Elephants drinking from water holes where toxic algae populations exploded due to climate change suggested to have caused mass die-off
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A new study led by King’s College London has provided more evidence that the mass die-off of more than 300 elephants in Botswana back in 2020 was the result of climate-related poisoning.
As the elephants’ deaths occurred during the pandemic, researchers were initially unable to prevent samples at the time, and for many years the sudden die-off only been speculated to be caused by algal growth. Now, researchers say their analysis all but confirms toxic algae as the cause.
Toxic blooms of blue-green algae – or cyanobacteria – were the likely culprit of the 350 African elephants’ deaths in the north-eastern region of Okavango Delta, after the creatures drank from water holes where toxic algae populations grew due to climate change.
The shift between the wet year of 2019, followed by the very dry spells of 2020 brought up sediments and nutrients from the ground, leading to an unprecedented rate of algae growth.
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Researchers used satellite data and spatial analysis to look at 3,000 waterholes in relation to the location of deceased elephants. Analysis showed that waterholes near carcasses experienced elevated algal levels and repeated bloom events in 2020 compared to previous years.
The team also showed that the locations of elephant carcasses in the 2020 mass die-off were more spread out across the region than in previous years, highlighting that the cause of their death was different to typical mortality patterns.
After drinking, it is estimated elephants walked an average of 16.5km before dying around 88 hours after exposure.
Home to a third of all African elephants, this die-off within their largest remaining populations emphasises the impact of drought and climate change on the Okavango Delta – one of the most important ecosystems on the planet.
‘Southern Africa is projected to become drier and hotter under climate changes, and as a result, waterholes across this region will likely be drier for more months of the year,’ said lead author and PhD student in the Department of Geography at KCL Davide Lomeo.
‘Our findings point to the potential negative effects on water quantity and quality, and the catastrophic repercussions on animals, this could have.’
Important players in the ecosystem
African elephants are a vital keystone species in the landscapes they inhabit and carry out behaviours that produce favourable repercussions for other animals in the ecosystems.
They’re often known as ‘landscape architects’ for their ability to inadvertently create clearings in wooded areas. This allows smaller animals to create pathways to move around ecosystems as well as the opportunity for new plants and forests to regenerate – which may have previously been shrouded from light – increasing biodiversity.
This seemingly ‘destructive’ behaviour of trampling through woodlands and forests also allows food sources typically too high up for smaller animals to reach – like branches – a way of coming back down to ground level.
The creatures also help to disperse seeds in their dung, with some tree species relying entirely on elephants for seed dispersal. This dung is also the perfect fertiliser to support other plant life.
By digging water holes in dry riverbeds, elephants also provide a way for other creatures to access water supplies during bouts of low rainfall.
Such important behaviours highlight how important the conservation and protection of these animals is in the wake of climate change and global warming.
