Rio de Janeiro, BRAZIL - Brazil’s Amazon rainforest experienced a record-breaking drought in 2023, fuelled at least in part by climate change. Research shows that restoring degraded forests could help solve both problems. Not only can restored trees sequester carbon, evidence shows they can also increase rainfall and cool the air.

Climate change fuelled the remarkable 2023 drought that drained major rivers, fuelled huge wildfires and threatened the livelihoods of millions of people in the Amazon rainforest, scientists said on Wednesday.

Deforestation of the Amazon, the world’s largest and most biodiverse rainforest, has decreased rainfall and weakened the ability of trees and soil to retain moisture, researchers found. That made drought more acute and caused the forest to be less resilient to environmental destruction and events like wildfires.

The Amazon River, the world’s largest by volume, and several of its tributaries reached their lowest levels in 120 years of record-keeping last year. One fifth of the world’s freshwater flows through the rainforest.

A severe drought would have still occurred if humans hadn’t so profoundly changed the climate. But the burning of fossil fuels gave it the ranking of “exceptional,” the highest category in the U.S. Drought Monitor classification system, according to the study published by the World Weather Attribution initiative, an international collaboration among scientists that focuses on rapid analysis of extreme weather events.

As global greenhouse emissions continue to increase, the world will see more extreme drought, said Ben Clarke, an author of the study and a researcher at the Grantham Research Institute on Climate Change and the Environment at Imperial College London. “We’re now in the highest classification, so we don’t have any more to assign.”

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An acute drought. Climate change fuelled the remarkable 2023 drought that drained major rivers, fuelled huge wildfires and threatened the livelihoods of millions of people in the Amazon rainforest, scientists said in a new study.

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Droughts around the world. The U.N. estimates that 1.84 billion people worldwide, or nearly a quarter of humanity, were living under drought in 2022 and 2023, a vast majority in low- and middle-income countries. The crisis, worsened partly by climate change, has been accompanied by soaring food prices and could have consequences for hunger, elections and migration.

The study is further evidence that global warming caused by human activity is accelerating the devastation of the world’s largest and most biodiverse rainforest. Parts of the Amazon have started to transform from rainforest that stores huge amounts of heat-trapping gases into drier regions that are releasing the gases into the atmosphere. The result is a double blow to the global struggle to fight climate change and biodiversity loss.

Awareness about the drought’s severity grew after more than 150 river dolphins suffocated to death in October. The drought cut off thousands of people living in remote communities who can only travel by boat. And it fuelled wildfires that made the air some of the most hazardous in the world.

The drought also forced a major hydropower plant to shut down in Brazil and severely reduced the output of others in the region, causing power outages in Ecuador and Venezuela. Countries in the region are highly dependent on river flows to generate electricity, and some had to turn to diesel-powered plants to meet demand.

The group of scientists from Brazil, the Netherlands, Britain and the U.S. used peer-reviewed methods to check whether and to what extent the drought has been influenced by climate change and the El Niño climate pattern, which is associated with drought in the region.

The El Niño did reduce rainfall, scientists found. But increased temperatures caused by the burning of fossil fuels made the lack of rainfall 10 times as likely as it would have been in a hypothetical world where humans hadn’t transformed the climate, they said. Global warming also made the dehydration of soil and plants as well as the reduced river flows 30 times as likely.

Though the study only covered the drought from June to November last year, the dry conditions have persisted into the region’s rainy season, marking the first time that has happened in such a significant section of the forest.

Rains have brought some relief to major rivers, but many remain below normal levels for this time of year. The drought is expected to end when El Niño subsides, which scientists expect within a few months.

Scientists said that governments can mitigate the impact of future droughts by decreasing levels of deforestation, restoring forests and helping communities adapt.

While Brazil and Colombia have recently slashed rates of deforestation in the Amazon, the forest continues to lose tree cover. It has already shrunk by almost a fifth of its original size.

Fuelled by global warming, the drought affected some of the most pristine sections of the forests, said Regina Rodrigues, a professor at Brazil’s University of Santa Catarina and one of the authors of the study.

“We have to reduce emissions,” she said. Otherwise the forest “will not survive climate change.”