Recently it was confirmed that around 350 elephants died due to climate change in Botswana. It happened during 2020 from drinking from water wells where toxic algae populations had increased.
The first elephant carcasses were sighted in the northeastern sector of the Okavango Delta between May and June of that year, but it was soon ruled out that poaching was the cause.
Hundreds of elephants died from climate change: how it happened
An analysis led by King’s College in London demonstrated that it is very likely that the animals were poisoned this way. Toxic blooms of green-blue algae, or cyanobacteria had developed there after a very wet year followed by a very dry one.
Davide Lomeo, a doctoral student in the Department of Geography at King’s College, confirmed it in a statement.
“Botswana is home to a third of all African elephants. This unprecedented mortality within its largest remaining population underscores the growing concerns about the impact of drought and climate change in the Okavango Delta, one of the world’s most important ecosystems,” he pointed out.
The event sparked global concern and it is now known that a total of 350 elephants died.
Toxins produced by algae growing in watering holes were one of the suspected causes, although the evidence has not been conclusive, in part because it occurred during the COVID-19 pandemic, when movements were restricted and this prevented the collection of samples at that time.
The deaths of 25 elephants in neighboring Zimbabwe from septicemia in the same year had raised some doubts about whether the algae toxins were the reason for the deaths in Botswana.
However, in an article published in the journal Science of The Total Environment, the team indicated that their analysis practically confirms that toxic algae are the cause.
The help of satellite data
By combining satellite data and spatial analysis, the team examined the relationship between around 3000 watering holes and the locations of the dead elephants.
The study revealed that the water wells near the carcasses showed elevated levels of algae and repeated bloom events in 2020 compared to previous years. Particularly during the period associated with the mass mortality event.
“We identified 20 water wells near fresh carcasses that experienced an increase in algae bloom events in 2020 compared to the previous three years combined,” said Davide.
“These water wells also exhibited the highest average algae biomass from the 2015-2023 period,” he added. After drinking, it was estimated that the elephants walked an average of 16.5 km from the toxic water wells and died within 88 hours of exposure.
These findings suggest a higher risk and likelihood of algae toxins being present in these water wells, he added.
The team believes that the shift from a very dry 2019 (the driest year in decades in the region) to an extremely wet 2020 may have caused a resuspension of significant amounts of sediment and soil nutrients, which promoted unprecedented algae growth.
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