vibrancy of=20 life. It's immediate and intense. Frankly, mangrove swamps don't do it = for=20 people like freshwater flood plains. Imagine those landscapes with dead = trees,=20 salt-poisoned. It would be a major negative for tourists."

That's not all. Bowman believes that Kakadu, indeed Darwin, won't be = a nice=20 place to visit as the Earth warms. The Northern Territory's extreme = weather will=20 be even more extreme and research has shown that higher temperatures = will make=20 it harder to keep tropical diseases such as dengue fever at bay.

And of course Kakadu is special because the land belongs to the = numerous=20 traditional owner groups who lease it to the Commonwealth to manage. = They =97 the=20 Bininj in the north and Mungguy in the south =97 have been in Kakadu for = at least=20 50,000 years. When Europeans first arrived, 2000 lived there.

After school, young Aboriginal kids play in the mud, looking for = turtles, and=20 film school projects on the wetland. When you see a boy tuck a sick = jabiru under=20 his arm, its legs dangling past his waist, you know it is a lived-in=20 landscape.

THE FUTURE

WHAT'S BEING DONE
ALTHOUGH Kakadu is at the whim = of global=20 sea levels, there are some remedies, at least with small sea level = rises.=20 Barrages have been used before and bigger ones could be built to hold = back the=20 tides. But a finger in the dike only holds for so long.

"With a change in the tens of centimetres, barrages become a = questionable=20 response," says Peter Whitehead, the conservation representative on the = Kakadu=20 board. "They are difficult to build, they have to be longer and bigger = and able=20 to withstand more water. And barrages can change the character of the = freshwater=20 behind them."

Greg Hunt, the federal Parliamentary Secretary for the Environment, = has=20 Kakadu in his portfolio of Commonwealth parks. He says a 30-year plan = will=20 assess the needs of the federal parks, including the impact of climate = change on=20 Kakadu. Responses such as barrier methods and earthworks will be = canvassed, he=20 says.

Meanwhile Kakadu has other problems to worry about, including battles = against=20 weeds such as mimosa, mission grass, gamba grass and olive hymenachne. = Pests=20 include the newly arrived cane toad, bigheaded ants and ginger ants. = There's=20 also the impact of tourists. Given these threats, climate change has not = been a=20 top priority.

UNDER THREAT

MAGPIE GEESE
DAWN at Kakadu and the magpie = geese, in=20 their thousands, are talking among themselves. It's like pre-show = titter. In=20 nearby mud, a crocodile has left its footprints, a sign of a late-night = goose=20 snack. The geese are not exclusively found in Kakadu, but they are a = park icon=20 due to their sheer numbers. The birds, which can grow to 92 centimetres = long and=20 have a characteristic knob on their head, are also a main Aboriginal = food=20 source. Close to 2 million have been counted in Kakadu in the dry=20 season.

Watching on the side of the billabong is Dave Lindner, 61, one of = Kakadu's=20 great characters; a former ranger who lives on a park property scattered = with=20 buffalo skulls. A man who suffers no fools and has lost fingers to = crocodiles,=20 Lindner can be harsh, but his love of Kakadu is obvious. "I am an=20 environmentalist in the sense of a person who is interested in the = environment =97=20 but not the human environment.

I just find humans repugnant," he says, as the birds start to fly = off. In the=20 1980s, Lindner was part of the program to eradicate buffalo from the = park. Now=20 he is convinced that, having saved Kakadu at the eleventh hour from = buffalo,=20 global warming is going to undo the incredible recovery he has monitored = in the=20 past 15 years.

Six centimetres of water would be enough, he says, to spill over = these flats=20 and destroy the magpie geese's habitat. He has nagged park management to = consider climate change in the next park plan and to think about = building a=20 major barrage. "When you are looking at this environment," he says, = "you've got=20 to think big."