Amazon lakes reach ‘unbearable’ temperatures in spas amid mass die-off of pink river dolphins – study | Amazon rainforest

Amazonian lakes are turning into simmering pools hotter than thermal baths as severe heatwaves and drought grip the region, research shows.

One lake’s temperature rose above 40°C (104°F) as water levels fell under intense sunshine and cloudless skies. The extreme heat has caused mass die-offs among endangered Amazon River dolphins and fish, which cannot survive such high temperatures.

The shallow waters of Lake Tefé, which were only two meters deep, reached 41°C – hotter than an average thermal bath. “We couldn’t even put our fingers in the water. It was very hot, not just at the top, but all the way to the bottom,” said lead researcher Ayan Fleischmann of the Mamirauá Institute for Sustainable Development. “You put your finger in and instantly pull it out, it’s unbearable.”

Floating carcasses of up to 200 river dolphins washed ashore over a six-week period around September 2023. No one in the region had seen this happen in the last century, Fleischmann said. “It was completely surreal and really scary.”

This incident led them to examine other bodies of water in the Amazon region. Half of the 10 lakes studied experienced exceptionally high daytime water temperatures, above 37°C, according to the study published in the journal Science.

Researchers analyzed the water temperature of lakes in the central Amazon during the 2023 drought, which was followed by another extreme drought late last year, with new record water levels and significant warming of the lakes. On average, Lake Tefé reaches 30°C during the warmest months, but in 2024 it will reach 40°C.

Amazonian lakes have warmed by 0.3 to 0.8°C every decade over the past 30 years – rates higher than the global average, researchers found. At the same time, they are decreasing. During the 2024 drought, Lake Tefé lost around 75% of its surface area and Lake Badajós shrank by 90%.

Adrian Barnett, lecturer in behavioral ecology at the University of Greenwich, who was not involved in the research, said: “The paper shows the extraordinary impacts of climate change, even on ecosystems as large as the Amazon, and that these are not limited to forests, but also to the aquatic realm. »

“A 10°C increase in water temperature is unprecedented,” he said. “The volume of energy required to achieve this in such enormous volumes of water is breathtaking.”

Most fish, as well as dolphins and manatees, breed normally during the low-water season, Barnett said, adding that it was likely 2023 would have been a reproductively disastrous year for most species. “If this happens repeatedly, then their populations and those of species ecologically related to them will seriously decline. »

There are few local solutions to this problem, according to Barnett. “Something happening on such a scale really requires a systems approach, which means addressing the root cause of the problem, which is fossil fuel emissions and the causes of global warming itself,” he said.

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