На острове Манук в Индонезии планируют ликвидацию популяции крыс для спасения экосистемы

To anyone who has crossed the vast, deep stretches of Indonesia’s remote southern Banda Sea, the dark outline of Manuk Island is a memorable sight. Known to many divers as Snake Island, this uninhabited volcanic outpost earnt its nickname from the numbers of banded sea kraits and olive sea snakes that weave through its thermal vents. The area is reckoned to offer a good quality of expeditionary scuba diving. Some 40 dive liveboards visit every year, some of them four or five times, during the calmer crossing seasons of March-May and September-November. Manuk covers 100 hectares and soars to a peak of 282m above sea level. It has no harbour, shelter or onshore diving facilities, visibility can vary widely and currents can be strong and unpredictable. The rewards for divers include hard corals, gorgonians and sponges on the volcanic slopes and ridges, with geothermal bubbles emerging from parts of the seabed. Schools of fusiliers, trevally, tuna and barracuda can be seen along with reef sharks, sometimes scalloped hammerheads, and rays. Above the waterline, however, an ecological tragedy has quietly transformed Snake Island into Rat Island, affecting life both above and below the waterline. Enter the rats Invasive Pacific rats, likely introduced by passing fishing-boats, have taken over the island. With no natural predators the rodent population has exploded, laying waste to what was long regarded as the biggest seabird breeding colony in the Banda Sea, and one of the largest in the South China and Sulu Seas. There has been a domino effect on the quality of the diving too. Now a grass-roots conservation effort is underway, led by a pioneer of Indonesian liveaboard diving who hopes to reverse the damage. Diver, underwater videographer and owner of the Pindito Edi Frommenwiler is behind this campaign to fund the island’s restoration. When he first dived around Manuk in 1992 he was amazed by the number of red-tailed tropicbirds, frigatebirds and boobies to be seen, joined by the sea-snakes in laying their eggs on the land. However, by that time the numbers of seabirds had already been falling for years. Counts of 90,000 in the early 1970s had dropped as low as 7,000 a decade later, and by 2009 were half that. Now it is the rodents that are too numerous to count. “If you walk 20m along the beach you’re likely to see as many as 30 rats,” Frommenheiler told Divernet. After more than two years of discussions with international conservation NGOs, wildlife biologists and local authorities, Frommenwiler is setting about raising funds for the first phase of a rodent eradication campaign he has long dreamt of orchestrating. Diving community He has put down some seed money and is encouraging other dive-liveaboard operators on the region to do the same, but he also needs the wider diving community to help. He believes that US $25,000 (£18,500) could be enough to kick-start what he hopes will develop into a million-dollar operation supported by the Indonesian authorities. What would be their motivation to intervene? Marine science increasingly highlights how deeply oceanic health relies on intact terrestrial ecosystems, especially on isolated islands, says Frommenwiler. The major aspect of this is the “guano engine”. Seabirds forage across the open ocean, feeding on fish and squid before returning to islands such as Manuk to roost. The guano they leave behind is rich in nitrogen and phosphorus, and rainfall washes these marine-derived nutrients straight into the surrounding waters. Studies on tropical islands show that reefs adjacent to healthy seabird colonies boast up to four times more fish biomass, faster coral growth rates and greater ecosystem resilience than islands on which rodents rule the roost, consuming others’ eggs and young. Biosecurity protocols Eradicating invasive species from a remote volcano with steep, densely vegetated slopes requires meticulous planning. The initial funding, if realised, will cover feasibility studies by expert field teams, the designing of precise baiting strategies that safeguard local non-target species such as native reptiles or land crabs, and working with government agencies, Banda communities and technical conservation specialists to establish long-term biosecurity protocols to ensure that the rats never return. Frommenheiler has been working closely with New Zealand-based Island Conservation and the Ocean Earth Foundation, which have the expertise to carry out the required targeted eradication, using a helicopter or drones to poison the rats without jeopardising Manuk’s ecosystem. “The fact that there are no people or domestic animals on the island should make it easier,” says Frommenheiler. “I don’t want to have something halfway – I want to have a proper job done. “They say that within a year or two of such a rodent eradication there is an explosion of wildlife, not only birds but vegetation and marine life. By being part of this project, I want to give back to the ocean.” Operational details and updates on the campaign can be found here, and donations can be made there too.