River dolphins are dying by the dozens in the Brazilian Amazon rainforest over the past week, along with thousands of fish. Experts warn that worse could follow if water temperatures remain elevated due to a severe drought in the region.

The Mamiraua Institute, part of Brazil’s Ministry of Science, Technology, and Innovation, reported the discovery of over 100 dead river dolphins over the past nine days in the vicinity of Tefe Lake, a crucial area for local mammals and fish. Distressing video footage from the institute depicted vultures scavenging the dolphin carcasses along the lakeside, while local media documented thousands of fish fatalities.

Experts have attributed the dolphin deaths primarily to soaring water temperatures in the region. In the past week, temperatures in the Tefe Lake area have surpassed 39 degrees Celsius (102 degrees Fahrenheit).

The Brazilian government’s Chico Mendes Institute for Biodiversity Conservation, responsible for managing conservation areas, deployed teams of veterinarians and aquatic mammal specialists to investigate the escalating deaths.

According to Miriam Marmontel, a researcher from the Mamiraua Institute, approximately 1,400 river dolphins inhabited Tefe Lake, and as few as 2,000 of the animals in the world. “In one week, we have already lost around 120 animals… which could represent 5% to 10% of the population,” Marmontel said.

The impact of the drought extends beyond wildlife, affecting impoverished riverside communities and leaving boats stranded in dry rivers. Amazonas Governor Wilson Lima declared a state of emergency in response to the crisis.

Ayan Fleischmann, Geospatial coordinator at the Mamirauá Institute, emphasized the dire situation facing riverside communities in the Amazon region. “Many communities are becoming isolated, without access to good quality water, without access to the river, which is their main means of transportation,” he explained.

While investigations are still underway to determine the exact cause of the dolphin deaths, the prevailing theory points to the persistently high temperatures as the leading culprit.