According to a new study, more than 350 elephants that died in mysterious circumstances in Botswana’s Okavango Delta probably drank toxic water.
- The deaths were described by scientists as a “conservation disaster”. Elephants of all ages were seen walking in circles before collapsing and dying.
- The King’s College London’s study was published in the journal Science of the Total Environment.
What does the study say?
- It suggests the elephants were poisoned by water that contained toxic blooms of blue-green algae, or cyanobacteria.
- The climate crisis is increasing the intensity and severity of harmful algal blooms.
- The researchers believe that the elephants generally walked just over 100km from the waterholes and died within 88 hours of drinking.
- They examined 3,000 waterholes, and found those that experienced increased cyanobacteria blooms in 2020 had high concentrations of carcasses.
- This event underscores the alarming trend of sudden, climate-induced diseases. Mass-mortality events are becoming more common as the world heats up, and can push species toward extinction, experts warn.
- The new study adds to the growing body of evidence that climate change can have a range of lethal effects on wildlife (as well as livestock and people), from radically changing water availability, to providing the conditions for harmful bacteria and algae to proliferate and overwhelm animal populations.
About Harmful algal blooms
- Harmful algal blooms, or HABs, occur when colonies of Algae and cyanobacteria (also called blue-green algae) grow out of control and produce toxic or harmful effects on people, fish, shellfish, marine mammals and birds.
- Algae and cyanobacteria are plant-like organisms that live in water. The human illnesses caused by HABs, though rare, can be debilitating or even fatal.
- Three types —cyanobacteria, dinoflagellates, and diatoms—cause most blooms that make people and animals sick.
- Cyanobacteria (blue-green algae) are the most common cause of harmful algal blooms in fresh water, such as lakes or rivers.
- Dinoflagellates or diatoms are the most common causes of harmful algal blooms in salt water, such as oceans or bays. Harmful algal blooms can grow in fresh water, salt water, or brackish water.
- Ranging from microscopic, single-celled organisms to large seaweeds, algae are simple plants that form the base of food webs.
- Under the right conditions, algae may grow out of control — and a few of these “blooms” produce toxins that can kill fish, mammals and birds, and may cause human illness or even death in extreme cases.
- Other algae are nontoxic, but eat up all of the oxygen in the water as they decay, clog the gills of fish and invertebrates, or smother corals and submerged aquatic vegetation.
- Others discolor water, form huge, smelly piles on beaches or contaminate drinking water. Collectively, these events are called harmful algal blooms, or HABs.
Okavango Delta
- The Okavango Delta is a large low gradient alluvial fan or ‘Inland Delta’ located in north-western Botswana.
- The delta comprises permanent marshlands and seasonally flooded plains.
- It is one of the very few major interior delta systems that do not flow into a sea or ocean, with a wetland system that is almost intact.
- One of the unique characteristics of the site is that the annual flooding from the River Okavango occurs during the dry season, with the result that the native plants and animals have synchronized their biological cycles with these seasonal rains and floods.
- Botswana’s Okavango Delta is a UNESCO World Heritage site.
- It is an exceptional example of the interaction between climatic, hydrological and biological processes.
- The Okavango Delta is home to some of the world’s most endangered species of large mammal, such as the cheetah, white rhinoceros, black rhinoceros, African wild dog and lion.
(Sources: The Guardian, NOAA, CDC, UNESCO)
