Elephant deaths were first reported between May and June 2020, sparking worldwide concern. While poaching was ruled out, the involvement of algal toxins remained uncertain due to restricted sample collection during the COVID-19 pandemic.
Led by PhD student Davide Lomeo from King's College London and supported by Plymouth Marine Laboratory and the Natural History Museum, the research confirms a high likelihood that cyanobacteria toxins from waterholes were the cause.
"Botswana holds a third of all African elephants, making this event particularly alarming," said Lomeo. "It underscores the growing threats of drought and climate change to the Okavango Delta, a globally significant ecosystem."
Using satellite data and spatial analysis, the research team evaluated approximately 3,000 waterholes. Their findings revealed that waterholes near elephant carcasses experienced unusually high levels of algal blooms in 2020.
Fresh carcasses were often found near waterholes that had elevated algal activity. "We identified 20 waterholes where algal blooms were significantly higher in 2020 compared to previous years," said Lomeo. The average distance elephants traveled after drinking from toxic waterholes was 16.5 kilometers, with deaths occurring within 88 hours.
The extreme shift from a dry 2019 to a wet 2020 likely caused sediments and nutrients to resuspend, creating conditions for unprecedented algal proliferation.
Southern Africa's drier and hotter future, driven by climate change, could exacerbate water quality issues, the study warns. "This highlights the need for comprehensive water quality monitoring and the use of satellite-based tools to detect and address contamination risks swiftly," added Lomeo.
The study, published in Science of The Total Environment, emphasizes the need for proactive ecological management to mitigate similar environmental disasters.
Research Report:Remote sensing and spatial analysis reveal unprecedented cyanobacteria bloom dynamics associated with elephant mass mortality
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