It was a major mystery.
Between May and June in 2020, the dead carcasses of African elephants began appearing in Botswana’s Okavango Delta. Elephants of all ages were seen walking in circles before collapsing and dying. Aerial surveys showed that at least three hundred and fifty elephants died in the event, though the true toll was likely higher. It was a major conservation disaster.
The southern African country of Botswana is the home of one third of all African elephants. These animals are endangered and at risk of extinction due to the fragmentation and loss of their habitat and poaching for the illegal trade in the ivory of their tusks. At the time, travel restrictions due to the COVID-19 pandemic hampered investigation of the cause of the tragedy.
In 2024 a team of British and Botswanan environmental scientists published an analysis that identified the likely cause of the mass dying. The researchers used data from orbiting satellites to analyze the spectrum of light reflected from watering holes where elephants drank. In all, the researchers studied three thousand watering holes.
The data showed that some of these watering holes had experienced blooms of algae containing deadly toxins. An analysis of the distribution of the elephant corpses showed that they clustered near these watering holes. The researchers link the algae bloom to global climate change.
In southern Africa, 2019 was the driest year in decades, and the following rains in 2020 provided ideal conditions for algae growth. They warn that as the climate gets warmer due to human-caused global climate change, such events may happen more often.
Further Reading
- Satellite evidence bolsters case that climate change caused mass elephant die-off
- New study links Botswana’s 2022 elephant die-off to toxic algal blooms
- Climate induced poisoning killed more than 300 African elephants, study suggests
- Remote sensing and spatial analysis reveal unprecedented cyanobacteria bloom dynamics associated with elephant mass mortality