Will the climate emergency really drive great white sharks towards British waters?

What impact is the climate emergency having on our seas?

The world’s oceans reached their hottest temperatures since records began in 2020, a phenomenon blamed on the global climate emergency given that our seas absorb 93 per cent of the heat trapped in the atmosphere by carbon emissions.

Research published in the academic journal Advances in Atmospheric Sciences in January concluded that warmer oceans were in turn helping to drive extreme weather events like tropical storms, that seas are now at their highest temperatures for 1,000 years and that the pace of the increase is accelerating at a rate not seen for two millennia.

“Ocean warming is the key metric and 2020 continued a long series of record-breaking years, showing the unabated continuation of global warming,” said Professor John Abraham of the University of St Thomas in Minnesota, whose team led the analysis.

“Warmer oceans supercharge the weather, impacting the biological systems of the planet as well as human society.”

Another study published in The Proceedings of the National Academy of Sciences last October reported that the Atlantic was at its hottest for 2,900 years.

Marine ecosystems were already under duress from overfishing, pollution and noise, with every new disruption threatening devastating consequences for those delicate aquatic habitats and the creatures that depend on them for survival.

How are sharks specifically being impacted by rising temperatures?

While sharks may be apex predators with a fearsome (if distorted) reputation - in no small part thanks to Steven Spielberg’s classic blockbuster Jaws (1975) and its many imitators, from Deep Blue Sea (1999), Sharknado (2013) and The Shallows (2016) to The Meg (2018) - they are as vulnerable to the global climate emergency as any other species.

Another recent study carried out by the Monterey Bay Aquarium in California and published in Scientific Reports warned that the rising temperatures are already driving juvenile great white sharks in the Pacific northwards in search of cooler waters.

Marine biologists at the institution tracking the species since 2014 found that they were migrating 370 miles north and feeding on populations of sea otters and salmon, cutting down the former’s numbers by an estimated 86 per cent.

“Nature has many ways to tell us the status quo is being disrupted, but it’s up to us to listen,” Dr Kyle Van Houtan, chief scientist at the Monterey Bay Aquarium, told Oceanographic Magazine in a call for action.

“These sharks - by venturing into territory where they have not historically been found - are telling us how the ocean is being affected by climate change.”

He continued: “White sharks, otters, kelp, lobsters, corals, redwoods, monarch butterflies - these are all showing us that climate change is happening right here in our backyard. It’s time for us to take notice and listen to this chorus from nature.

“We know that greenhouse gas emissions are rapidly disrupting our climate and this is taking hold in many ways. Our study showed one example of juvenile white sharks appearing in Monterey Bay. But let’s be clear: The sharks are not the problem. Our emissions are the problem. We need to act on climate change and reduce our reliance on fossil fuels.”

A separate study carried out by Australian scientists examining the Great Barrier Reef reported in January that warming oceans caused by the climate crisis was also leading baby sharks to be born smaller, exhausted, undernourished and into environments that are already becoming increasingly difficult for them to survive in.

The Save our Seas Foundation emphasises the urgency of addressing the plight faced by sharks by reminding us that: “Sharks of some description have been on this planet for hundreds of millions of years. They have weathered major changes in climate - periods of glaciation and warmth - but the rapid and acute change that they’re currently experiencing is something new.

“Sharks are slow to evolve - they generally grow slowly, mature late in life and have long generation times - so it is difficult for them to adapt to the new conditions brought about by the rapid climate change we’re inducing now.”

What might global heating mean for sharks off Britain’s coastlines?

The trends identified above raise the possibility that great white sharks could be more likely to be driven towards Europe in pursuit of cooler climes as the temperature of the Atlantic continues to rise.

One did actually make that trip as recently as April this year, when a 17-foot, 253-stone female great white named Nukumi crossed the Mid-Atlantic Ridge, only the second such incident recorded after another named Lydia did the same in April 2014, reaching the coast of Portugal.

Nukumi, 50 years old and pregnant, had set out from the coast of North Carolina and was thought to be looking for somewhere safe to give birth away from male aggressors, coming within 1,700 nautical miles of the UK.

“She is capable of reaching the UK coast,” OCEARCH’s chief scientist Dr Bob Hueter said at the time. “But we would not predict that she will do that, as white sharks are rare off the UK.”

The UK is, however, home to “an incredible diversity of sharks and rays - over 80 species”, Ali Hood, The Shark Trust’s conservation director, told The Independent.

“From a UK perspective, we have some species that prefer warmer water so are at the northerly extremes of their ranges like thresher sharks. And some species which prefer cooler waters, so are at the southerly extreme like Arctic skate or starry ray.”

At least 21 varieties of shark species are thought to live around Britain’s coastlines all year round.

These species include the small-spotted catshark, the nursehound, a large catshark, and the porbeagle shark, as well as 11 deepwater species, including the Portuguese dogfish and gulper shark.

In addition, some sharks visit the UK only during certain months, including the basking shark, one of the largest fish in the ocean.

“Cornwall, outstretched as it is into the mild, oceanic currents of the North Atlantic, is Britain’s unofficial shark capital - both for attracting seasonal visitors of the shark kind, and plenty of tourists to document the evidence,” writes National Geographic. “But Devon, the west coast of Scotland and Ireland all have their own hotspots.”

None of Britain’s native shark species are considered dangerous to bathers or fishermen, however, and not a single shark attack has been recorded off these shores since records began in 1847.

Nor has there ever been a verified sighting of a great white. Yet.

“White sharks are considered to tolerate temperatures from 5-25C so the perennial question is why do we not see them in UK waters already?” says Ms Hood.

“The closest verified sighting was in the top of the Bay of Biscay, but there has been no confirmed sightings of white sharks in UK waters despite suitable habitat.”

Why are we asking this now?

The migration detected off the coast of California is unlikely to prove an isolated incident and, should sea temperatures be allowed to continue to rise at their present alarming rate without aversive action by world governments, further disruption to the existing behavioural patterns of sharks and other marine species appears likely.

While the alarming prospect of a great white’s dorsal fin carving its way through Newquay Bay might not be a realistic prospect for decades to come, the English Channel certainly offers cooler waters that could provide a refuge from an overheated Atlantic.

The effects of climate change are already being felt by at least one British shark species, according to Ms Hood.

“One shark which is directly affected by erratic weather, or stormy sea conditions, is the basking shark,” she told The Independent.

“[They] benefit from calm summer conditions, creating layers of different temperature water (stratification) which traps and concentrates plankton in surface waters, making feeding far more efficient.

“Storms break up the layers, distributing plankton through the water column, making feeding less efficient.

“A key factor in sharks distribution is prey - food - and if warming temperatures cause prey items, shoals of mackerel for example, to move then certain sharks will move with them. In recent years we have seen blue sharks remaining closer to the UK coast for longer periods, following the mackerel.”