A new study led by King’s College London has provided further evidence that climate change was behind the tragic deaths of 350 African elephants in Botswana in 2020. The research was published in Science of the Total Environment. It reveals that toxic algae blooms in waterholes poisoned the elephants. This poisoning is a phenomenon exacerbated by climate change. This die-off occurred in the Okavango Delta. The area is home to a third of Africa’s elephants. This underscores the escalating threats climate change poses to ecosystems and wildlife.
ALGAL BLOOMS AND CLIMATE CHANGE: A DEADLY COMBINATION
The study suggests that after an unusually dry 2019, followed by an exceptionally wet 2020, the environmental conditions in Botswana changed significantly. This change triggered a rapid growth of cyanobacteria, or blue-green algae, in waterholes. These algae are capable of producing toxins that are deadly to animals when ingested.
Davide Lomeo is a PhD student at King’s College London and the lead author of the study. He explained that the drastic shift in weather patterns created the perfect conditions for these toxic blooms. This shift involved moving from extreme dryness to excessive rainfall. “Botswana’s Okavango Delta is one of the world’s most important ecosystems. This unprecedented die-off of elephants highlights the escalating impact of drought and climate change on such delicate environments,” Lomeo stated.
THE EVIDENCE: SATELLITE DATA AND ALGAL BLOOM ANALYSIS
Using satellite data and spatial analysis, the research team examined around 3,000 waterholes. They also studied their relationship to the locations where elephant carcasses were found. The results were startling. Waterholes near the carcasses showed elevated levels of algae. There was a significant increase in algal blooms during 2020 compared to previous years. This indicates a clear link between the toxic algae and the mass die-off.
The analysis also revealed that decayed elephant carcasses were more widely spread across the landscape than fresh carcasses. This signals that the mortality event in 2020 was not typical of usual elephant death patterns. “We identified 20 waterholes near fresh carcasses that experienced higher-than-usual algal blooms in 2020 compared to the previous three years,” said Lomeo.
THE IMPACT OF TOXIC WATERHOLES
Elephants that drank from these waterholes were found to have traveled an average of 16.5 km before succumbing to the toxins within 88 hours of exposure. The rapid onset of poisoning indicates the event was unique. The wide dispersion of the carcasses also suggests it was unlike typical mortality events for elephants in the region.
A BROADER ENVIRONMENTAL CRISIS: THE ROLE OF CLIMATE CHANGE
This research highlights the complex relationship between climate change and the growing prevalence of toxic algae in water sources. The region’s extreme weather—fluctuating between drought and heavy rainfall—will increase the frequency and severity of algal blooms. “Southern Africa is projected to become drier and hotter under climate change,” said Lomeo. “As a result, waterholes will likely be drier for longer periods. This will lead to more frequent and severe issues with water quality. Such changes be potentially devastating for wildlife.”
A CALL FOR COMPREHENSIVE WATER QUALITY MONITORING
The study underscores the importance of monitoring water quality across all bodies of water, no matter how small. With climate change exacerbating the risks of algal blooms and water contamination, researchers emphasize the need for robust environmental surveillance. “This research highlights the effectiveness of satellite-based detection in identifying contamination sources. It also emphasizes the urgent need for improved Earth observation technologies to address environmental threats quickly,” Lomeo concluded.
