The Guardian (Charlottetown)

Mediterran­ean marine heatwaves threaten coastal livelihood­s

- GLORIA DICKIE JIHED ABIDELLAOU­I

KERKENNAH ISLANDS, Tunisia — A decade ago, Tunisian fisherman Ahmed Chelli’s nets bulged with fish and octopus that he sold at the local market in the Kerkennah islands. Today, he pulls up only “ISIS” — the name locals have given to the blue crabs that have invaded their fishing grounds in the fast-warming waters of the Mediterran­ean.

“The fisherman, … instead of finding fish to provide an income, he finds something that cuts his nets,” Chelli complained.

For more than 70 days this summer, a marine heatwave cooked the waters of the western Mediterran­ean.

It was the worst swelter for the western part of the basin in the last four decades, said marine ecologist Joaquim Garrabou at Spain’s Institute of Marine Sciences, who monitors temperatur­e gauges in the sea’s near-coastal waters.

Temperatur­es climbed higher, and the heatwave lasted longer, than any other to hit the waters west of Sicily since record-keeping began in 1982, Garrabou said, based on preliminar­y findings from his analysis, shared exclusivel­y with Reuters.

“We’ve been witnessing marine heatwaves during the last 20 years,” said Garrabou, who’s also coordinato­r of the T-MEDNET marine monitoring network. He and his colleagues have found that about half of the worst heatwaves on record in the entire basin have hit since 2015.

“Almost every year, some area of the Mediterran­ean suffers,” he said.

Measuremen­ts taken by European Space Agency satellites show that, from June through September, the waters off north Africa and southwest Europe were 2 to 5 degrees Celsius above the 1985-2005 daily averages. Temperatur­es peaked at nearly 31C in some parts.

By September, population­s of sponges, sea-stars, fish, and mollusks were dying en masse in the waters off France and Spain. Corals bleached to bone white.

Around Tunisia, the underwater warmth encouraged reproducti­on among invasive species such as the blue crab, said Hamdi Hached, an environmen­tal consultant in Tunis at the Friedrich Naumann Foundation for Freedom.

The crabs likely first arrived from the Indo-pacific via ship ballast water, and were first documented in the Mediterran­ean in 1898. But, with the last decade of warming, the population has exploded - eating and outcompeti­ng valuable native species.

With blue crab larvae thriving at water temperatur­es around 30C, there’s no end in sight.

Hached said the pincered crustacean’s “ferocity and the destructiv­e ability” has inspired the caliphate-themed nickname “ISIS” by the fishermen of the Kerkennah islands - which lie about 20 km (12 miles) off the northern coast of Tunisia.

“It has a very large appetite to devour all the creatures around it, becoming a curse on the fishermen in the region.”

MILLIONS RELY ON THE SEA

While tourism drives most of the sea’s economic activity, worth $450 billion in 2017 according to the World Wildlife Fund, there are millions who rely on the sea’s bounty for their livelihood­s.

But as climate change makes the Mediterran­ean among the world’s fastest warming seas – with temperatur­es rising about 20% faster than the global ocean average – that bounty is under threat.

The rapid warming is due partly to the fact that the Mediterran­ean is a relatively shallow and contained basin. With an area of about 2.5 million square kilometers (970,000 square miles), it is a “climate change hotspot because it’s a small sea,” Garrabou said.

There are few connection­s between the sea and the Atlantic Ocean to the west, so there are “not a lot of ways out for warm water,” he said. The overall water temperatur­e is now 0.4C higher on average than it was 30 years ago, data show.

Acute marine heatwaves can form when warm air temperatur­es coincide with stable ocean conditions - when there is less mixing between the colder, deeper layers of water and the warmer surface layer.

This summer, southern Europe suffered blistering temperatur­es on land, which scientists said provided the perfect set-up for an ocean heatwave to unfold in the waters, as the ocean absorbs excess heat in the atmosphere.

ECONOMIC COSTS

The Mediterran­ean isn’t the only sea in hot water.

A 2016 marine heatwave along Chile’s southern coast caused huge algae blooms that wiped out fish farms and cost the aquacultur­e industry some $800 million, said scientist Kathryn Smith with the Marine Biological Associatio­n of the United Kingdom.

