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The SGHT helicopters could treat 7 square kilometres of South Georgia per flying hour.

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Kill a rat, save an ecosystem

A.R. Martin

8th August 2013

Professor Tony Martin reports on the latest phase of the world’s largest rat eradication project, which seeks to restore a threatened habitat and secure the existence of the remarkable birds and sea life that call the island home.....

It's important to recognise and be ready to justify the reality of what's being done

Worldwide, invasive alien species are second only to habitat destruction in reducing the planet's biodiversity. Their effect is especially potent on islands. Cats, rats, weasels and stoats wreak havoc on native faunas which evolved in the absence of predatory mammals.

When, in 1775, Captain Cook discovered a large glacier-riven island in the sub-Antarctic, he named it after King George III and quickly moved on, desperately disappointed that it wasn't part of the fabled southern continent. But the impact of his discovery was to have much longer-term consequences for the island and the biologically productive seas around it.

Cook returned to civilisation with news of an extraordinary abundance of seals on South Georgia's beaches. Within years, many wooden ships had descended on the island from both the New and Old Worlds, replete with sealers and their unintended cargo - rats and mice. While the sealers reaped over a million seal pelts, the rodents began devouring what was possibly the greatest concentration of seabirds in the world.

Two centuries later, the sealers and their whale-hunting successors have long since departed, and the marine mammal populations they exploited are well on the road to recovery. But their legacy lives on. Rats and mice have spread to almost every habitable part of the island.

Though South Georgia is famous for its wildlife, few visitors today realise that it is but a shadow of what it was before man's arrival. What should be the most abundant birds - the many species of burrow-nesting prions, storm-petrels and diving petrels - are essentially restricted to small offshore islands by the presence of rodents. Similarly, the endemic South Georgia pipit, the world's most southerly songbird, is clinging to survival, unable to rear young in the presence of predatory rodents.

But it's not just the birds that have been impacted by the alien invaders; the entire ecology of the island has changed. Rats eat insects, which have a hard enough time as it is. More obviously, the vegetation changes, too. By excluding the seabirds and the energy they bring back to South Georgia in the form of food for chicks (which becomes a nitrogen-rich fertiliser once excreted by the chicks), the rats profoundly impact the standing vegetation and the depth and quality of the soil that it produces. It is hard to exaggerate the cumulative effect of generations of rats on the terrestrial ecology of the island and, through the seabirds, the local marine ecology too.

But what could be done? How could rodents be removed from every nook and cranny on this 170km-long, remote mountainous island? Enter the South Georgia Heritage Trust (SGHT), a small UK charity with no previous experience of island eradications, but a steely determination to somehow fix this problem.

The solution potentially resided in techniques pioneered in New Zealand, where helicopters have been used to spread toxin-laced bait pellets to eradicate pests over ever-larger islands for many years, usually with finance and expertise provided by Government. But South Georgia is ten times larger than any island tackled before, more remote and with notoriously ferocious weather.

Just as sobering was that, at the outset, SGHT had neither the money nor the expertise to tackle rodents anywhere, let alone on an island as daunting as South Georgia. Encouragement lay in the fact that South Georgia's rat-proof glaciers divided the island into many smaller and more manageable chunks, allowing the problem to be solved piece-by-piece over several years. But those glaciers are retreating rapidly. This would be a race against time.

After buying two sturdy veteran ex- air ambulance helicopters and sending them the length of the Atlantic, SGHT mounted a trial operation in 2011. This treated 128 square km of South Georgia, which was just 12.5% of the rodent-inhabited land on the island but equalled the largest area ever tackled for rodent eradication worldwide. Almost miraculously, the rats disappeared within a week, and within three weeks some of the native wildlife was already showing symptoms of recovery. Two years later, there are still no signs of rats there.

Emboldened by apparent early success, the Trust has just completed the second year of fieldwork on South Georgia. This time, 580 sq km of land was treated, using 180 tonnes of pelleted bait, three helicopters and a team of 25. Four abandoned whaling stations - prime habitat for rats - were baited by hand, room by collapsing room. Delayed by the worst weather in a decade, the team faced an ignominious retreat brought on by deep winter snows. But luck rewarded patience, and the last bag of bait was spread on the westernmost tip of the island in frigid temperatures on May 18th.

