The sardine run in South Africa is the world's largest marine migration event each year. But as warming oceans disrupt the sardines' migratory patterns, it's threatening to leave several major species without a food source.
What's happening?
Each year, enormous shoals of sardines embark up South Africa's eastern coast, following cooling ocean currents that are packed with nutrients. The shoals — often several miles long, per UNESCO — attract predators, who feast on the abundant bait balls.
"The sardine run is an exceptional event and an important part of the food web," Peter Teske, with the University of Johannesburg, told the BBC. "Suddenly, [with the arrival of nutrients and the sardines,] there is this huge source of protein."
The sardine run is also an important economic event for South Africa; it draws in thousands of divers each year who want to witness the once-in-a-lifetime event.
Unfortunately, all of this is threatened by myriad factors disrupting the sardine run — namely, global overheating and overfishing, according to the BBC.
Rising atmospheric temperatures have caused a corresponding jump in ocean temperatures, where a difference of even a few degrees can mean big trouble — particularly for sardines, who can't survive in warm water.
The sardine run's numbers are already plummeting. According to Cape Town's Department of Environment, Forestry, and Fisheries, sardine biomass is already at less than a quarter of what it was just two decades ago.
Given that and severe overfishing, the migration could be at risk of vanishing within just a few short decades. And for the major species that migrate around the globe to feed on the bait balls — including endangered whale, dolphin, and seabird species — this could result in "predatory species left stranded" without a food source, according to the BBC.
Why is this concerning?
"When events like this are disrupted it can have a knock-on effect," Stephanie Plön of Stellenbosch University told the BBC. "It's like we're just documenting extinction."
Already, Plön and her colleagues have found that dolphins — one of the species that relies most heavily on the sardine run — have been forced to shift their diet from sardine to mackerel. This is troubling in both a short- and a long-term perspective. By snipping away at strands in the food web, massive shifts in feeding patterns will creep up the food chain — all the way to humans.
What's being done?
The best way to ease disruptions to the sardine run would be to cool the oceans — but unfortunately, the major contributors of planet-warming pollutants are slow-to-adapt mega-corporations and governments.
However, on an individual level, eating vegetarian — or just reducetarian — to lower fishing demand is a great way to be part of the solution.
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