Global warming was the main driver of the severe drought that parched the Amazon River Basin in 2023. That is the alarming conclusion of a new report from World Weather Attribution (WWA), a team of international climate scientists that analyze extreme weather events. El Niño, a natural weather phenomenon long suspected as a key driver of the drought, played a much smaller role.

The authors reviewed the Amazon region’s weather data, drought indices and statistical models from June through December. They found that both El Niño and climate change contributed to reduced rainfall during that period. However, climate change also led to high temperatures, significantly increasing water evaporation from plants and soils.

The combination of little rain and high evaporation triggered what the authors have classified as an exceptional “agricultural drought.” The condition was made 30 times more likely due to global warming. Global temperatures are currently 1.2° Celsius (2.16° Fahrenheit) above preindustrial levels, according to the Intergovernmental Panel on Climate Change (IPCC).

Ben Clarke, one of the report’s authors and a researcher at the Imperial College London, said the results might come as a surprise to some. “As the Amazon drought worsened in 2023, many people pointed to El Niño to explain the event,” he said in a press conference announcing the results. “While El Niño did lead to lower levels of rainfall, our study shows that climate change is the main driver of the drought through its influence on higher temperatures.”

As further evidence of their findings, the authors point to additional impacts climate change has brought to the region. The dry season has been longer and harsher with each passing year. In 2023, the hottest on record, an exceptionally warm North Atlantic Ocean kept rain clouds away, and a series of heatwaves triggered record wildfires.

“These are all footprints of climate change and greatly contributed to this drought,” Regina Rodrigues, co-author of the study and professor of physical oceanography at the Federal University of Santa Catarina in Brazil, said in the press conference. “While droughts are [a] key part of this biome’s history, they are becoming increasingly stronger and widespread.”

With their conclusion that climate change is largely responsible for the drought, the authors predict that dry spells in the Amazon will become more frequent and harsher. If global temperatures exceed 2°C (3.6° F) above preindustrial levels, which could happen by 2034, severe droughts could occur every 10-15 years.

The authors said they believe the worst-case scenario is directly linked to the indiscriminate use of fossil fuels. “With every fraction of a degree of warming caused by the burning of fossil fuels, the risk of drought in the Amazon will continue to increase, regardless of El Niño,” said Clarke.

The report also points to the need to end deforestation, which has reduced the capacity of the forest to retain water, making the region more susceptible to drought.

A hotter and drier future

The 2023 drought started in June when the Amazon River Basin received below-average rainfall. Initially, only the northern part of the basin was affected, but by September, the entire region was experiencing drought conditions. The Solimões, Negro, Madeira and other Amazonian rivers quickly dropped to their lowest levels in 120 years.

More than 30 million people living in the Amazon basin across several countries — including Brazil, Peru, and Colombia — were severely impacted. Many Indigenous, rural and river communities that depend on river transportation to access food, water, health assistance and income were isolated for months.

“The situation was dramatic, especially among the most vulnerable,” said Patricia Pinho, deputy science director of the Amazon Environmental Research Institute. She was not involved in writing the WWA report but is concerned about its findings for local communities. “If extreme droughts continue, what will these communities have to endure in the year 2100?”

For Pinho, the new report sparks a much-needed conversation about how to adjust to climate change. “We need to start talking about the white elephant in the room,” she told Mongabay. “It’s time to invest in adapting the fragile Amazon ecosystem and those who live [in] it to a warmer world.”

A drier Amazon will not only impact humans but also the forest itself. Scientists are still trying to understand what that will look like in the coming years.

“We still don’t know the tree mortality triggered by the 2023 drought because it can take months for trees to die,” Julia Tavares, plant ecologist at Uppsala University in Sweden, told Mongabay. “But I believe they have been severely impacted, either by high tree mortality or reduced growth.”

Tavares is a National Geographic Explorer and the lead author of a 2023 study published in the journal Nature analyzing how Amazon trees cope with extreme drought. In November, she traveled to the Amazon basin to conduct fieldwork, but she could not access parts of the forest due to low water levels in the rivers. “Solimões River was completely dried up. It was very shocking and sad,” she said.

Once she has the data, she expects they will show that trees in the south have borne the burden of the drought. In past research, she found that they were under the greatest pressure from hot and dry conditions. “The area has already seen rapid climate change and disruption to rainfall patterns caused by deforestation, pushing trees to the limits of their ability to cope,” she explained.

Tavares also expressed concerns about what severe droughts in the Amazon would mean for climate change itself. “The forest has the ability to accumulate carbon and balance global warming,” she said. “But as tree mortality increases, they could release carbon and contribute to an even harsher climate change scenario.”

 

Banner image: The river that supplies water to the Kokama Indigenous People of the Porto Praia community was mostly dry in October of 2023. Image © Marizilda Cruppe / Greenpeace.

With half its surface water area lost, an Amazonian state runs dry

Citation:

Tavares, J. V., Oliveira, R. S., Mencuccini, M., Signori-Müller, C., Pereira, L., Diniz, F. C., … Galbraith, D. R. (2023). Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests. Nature. Retrieved from https://www.nature.com/articles/s41586-023-05971-3

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