Islands are nature’s laboratories. Their small self-contained ecosystems can allow animals and plants to flourish that wouldn’t be possible elsewhere. But their size means that those ecosystems can be fragile when exposed to outside influence. Within 60 years of the first sailors landing on the Indian Ocean island of Mauritius, the flightless dodo had been consigned to extinction, thanks to the introduced rats and pigs that tore through its nests.
But nature can also prove astonishingly resilient even when subject to a terrific battering. One such example is Australia’s stunning Subantarctic Macquarie Island, which lies halfway between Tasmania and Antarctica. Over the centuries its wildlife was subject to both direct exploitation and the ravages of invasive species, but thanks to a pioneering conservation programme it is now once again one of the jewels of the Southern Ocean.
Wildlife exploitation
The first recorded humans to visit Macquarie Island landed there in 1810. Although the island was just 21 miles (34 km) long it was absolutely packed with wildlife: vast colonies of penguins and beaches packed with fur seals and elephant seals. Macquarie lies at an almost identical latitude to South Georgia and is something of a mirror to that island, albeit a much smaller and low-lying one.
Just like South Georgia, it didn’t take long for entrepreneurs to take advantage of this natural bounty. The fur seals were the first to go, driven to complete extinction in the hunt for pelts. Elephant seals were flensed for the oil-rich blubber. And each new ship that arrived brought their own deadly cargo: not just rats and mice, but cats and rabbits too which ravaged the nesting seabirds and nibbled their way through the island’s unique flora.
The deadliest innovation that people brought to Macquarie was the steam digestor: immense pressurised boilers that could be used to render blubber into oil. As astonishing as it seems today, the main target wasn’t elephant seals but penguins.
Penguin oil was reputedly good for lubricating the natural fibres used in the manufacture of rope and twine. First Macquarie’s king penguin colonies were targeted, followed by royal penguins, whose immense rookeries disguised the fact that the island was the only place on Earth where they were found. At the height of the oil season, as many as 3,500 royal penguins were reduced to oil. In a macabre twist, the steam engines themselves were often fuelled by penguins to save on expensive coal.
First conservation steps
It took the intervention of the early Antarctic explorers to draw the public’s attention to the plight of the penguins. Edward Wilson, the naturalist who accompanied Captain Scott on this first Antarctic expedition (and died with him on their return from the South Pole) was an early campaigner to protect the penguins. To better protect Macquarie, the Australian explorer Douglas Mawson, who had set up the first radio relay station for Antarctica there, proposed it be turned into a purely scientific reserve.
When Frank Hurley, the celebrated photographer of Shackleton’s Endurance expedition, visited Macquarie Island in 1919, he shared his horror at the penguin oil industry and further helped build the protests against it. The public remained ambivalent about seals, but the penguins’ unflappable charisma helped carry the public mood. By the mid-1920s, the last penguin oil license had been revoked, and supporters of Macquarie Island’s wildlife could breathe a little easier.
What was less well understood or appreciated at the time was the quiet but deadly effect that the invasive mammals were having on Macquarie Island’s ecosystem.
Invasive destruction of native species
Throughout the 20th century there were a few ad hoc programmes to address the situation. By the time that Macquarie was designated as a World Heritage site in 1997, the invasive mammals were running rampant. Feral cats had driven two native bird sub-species into extinction – the Macquarie Island rail and the Macquarie Island parakeet, the most southerly parrot in the world. Before a feline trapping programme was instigated, they were estimated to be killing around 160,000 seabirds a year.
The last cat was removed from Macquarie Island in 2000, but in doing so the conservationists also discovered the laws of unintended consequences. Freed from their only potential predator, the rabbits did exactly what rabbits are known to do, and their population exploded. Macquarie was soon home to a staggering 300,000 rabbits.
When people had first landed here, the island was covered with megaherbs, including a species of cabbage that grew taller than a person and was well known for its potent protection against scurvy in sailors. Now, it had been reduced to a handful of stumpy plants. Rabbit burrows disrupted the vegetation further, and provided secure homes for rats and mice to venture forth from to raid the nests of seabirds, which were equally now vulnerable to raids from skuas. A number of species, such as blue petrels and Antarctic terns had been reduced to remnant populations only able to breed on offshore rocks.
Eradication plans
To deal with this, the Macquarie Island Pest Eradication Project (MIPEP), which at the time was the most ambitious invasive species removal project in the world. The total cost was A$24.6 million (just over US$ 15 million), supported by the Tasmanian and Australian governments. Starting in 2007, it aimed to completely eradicate all rabbits, rats and mice from the island.
Macquarie is an exposed island fringed with cliffs, so helicopters were put into service to cover such rough terrain and drop poison bait. The operating conditions were made more difficult by the need to carry out the baiting programme in winter when the weather was at its worst, as much of the native wildlife leaves the island completely during this season.
Although the project had been based on similar eradication efforts on small New Zealand islands, there were more challenges than just the weather. Although large decreases in rabbit and rodent numbers were observed in baited areas, at one point the project had to be paused when it was found that the scavenging of rabbit carcasses was causing unexpected seabird mentality.
To address this, calicivirus, a rabbit-specific virus, was introduced to further cull the rabbits, and more people were enlisted to remove dead animals. Hand baiting continued in areas covered by the aerial baiting, and detector dogs and hunters worked in tandem to remove the last surviving rabbits. In turn, the experiences of the Macquarie programme were used to help guide an even more ambitious rodent eradication project in South Georgia.
Success – and vigilance
In 2014 it was announced that there had been no confirmed sightings of rats, mice or rabbits on Macquarie Island for three years. The project was a success and a major threat to the survival of many seabird species on the island had been permanently removed.
Ecologists estimate that it will take around two decades for Macquarie’s ecosystem to fully recover. But visitors on a Subantarctic Islands expedition cruise today can already see the difference. Away from the beaches packed with the obvious attractions of the king and royal penguins and the elephant seals, the slopes are once again covered with tussock where until recently there was just bare earth. From protective walkways it’s possible to see the slow return of the megaherbs as well as species such as orchids. As sea bird numbers recover, their guano returns nutrients to the soil, helping to create a virtuous circle of regrowth. And with no mice to gobble up their larvae, even the island’s invertebrate life is thriving.
There is a continued need for vigilance of course. Any one visiting Macquarie Island is subject to strict biosecurity rules to prevent a repeat of the disasters of the last century. Rodent detector dogs still continue their work where needed.
One striking monument remains on the island. At Sandy Bay, home of one of the most spectacular king penguin rookeries, it’s still possible to see the rusting remains of the old steam digesters that once rendered these amazing birds into oil. Now when you look up, you can see a sky that was once in danger of emptying completely but is now thick with seabirds once again.
In a world where islands are nature’s laboratories, it’s a happy reminder that while some experiments can go disastrously wrong, others can prove to be a success beyond an ecologist’s wildest dreams.
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