Botswana is home to one-third of the elephant population in Africa. So when hundreds of elephants mysteriously died starting in May 2020, scientists and news organizations sounded the alarm.
Now, scientists have confirmed that neurotoxins in the water are behind the untimely deaths — the source of which is a type of algae directly intertwined with the evolution of humans.
Toxic cyanobacteria, or blue-green algae, has been poisoning the elephants' drinking water, resulting in more than 300 deaths, officials said this week.
Cyril Taolo, deputy director of the Department of Wildlife and National Parks in Botswana, broke the news, saying this specific type of neurotoxin that is responsible for the deaths is yet to be studied: "What we just know at this point is that it’s a toxin caused by cyanobacteria,” Taolo said.
Cyanobacteria, indeed, can be toxic, causing damage to animal and human nervous systems. But not all classes of the microorganism, which lives in soil and water, are harmful.
In terms of natural history, some types of cyanobacteria have been a force for good. Humankind, in fact, owes it our existence to one class of cyanobacteria called oxyphotobacteria. Some 2.5 billion years ago, research shows, these organisms became the first to produce oxygen, paving the way to modern forms of life.
A 2017 study examined the genomes of cyanobacteria across each of its three classes. (The other two, called Melainabacteria and ML635J-21, do not produce oxygen.) Researcher that all of the genomes were closely related to the oxygen-producing bacteria — but could not themselves produce oxygen, suggesting that photosynthesis dates far back in cyanobacteria evolution.
“Cyanobacteria are really special from a planetary perspective, because they’re the ones that figured out how to do the photosynthesis everyone knows and loves,” study co-author Woodward Fischer told Inverse at the time. “Everything we breathe, we owe in some way to these guys."
Oxygen-creating photosynthesis naturally gave rise to oxygen in the atmosphere — and that paved the way for oxygen-breathing organisms, like humans, to dominate the Earth.
Like other algae, cyanobacteria photosynthesize, and they do well in warm, nutrient-rich waters. Algae are altogether responsible for half of Earth's photosynthetic activity, and the plants are a key part of aquatic food chains.
An excess of nutrients, though, can lead to algal blooms that choke out other aquatic life. And in the case of certain types of bacteria, they can also leak toxins into the water that are harmful to humans.
Algal blooms in Lake Erie have made hundreds of people sick. In 2014, officials in Toledo, Ohio, had to ask nearly half a million residents to stop drinking their tap water while the contamination was dealt with, NPR reported.
That wasn't the first time local residents had such an experience: A similar effect happened one year earlier, when a toxin was detected in numbers 3.5 times the safe levels for drinking.
That span of time was particularly bad for Lake Eerie, which sees algal blooms every year. But the blooms, which are monitored by NASA satellites and the US Environmental Protection Agency, are not stopping any time soon.
As warming global temperatures make for perfect algae-blooming conditions, these upticks in the summer aren't expected to slow down. Excess nutrients, like those from sewage and agriculture, are also big contributors to algae growth.
We don't yet know what this means for the health of humans or elephants. Taolo said authorities are monitoring water supply for elephants but are no longer seeing elephant deaths.