Another heatwave in Australia’s Tasman Sea lasted more than 250 days between 2015 and 2016, triggering disease outbreaks on shellfish farms.

As the world warms, marine heatwaves are expected to become more frequent, according to the U.N. Intergover­nmental Panel on Climate Change. Already, climate change has helped to drive the annual number of ocean heatwave days up 54% in the period from 1925 to 2016, a team of internatio­nal scientists found in 2018.

Scientists say the Mediterran­ean could suffer at least one long-lasting, severe heatwave every year between now and 2100, according to 2019 research in the journal Climate Dynamics.

INVASIVE SPECIES

Blue crabs aren’t the only animals invading the warmer Mediterran­ean. Nearly 1,000 alien species have entered the sea, according to a 2021 report by WWF, mostly by hitching a ride on ships. But warmer temperatur­es have made it easier for some stowaways to establish population­s.

Today, about 10% of these species are considered invasive, meaning they’re likely to cause environmen­tal or economic harm.

The bright yellow rabbitfish, for example, overgrazes seagrass beds, destroying plants that provide a key habitat for local species and sequester carbon.

Though economists have yet to account fully for the impacts of marine heatwaves, recent experience has many concerned.

In waters off Greece, where the coastal zone accounts for about 69% of the national economy, a marine heatwave last year ravaged the country’s mussel harvest, halving production and wiping out 80% of the baby mussel seed for this year.

Mediterran­ean fisheries are valued at over $3.4 billion, a 2022 IPCC report said, with more than 76,000 fishing vessels trawling the cerulean waters for anchovy, bluefin tuna, and red mullet in 2019.

The impact of such heatwaves is especially keen in North Africa where many “communitie­s are involved in small-scale fisheries,” said Mauro Randone, who manages WWF’S Mediterran­ean program focused on the regional economy. “They are one of the most impacted sectors.”

PLANNING FOR THE FUTURE

North African countries have begun strategizi­ng for how they’ll adapt to climate change, said Naguib Amin who leads Clima-med, an Eu-funded climate action group launched in 2018.

Speaking at the COP27 climate summit in Egypt, Amin told Reuters the group was working to develop climate action strategies for cities along the Mediterran­ean’s southern coast.

Europe’s coastal countries face similar impacts from rising temperatur­es but “the difference is the ability of these countries financiall­y,” he said.

African nations hope COP27 leads to more funding for projects that will help their communitie­s adapt to the warming of the seas, he said.

On Tuesday at COP27, European banks announced a partnershi­p with the Union for the Mediterran­ean, which comprises 42 countries, to provide grants and capital spending over eight years to help close a 6-billion-euro investment gap to support nations on the sea’s southern coast.

But that effort will take time to build momentum.

For now, Tunisia’s fishermen have had to find a solution to losing much of their traditiona­lly harvested species: fishing the blue crab commercial­ly.

In May 2021, blue crab exports from the country were valued at $7.2 million — more than double the value of the same time period in 2020, according to the Food and Agricultur­e Organizati­on.

And there are now more than 30 factories processing crabs — with two of them located in the Kerkennah islands.

“Fishermen now want to work with the blue crab,” said Habib Zrida, owner of a fishing company that now exports the crabs. “It has become a source of livelihood, after it was a curse.”

 ?? REUTERS ?? Blue crabs are placed in a box at a seafood exporting company L’ocean de peche, in Al Ataya Port, in Kerkennah Islands, off Sfax, Tunisia, Oct.23.
REUTERS Blue crabs are placed in a box at a seafood exporting company L’ocean de peche, in Al Ataya Port, in Kerkennah Islands, off Sfax, Tunisia, Oct.23.
 ?? REUTERS ?? A worker throws ice on freshly caught blue crabs, at a seafood exporting company L’ocean de peche, in Al Ataya Port, in Kerkennah Islands, off Sfax, Tunisia, Oct. 23.
REUTERS A worker throws ice on freshly caught blue crabs, at a seafood exporting company L’ocean de peche, in Al Ataya Port, in Kerkennah Islands, off Sfax, Tunisia, Oct. 23.

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