Satellite data analysis reveals that algal blooms may have been the culprit behind the mass death of elephants in 2020.
More than 350 elephants mysteriously died after potentially drinking contaminated water, according to a new study published in the journal Science of the Total Environment. The event serves as a warning about the concerning trend of toxin outbreaks driven by climate change. The deaths of the elephants in Botswana’s Okavango Delta were described by scientists as a “conservation disaster.” In 2020, hundreds of elephants of all ages were seen walking in circles before collapsing and dying. Their carcasses were first discovered in northeastern Botswana in May and June 2020, with multiple theories surrounding the cause of death, including cyanide poisoning or an unknown disease, according to The Guardian.
This incident is the largest mass death of elephants ever recorded with an unclear cause, said Davide Lomeo, the study’s lead researcher and a PhD candidate at King’s College London. The study findings suggest the elephants were poisoned by water containing toxic blue-green algal blooms. The climate crisis is increasing the frequency and severity of these harmful blooms.
Researchers used satellite data to analyze the distribution of elephant carcasses in relation to waterholes. Direct sampling was not possible due to a lack of available specimens. The study concluded that elephants traveled over 100 kilometers from waterholes and died within 88 hours of drinking the water. The team examined 3,000 waterholes and found those with a higher frequency of algal blooms in 2020 had higher densities of elephant carcasses. According to Lomeo, the elephants had no choice but to drink from these water sources. It is possible other animals also died after drinking from the contaminated waterholes, but their carcasses were not visible during aerial surveys, and smaller animals’ remains may have been carried off by scavengers.
In the same year, 35 elephants died in neighboring Zimbabwe due to a bacterial infection in their bloodstream linked to prolonged drought conditions. In 2015, 200,000 saiga antelopes died during an outbreak of hemorrhagic septicemia caused by Pasteurella multocida bacteria in Kazakhstan. Such mass die-offs are becoming increasingly common as the planet warms, potentially pushing species closer to extinction.
In southern Africa, 2019 was the driest year in decades, followed by an exceptionally wet 2020. These conditions resulted in significant sediment and nutrient runoff into water bodies, fostering unprecedented algal growth. As climate change progresses, much of the world is expected to become hotter and drier, with sporadic heavy rainfall. Experts conclude that this research highlights the urgent need to monitor water quality to address such issues proactively.
