At least 350 elephants died under mysterious circumstances in Botswana in 2020, sparking global concerns as scientists puzzle over the cause of the deaths. Four years later, a study conducted at King’s College London finally revealed the answer. According to the research, a “toxic mix” of open water contaminated by a species of cyanobacteria that releases cyanotoxins contaminated water holes in the area, leading to mass elephant deaths.
The study, combining satellite data and spatial analysis, revealed that 20 water holes across approximately 6,000 square km in the Okavango Delta were contaminated. It is estimated that after drinking alcohol, elephants walked an average of 16.5 km from poisoned bodies of water and died within about 88 hours of exposure.
“Our results highlight that seasonal, primarily rainfall-based pans, rather than permanent water bodies (i.e., lakes, rivers, and lagoons) within the Panhandle, were the likely source of cyanotoxin exposure,” said David Lomio, lead scientist. Said study.
Notably, the dead elephants were of different ages, with their tusks intact, leading scientists to rule out death due to poaching. Additionally, no carcasses of other wildlife or livestock species were observed at the time of the aerial survey.
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What promoted the growth of algae?
Not all cyanobacteria or blue-green algae are poisonous, but some cyanobacteria produce a type of lethal algal bloom (HAB) in standing water. According to the study, the transition from a dry 2019 (the driest year in the region in decades) to an extremely wet 2020 could spur unprecedented algae growth due to the resuspension of significant amounts of sediment and nutrients from the ground.
“Scientists believe that cyanotoxin production is related to certain environmental factors, for example, sudden increases in water temperature, nutrient loading, salinity,” Mr Lomio said.
Scientists have warned that due to climate change such incidents may happen again and again in the future.
“Southern Africa is projected to become drier and hotter due to climate change, and as a result, water sources in the region are likely to dry up for more months of the year. Our findings point to potential negative impacts on water quantity and quality , and it can have devastating effects on animals.
The study outlines the serious ecological consequences of toxic algae accumulation, while emphasizing the critical need for water quality monitoring in all water bodies, including the smallest water bodies.
