Warren Peace Australia missed its first chance to wipe out the rabbit scourge. Now, 50 years on, it has another. Can it seize the moment?

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For decades the dunes of the Hattah-Kulkyne National Park were bare of green growth, their exposed rose-pink soils shifting and sliding in the wind and rain. Even where eucalypts and other trees survived, the undergrowth was reduced in patches to gnawed stubble. Not anymore: now new life is rippling through this eroded and depleted landscape in northern Victoria. Saplings of rosewood, native cypress pine and acacia stand slender in the winter sunlight. Pale green shrubs crouch next to sturdy native grasses, yellow and brown and plump with seeds. They form a precious mosaic, for some are species that have not germinated here for more than a century. Chief park ranger Phil Murdoch picks his way through the erupting groundcover and finds plants previously unrecorded here. Last year he saw his first bluebell. He waves an arm across the huge semi-arid space. "This whole place is changing," he says.

This wouldn't be happening in Hattah, or in places like it around the country, but for a dramatic reduction in the past six years of one animal: the wild European rabbit. A handful were released on a Victorian property in 1859, and by 1886 their progeny had reached Queensland. Since then, rabbits have spread across the country in a plague that has withstood every remedy. But in 1995 came the best chance in half a century for a massive assault on the rabbit by the deliberate spread of rabbit calicivirus disease (rcd), also known as rabbit hemorrhagic disease. Swiftly lethal, it tore through Australia's wild rabbits and has reduced the national population, experts say, by at least half. Where it's worked best, the virus is allowing the landscape to slowly recover from years of degradation. But some experts fear government inaction may prevent the disease's potential from being fully realized.

Australia's battle against Oryctolagus cuniculus has been long and costly. Farmers, park rangers and land managers have ripped (destroyed) warrens and shot, trapped, poisoned, fumigated and cursed the rabbit, but it has continued to flourish-feasting on seedlings, crops, saplings, bark and grasses; competing with stock and native animals for food and habitat. "You're forever chasing your tail when you're dealing with such large areas," says Peter Sandell, a Parks Victoria ecological management officer in Mildura, who oversees a million hectares of national park. "It was difficult to see how we would ever get on top of the problem." Despite the 1950s release of the viral disease myxomatosis, by the mid-1990s rabbits infested most of Australia south of the Tropic of Capricorn. Along the way, they had contributed to environmental disasters like soil erosion and the local extinction of native fauna in places like Hattah-Kulkyne: 10 of the 22 local mammal species found there in the 19th century have vanished. At the same time, they had plagued farmers-it's estimated that nine rabbits eat as much as one sheep -causing about $600 million worth of agricultural damage each year. Trevor Ablett, a ranger with Wentworth's Rural Lands Protection Board, grew up in western New South Wales and remembers the hopelessness many felt about tackling the rabbit nightmare: "It was such a big job-where would you start?"

first recorded in china in 1984, the lethal virus later spread to Europe. Brian Cooke, now a principal research scientist at the csiro and a leading expert on rcd, saw it at work there and argued for its introduction into Australia. It had an embarrassing start, escaping in October 1995 from quarantined trials on South Australia's Wardang Island. From there it spread at a phenomenal rate-up to 90 km a week-and within eight months had reached every mainland state and territory. Rabbit numbers plummeted by up to 95%, and in many areas have remained extremely low. "It's been a big transition," says Peter Kelly, who manages 350,000 hectares of state forest in northern Victoria, "going from seeing rabbits all the time to getting a shock when you see one."

While some people were happily shocked, others were asking when they would have that pleasure. That's because the impact of the virus, which is spread mainly by insects and by contact between rabbits, has varied widely. The highest mortality rates, of 90-95%, have been in drier areas where annual rainfall averages less than 300 mm. In cooler, more humid areas the effect has been, for reasons not fully understood, patchy or negligible. But across large tracts of northern Victoria, western New South Wales, inland Western Australia, central Australia and most of South Australia, rcd is widely praised. Arriving in central Australia in 1996, it spread "like a wildfire," says Will Dobbie, project officer at the Centralian Land Management Association, which covers about 300,000 sq. km of central Australia. "It's done a magnificent job." Rabbit numbers at eight monitoring sites in the region fell by 90%, and despite some high-rainfall years-which normally spark breeding -have changed little. "They've had every opportunity to come back and they haven't," says Dobbie. That's meant the regrowth of natives like umbrella and Queensland blue grass, and the first regeneration of mulga trees in 50 years.

