On 4 October, Brazilians will go to the polls to elect a president and government. Former president Jair Bolsonaro, under house arrest, cannot run. But his son Flávio is on the ballot. If elected, the 45-year-old senator is widely expected to govern as his father did, which is sparking fears for the future of the Amazon rainforest.

During Jair Bolsonaro’s presidency between 2019 and 2023, deforestation in the Amazon soared, reaching a 15-year-high in 2021.

“We have nothing to believe Flávio will do anything differently from his father. If anything, the signs are that it’s going to be far worse,” says Claudio Angelo, international policy coordinator at Brazil’s Climate Observatory. “This is a do-or-die moment for the Amazon, really.”

Flávio Bolsonaro is looking to unseat President Luiz Inácio Lula da Silva, known as Lula. With the younger Bolsanaro currently embroiled in a corruption scandal, the environment has received relatively little attention during campaigning

“But for the rest of the world, the major question here is the Amazon,” says Philip Fearnside, an ecologist at Brazil’s National Institute for Amazonian Research (INPA).

The Brazilian Amazon’s 4.2 million square kilometres of rainforest regulate global climate patterns and hold huge stocks of carbon – roles that are increasingly important as climate change accelerates.

“The Amazon is a key element in whether climate change escapes human control, which is very close to happening,” says Fearnside. If the forest collapses, he says, the associated increase in emissions “would be the straw that breaks the camel’s back”.

Annual Amazon deforestation surged from 7536 square kilometres in 2018, before Bolsonaro took office, to 11,594 square kilometres in 2022, shortly before he departed.

Experts say the former president encouraged a wave of land-grabbing and illegal mining with his pro-development rhetoric and gutted environmental agencies so they were powerless to stop invaders.

“It’s still hard to believe what happened,” says Izabella Teixeira, Brazil’s environment minister between 2010 and 2016, initially under the presidency of Lula and later under the presidency of Dilma Rousseff.

Since returning to office in 2023, Lula has restored the power of environmental agencies, halving Amazon deforestation to 5731 square kilometres between August 2024 and July 2025.

In a recent TV interview, Flávio Bolsonaro refused to say that climate change existed, instead referring to “extreme climate events” and “cyclical periods”. And during his time as a senator, he proposed legislation that critics said threatened Brazil’s native vegetation. Given this record, and his close ties to his father – and to Donald Trump – experts are concerned that his election would be followed by an increase in deforestation rates.

“We don’t know exactly what Flávio Bolsonaro’s policy will be,” says Teixeira. “But we do know he is a climate change denialist and believes environmental protections are irrelevant.”

Brazil’s largest Indigenous organisation, APIB, had said it fears Flávio Bolsonaro will open Indigenous lands to critical-mineral extraction, and that a Bolsonaro victory would mark “the return of a death project”.

Flávio Bolsonaro’s campaign also pledges zero illegal deforestation by 2029. “There are two ways to achieve that. One is to actually stop deforestation. The other, more likely way, is to just legalise the deforestation that’s going on,” says Fearnside.

A spokesperson for Lula’s campaign told that the president’s current term was about rebuilding environmental institutions after Jair Bolsonaro’s presidency of “total neglect and denialism”. The next term would be about “implementing and gaining scale”, with a focus on tougher enforcement, climate adaptation and Brazil’s 2035 climate targets.

The Flávio Bolsonaro campaign did not respond to questions about its environmental policy.

Angelo says Brazil’s environmental organisations fear a Flávio Bolsonaro government would resemble Trump’s second term. He says the political know-how gained from the Jair Bolsonaro presidency could allow them to enact laws more quickly.

Flávio is also likely to face fewer political constraints than his father, not least because he has said he would appoint five new supreme court judges.

“Wildcat mining would explode, deforestation would go up and everything we already had during the first Bolsonaro administration would come back even stronger,” says Angelo.

Lula’s environmental policy has also been criticised.

His government has promoted major infrastructure projects such as improving the BR-319 Amazon highway and backed new oil exploration near the mouth of the river basin – projects that would drive deforestation and lock in fossil fuel production.

Still, the choice remains stark, says Angelo. The election will shape not only the future of the rainforest but also global climate diplomacy.

In an era of failing climate leadership, Lula oversaw new initiatives including a self-sustaining fund to pay tropical countries for keeping forests standing and a global road map to transition away from fossil fuels.

Under Flávio Bolsonaro, Angelo predicts that Brazil would probably withdraw from climate diplomacy and ignore its own international climate commitments.

“I don’t think a fourth Lula term would be great for the environment – but it’s really our only hope of keeping the forest standing and keeping any climate policies in place,” says Angelo.