In hot water: why we should be worried about a warming Mediterranean

With the rising mercury come violent storms and the creation of undersea wastelands

The lifeguard station in the French resort of Le Lavandou in early August. The sign, updated daily in summer, gives air, sea and wind information. The sea temperature at the time was 28°C. Colin RandaShow more

The notice on the wall of the lifeguard station in Le Lavandou, a popular resort on France’s Cote d’Azur, indicated that the sea temperature was 28.5ºC.

At the height of the holiday season, even that reading was an understatement of the abnormally rising temperature of the Mediterranean.

Off the eastern coast of Corsica, between the island and Italy, one of the special buoys used by the French meteorological service France Meteo recorded a level of 30.7ºC.

A heatwave on land has caused gardeners, industry and agriculture to bemoan the lack of rain for much of the summer of 2022. When the weather did break around the Mediterranean basin, it came in torrents, sometimes accompanied by fierce hailstorms and inflicting destruction.

Each period of canicule ― extreme heat ― sets up devastating downpours causing huge damage and often loss of life.

On the French Riviera, residents recall that very high sea temperatures tend to be followed by severe flooding, weeks or months later. This month, television news footage of desperately dry, cratered river beds and farmland has given way to scenes of inundation.

There has been flooding and storm damage with rare but heavy rainfall battering towns and villages, flattening trees and engulfing properties in parts of the French Riviera and, more seriously, Corsica.

The storm that hit Corsica has been likened to a “derecho”, uncommon in the region but pursuing a violent, 1,500-kilometre path from Majorca to the Czech Republic.

Even worse, in October 2020, in the valleys around Saint-Martin-Vesubie, a picture-postcard town north of Nice, Storm Alex caused at least 10 deaths ― eight other people are still listed as missing ― and destroyed hundreds of houses, 50 bridges and stretches of roads and ramblers’ footpaths.

It was described as a “meteorological bomb”, although the link with warming seas is said to be indirect.

“High sea temperatures are not actually something that provokes flooding,” Gaetan Heymes, a senior France Meteo forecaster, told The National.

“The actual cause is atmospheric disturbance. But those higher temperatures intensify the storms and can therefore aggravate storm damage.”

Mr Heymes rules out any connection between sea warming and the forest fires that have also ravaged some coastal areas “even if both are enhanced by atmospheric heatwaves”.

Most fires are not caused naturally but by arsonists or negligence, such as reckless barbecues or discarded cigarette butts. But shocking images of overworked firefighters battling the flames, and the damage inflicted on nature, add to popular impressions of a climate out of control.

The World Wildlife Fund said that some aspects of climate change, notably the transformation of the Mediterranean’s most important marine ecosystems, were irreversible. Its 2021 report The Climate Change Effect in the Mediterranean: Stories from an overheating sea claimed increasingly severe weather is causing significant damage to vulnerable coral beds, presenting an unseen menace to coastlines and the towns located there.

Average seasonal summer sea temperatures can go as low as 20ºC off the French and Italian rivieras, peaking in late August at 25ºC off the Cote d’Azur, 26ºC off Corsica. Le Lavandou's little blackboard reading demonstrates that higher sea temperatures in the Mediterranean are part of a changing reality.

As temperatures reach tropical levels, an estimated 1,000 types of alien fish have migrated to the warmer Mediterranean, sometimes replacing endemic species.

People flock to the Mediterranean on holiday, sunshine more or less guaranteed, but now find themselves sweltering in abnormal heat. Without air conditioning, nights can be sleepless, sweaty ordeals.

Even the relief of a dip in the sea is marred by the heat-related profusion of jellyfish. Having to rub sand into the skin to alleviate painful stings, or seek antibiotic treatment, is not what tourists bargain for.

The WWF report discussed the serious consequences for fisheries, tourism and the nature of human fish consumption. It admits now that little has changed.

Storms in Corsica - in pictures

“The Mediterranean of today is not the same as it used to be,” said Guiseppe Di Carlo, director of the WWF’s Mediterranean Marine Initiative.

“Its tropicalisation is well under way. Climate change is not in the future, it is a reality of today that scientists, fishers, divers, coastal communities and tourists are already experiencing.

“There is a lot at stake for the economy and the benefits that the Mediterranean provides. If we want to reverse the current trend, we must reduce human pressure and build resilience. Healthy ecosystems and thriving biodiversity are our best natural defences.”

For the WWF, climate change is the “biggest single threat to the human species”. The only feasible solution, it argues, is for governments to translate fine words into urgent action to reduce greenhouse gas emissions. WWF studies show that the Mediterranean is becoming the “fastest-warming and the saltiest sea on our planet”.

In the Mediterranean as a whole, key fish species have mutated with harsh local economic consequences.

The report warns of a “dangerous relationship between climate-driven impact and existing human pressures on marine life, such as overfishing, pollution, coastal development and shipping that have already dramatically reduced the ecological resilience of our sea”.

Stocks of native molluscs in Israeli waters have declined by almost 90 per cent and invasive species such as rabbitfish now account for 80 per cent of catches by Turkish fishermen.

But the changes in habitats and fish populations are occurring across the whole Mediterranean.

Typically southern species, including barracudas and dusky groupers, are commonly found off the Italian region of Liguria, especially north of Genoa towards to the border with France east of Monaco.

On one slightly positive note, coastal communities are learning to adapt to “the new reality”, catching rabbitfish, jellyfish and other alien species as new seafood delicacies.

But the WWF report highlights the spread of non-indigenous species in Mediterranean waters warm enough to support them, spreading north and west every year.

“Other native species are shifting their ranges north as they track cooler waters, while some endemic species have been left on the verge of extinction,” it says.

“At the same time, jellyfish plague fishermen and tourists alike … these are not future projections, they’re things that are happening right now in the Mediterranean, all caused or accelerated by climate change.”

The deep-sea bottom is affected, too. The WWF says endemic Posidonia oceanica meadows, gorgonian corals and Pinna nobilis, or fan mussel, are in decline and sometimes extinct. The threat to Posidonia is particularly worrying because it provides essential oxygen to the seabed.

“Losing these species would have dramatic impacts on the whole marine ecosystem as they provide vital habitats for many species, for the climate as some of them function as natural carbon sinks, and also for our economy as they often attract divers and tourists,” the report said.

This year there have already been three marine heatwaves in the Mediterranean, according to Samuel Somot, a researcher and climatology team leader with France’s National Centre for Meteorological Research (CNRM).

He told the French newspaper Les Echos that while there have always been peaks, incidents of global warming are increasing in number, size and duration.

The effect on biodiversity is striking. Among the alien species now found in the Mediterranean, rabbitfish devours underwater flora and lionfish eat fish larvae, enough to "create a big shock for the ecosystems", Mr Somot said.

Nearly three weeks after his first conversation with The National, France Meteo’s Gaetan Heymes said there had been little significant change, with sea surfaces still abnormally warm.

“It is a complex global issue,” he said. “There is no easy solution.”