Ahead lays intensive and expensive monitoring to discover if every single rodent has disappeared (killing 99.999% represents failure), and then a final season of fieldwork in 2015. A third of the island has still to be treated. If successful, tens of millions of seabirds should eventually return to their ancestral home, and two centuries of human-induced damage will have been reversed in just a few years. A small British charity will have brought about a conservation miracle of global importance.

Many would argue that, as a point of principle, every effort should be made to remove or eliminate damaging alien (i.e. non-native) species, wherever they appear. Unfortunately, in many instances our ability to do so was lost many years, decades or even centuries ago.

The feasibility and cost of now removing from the UK rabbits (introduced in the 12th century), grey squirrels (late 19th century), Chinese Mitten Crabs (early 20th century) or signal crayfish (1970s), to name but a few species, is well beyond us. But with Brown Rats on South Georgia, the SGHT perceived that this was not necessarily the case. With the right techniques, and the careful implementation of a good plan, success seemed feasible.

Though of proven effectiveness in restoring native fauna and flora, and in preventing the extinction of numerous species, the eradication of alien animals from islands is not without ethical dilemmas. Whether the work is carried out by shooting, trapping or poisoning, the simple fact is that animals die in the process. That can make some people uncomfortable, perhaps including those carrying out the work.

Rats have few friends, so the project I lead on South Georgia tends not to generate much in the way of moral indignation. But the same is not true for eradications of creatures we humans find more attractive - cats, rabbits and goats, for example, even though they too can be astonishingly destructive if let loose in a fragile habitat. Whatever the 'pest', I do believe it's important to recognise and be ready to justify the reality of what's being done.

Arguments against the restoration of island wildlife by removing animals put there by humans may involve perceptions of animal rights, welfare or religion. For example - 'rats have been on South Georgia for more than a century and have become part of a 'new' ecology, with as much right to live there as the native fauna'. 'Causing pain and death to millions of sentient animals is unjustified in any circumstances'. 'Who are you to decree that rats are bad and should die, whereas pipits and albatrosses are good and should live? All are God's creatures with an equal right to life.'

Rather than engage in a debate that would likely have no end, because there's no infinite wisdom available, my response to those who may have concerns about what we do is simply to explain what is really happening on (and under!) the ground, and let them reach their own conclusions.

Every year, an average rat on South Georgia will kill and eat many defenceless bird chicks. Brown rats typically kill by subduing their prey with sharp teeth and then eating their brain, often while the prey is still conscious. The dilemma, therefore, is not whether you do or do not want to kill rats. It is whether, knowing that you have the ability to intervene, you would prefer to do nothing and thereby condemn to a gruesome death many times as many seabird, pipit and duck chicks. And this will happen year after year for centuries and millennia. Oh, and by standing aside you will be condemning one or more species of bird to extinction, species which you have the chance to save. The world would not stop turning if the South Georgia pipit or the South Georgia pintail became extinct, but we believe that it would be a poorer place for their loss.

So, why are we freeing South Georgia of alien rodents? Because we can. Because thousands of people who care about South Georgia may, with their cash and goodwill, stand a good chance of undoing the damage of human generations past and leave this fabulous part of the world a better place. What's more, success breeds success. Around the world many other NGOs are watching the South Georgia story, and wondering whether they, too, might dare to tackle what may seem an impenetrable problem on an island in their own part of the world. If an island this big, this remote and this challenging can be restored by a small charity with private money, then surely almost any other island around the globe can also be rejuvenated and given another chance. As conservation legacies go, this one would be hard to beat.

Tony Martin is Professor of Animal Conservation at the University of Dundee, and has been seconded to the South Georgia Heritage Trust to direct its Habitat Restoration Project on the island. Tony is a career zoologist, specialising in marine mammals and seabirds, and sees this as an opportunity to make a real difference to his beloved South Georgia.

For more information and to 'sponsor a hectare' of this beautiful island please visit the South Georgia Heritage Trust website.

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