Deforestation in the Brazilian Amazon has fallen to its lowest level since records began, new government data shows.

But whether this globally important success is maintained or reversed is on a knife edge ahead of a presidential election run-off on 25 October between two candidates with sharply different visions for the future of the rainforest and how that affects relations with the US under Donald Trump.

The incumbent, Luiz Inácio Lula da Silva, fell behind in the first round of voting despite an impressive record in slowing the destruction of the Amazon while also reducing poverty and food insecurity. He is up against Flávio Bolsonaro, son of the former president Jair Bolsonaro.

The Prodes satellite data series, which is considered the most accurate measure of deforestation, showed forest clearance in the Amazon fell by 41.8% over the past year to 3,335 square kilometres, the lowest value since the start of such measurements in 1988.

This beats the previous record low by 1,236 sq km, equivalent to an area the size of Rio de Janeiro.

Since the start of the Lula administration in 2022, the deforestation rate has slowed by 71.2%, according to the data collated by Brazil’s National Institute for Space Research. This was largely as a result of stronger enforcement measures and state investments in environmental agencies.

The Brazilian states with the worst records in 2026 were Pará, which registered 33.9% of all Amazon deforestation in the year, Mato Grosso (25.5%) and Amazonas (15.7%).

However, even in those places the figures were down by more than 45% on the previous year. The state where the problem grew worse (up 0.4%) was Roraima, which is a Bolsonaro stronghold.

Outside the Amazon, the neighbouring biome of the Cerrado – an area of savannah – registered its lowest annual deforestation since 2001, at 5,516 sq km. This is significant as the Cerrado has long been treated as an area of environmental sacrifice, where soya and beef producers could clear more forest than they were allowed to do in the Amazon. Over the past four years, Cerrado deforestation has fallen by 48.4%.

These spectacular results, which brought some conservationists to tears, stand in sharp contrast to the 2019-23 term of Jair Bolsonaro, who oversaw a 59.5% increase in Amazon deforestation, roughly equivalent to destroying more than a million trees a day, through cuts to forest protection agencies, reduced implementation of penalties for environmental crimes, and verbal encouragement for illegal miners, loggers and land grabbers.

Bolsonaro was then convicted for attempting a coup but his son has vowed to release his father and let him take any position in government that he chooses.

The younger Bolsonaro has followed his father’s example in courting support from predatory landowners in the Amazon and other extractivist interests while ignoring the climate crisis in his manifesto.

The former environment minister Marina Silva, who has arguably done more than anyone to defend the rainforest, has warned that Flávio Bolsonaro will try to finish his father’s “perverse project” to destroy the Amazon.

The stark contrast between the two candidates is evident in the electoral results map in the Amazon, where Bolsonaro secured the most votes near areas of degraded forest, mines, ranches and soya monocultures, while Lula’s support was higher in big cities or areas of forest where the vegetation was relatively intact.

It is also evident in their very different relations to the US. Lula has warned that Trump is trying to colonise the country and capture its resources. He defends the Amazon as a sovereign asset for Brazil, an important home for Indigenous peoples and an essential element in global efforts to stabilise the climate.

The Bolsonaro family, by contrast, has close ties to the US. Flavio’s brother Eduardo has lived in Texas since last year and called upon the Trump administration to impose punitive tariffs on his own country.

Jair has saluted the US flag and led chants of “USA, USA”. If the family secure power, they are expected to shift Brazil’s trade priorities, particularly when it comes to critical minerals, from China and Europe to the US.

The biggest difference, however, is likely to be the far right’s willingness to exploit natural resources in the Amazon and elsewhere in Brazil and then sell them to the highest bidder, regardless of environmental and social concerns.

Conservation groups said the new deforestation data showed how much was at stake in the presidential run-off.

Marcio Astrini, the executive secretary of the Climate Observatory, said: “The figure makes it clear that putting an end to forest destruction in Brazil is entirely possible.

“However, everything depends on the election result. The country will decide whether we move toward the end of deforestation or toward the end of the forest.”