Ambatovy mine on the east coast of Madagascar is an environmental conundrum fit for the 21st century. Beginning operations in 2012, the multibillion-dollar open-pit nickel and cobalt mine is the largest investment in the history of the country, one of the poorest on Earth. About 9,000 Malagasies are employed by the project, owned by the Japanese company Sumitomo Corporation and Korean firm Komir, which mines minerals destined for the world’s electric car batteries. To construct the mine and the 140-mile (220km) slurry pipeline to port on the Indian ocean, 2,000 hectares (5,000 acres) of pristine rainforest was cleared, destroying vital habitat of the endangered indri, the largest living lemur, and thousands of other species. Alongside the land clearing in a country that has lost nearly a quarter of its tree cover since 2000, the mine has been blamed for air and water pollution, as well as health problems in the local population. The smell of ammonia in residential areas and the pollution of drinking water were revealed in a 2017 investigation. But now the project is set to gain another controversial accolade: the first mine to successfully offset the destruction it caused to a forest, according to an independent scientific study. In a wild west of environmental claims, research published in Nature Sustainability, led by scientists at Bangor University, is likely to be contentious. The theory behind offsetting is that good can cancel out bad. In carbon offsetting, polluters can pay to neutralise emissions from flying or driving by paying for equivalent emission reductions elsewhere. With biodiversity offsetting, the destruction of an ecosystem can be counteracted by protecting another threatened area. Guardian writer George Monbiot has compared offsetting to the sale of indulgences by the Catholic church in the 16th century, when sinners could, in effect, pay to cancel out their bad deeds. Evidence that most offsets do what they claim to do is scarce. “Over 12,000 biodiversity offsets exist worldwide, yet evaluations of their effectiveness are rare and most do not use robust methods,” according to the study of Ambatovy’s offsets. The researchers say Ambatovy is on track to protect an area of rainforest equivalent to the amount it destroyed in other parts of the island. Scientists used statistical analysis to compare the four offsetting schemes established by the mine with similar areas of threatened forest not under protection. The researchers say 1,644 hectares was protected between 2009 and January 2020 by the mine’s conservation schemes, and that if continued at the same rate, 2,174 hectares of rainforest loss would have been avoided by the end of 2021, fully offsetting the destruction at the mine site. “This is a really encouraging result. It suggests that the really large contributions the mine makes to the Malagasy economy can be achieved while minimising tradeoffs with the unique forest habitat,” says lead author Katie Devenish. How the mine is offsetting its forest destruction But the researchers add that “there remain important caveats”. First, the result shows how difficult and expensive biodiversity offsetting is, according to the scientists. Although no official figures were published, it is understood the offsets were backed by heavy investment from the mine, to protect an area of rainforest smaller than most London boroughs. “Ambatovy is interesting to study, in part because it is a flagship project. It’s not in any way representative of most offsets. This isn’t a get-out-of-jail-free card for mines and dams in important biodiversity areas. Offsetting is really hard. The company had to work really, really hard to achieve those biodiversity gains,” says Julia Jones, a conservation professor at Bangor University, and study co-author. “This study should encourage companies to invest more in avoidance and minimisation because if they’re genuinely going to have to offset unavoidable impacts, it’s going to be really hard and expensive,” Jones says. Second, the burden of offsetting falls on vulnerable people who depend on the forest for their livelihoods – forcing them to change their behaviour – rather than the mine, say researchers. The reductions in the Ambatovy offsets were gained by slowing land clearing by subsistence farmers in other areas. “The poorest people most dependent on the forests are the ones that will bear the cost of achieving no net loss outcomes because they can no longer exploit the forest in the way that they traditionally did,” says Martine Maron, a professor at the University of Queensland and author of a paper on the many meanings of no net loss in 2018, who was not involved in the study. “It’s an issue that has to be solved because we can’t be beholden to tradeoffs between people and nature. We’ve got to find solutions that work for both,” she says. Dr Sarobidy Rakotonarivo, an environmental socioeconomist and fellow at the Forest4Climate&People project at Bangor University, has studied the impact of conservation policies on people in eastern Madagascar. She says there has been too little investment in livelihoods and food security. “All too often, I think there is this lack of understanding about how much is needed to support people reliant on subsistence agriculture,” she says. Many agree there is the need for more research on offsetting schemes. While they underpin the environmental commitments of some of the biggest companies on Earth, all too often it is unclear whether the projects are having any impact on the environment. Sophus zu Ermgassen, an ecological economist at the University of Kent, who was not involved in the latest research, says: “The paper is awesome. It is at the very cutting edge methodologically as it’s really hard to know if nature conservation works. “Offsetting can be done but it cannot be overstated how unique this case is and how much resource needs to go into making it work – levels of resourcing that nearly all state or national biodiversity offsetting policies fail to provide,” he says. Ambatovy has welcomed the report and told the Guardian: “Ambatovy is committed to acting in a responsible manner and to working with integrity, transparency, respect and the highest ethical standards.” In response to the 2017 allegations, it said pollution and water quality are monitored in line with international standards and a grievance mechanism is open to those affected.