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Total wipeout

  • Written by  James Howe
  • Published in Wildlife
Rats were introduced to the island in 1918 when SS Makambo ran around on its way out of the harbour Rats were introduced to the island in 1918 when SS Makambo ran around on its way out of the harbour Ian Hutton
01 Mar
2012
After a shipping accident introduced rats to Lord Howe Island in 1918, the rodents have slowly been destroying its biodiversity. A controversial plan hopes to eradicate them for good

After five solid hours of clambering, my legs are starting to feel it. Arriving at the base of another rock face, I grab the dangling rope and start to haul myself up into the swirling fog.

There’s no safety harness, which is part of the thrill. Serious accidents are rare, my guide tells me; there have only been one or two in the climb’s history. But during my stay on Lord Howe Island, a man falls during one of these cliff ascents, breaking his ankle and prompting a AU$1.1million (£740,000) rescue operation involving two military helicopters flying the 760 kilometres from Sydney.

Before he can be lifted to safety, he’s forced to spend a night up on the mountain. ‘I can’t say I envy him,’ my hotel manager remarks that evening, glancing at the gloomy shape of Mount Gower in the distance. ‘Being stuck up there in the bush with all the rats.’

That she doesn’t feel the same trepidation in her own bed at night is thanks to a AU$70,000-per-year grid of strategically laid rat baits that virtually eliminates rodents from the settlement; on Lord Howe, you won’t open your kitchen cupboard and find a rat. But only ten per cent of the island receives this treatment. If, as I did, you take a hike up Malabar Hill on the southern end of the island, sprinkle a few crumbs on the ground and wait quietly, you’ll soon be surrounded by giant, kink-tailed, battle-scarred rats, rampaging through the tree tops and fighting raucously in the undergrowth.

Lord-Howe-Island-map-web

 

IT HAPPENED AT SEA

The nightmare began on 23 December 1918, when the Australian steamship SS Makambo was leaving the island after a routine stop on its regular Sydney–Vanuatu run. The ship struck a rock on its way out of the harbour and needed to be run aground for repairs. Tonnes of fruit cases and copra were thrown overboard, and the ship’s opportunistic stowaways scampered ashore to rodent paradise.

In time, the Makambo would receive its comeuppance in the form of a British torpedo, having been repaired, refloated and sold to the Japanese shortly before the Second World War. But well before she hit the seafloor in 1944, Lord Howe Island had already been ravaged. Six unique bird species had disappeared, as had 13 of the island’s endemic insects and at least one plant species. Foreign owls, released in a failed bid to rein in the rodent tide, had wiped out the island’s endemic owl species and begun preying on other native birds. It was an ecological catastrophe.

But now, environmentalists believe it’s possible to completely and permanently eradicate rats, mice and masked owls from the island. The AU$9million plan will involve dosing the entire island with 42 tonnes of rat poison. GPS-guided helicopters will execute the drop, spraying pellets laced with brodifacoum – a potent anticoagulant – across the island’s 1,455 hectares.

With two mountains higher than 700 metres, numerous offshore islets and the tallest sea cliffs in Australia to deal with, this is no small ambition. Indeed, the very concept of complete eradication – pioneered by ecologists in New Zealand during the 1980s – was unheard of until relatively recently. ‘It’s something that 30 years ago, at the first Island Invasives Conference in Auckland, they said was impossible. But then the New Zealanders gradually just did it,’ says local naturalist and museum curator Ian Hutton, who initiated the push to eradicate Lord Howe’s rodents.

woodhenA Lord Howe Island woodhen. Prior to the eradication, scientists will try to catch every one of these endangered birds to prevent them eating the poison bait (Image: Ian Hutton)

 

WIDESPREAD IMPACT

Rat eradication on Lord Howe, which was World Heritage listed in 1982, will bring challenges beyond the topographical. Not least of these is ‘collateral damage’ to the island’s unique wildlife, some of which is partial to rat poison. In 2006, pellets identical to the brodifacoum baits but containing a harmless bioluminescent marker designed to show up in bird faeces were dropped on Transit Hill on the island’s eastern side.

