Satellites find likely cause of mysterious African elephant deaths in 2020

The shocking and unexplained deaths of over 300 African elephants in early 2020 – one of the largest mass mortality events of wild mammals in recent history – were most likely due to toxins in the water increasing due to climate extremes, according to a new analysis of a decade of satellite data.

In the mass die-off, a “conservation disaster” that occurred over a three-month period in Botswana’s Okavango Delta, some elephant carcasses crowded around waterholes and others fell face-first to the ground. Although the region is a known poaching hotspot, the elephants’ tusks were found intact, ruling out human intervention and prompting scientists to look for other causes.

But efforts to determine a definitive cause of the mass mortality event – which would have included taking water and tissue samples to test directly for the presence of cyanotoxins – were hampered by the Okavango Delta’s remote location and further complicated by logistical challenges COVID-19 pandemic. The tragedy occurred at the height of the pandemic, restricting movement and delaying critical fieldwork, preventing researchers from collecting direct evidence.

But now a study that combines satellite Observations and aerial photography of over 3,000 waterholes in the region revealed elevated levels of algae near the deceased elephants, leading to amplification previous evidence that cyanobacterial neurotoxins – toxic compounds produced by microscopic blue-green algae called cyanobacteria – are likely responsible for the mass extinction.

“Algal blooms are routinely monitored by satellite, but this data is not often used to study mass mortality events,” the study’s lead author, Davide Lomeo of King’s College London, said in a opinion. “Because the scale of elephant deaths for unknown reasons was much higher than anything previously observed, it is important to use all sources of evidence to investigate what happened to these endangered animals.”

Concentrations of cyanotoxins in African inland waters are often thousands of times higher World Health Organization guidelines regarding safe drinking water for animals and people. Still, satellite images of the Okavango Delta between 2015 and 2023 showed cyanobacterial blooms exploded to unprecedented levels during an unusual rainy season in early 2020, following the driest season in decades the year before.

This extreme switch from drought to heavy rainfall resulted in dramatic amounts of water at waterholes that were either completely dry or had very little water left after the 2019 drought, according to a report by a new study published in the journal Science of The Total Environment. This sudden influx of water resulted in the resuspension of large amounts of nutrients and sediment from at least 20 waterbeds of varying sizes, resulting in frequent and heavy growth of cyanobacteria, which are known to thrive in nutrient-rich waters.

Satellite images also showed that the algae multiplied most strongly between March and May 2020, the end of the rainy season. As temperatures rose, the water stagnated, further improving conditions for cyanobacteria to thrive and produce unprecedented amounts of toxins.

Several elephants stand amid swampy waters and grassy banks in an arid landscape.

Satellite data has shown that the sudden deaths of more than 300 African elephants in early 2020 were likely caused by extraordinary levels of toxins in the water. (Image credit: guenterguni/Getty Images)

When the elephants drank from these contaminated waterholes, they ingested lethal doses of cyanotoxins, which may have led to organ failure and ultimately their death.

The suffering animals likely traveled about 10.25 miles (16.5 kilometers) and died within 88 hours of being exposed to the toxins, according to the study, which compares with reported time series of deaths linked to cyanobacteria poisoning in other large mammals matches. Elephants may also have moved closer to water sources in their final years of life and may have sought fluids at increasingly toxic watering holes as they became weaker. The close proximity of the carcasses to these waterholes supports the hypothesis that the elephants’ deaths were linked to the toxicity of the water, researchers say.

“You have no choice but to drink from it,” Lomeo said The Guardian. “Botswana is home to a third of all African elephants, and these unprecedented die-offs within the largest remaining population underscore increasing concerns about the impacts of drought and climate change on the Okavango Delta, one of the world’s most important ecosystems,” he added opinion.

It is possible that elephants were particularly vulnerable to poisoning because of their drinking habits. According to the new study, elephants can drink between 100 and 200 liters of water each day and likely drank from multiple waterholes before they died. Unlike other animals that drink from the side of waterholes, elephants also tend to wade to the middle and submerge their trunks, potentially exposing them to higher concentrations of cyanotoxins than other animals using the same resource. However, smaller animals may have died after consuming the contaminated water, but it is likely that their carcasses were either eaten by other animals or had already been decomposed by them Time the aerial photograph.

Although toxin-producing cyanobacteria strains have been observed on the African continent, the toxins themselves cannot be detected SpaceThis makes it difficult to determine which waterholes were contaminated and for how long.

Niall McCann from Britain’s National Park Rescue, who was not involved in the new study, said The Guardian that these findings “add to the growing evidence that climate change can have a range of deadly effects on wildlife (as well as livestock and humans), from radical changes in water availability to creating conditions for the proliferation of harmful bacteria and algae.” Overwhelming animal populations “.

The results raise broader concerns about impacts Climate change Impact on Africa’s wildlife, particularly as southern Africa is expected to become hotter and drier in the coming decades. As temperatures rise and precipitation patterns change unpredictably, these results underscore the need for comprehensive water quality monitoring of all water sources, even the smallest ones, the researchers said. Globally, the mass deaths underscore an alarming trend toward rapid, climate-related diseases, Lomeo said.

There is “no reason to believe that such an event will not happen again.”

Satellites find likely cause of mysterious African elephant deaths in 2020

ByAmelia Journalton

By Amelia Journalton

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