The Tagus estuary near Lisbon is Portugal’s largest wetland, a vital habitat and stopover for tens of thousands of migratory birds, including flamingos, black-tailed godwits and glossy ibis. It has also been earmarked as the site of a new airport, leading the environmental law charity ClientEarth and a group of Portuguese NGOs to sue Portugal’s government. When they get their day in court, they will argue that the authorities failed to properly consider how the project would affect an internationally protected nature reserve, and the knock-on effects on other countries visited by the birds. “If you destroy that site, you have an impact not only in Lisbon, but on all the sites up the flyway,” says Anna Heslop, head of wildlife and habitats at ClientEarth. “If the bird populations don’t arrive, they never get breeding.” While environmental lawsuits are not a new phenomenon – the earliest known case, a dispute over water resources, dates back 4,500 years – campaigners are thinking more deeply about how they can tackle the complex problem of modern biodiversity loss. Heslop says litigants are increasingly looking beyond a single site or narrow issue. “Those older school cases will continue. What we aim to do is to have a bigger impact across the whole, like every site in Europe or south-east Asia, or to push governments to be more ambitious. The trick for us is finding cases that will have a more strategic impact; I don’t think that was happening on the same scale before.” The lack of a strategic approach to date is partly a reflection of a wider misunderstanding of the scale of the global biodiversity crisis, says Heslop. “Climate change advocates have done a great job over the last 10, 20 years, of making people realise this is a massive issue and therefore they get more of the resources,” says Heslop. “But they’re twin and equal crises and if you fix climate change and not biodiversity, we’re all screwed.” Guillaume Futhazar, a senior research fellow at the Max Planck Institute for Comparative Public Law and International Law, is part of a team that has been studying biodiversity litigation around the world and is publishing a book on their findings. They knew it was an important issue, but it was not getting the same attention as the growing wave of lawsuits on the climate crisis. Futhazar notes that laws governing different facets of biodiversity, such as endangered species, clean water or land use, are well established in many countries. But he says a better understanding of ecosystem dynamics, the increasingly central role of science in lawsuits and greater judicial awareness of the systemic nature of the problem are helping lawyers choose and structure their cases more carefully. Founded in 1971, the US NGO Earthjustice is no stranger to bringing environmental lawsuits in defence of wildlife and habitats. But, last summer, it launched a new initiative “laser-focused” on using the law to address major drivers of the biodiversity crisis. Timothy Preso, managing attorney of the organisation’s new biodiversity defense program, says it wants to partner with groups whose voices have been ignored in environmental litigation, such as indigenous and frontline communities, as well as raise awareness of critical biodiversity problems. The first case brought under the project was on behalf of the Ojibwe tribes of Wisconsin, challenging the state’s wolf hunting plans on the grounds that they conflict with treaties negotiated in the 19th century. “It raises really critical questions about wildlife management from the perspective of peoples who have been stewards of the environment in Wisconsin for about 15,000 years,” says Preso. “It’s a different approach to those issues.” Biodiversity campaigners are also learning from the success of climate litigation, which, Futhazar says, has “initiated a new creative way of thinking about how to deal with the environment”. Zaneta Sedilekova, a lawyer at Clyde & Co, thinks biodiversity litigation will go through a similar arc to its climate counterpart, with campaigners targeting countries first and then companies. She sees pollination as being at the forefront of such cases because of its importance to food security, “an issue that Covid has really highlighted”. In 2019, Costa Rica’s supreme court ordered the country’s agriculture ministry to undertake a scientific study into the ecosystem impacts of neonicotinoids, while legal action has more recently been threatened against the French government for failing to implement strong regulations to curb the use of bee-harming pesticides. Just as the fossil fuel industry is now in the direct sight of climate litigants, biodiversity campaigners are targeting the private sector too. Last year, indigenous peoples from the Brazilian and Colombian Amazon and NGOs filed a lawsuit against French supermarket chain Groupe Casino for allegedly selling beef products linked to deforestation. Casino argued it took a “rigorous” approach to its supply chains. Heslop sees more corporate liability cases related to biodiversity on the horizon. “The traditional way of telling companies that they were doing the wrong thing environmentally was to convince them that they needed to have some corporate social responsibility,” she says. “But the approach we’ve now taken is to say, well actually you have a duty to your investors and they will be let down if you do this because you’ll end up with a stranded asset or you’ll be sued. We’ve made that narrative for climate and we’re currently looking at how those sorts of cases could be applied for biodiversity.” Just as attribution science is enabling climate campaigners to link the emission of greenhouse gases with the harms caused by subsequent global warming, Sedilekova says growing requirements for corporations to be transparent about their supply chains and to exercise due diligence will help draw a line between a product and biodiversity loss, and hold companies accountable. She adds that the “corporate veil” that has historically shielded parent companies from action against their subsidiaries is increasingly being lifted. “The more supply chain data we have, the easier it will be to trace that ecosystem damage to a jurisdiction which has fast and efficient judicial service or judicial provision which is not corrupted, and where the defendant has a lot of money.” Sedilekova admits it is still hard to persuade businesses that biodiversity litigation is a real risk, but argues that it could be a powerful tool to change corporate behaviour. “The importance of litigation is to not turn one ship around, but to set a precedent so that others don’t wait for it to happen to them.” In the Tagus estuary case, ClientEarth argues the project breaches EU law and could have catastrophic effects on the migratory birds. Heslop hopes the case will have a wider impact and could set a precedent for the protection of other species in the world. “Not just birds, but maybe dolphins or whales or others. That’s where what feels like a very local issue actually could have a huge impact if we’re successful,” she says.