Dead as a dodo
Mauritius is no stranger to environmental disaster
There are certain advantages to being an island. While it’s not always easy having miles of ocean between you and your nearest neighbour, it does make it easier to control your borders, which gives you a real head start in a global pandemic. New Zealand is only one of a number of island nations keeping Covid-19 at bay with its ocean borders. Our Pacific neighbours such as the Cook Islands, Samoa and Tonga remain free of the virus. In the Indian Ocean, Mauritius acted quickly like us, and has kept its total case numbers below 400.
But living on remote islands can also bring vulnerability. One of the reasons that our Pacific neighbours acted so swiftly in response to Covid-19, almost all closing their borders before they’d seen a single case, was that they knew what had happened in the 1918 influenza pandemic. In New Zealand, about 9000 people died out of a population of 1.1 million, not quite 1% of the total population. That figure suggests that New Zealand did rather well – estimates of the global death toll suggest that somewhere from 1-5% of the world’s population died in that pandemic. Mauritius is estimated to have lost around 12,000, just over 3% of its population. In comparison, Pacific Islands suffered a truly horrific toll. Fiji lost 5% of its population, Tonga 10% and Samoa 22%.
These terrible losses are thought to have occurred because isolated populations hadn’t been exposed in previous outbreaks. In particular, the strains of influenza that had dominated prior to 1889 were close enough to the pandemic strain of 1918 to give partial immunity – which meant that in most countries there was a lower death rate among those over 40, in comparison to those who were younger. However, isolated communities which had escaped those earlier influenza outbreaks had no immunity in any age group, and so were devastated.
There’s a similar vulnerability in the animal and plant species which live on isolated islands. Islands comprise just 5% of the world’s land area, but are the site of more 60% of recorded extinctions for both plants and animals. For some groups, the figures are much higher – 95% of recorded bird extinctions are from islands. Many of the species which remain on islands are endangered too – around 50% of critically endangered plants and just under 40% of animals are found on islands.
While there are many different factors which contribute to species extinctions, on islands the most common cause, by a significant margin, is invasive species. In a parallel with the situation seen with infectious disease, the introduction of new species, especially mammals, has been disastrous for many island animals and plants. This has been especially so for birds, because many island bird species are flightless or at least weak fliers, and have proven easy prey for ground-based predators.
Since humans arrived in New Zealand, around 53 species of birds are known to have become extinct. Of these, at least 15 were flightless and a number of others were poor fliers. While hunting is thought to have been the main reason that moa species became extinct, and also to have contributed significantly to the extinction of birds such as the huia, it was predators such as rats which drove the smaller species to extinction. Many other native bird species were wiped out on the mainland and only survived in small, remnant populations on islands which remained free of rats, cats and other mammals.
Much of the narrative about flightless birds on islands has them as trusting and naïve, simply not adapted to predators. Early descriptions highlighted this; take for instance the words of Charles Douglas, who spent years mapping South Westland:
“the Kakapo appears to have little idea as to how to defend itself against dogs, ferrets or men… he has little idea of attack or defence.”
But it’s a myth that New Zealand’s native birds weren’t adapted to predators, and were wiped out because they were naïve. The problem our native birds faced following the arrival of humans was not that they weren’t adapted to predators – but that they were adapted to the wrong predators. New Zealand had no mammals, apart from three bat species, but it had a number of predatory birds, and it is these predators that our native species were adapted to. Among New Zealand’s predatory birds, there was the formidable Haast’s eagle, with a wingspan of nearly 3 metres and able to take on moa weighing 200 kgs and the Eyles harrier, a fast hunter capable of hunting flighted birds in the forest.
With predators such as these, flying was a distinct disadvantage – not only costly in terms of energy, but actually dangerous. It was much safer to live mostly or entirely on the ground, shielded by the vegetation. As well as staying out of harm's way by avoiding flight, other effective strategies against predatory birds, which hunt by sight, were camouflaged plumage, being nocturnal and staying still. What appears to be fatally fearless behaviour was actually once very effective in protecting our native birds. But none of their strategies were any use against mammals, which hunted from the ground and used their sense of smell.
The first published suggestion that New Zealand’s offshore islands could be used as refuges for native species came from the conservationist Thomas Potts, in 1878. While he didn’t explicitly state that this would protect native species from predators, Richard Henry, writing around the same time or slightly later, certainly did. Henry, who opposed the introduction of mustelids like stoats because of the threat to native birds, was the first caretaker of Resolution Island in Fiordland – the world’s first island sanctuary.
Despite Henry’s efforts, Resolution Island was too close to the mainland and was invaded by stoats, but the principle was sound, and further islands were purchased for conservation – Little Barrier Island in 1896 and Kapiti island in 1897.
Without islands such as these, many species once common on New Zealand's larger islands would be extinct. Instead, species such as tuatara, saddleback, stitchbird, black robin, Cook Strait giant weta, Little Barrier giant weta and Hamilton’s frog survived only on island refuges. Other species, such as the kakapo, kaka and kokako survived on the mainland well into last century, but islands have still been a critical part of their survival.
By the middle of last century, islands were well-established as a central part of the conservation strategy for many of New Zealand’s native birds, reptiles, amphibians and insects. But there was also a problem. At least a third of New Zealand’s larger islands already had rats, and it was becoming increasingly clear just how dangerous rats were to native birds. Then, in the 1960s, there was a turning point for conservation in New Zealand - ship rats arrived on a small island off the coast of Stewart Island, Taukihepa, or Big South Cape. Within a couple of years, two species of bird and one bat were extinct.
