Rising water levels threaten the survival of the lesser flamingo

The world’s most common flamingo is in danger of running out of food.

Lesser flamingos are highly specialised birds that feed on just a few kinds of bacteria and algae that only live in salty, alkaline lakes. The vast majority are found in east Africa, where around three quarters of the birds live.

But over the past decade the water levels in the African lakes the birds feed in have risen, reducing the salt levels and consequently the amount of prey available to the flamingos. While the exact causes aren’t clear, a combination of climate change, deforestation and changes in water use are thought to be to blame.

Aidan Byrne is a PhD student who was the lead author of the new study, published in the journal Current Biology.

“While lesser flamingos have dealt with environmental change over the past few million years, the rapid increase in water levels in such a short space of time mean they’re much less able to adapt,” Aidan says.

“We’re also impeding their ability to move to more suitable habitats by constructing dams, power cables and other facilities. In the past, the flamingos would have been able to spread to suitable shallow salt pans across the region, but by limiting access, humanity is making it more difficult for these waterbirds to survive.”

Salt lake specialists

Flamingos are divided up into six species which live across the world’s warmer regions. Four species, including the James’ flamingo and Chilean flamingo, live in southern and central America, while the greater and lesser flamingo live across Africa and Asia.

With an estimated two to three million birds, the lesser flamingo is the most numerous of these species. But despite this population size, many of the birds will have hatched at just a handful of breeding sites around the world. The most important of these is at Lake Natron in east Africa.

With temperatures and alkalinity high enough to burn the skin the lake is inhospitable to most life, but due to the mineral rich waters it has thriving populations of algae and bacteria. It is these characteristics that make the salt lakes like Lake Natron some of the most productive environments on the entire planet.

Flamingos are among the only animals able to exploit the bacteria. While this strategy has been a success for millions of years, the specialisation of their diet is now coming back to haunt them.

Using satellite observations, the researchers found that many of the salt lakes most important to lesser flamingos are getting larger. Growing lakes might not seem so bad, but it makes them less suitable for the photosynthetic bacteria and algae the flamingos depend on. While the species is currently considered Near Threatened, its conservation status could rapidly worsen if food levels continue to fall.

For example, Lake Nakuru is another salt lake critical for the lesser flamingo. It doubled in size between 2009 and 2022, while levels of photosynthetic microbes fell over the same period. This is a serious problem for the one million birds that feed on the algae.

“Lesser flamingos are specialist feeders and breeders, with populations already thought to be declining,” Aidan says. “If lakes like Natron and Nakuru continue to become less suitable, then there could be a sudden drop in population in just a couple of decades.”

What’s behind east Africa’s rising lakes?

The challenge is now to identify exactly why the lakes are growing in size. However, with so many possible causes doing so is no easy feat.

“It's challenging to disentangle the different interacting factors, as there are just so many of them,” Aidan explains. “Natural processes like rainfall and temperature have an impact, as do human factors like land use and water abstraction.”

“On top of that, different lakes have different responses to these drivers, based on their depth or shape. It’s really difficult to identify them, but this is work I’m doing at the moment to try and separate them out.”

One factor that appears to be a major driver of the changes is El Niño, a natural fluctuation in sea temperatures that normally occurs every few years. Significant changes in the size of the lakes are associated with El Niño events, which are becoming more severe as a result of climate change.

Rising temperatures are also intensifying rainfall across east Africa, causing further changes in the salt lakes. The removal of vegetation in the surrounding area is also probably having an impact, as fewer plants mean less water is being absorbed before it drains into the lakes.

As their current feeding and breeding grounds become less productive, the lesser flamingos may be able to disperse to other lakes. However, while their current breeding and feeding grounds are protected by international treaties many other lakes are not.

“If they move to lakes which are outside protected areas, there’s a greater possibility they’ll be disturbed,” Aidan says. “When flamingos begin to establish in new areas, they will struggle unless the water quality is protected.”

At the moment, identifying this is challenging. Flamingo counts are usually taken once or twice a year, and only at lakes with known populations. The researchers have called for more regular counts, over a wider area, to give a better idea of how the birds’ lives are changing.

Together with wider action on tackling the climate and biodiversity crises, these steps can help to make sure the lesser flamingo won’t be going anywhere anytime soon.