elephant watering hole – AMANDA STRONZA – ECOEXIST
Nov 29. () –
New evidence supports that the death of 350 elephants in Botswana during 2020 was due to drinking water wells where toxic algae populations had increased due to climate change.
An analysis led by King’s College London shows that the animals were most likely poisoned by drinking from water holes where toxic blooms of blue-green algae, or cyanobacteria, had developed after a very wet year followed by a very dry one.
Davide Lomeo, a PhD student in the Department of Geography at King’s College, said in a statement: “Botswana is home to a third of all African elephants, and this unprecedented die-off within its largest remaining population underscores growing concerns around the impact of drought and climate change. in the Okavango Delta, one of the most important ecosystems in the world“.
The first elephant carcasses were sighted in the northeastern Okavango Delta between May and June 2020, but poaching was soon ruled out as the cause.
The event sparked global concern and A total of 350 elephants are now known to have died.
Toxins produced by algae growing in waterholes were one of the suspected causes, although tests have been inconclusive, in part because it occurred during the COVID-19 pandemic, when movement was restricted and this prevented the collection of samples at that time.
The deaths of 25 elephants in neighboring Zimbabwe from sepsis in the same year cast some doubt on whether algae toxins were the reason for the deaths in Botswana.
However, in an article published in the magazine Science of The Total Environmentthe team says their analysis practically confirms that toxic algae is the cause.
SATELLITE DATA
Combining satellite data and spatial analysis, the team examined the relationship between some 3,000 watering holes and the locations of dead elephants.
Their analysis revealed that water holes 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.
The team also showed that decomposing elephant carcasses were more dispersed across the landscape than fresh carcasses, indicating that mortality in 2020 was different from typical elephant mortality patterns.
“We identified 20 water wells near fresh carcasses that experienced an increase in algal bloom events in 2020 compared to the previous three years combined. These water wells also exhibited the highest average algal biomass of the period 2015-2023“said Davide.
After drinking, the elephants were estimated to walk an average of 16.5 km from the toxic water holes and died within 88 hours of exposure.
These findings suggest an increased risk and likelihood of the presence of algal toxins in these water wells, he added.
The team believes that the change 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 has promoted unprecedented algae growth.
Davide said: “Southern Africa is expected to become drier and warmer due to climate change and, as a result, water wells in this region will likely be drier for more months of the year. Our findings point to possible negative effects on water quantity and quality, and the catastrophic repercussions on animals that this could have.
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