Judith Murphy arrived on Idracowra station, a cattle property south-east of Alice Springs, in 1954 and with husband Leo watched rabbits become a plague. Nothing was spared-from bush and feed to backyard daisies and citrus trees-and nothing the Murphys did, from trapping to releasing myxomatosis, broke the rabbits' stranglehold for long. Now they're astounded by what they see. "Every time I go out there I see something new flowering," says Judith. "I've seen nothing like it in all these years. I'm glad I've lived to see it." At Rex Fuller's De Rose Hill cattle station, across the border in S.A., rabbits used to drop from the branches of old mulga trees. Warrens scarred three-quarters of his 1,800-sq.-km property and dust storms caused by erosion were common, but "there was nothing we could do about the rabbits," says Fuller. "They ate more than the cattle did." After rcd killed 90% of the rabbits, "the only bit of dust we get now is when someone drives along the road."

Signs of recovery are everywhere in western N.S.W., too, says Ron Rees. His family have had properties near Ivanhoe since 1878, and Rees watched his father fighting rabbit plagues in the 1930s. His three sons run the family properties now, but Rees travels widely in the region and "I see only improvement in the landscape -box trees, apple bush, belah and a lot of young trees I've never seen before." Though some of the new vegetation is weed, "we get feed now where there was never feed before." Rees says most landholders won't increase stocking rates: "Getting rid of rabbits means you can run what you already have with better lambing percentages, better wool and you won't be so badly affected by droughts."

There's evidence from around the country of the change underway: from orchids reappearing in the Coorong National Park in South Australia's south-east to mulga on the remote Nullarbor Plain. Phil Murdoch used to call acacias "lollipops" because rabbits at Hattah couldn't resist them; now they're appearing unscathed across the landscape. The park's annual budget for rabbit control was $A250,000 before rcd arrived; now it's $A45,000. "Plants that were once considered rare are now relatively common," says Sandell, who has measured rcd's impact in his region since 1996. "Our hope is that vegetation will recover under its own steam without our intervention. But we'll probably never see it recover completely."

The damage done to fragile semi-arid and arid zones has been severe. At places like Hattah, several generations are simply missing from the tree line-there are old and dying trees and the saplings which have shot up in the past few years, but not many in between. The damage has been compounded by stock, goats and kangaroos, but the rabbit has been the chief culprit. Some species, like the mulga, which can reach 200 years of age, will need more than a decade of respite for seedlings to grow tall enough to survive gnawing. But it's hoped that, if rabbits can be held in check long enough, the plants will regain a foothold.

The same is true of native animals pushed out by rabbits. There are already hopeful signs: in the Coorong National Park, where rcd is endemic, common wombats are thriving now that they don't have to vie with so many rabbits for native grasses. At Roxby Downs in central S.A., more grass seeds and fewer of the rabbit's predators-not a single fox was found at Roxby for two years after rcd arrived-has seen native hopping mice reappear and become the area's most common small mammal, says John Read, land manager for Western Mining Corp., which operates the 100-sq.-km mining lease at Roxby. Elsewhere, there's less use of poison baits, which often inadvertently killed native fauna, and fox and feral cat numbers are expected to fall away. In S.A.'s Flinders Ranges National Park, intensive pest control and six outbreaks of rcd have cleared rabbits from an area of 150 sq. km-and, it's thought, helped increase numbers of the dasyurid, a mouse-sized marsupial, and yellow-footed rock wallabies.

The strength of the ecological recovery clearly depends on the continued strength of the virus. "It's a matter of how long it's going to last," says the csiro's Brian Cooke. He says there is no sign rabbits are developing inherited resistance, but there's no guarantee that rcd's effectiveness won't eventually wane-as did that of myxomatosis, which, though still a useful weapon, now has a mortality rate as low as 50%. Some land managers are already worried by community complaints that rabbits are slowly reappearing. Ranger Peter Kelly has heard those stories and, though the reported numbers aren't anything like those seen before rcd, "you start to get nervous," he says.

