How we're going to save the little paradise in the Pacific
The rare native wildlife of a remote island has retreated to a precarious existence on vertical cliffs. An urgent project supported by the 2017 Birdfair is leading the counter-attack against invasive species to save the “little planet” of Rapa Iti
"Rapa is extremely isolated, even by Pacific standards”, says Steve Cranwell, BirdLife’s Invasive Alien Species Programme Manager. This, coming from a man who knows a thing or two about restoring remote Pacific islands, accustomed to locating coral atolls or tiny rare seabirds, both specks in an endless ocean, before helicopter fuel runs out or a tropical storm hits. Saving Rapa’s native wildlife is his next urgent challenge.
About four million years ago, midway between South America and Australia, a volcano erupted beneath the vast expanse of the Pacific Ocean, bringing into existence the beginnings of a unique new world. A four-thousand-hectare island, Rapa Iti (“little Rapa”, named to distinguish it from the distant, larger Rapa Nui or Easter Island) is one of the Bass Islands in the southernmost reaches of French Polynesia, where access for the island’s 500 inhabitants is provided only by monthly supply boat.
Despite such isolation, nature somehow flourished, says Cranwell. “With no connecting landmass, the diverse native wildlife are testimony to astonishing oceanic and windborne journeys and a subsequent species radiation.” Think parachuting spiders, seeds and seabird-dropping fertiliser. Thus, Rapa is famed for its endemism: three taxa of rare bird, 31% of plants, hundreds of invertebrates (including 68 weevil species), plus some fish, can be found nowhere else in the world.
Once, clouds of seabirds were said to have blocked out the sun, but, as is the case on many Pacific islands, humans brought with them rats and other invasive mammals, leaving them unchecked to wreak havoc on the evolutionarily unprepared and defenceless native flora and fauna. Sadly, less than 5% of native forest cover remains today, while the island’s bird species are a few rat attacks away from oblivion. Like a mini-planet under siege by alien invaders, Rapa’s “moons” are where some native species have retreated, literally clinging to existence on rugged predator-free islets and inaccessible cliff sanctuaries.
The birds, all globally Endangered, include Newell’s Shearwater Puffinus newelli, Polynesian Storm-petrel Nesofregetta fuliginosa, and Rapa Fruit-dove Ptilinopus huttoni; Murphy’s Petrel Pterodroma ultima (Near Threatened) is also present. This April, a BirdLife expedition, supported by the David and Lucile Packard Foundation, set out to Rapa to scope out the logistics of an urgent operation to save them. Proceeds from the 2017 British Birdwatching Fair (“Birdfair”) will enable the project Saving Paradise in the Pacific to build on our invasive species removal techniques pioneered on many other Pacific islands, such as our recent success on the Acteon & Gambier island groups, giving the birds the safe space they need to recover.
There’s no time to waste, either. “The thing about Storm-petrels”, says Cranwell, “is that they’re so small (only 20-100g) – smaller than a sparrow – and defenceless on land that they’re at the mercy of invasive species: either by being eaten, having their nests trampled, or weeds degrading the habitat they need to raise their young.” Until this year’s expedition, the fate of Polynesian Storm-petrel on Rapa was largely unknown, but surveys gave a glimmer of hope. “While we couldn’t find them in April, we did confirm that the two (small) islets on which they were known to occur remain free of rats, and with the commencement of the breeding season we expect they will return and continue to successfully raise their young”, says Cranwell.
Too remote for science?
Let’s face it, accessing Rapa is not easy; such isolation has implications for how well a species is known to science. Two of the seabirds, a local form of Newell’s Shearwater called Rapa Shearwater Puffinus newelli myrtae, and the titan subspecies of White-bellied Storm-petrel Fregetta grallaria, have been so understudied that we are not certain whether they are fully separate species or not, although recent evidence points toward Rapa Shearwater being a distinct species Puffinus myrtae. Despite taxonomic disputes, wanton predation and habitat degradation leaves little time to find out for certain. “We can’t let these be species of tragic posthumous fame”, says Cranwell. “There’s still a lot we need to find out, but this doesn’t mean they’re any less important.” From the birds’ perspective, on “planet Rapa”, one thing’s for sure: the removal of invasive species would mean that they could securely recolonise islets to increase their numbers and range. Truly, conservation in action.
The most colourful bird species found on the island stands out against the sombre rainy landscape. Yet, the appearance of the Rapa Fruit-dove Ptilinopus huttoni reflects the vibrant native forest that once carpeted the island: the dove’s plumage of camouflage green gives way to a blaze of yellows, rose-purples and berry-reds as they glide from tree to tree and puff themselves up in display. Dependent on the fruits and flowers of Rapa’s native forest, never has restoration of this habitat been more urgent for this species. Our census shows a significant decline, the population having possibly halved since the last survey – 30 years ago. “This suggests there are fewer than 200 birds left”, says Caroline Blanvillain of Société d’Ornithologie de Polynésie (SOP Manu, BirdLife in French Polynesia), who led the census, “almost certainly qualifying the species as Critically Endangered”. As Cranwell puts it, the Rapa Fruit-dove is a mere “huff and a puff from extinction”. Confined to tiny forest fragments not yet lost to feral goats, cattle, felling and fires, a replanting programme combined with invasive species control will help save this beautiful bird, and a whole suite of less conspicuous species.
"The Rapa Fruit-dove is a mere huff and a puff from extinction"
For protecting Rapa and its islets from invasive alien species means restoring them to their former glory, with benefits far more than the birds. At the bottom of the food chain, you will find hundreds of endemic land-snail species, all on the slippery slope to extinction. There’s a battle between plants too, as weeds like the “horrendously dense thickets” of strawberry guava, plus introduced pines, march across the landscape, aided by feral goats, cattle and horses munching and trampling delicate native flora. Sadly, April’s survey confirmed the extinction of the last known stand of Rapa’s endemic sandalwood.
Whole ecosystems are affected, but if we act quickly, nature is resilient enough to bounce back. “Seabirds returning to these islets, for example,” says Cranwell, “will restore important ecological processes through their ‘inputs’”. By removing feral goats from the islets, the team of BirdLife and SOP Manu will provide a foundation for forest species to recover and stem the erosion that effects ground-nesting seabirds. Rapa’s resident islanders will be involved throughout, helping tackle the daunting Strawberry Guava challenge, and changing the way they manage their grazing livestock, safeguarding Rapa’s unique natural heritage. The steep terrain will make rat eradication on the islets challenging; however, the use of new technologies such as drones may provide a solution.
Restoring these islands, which includes transporting people and equipment 1,500 km, won’t be short on challenges for the team. Cranwell remains hopeful: “The support from Birdfair is an opportunity like no other for the birds, biodiversity and people of Rapa. With this assistance we will ensure what’s so unique about this remote Pacific island continues for generations to come.”