The sub-Antarctic island of South Georgia sits at the convergence of several favourable oceanographic and biological phenomena. Bathed in waters richer in life than almost anywhere else on Earth, it’s a magnet for an incredible density of wildlife. Tens of millions of birds nest on the island each year, including four species of penguin, four species of albatross and some 22 million pairs of Antarctic prions.
Probably the last people to see South Georgia in its natural state were English merchant Anthony de la Roché and his crew, who were blown there by Drake Passage storms in 1675. They may have somehow managed to come and go without leaving rats on the island, but James Cook and his crew, who arrived a century later, almost certainly didn’t.
Cook surveyed and claimed the island for the British crown. His reports of the tens of thousands of seals and whales to be found in the surrounding waters – perhaps the greatest concentrations of marine mammals on Earth – brought the sealers that took just a decade to almost exterminate the fur seals, and, inevitably, even more rats, which inadvertently wiped out millions of seabirds at the same time.
Today, a few offshore islands and areas isolated from rats by glaciers and topography are the island’s only remaining seabird havens. But that, hopefully, is about to change, thanks to a habitat-restoration project being run and funded by the South Georgia Heritage Trust (SGHT).
There’s an urgency to the operation. At the moment, glaciers, which rats can’t cross, separate the island into discrete areas, but many of them are retreating rapidly. If a glacier pulls back enough to allow rats to cross from a rat-infested area to a rat-free area, the newly exposed birds will quickly be wiped out.
The first phase of the project, which took place in March last year, consisted of dropping poisonous baits from helicopters on the Thatcher, Mercer and Greene peninsulas, close to the administrative centre and British Antarctic Survey base at King Edward Cove and Grytviken – a total area of 128 square kilometres. Although this represents little more than 12 per cent of the total area that will need to be cleared, it’s also ten times larger than any previous area from which rats have been eradicated.
The team drew on experience from successes on a smaller scale on the New Zealand sub-Antarctic islands. The plan was to keep navigation tight using GPS, ‘painting’ the island with bait in narrow strips, allowing a tiny overlap and aiming to ensure that any rat within the area would have access to bait.
March – the end of summer – was chosen because many of the birds had fledged and left the island, but the rats were still largely out and about. The 11-strong team had only three weeks to bait the whole area.
Two helicopters, piloted by New Zealanders with experience of rat clearances in their homeland, were fitted with 300-kilogram bait hoppers that were themselves fitted with a spinning disperser, rather like a lawn sprinkler. When over the narrowly defined track, the pilots set the spinner going and painted a strip of island with bait.
The team covered about three square kilometres with bait per hour, and on its best day managed 33 hopper reloads. The weather proved cooperative, but the team was keenly aware that an attempt to bait Macquarie Island, which is an eighth the size of the first area to be cleared on South Georgia, had failed largely due to inclement weather and insufficient flying opportunities.
Accepted ‘normal’ bait densities from past rat clearances would have been prohibitively expensive on South Georgia, but the team estimated that the combination of tight navigation and an even spread of bait would mean that there was enough, spread evenly enough, for every rat. The bait is still the project’s major cost – even though the helicopters and other equipment have been bought, baiting the rest of the island will cost another £5million, assuming phase one proves a success. The team hopes to restart in February 2013.
The obvious concern on an island with an almost unparalleled density of wildlife is the impact on the native species. Fortunately, almost all of South Georgia’s wildlife gets its food offshore. Skuas will take some of the bait, but the island supports the world’s densest skua population, which is expected to recover quickly. The scativorous snowy sheathbills, cleanup crews for the penguin colonies, are likewise expected to take some of the bait but recover quickly.
Of most concern are the small populations of South Georgia’s two duck species, one of which, the South Georgia speckled teal, is represented by an endemic subspecies. Another litmus test is the tiny, endemic South Georgia pipit – the only songbird south of the Antarctic Convergence. It nests among the tussocks and is largely restricted to small offshore islands free of rats.
So far, signs of the ducks and the pipits are good. Last May, Professor Tony Martin of the University of Dundee, who heads the project for the SGHT, reported with obvious excitement that the first ducklings in a century had already been seen in some areas, and the habitat-restoration team couldn’t find any sign of surviving rats before it left. The island’s 14 year-round residents are continuing to scour the areas cleared for any sign of rats; none had been seen as of late July.
Sarah Lurcock, who has spent most of the past 18 years on the island, reports a nervous excitement on the base. Pipits were heard in the cove for the first time this autumn, and a bottle of Champagne is on offer for whoever finds the first nest next spring. And recently, as winter settled around base, she reported that ‘with the new snow, there is no sign of rat prints’.
This article was published in the March 2012 edition of Geographical Magazine