If there is a glimmer of light amid the darkness of recent reports from the Brazilian Amazon, where deforestation is accelerating along with threats to the indigenous people who live there, it could lie in the growing power of climate diplomacy, combined with increased understanding of the crucial role played by trees in our planet’s climate system. The deal agreed a month ago between the EU and the Mercosur bloc of Brazil, Argentina, Paraguay and Uruguay (Venezuela is suspended) enhances European leverage with its South American trading partners. Already, the prize of access to EU markets is credited with having convinced Brazil not to follow Donald Trump’s lead by withdrawing from the Paris climate deal. Now the EU must strengthen its environmental commitments, as a letter from 600 scientists demanded before the deal was agreed.

Brazil’s president, Jair Bolsonaro, made no secret of his plans to promote development, and drew powerful support from Brazil’s agribusiness and mining interests before last year’s election. He scorns conservation and indigenous rights, claiming recently that his foreign opponents want Amazon tribes to live “like cavemen”. Satellite data shows the message is getting through, with clearances up sharply and this month set to be the first in five years in which Brazil has lost an area of forest bigger than Greater London. Illegal gold mining too is spreading. Last week one of the leaders of the Waiãpi people, Emyra Waiãpi, was found stabbed to death on a remote reserve in the state of Amapá, after armed men raided his village.

The situation is of critical importance, and all the more disturbing given recent climate projections. Protecting the world’s largest tropical rainforest, thought to contain 30% of all species, has rightly been an important focus for Brazilian and global environmental policies for two decades. But less than a year after Mr Bolsonaro’s election, the national environment agency appears significantly weakened, with enforcement actions during the first half of 2019 down 20% on the same period in 2018. Prosecutors and activists have been intimidated, while public opinion is mostly engaged elsewhere (for example, on pension reforms).

Mr Bolsonaro’s pitch to domestic and foreign audiences is the same: the Brazilian Amazon is none of anyone’s business but Brazil’s. With this in mind, the forest’s international defenders must tread carefully. Denunciations of the new government’s pro-business policies in the name of biodiversity could prove counterproductive. Instead, environmentalists, including Green politicians, should work through European political institutions, in the knowledge that the EU is the second-biggest market for Brazilian exports. Firm pressure must be brought to bear in the form of strong environmental regulations, and a refusal to compromise on transparency. Beef or soya farmed on illegally cleared land must not be imported to Europe.

At the same time, Brazilian civil society organisations need support to challenge and resist illegal incursions, and to champion their country’s existing commitments – including to reforestation of cleared areas. Climate education must be promoted globally, so that people can better understand what is going on (the murder of a journalist linked to rainforest exploitation is already the subject of a drama on Brazilian TV). Forest clearances may produce short-term gains, but in the longer term they can only bring disaster. Brazil is in a strong position, at the next round of UN climate talks (moved to Chile after Mr Bolsonaro withdrew an offer to host), to demand increased international aid for the vast Amazon region. If we claim this tropical wilderness as a green lung for the world, we cannot expect Brazil to conserve it alone.