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26 November 2025
Tragedy in the Amazon
Hydrologist Ayan Fleischmann will never forget what he saw when he arrived at Lake Tefé. Dozens of dead freshwater dolphins floated on the surface of the water body. Most of the water had dried up, and what remained was extremely hot. “You couldn’t put a finger in the water,” recalls the scientist from the Mamirauá Institute.
In less than two months, researchers found 209 dead Amazon River dolphins. That represents almost 10% of the local population, wiped out at an astonishing speed. Why did this tragedy occur, and could anyone have prevented it? Research recently published in the prestigious journal Science reveals the true scale of this catastrophe, which extended far beyond Lake Tefé.
Water Heating Up, Lakes Drying Out Due to Amazon climate change
Fleischmann’s team visited 10 lakes in Central Amazonia—in five of them, the water temperature exceeded 37°C. In comparison, the normal temperature of these waters is 29°C to 30°C. In Lake Tefé, which shrank by 75% due to the drought, thermometers showed a record 41°C—not just near the surface, but across the entire two-meter water column.
The Amazon river dolphin is one of the few dolphins living in freshwater
This species is also known as the Amazonian boto. It is found mainly in the Amazon Basin and is considered endangered.
This species is also known as the Amazonian boto. It is found mainly in the Amazon Basin and is considered endangered.
Ecological Disaster in the Heart of the Rainforest
“It was like a big frying pan,” says Fleischmann, describing the mechanism of the catastrophe. Intense solar radiation, shallow water, weak wind, and high turbidity—these four factors created the perfect recipe for ecological disaster.
Temperature Swings Destroy Ecosystems
Worse still, the temperature was not constant: it fluctuated by as much as 13°C over a 24-hour period, from 41°C in the afternoon to 27°C in the early morning. Such rapid temperature changes cause thermal stress, which is fatal to most aquatic organisms.
Dolphins are only the tip of the iceberg. Fish also died en masse, and the lake surface became covered with a red scum of algae. For local communities who rely on fishing and river transport, this was not only an ecological blow but an economic one.
The Amazon river dolphin is much smaller than marine dolphin species
It typically reaches 1.3–1.6 meters in length, placing it among the smallest dolphins in the world. It is usually found in larger groups of 10 to 15 individuals.
It typically reaches 1.3–1.6 meters in length, placing it among the smallest dolphins in the world. It is usually found in larger groups of 10 to 15 individuals.
Amazon Climate Change: It’s Worse Than We Thought
Scientists did not stop at field measurements. They analyzed NASA satellite data dating back to 1990 and discovered a disturbing trend: Amazonian lakes are warming at a rate of 0.6°C per decade—faster than the global average.
Abnormally high temperatures—by definition, something that should occur sporadically—have been appearing regularly in Amazonian lakes since 2013. Since 2018, this state has become almost continuous. “The climate crisis is here and now; there is no doubt about it,” Fleischmann stresses. Furthermore, he issues a warning: one year after the tragedy at Lake Tefé, the Amazon experienced another extreme drought. According to the researcher, such events are no longer incidents; they are the new reality.
Scientists Overlooked the Problem
“This is an overlooked problem,” the scientist admits. Tropical lakes, which are crucial for the food security of local communities, were previously much less studied than those in Europe or North America. Researchers assumed they were stable. How wrong they were is shown by the dead dolphins and the lakes covered in red algae. Urgent action is required to combat Amazon climate change.
Read this article in Polish: Amazonia umiera szybciej, niż myśleliśmy. Nowe szokujące dane NASA
