42 tons of poison to purge island of rats

Desperate measure to save Lord Howe Island's native species

Lord Howe, an idyllic island off the Australian mainland, carefully conserves its natural treasures. The World Heritage-listed chunk of rock has strict quarantine laws, and limits the number of tourists who may visit. But its unique birds, insects and plants are under threat from an implacable foe: the black rat. Accidentally introduced in 1918 when a ship ran aground, rats are blamed for the extinction of five endemic bird species.

Wildlife experts warn that 13 other native birds, two reptiles, five plants and numerous invertebrates are at risk. Rats are also a threat to the vital tourism industry, which relies on the island's pristine image.

Now Lord Howe, 500 miles north-east of Sydney, has decided to rid itself of rats and mice – and has put together one of the most radical pest-eradication programmes ever attempted. If the plan is approved, the island will be blitzed with poison from the air.

In order to protect local wildlife, entire populations of native birds will be caught and kept in cages for 100 days for their own protection. All cows and chickens will be slaughtered or shipped to the mainland beforehand, while dog owners will be offered muzzles for their pets, and parents will be advised to keep a close eye on their children.

A number of islands have been made predator-free, most notably in the Seychelles and New Zealand, and pest-elimination projects have occasionally been carried out on inhabited islands. But nowhere has such a project been contemplated in a place with a substantial population: Lord Howe has 350 permanent residents as well as 400 or so visitors at any one time.

Stephen Wills, chief executive of the Lord Howe Board, which administers the island as part of New South Wales, agrees that the plan – which involves dropping nearly 42 tons of poison-laced bait from helicopters – is radical. But there is no other option, he believes. "This is one of the most beautiful places in the world, which is why it warrants such a significant and detailed programme," he says.

A crescent-shaped island with a lagoon and coral reef, Lord Howe is said to be washed by the cleanest ocean on the planet. Two-thirds of it is a protected reserve, while its surrounding waters are a marine park. The World Heritage listing was granted in 1982 because of its outstanding natural beauty and exceptional biodiversity.

When it was discovered by the crew of HMS Supply, a British ship, in 1788, the island was home only to birds, insects and reptiles. During the decades that followed, various predators were introduced, of which the rat was by far the most destructive. The effects of its presence were swift and disastrous.

In 1921 an Australian naturalist, Alan McCulloch, wrote: "Two short years ago the forests of Lord Howe were joyous with the notes of myriads of birds, large and small and of many kinds ... Within two years this paradise of birds has become a wilderness, and the quietness of death reigns where all was melody."

In recent years, the island has banished feral goats, pigs and cats. But rodents are still a serious problem. As well as threatening native wildlife, they eat the seeds of the kentia palm, an endemic plant, which forms the basis of Lord Howe's only industry apart from tourism. Up to 1.5 million kentia palms – the world's most popular indoor plant – are exported ever year.

The rat-eradication plan, pencilled in for August 2012, has yet to be approved by the Lord Howe board and the Australian government. It would involve two separate aerial bombardments a fortnight apart, as well as baiting by hand. The poison is expected to become harmless after 100 days.

During that period, two endangered bird species considered at particular risk of consuming the poison – the Lord Howe woodhen and the pied currawong – will be kept in aviaries. Each species consists of about 200 individuals. The woodhen was saved from the brink of extinction after the population dropped to about 20 in the late 1970s.

Beef cattle and chickens will be removed from the island, with the board compensating owners and restocking herds and flocks later. Milk cows will remain on the island, but will be kept in pens and fed on pre-cut grass.

Mr Wills admits that while most locals want to get rid of the rats, "many people, understandably, have concerns". They include Clive Wilson, who believes the rat plague has been exaggerated. "The poison exposes the island, its environment and the people to a great deal of danger," he told the Sydney Morning Herald. "I think they will do a lot of damage and in the end there will still be rats."

Among the native creatures believed until recently to be extinct on the island – which prides itself on having no marine or air pollution, and no litter – was the Lord Howe stick insect. Then, in 2001, a team of conservationists who landed on Balls Pyramid, a large rock south-east of the island, were astonished to discover a small population of the stick insects, living under a single shrub.