The New Zealand Wildlife Service, a precursor to the Department of Conservation, is perhaps best remembered for Don Merton and his team’s efforts in saving the black robin. But, at the same time, those same people recognised that if New Zealand’s islands were to continue to be a refuge for native birds and other species, something had to be done about rats. And so they developed a completely different conservation approach – eradicating mammals from islands.
At first there was no expectation that rats could be eradicated from islands. Baits or traps were set out simply with the intention of reducing rats numbers. However some early control efforts were so effective that rats were never found again, and an idea took hold. The early, inadvertent, eradication success led to more systematic efforts, and, by the 1980s, techniques for eradicating rats and other mammals, from islands of significant size were established.
But New Zealand was not the only country where introduced mammals such as rats had destroyed native birds. So, the techniques developed in New Zealand to eradicate rats and other invasive mammals from islands were exported to other countries with similar problems. Among them was the island nation of Mauritius, once home to the world’s most famous extinct bird – the dodo.
The dodo was a type of pigeon, although with its heavy beak and solid build, you’d never guess . It had already been extinct for 150 years before a Danish museum curator realised that dodos and pigeons were related. Even then, the relationship wasn’t accepted until the publication of the authoritative book on the subject, The Dodo and its Kindred, in 1848. But the dodo was only one of at least 40 species to become extinct following human arrival on Mauritius and the neighbouring island of Rodrigues. Other lost species included giant tortoises, bats, reptiles and most of the endemic birds.
Because Mauritius, like New Zealand, had no mammals except for bats, the conservation challenges in the two countries are similar. From the 1980s, New Zealand began to export eradication and pest control techniques to Mauritius, and the two countries formed a link, especially between the Mauritian Wildlife Foundation and the Department of Conservation. Over the years, a number of New Zealand conservation workers have travelled to Mauritius to work on conservation projects there – one of those, in 2002, was me.
I have fond memories of my time in Mauritius for many, many reasons. The food was delicious, the landscape spectacular and the water clear and warm, and I met some fascinating and inspiring people. But I certainly didn’t have the tourist experience of Mauritius. I worked hard, and the first piece of work that I did was review 15 years’ worth of weed control records for Île aux Aigrettes, a 26 hectare island near Pointe d’Esny. After I’d worked through all the records I spent a couple of weeks on the island, scrambling about on the sharp coral rock or walking on the rather more pleasant tracks through the coastal forest, and then I put together a weed management plan.
The view across the lagoon to the town of Mahébourg, from the Ile aux Aigrettes jetty.
Compared to the scale of many island restoration projects in New Zealand, Île aux Aigrettes is tiny. It is only one tenth of the size of Tiritiri Matangi, near Auckland, and is not much larger than Little Mangere, the tiny island where the black robin clung to survival in the 1970s. But it contained the last remnant of the coastal ebony forest that once covered the Mauritian lowlands, as well as other endangered plants. After most of the introduced mammals were eradicated, it became a refuge for a number of highly endangered species like the pink pigeon.
Coastal forest with a peak at the sea, Île aux Aigrettes
When I think of Île aux Aigrettes, I remember a stunning green island with clear blue water lapping at the rocks on its edge. But, right now, Île aux Aigrettes is ground zero for yet another of 2020’s disasters, the oil spill from the Wakashio. The ship struck a reef only two kilometres from the island (this link has a truly shocking photo), and by mid-August, the stench of petroleum vapour was too strong for people to spend more than a few hours on the island. Some of the endangered species were being removed temporarily and kept in captivity as there was nowhere else safe.
It’s not just Île aux Aigrettes threatened by the spill. The Wakashio managed to run aground beside one of the most ecologically important and sensitive areas of the Mauritian coast. Apart from Île aux Aigrettes, there’s the RAMSAR-listed Pointe d’Esny mangrove wetlands, four islets which are home to nesting seabirds – although it’s fortunately not breeding season – and the stunning Blue Bay Marine Park. Blue Bay was described to me as the best place to go snorkelling in Mauritius, and certainly it is, or rather was, the most beautiful coral and the best snorkelling that I have experienced.
Right now, it’s too soon to fully appreciate the damage that the oil spill will do. The situation is still developing – nearly 40 dead dolphins have washed up on the Mauritian coast nearby although the cause is debated. Other impacts could take years to become apparent. Although the ship’s captain has been arrested, the cause of the accident is not known.
But one thing is already clear . Mauritians will be determined to see those responsible pay. In the last 24 hours, reports have been coming out of tens of thousands protesting at the government’s handling of the disaster. I thought that the headline was wrong when I saw that 100,000 had protested – Mauritius has a population of only 1.5 million. However, another source indicated that the protests were the largest in 40 years, and that up to 75,000 had protested. Whatever the numbers, I can’t blame them for their anger. We can look back on the extinctions of the past and see that people simply didn’t realise the harm that introduced species could do on such sensitive islands as Mauritius and New Zealand. But a ship running aground on a coral reef and leaking 1000 tonnes of oil into precious protected areas? It’s very hard to see how that could be anything but a completely preventable environmental disaster.
For the next few months, I’ll be writing The Turnstone once a fortnight instead of once a week, while I do a course.
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