TEF, Brazil Each morning for the last several weeks, researcher Miriam Marmontel has gazed out at Lake Tef and the Amazon River, through a thick curtain of smoke from thousands of wildfires raging throughout the region, with a sense of dread and dj vu.

Brazil is in the grip of severe drought for the second time in as many years this one already topping 2023 as the worst, most widespread drought in Brazils recorded history. Major rivers throughout the Amazon Basin have plummeted to record low levels, and water temperatures are approaching those that triggered mass die-offs of two species of endangered river dolphins this time last summer.

A year ago, drought drove water temperatures in Lake Tef, in the northern Brazilian state of Amazonas, to as high as 105 degrees Fahrenheit the upper threshold of a hot tub. By late September, the pink and gray carcasses of freshwater dolphins began washing ashore in large numbers.

It was really horrible to see. We saw them dying in front of us, recalled Marmontel, an aquatic mammal expert at the Tef-based Mamirau Institute for Sustainable Development.