A new study from King’s College London has provided further evidence that deaths of 350 African elephants in Botswana during 2020 resulted from the their water consumption from wells where toxic algae has exploded because of climate change.
The lead author of , Davide Lomeo, says analysis shows the animals were likely poisoned where cyanobacteria developed after a very rainy year followed by a very dry one.
The researcher, who is a PhD student in the Department of Geography at King’s College London and co-supervised by the Plymouth Marine Laboratory (PML) and the Natural History Museum, said the country holds a third of all elephants on the African continent.
“This unprecedented die-off within its largest remaining population highlights growing concerns around the impact of drought and climate change on the Okavango Delta, one of the world’s most important ecosystems.”
Elephant carcasses were first spotted in the northeastern sector of Botswana’s Okavango Delta between May and June 2020, but poaching was soon ruled out as the cause.
The event generated global concern, with a total of 350 elephants killed.
Toxins produced by algae growing in water wells were one suspected cause, although evidence remains inconclusive.
The deaths of 25 elephants in neighboring Zimbabwe, also in 2020, raise some doubts about algal toxins being the reason for the deaths in Botswana.
However, as published in the journal Science of The Total Environment, the research argues that its analysis all but confirms toxic algae as the cause.
Combining satellite data and analysis, the study team examined the relationship between around 3,000 water wells and the location of dead elephants.
The analysis revealed that water holes near the carcasses showed high levels of algae and repeated bloom events in 2020 compared to previous years — particularly during the period associated with the mass mortality event.
The team also showed that decomposing elephant carcasses were more widespread across the landscape than fresh carcasses, indicating that die-offs in 2020 were different from typical elephant mortality patterns.
After drinking, it is estimated that the elephants walked an average of 16.5 km from the toxic water holes and died within about 88 hours of exposure.
These findings suggest an increased risk and likelihood of the presence of algal toxins in these water holes.
The team believes that the change from a very dry 2019 — the driest year in decades in the region — to an extremely wet 2020 may have led to the resuspension of significant amounts of sediment and nutrients from the soil, promoting unprecedented algal growth.
The research also involved researchers from the University of Botswana, the Natural History Museum in London, Queen’s University Belfast and the Plymouth Marine Laboratory (PML).
*Published by Pedro Jordão, from CNN in São Paulo
