In October this year, the depth of some sections of the Negro River in the Amazon rainforest near Manaus, Brazil, shrank to 12.7 meters, the lowest water level in the 120 years of recorded measurement. In Lake Tefi, about 500 kilometers west of the area, scientists found the bodies of more than 150 dolphins. The cause of the death of the dolphins was not low water levels, but probably because the temperature of the lake was close to 40°C.
Rivers flowing through the Amazon rainforest are falling to their lowest levels on record. Image source: "Nature" website
These are all symptoms of the unprecedented drought in the Amazon rainforest this year. Climate change is certainly at play, but rainforest researchers say two other factors, including deforestation, are exacerbating the crisis. Moreover, the drought crisis has cut off food supplies to communities around the river, forcing First Nations to use dirty, contaminated water, causing them gastrointestinal distress and other illnesses.
The British "Nature" magazine quoted Luciana Getty, a climate change researcher at the Brazilian National Institute for Space Research (INPE), as saying that there are three reasons for the drought. The first is indiscriminate deforestation in the forest. "This is killing the resilience of the rainforest and making it drier and hotter."
Deforestation stifles rainforest resilience
INPE data shows that although deforestation in the Amazon fell by 42.5% from January to July this year compared with the same period last year, deforestation has been at record highs for many years. Researchers point to agribusiness as the main culprit. MapBiomas is a consortium of academic, business and non-governmental organizations monitoring land use in Brazil. A report from the alliance noted that over the past 40 years, ranchers and farmers have expanded Brazil's agricultural area by about 50%, mostly in the Amazon, by cutting down trees.
Getty notes that about 20% of the Amazon rainforest has been logged and 40% is degraded, meaning that while the trees are still standing, their health has deteriorated and they are prone to fires and droughts.
El Niño causes less precipitation
The second factor contributing to the drought is the El Niño weather pattern that has begun to emerge this year.
El Niño occurs every 2-7 years. During El Niño, the winds that normally blow from east to west along the equator weaken or reverse, and warm water rushes into the eastern tropical Pacific. El Niño changes precipitation patterns in South America, causing air to be dry in the north, where the rainforests are located, and humid in the south. As a result, Uruguay has been hit by torrential rains, and over the past few months, flooding has killed dozens and left thousands homeless in Paraguay, Argentina and southern Brazil.
At the same time, data from Brazil’s National Natural Disaster Warning and Monitoring Center showed that between July and September this year, precipitation in eight states in northern and northeastern Brazil was the lowest in 40 years. These months are the peak of “fire season” across much of the Amazon.
Additionally, Erica Berenguer, an ecosystem researcher at the University of Oxford in the United Kingdom, noted that ranchers and other rainforest clearers generally do not burn trees when it rains or the air is moist. But as El Niño dries the air in the rainforest, tree clearers are now also burning trees. This not only exacerbated the harsh conditions but also sparked some uncontrollable fires. In September this year, Berenguer visited Pará in the north.
Warming sea water is also an important reason
The third factor causing severe drought in the Amazon is unusually warm waters in the North Atlantic.
María Assuncao Díaz, a climatologist at the University of São Paulo in Brazil, pointed out that climate change is one of the reasons for the warming of seawater. Warming of certain waters affects the Intertropical Convergence Zone. Karina Lima, a geographer at the Federal University of Rio Grande do Sul, pointed out that this area around the earth close to the equator is one of the main weather systems in the tropics and is also an area where clouds and rain form. The area has shifted northward, away from northern Brazil.
All of these factors have combined to cause a record drought in the Amazon this year. Dias said that the Amazon has experienced droughts and even extreme droughts in 1912, 1925, 1983, 1987, 1998, 2010, 2016 and 2023, but severe droughts are "increasingly frequent."
What's more worrying, Getty said, is that the current El Niño phenomenon has just begun, so "the situation is not going to get better for a while." Dias also pointed out that if the sea surface temperature in the tropical Pacific is 2.5°C higher than the average temperature, a "super El Niño" phenomenon may even occur. The World Meteorological Organization issued a report on November 8 saying that there is a 90% chance that the El Niño phenomenon will last until at least the end of April next year.
It's difficult to predict when the next drought will hit the Amazon, and Lima said climate change is disrupting the timing of El Niño events, which would be a serious blow to the Amazon rainforest, which is already suffering from deforestation, warming and drying.