Joe Biden will become the first sitting U.S. president to set foot in the Amazon rainforest during a brief stop Sunday in the Brazilian city of Manaus, coming as the U.S. is expected to scale back its commitment to combating climate change under the incoming administration of Donald Trump.

The massive Amazon — it’s about the size of Australia — stores huge amounts of the world’s carbon dioxide, a greenhouse gas driving climate change, even as it's rapidly deforested.

Biden is expected to take an aerial tour over part of the world's largest tropical rainforest, meet local and indigenous leaders and visit an Amazonian museum as he looks to highlight his commitment to the preservation of the region.

The Biden administration announced plans last year for a $500 million contribution to the Amazon Fund, the most significant international cooperation effort to preserve the rainforest, primarily financed by Norway.

So far, the U.S. government said it has provided $50 million, according to a July statement from its embassy in Brazil, adding it would “continue to work with Congress to secure the remaining funding for the Amazon Fund and related activities through 2028.”

“It’s significant for a sitting president to visit the Amazon. ... This shows a personal commitment from the president,” said Suely Araújo, former head of the Brazilian environmental protection agency and public policy coordinator with the nonprofit Climate Observatory. “That said, we can’t expect concrete results from this visit."

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She doubts that a “single penny” will go to the Amazon Fund come January.

The Trump administration is highly unlikely to prioritize the Amazon — or anything related to climate change. The Republican president-elect already said he'd again pull out of the Paris agreement, a global pact forged to avert the threat of catastrophic climate change, after Biden recommitted to the agreement.

Trump has cast climate change as a “hoax” and said he will eliminate energy efficiency regulations by the Biden administration.

The Amazon is the world’s largest tropical rainforest, home to Indigenous communities and 10% of Earth’s biodiversity. It also regulates moisture across South America. About two-thirds of the Amazon lies within Brazil, and scientists say its devastation poses a catastrophic threat to the planet.

The forest has been suffering two years of historic drought that have dried up waterways, isolated thousands of riverine communities and hindered riverine dwellers’ ability to fish. It's also made way for wildfires that have burned an area larger than Switzerland and choked cities near and far with smoke.

When Brazilian President Luiz Inácio Lula da Silva took office last year, he signaled a shift in environmental policy from his predecessor — far-right Jair Bolsonaro. Bolsonaro prioritized agribusiness expansion over forest protection and weakened environmental agencies, prompting deforestation to surge to a 15-year-high.

Lula has pledged “zero deforestation” by 2030, though his term runs through the end of 2026. Forest loss in Brazil’s Amazon dropped by 30.6% in the 12 months through July from a year earlier, bringing deforestation to its lowest level in nine years, according to official data released last week.

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In that 12-month span, the Amazon lost 6,288 square kilometers (2,428 square miles), roughly the size of the U.S. state of Delaware. However, that data fails to capture the surge of destruction this year, which will only be included in next year’s reading.

Despite the success in curbing Amazon deforestation, Lula’s government has been criticized by environmentalists for backing projects that could harm the region, such as paving a highway that cuts from an old-growth area and could encourage logging, oil drilling near the mouth of the Amazon River and building a railway to transport soy to Amazonian ports.

Biden is making the Amazon visit as part of a six-day trip to South America, the first to the continent of his presidency.

On Sunday morning, he's wrapping a visit to Lima, Peru, where he took part in the annual Asia-Pacific Economic Cooperation summit and met with Chinese President Xi Jinping.

After his brief stop in Manaus, he's headed to Rio de Janeiro for this year's Group of 20 leaders summit.