Phil Murdoch at Hattah, John Read at Roxby, and Rex Fuller at De Rose Hill station all say rabbit numbers on their land are creeping up. Murdoch is pessimistic: "We might get a couple more good years out of the virus and then be back to spending [$A250,000] a year again." He's infuriated by local landholders who, he says, haven't got rid of the stragglers the virus missed. Peter Kelly also worries that "people tend to think it's all over, that the war is finished. We have to keep reminding people that they have the potential to make a comeback." The rabbit is both fecund (a doe can produce on average six kittens a month) and insatiable: in S.A.'s Gammon Ranges in 1997, rabbits at a density of just one per square kilometer ate half of all mulga seedlings that regenerated, says Robert Henzell, of the state's Animal & Plant Control Commission. That indicates how risky complacency would be. As Nicki de Preu, National Parks & Wildlife Service ecologist for the Flinders Ranges, says: "It doesn't take many rabbits for them to be a problem."

The best success has come where the virus has been backed up with conventional controls like the practice of ripping warrens, which destroys breeding sites but can be costly when rabbit numbers are high. The need for follow-up work is a lesson from Australia's experience with myxomatosis-its initial mortality rate was even higher than that of rabbit calicivirus, but little ripping was done in its wake and when rabbits began developing immunity, they had plenty of warrens in which to resume breeding. People saw myxomatosis as the final solution, says Parks Victoria's Sandell, "and obviously it wasn't. We have to look at biological control agents as one control among several-we can't afford not to continue with conventional controls as well."

That message has been heard by many, including N.S.W. farmer Ron Rees. After the failure to build on myxomatosis' success, he sees rcd as a priceless second chance. He remembers the days when rabbits were "packed in like sardines" on his father's farm-and he doesn't want to return to them. He helped set up the South West Rabbit Control Group in 1996, which, with government and landholder funds, has since ripped 230,500 warrens on 154 properties. "We don't know how long it will be effective for," he says, "and we can't miss the opportunity we've got." At a cost of $A7 a warren, the project has tackled heavy infestations-such as one 100-hectare patch containing 800 warrens, each housing about 10 rabbits. The problem is, some areas of outback Australia are too vast or inaccessible to rip, says ranger Will Dobbie. He says local landholders are "all very appreciative of what the calicivirus has done, but it's the expense [of follow-up ripping] that puts them off."

In those areas, as Western Mining's John Read says, "we're really in the hands of rcd." The csiro's Cooke is trying to pinpoint how to prolong the virus' potency and boost its effect in wetter areas. But he has spent much of the past few months struggling to secure research funding, on top of the csiro's contribution, for another two years' work.

That's another lesson from Australia's experience with myxomatosis: the importance of ongoing research. The long-term effects of "myxo" were poorly monitored-and some say the same is happening with rcd. Since 1999, when the national surveillance program published its final reports on rcd's impact, no national survey has been done. Instead, what is known about the disease's effects comes from local research projects, run on a patchwork of government and industry funding and providing fragmentary data. "We have not done anywhere near as well as we could have done," Cooke says. "Any of these introductions of biological controls are a giant experiment-and unless we assess what happens, we're missing out on an opportunity."

In the arid and semi-arid zones where rcd has been most effective, rainfall is highly variable and much of the flora is slow-growing, meaning the full impact of fewer rabbits will take years to become clear. "In effect, two years' study in that area gives you two data points-and you can't say anything about long-term effects on the basis of two data points," says Greg Mutze, senior research officer at S.A.'s Animal & Plant Control Commission. Many monitoring projects, such as one looking at the return of small native vertebrates to the Coorong, which was refused $A13,000 in funding last year, have had to fold.

But it's not only the benefits of rcd that experts want to document-there are also unknown long-term effects on predators which relied heavily on rabbits for food, and on vulnerable native species like mallee fowl, to which foxes seem to be turning their attention as rabbit numbers decline. Cooke believes it would take just one person working in each state and territory-at a total cost of perhaps $A500,000 a year-to complete a national analysis. But, he says, national monitoring is "that area that really people were not willing to invest in. The argument is that it's out there now and it will do what it will do."

Where rcd has relieved the land of its burden of ever-hungry pests, a new ecological balance is still settling into place. What role rabbits play in it is yet to be seen. But rcd has given Australia a tantalizing glimpse of what could be achieved if rabbits were finally beaten. At Roxby Downs, Western Mining, National Parks and Adelaide University are finishing off the fencing around a 60-sq.-km area free of rabbits and predators. Without rabbit control, says John Read, that would not have been possible: "We couldn't have got rid of rabbits from a couple of square kilometers before." Now, almost a century after they were driven out, bilbies, stick-nest rats and burrowing bettongs have been reintroduced-and they're thriving. "We want them to reclaim their place," Read says. The great hope is that one day, they may be able to do so without the need of a fence.