Climate change triggered the remarkable drought of 2023 that drained major rivers, fueled massive wildfires and threatened the lives of millions of people in the Amazon rainforest, scientists said Wednesday.
Deforestation in the Amazon, the world’s largest and most biodiverse rainforest, has reduced rainfall and weakened the ability of trees and soil to retain moisture, researchers have found. This made the drought more acute and made the forest less resilient to environmental destruction and events such as fires.
The Amazon River — the world’s largest by volume — and several of its tributaries last year reached their lowest levels in 120 years. One fifth of the world’s fresh water flows through the rainforest.
A severe drought would still have occurred if humans had not altered the climate so profoundly. But burning fossil fuels gave it a rating of “excellent,” 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 focused on rapid analysis of extreme weather events.
As global greenhouse emissions continue to rise, the world will see more extreme drought, said Ben Clarke, study author and researcher at the Grantham Research Institute on Climate Change and the Environment at Imperial College London. “We are now at the highest rank, so we have no more to assign.”
The study is further evidence that human-induced global warming is accelerating the destruction of the world’s largest and most biodiverse rainforest. Parts of the Amazon have begun to transform from a rainforest that stores vast amounts of heat-trapping gases to drier areas that release the gases into the atmosphere. The result is a double whammy in the global fight to combat climate change and biodiversity loss.
Awareness of the severity of the drought grew after more than 150 river dolphins died of suffocation in October. The drought has cut off thousands of people who live in remote communities that can only travel by boat. And it sparked wildfires that made the air one of the most dangerous in the world.
The drought also forced the shutdown of a large hydroelectric plant in Brazil and significantly reduced the output of others in the region, causing blackouts in Ecuador and Venezuela. Countries in the region depend heavily on river flows to generate electricity, and some have had to switch to diesel-powered plants to meet demand.
The team of scientists from Brazil, the Netherlands, Britain and the US used peer-reviewed methods to test whether and to what extent the drought has been affected by climate change and the drought-related El Niño climate in the region. .
El Niño actually reduced rainfall, scientists found. However, increased temperatures caused by burning fossil fuels made a lack of rainfall 10 times more likely than it would have been in a hypothetical world where humans had not changed the climate, they said. Global warming also made soil and plant dehydration as well as reduced river flows 30 times more likely.
Although the study only covered the drought from June to November last year, the dry conditions persisted into the region’s rainy season, marking the first time this has happened in such a large part of the forest.
The 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 governments can mitigate the impact of future droughts by reducing deforestation levels, restoring forests and helping communities adapt.
While Brazil and Colombia have recently reduced deforestation rates in the Amazon, the forest continues to lose tree cover. It has already shrunk to almost a fifth of its original size.
Fueled by global warming, the drought affected some of the most pristine parts of the forest, said Regina Rodrigues, a professor at Brazil’s Santa Catarina University and one of the study’s authors.
“We need to reduce emissions,” he said. Otherwise the forest “will not survive climate change”.