Problematically, the much-loved Lord Howe Island woodhen devoured the pellets with gusto. This bumbling kiwi look-alike was only recently brought back from the brink of extinction by a dramatic rescue operation that involved the eradication of feral pigs and cats, and an extensive captive-breeding programme. Now, scientists plan to catch the island’s 200 woodhens and hold them captive during the entire 100 days of the eradication programme. The same will be attempted with the Lord Howe Island currawong (which is known to scavenge poisoned rat carcases), and various other species at risk of consuming the baits.

Of course, it won’t be possible to capture every bird, but World Heritage manager Hank Bower takes an expedient view. He believes that despite the inevitable losses, a one-off drop of brodifacoum will be less harmful in the long-term than the island’s ongoing baiting campaign. ‘We’ve had woodhens brought in bleeding out of their mouths and eyes, which is due to brodificoum poisoning. So people are doing it already – we’re already poisoning the island,’ he says.

Eradication is slated for 2014–15, and to Bower, it can’t come quickly enough. He’s adamant that unless the project goes ahead soon, there will be further extinctions. Take, for example, Rentz’s strong stick insect, first discovered in 1986 and only glimpsed 12 times since. Scientists know almost nothing about it, but fear it will go the same way as the Lord Howe Island stick insect, which had disappeared from the island by 1930. ‘I’m sure there are loads of insects that are in the same predicament,’ says Bower. ‘Once we relieve them of the predation pressure, they’ll start reproducing en masse.’

Plants are also under attack. The little mountain palm – a species that belongs to a genus that’s unique to Lord Howe – was recently listed as critically endangered, its decline attributable to rats browsing on its seeds and shoots. Bower says this besieged species may now be so weakened by rats that it won’t be strong enough to survive global warming. ‘Climate change has happened in the past, and it’s always happening; whether species get through it depends on their robustness,’ he says. ‘If the little mountain palms continually get their seeds eaten by rodents, and then climate change kicks in, they’re stuffed.’

There’s also the concern that rodents will become resistant to brodifacoum, the only proven agent for eradication. Mice on the island have already become resistant to Warfarin (another anticoagulant), and are actually able to sustain a higher population by eating Warfarin-laced grain left for rats. Brodifacoum is commonly bought by islanders for household baiting, and the board is powerless to prevent people using it. ‘Once there’s resistance in rodents on the island, we’ve lost the only proven mech­anism to eradicate them,’ Bower says.

If eradication goes ahead and is successful, environmentalists will have the privileged opportunity to reintroduce animals muscled out by rodents, including the Lord Howe Island stick insect. Remarkably, more than 70 years after the insect was thought to have become extinct, a handful were found under a single melaleuca bush on Balls Pyramid, a desolate volcanic stack that rises 562 metres out of the sea 21 kilometres off the coast of Lord Howe.

Close relatives of extinct birds will also be sourced from the Australian mainland and neighbouring Norfolk Island to be reintroduced, and there’s even talk of propagating an extinct plant species from ancient dried fruit specimens kept at the Royal Botanic Gardens in Sydney.

 

ECONOMIC BOOST

But it isn’t just the natural environment that stands to benefit. Since the 1920s, Lord Howe has been exporting the endemic kentia palm for office decoration; it remains the island’s only major non-tourism-related industry.

Gathering seed for the palm nursery involves scaling the giddily tall palm trunks. ‘In past years, the young guys all seeded,’ says seed-collector-cum-tour-operator Dean Hiscox. ‘It was very competitive – it was a race to get the best seed first.’

Although interest in seed gathering has dipped in recent years, collectors still gathered 665 bushels (a bushel is the equivalent of about four garden buckets) in this year’s harvest. But rats are a huge problem – they browse new seedlings, raid packing sheds and eat ripe seeds directly from the palms, dramatically reducing the yield. ‘Prior to the introduction of rodents, they were collecting about 4,000 bushels,’ says Mark Smith, the Lord Howe Island Board’s business manager.

The board’s early control programme, including a bounty on rat tails and the introduction of masked owls, was set up to protect the industry, and while ongoing baiting thins rat numbers in the palm nursery, only complete eradication will bring seed yields back to past levels.

Tourism, which today is Lord Howe’s biggest industry, could also receive a boost. Comparable top-end holiday destinations, including North Island in the Seychelles, boast rodent eradications as part of their eco-friendly branding. Private owners of islands have even funded their own eradications to better cash in on the lucrative ecotourism market.

Hiscox, who runs several tourism businesses, believes eradication would make Lord Howe more palatable to its target market. ‘What we see here is a lot of people who are very environmentally aware,’ he says. ‘So we certainly have a lot of people who feel that it would be good to eradicate rodents – you do get that feedback quite strongly.’

staffLord Howe Island Board staff gather data for a study of rat numbers and density in preparation for the eradication programme (Image: James Howe)

 

LOCAL TROUBLE

But unfortunately for proponents of the eradication, the islanders themselves aren’t so keen. There are 350 permanent residents, making this by far the largest community on an island slated for rodent eradication. In my conversations with locals, it soon becomes apparent that they are wary of, if not outright opposed to, the plan. They talk of concerns ranging from wildlife deaths to birth defects.

One elderly lady I call – Thelma Wilson – says that she has been losing sleep over it. She invites me to visit the house she shares with her husband, Gower, later that evening. It’s a quaint little cottage with a garden full of lavender; inside, the walls are covered in monochrome photographs of island life: pig-hunting parties, fishing trips, beach picnics.

Both Thelma and Gower have lived on the island their entire lives and can trace their lineage back to the original settlers. Gower tells me that if the eradication goes ahead, he’ll be forced to slaughter his entire herd of beef cattle. The board has promised that his cattle will be replaced with better-quality stock, but Gower isn’t impressed. ‘I artificially inseminate my cows anyway and get whatever stock I want,’ he says. ‘It’s fine to say you can replace them for me, but they’ve got to be broken in.’

He says that he plans to defy the authorities when they order the slaughter. ‘You rear them by hand; they’re fed out of a bucket from this high,’ he says. ‘You care for them every day. To have someone come along and say, “We’re just going to put them in a hole” – well, what a waste.’

Speaking with the islanders, you quickly pick up on the resentment they feel towards the changes – many of which they link to World Heritage listing – that have been imposed upon their way of life in recent years. There are no more hunting excursions; goats and pigs have been eradicated, and mutton birds – once a popular meal – are now off-limits. Seabird eggs can’t be harvested, cats can’t be kept as pets, and there’s even talk of cutting down the majestic (but introduced) Norfolk Island pines.

Naturally, the eradication is placed in the same basket. ‘The community have a perception that they were the ones that actually looked after the island, and then all of a sudden we have all of these other authorities coming and saying, “Well hang on, you guys don’t know what you’re doing. Step back and let us manage it,”’ says Hiscox. ‘A lot of people forget that the reason we have a World Heritage property is because the original island community were proactive in protecting it.’

Proponents of eradication admit that the consultation associated with the eradication programme was grossly inadequate, considering the community’s size and nature. New Zealand employs a highly sensitive approach that sees a professional community-relations team sent in ahead of the scientists. ‘Here, it was done backwards: the scientists put together the eradication plan and thought that public consultation was giving a talk at the public hall,’ says Hutton. ‘There was an inevitable backlash.’

The board is still paying for its blunder. With such a low level of public support, it has already been forced to postpone the eradication by two years. The fear is that if it goes ahead without getting the bulk of the community on board, someone will sabotage the operation by keeping rats alive and then releasing them after the drop. ‘There are some people on the island who are bitter and twisted enough to say, “We told you so,”’ says Bower. But he’s willing to do what it takes to make sure this doesn’t happen, even to the point of getting approval to search people’s homes with sniffer dogs. ‘There’s no way we’re going to invest AU$9million and then see that money get wasted by sabotage.’

I ask if he thinks the eradication will ultimately go ahead. ‘It has to,’ he says. ‘It has to happen; it’s too important. There are too many threats, there are too many things slowly being whittled away. It’s very difficult to get these kinds of wins on the mainland; here, you can actually fix a problem forever.’

This article was published in the March 2012 edition of Geographical Magazine

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