How people put pressure on the Mediterranean Sea

The Mediterranean is widely regarded as a crucible of civilisation. Its waters, which form the deepest and largest enclosed sea on Earth, have seen the trade of goods and ideas between three continents for millennia. Packed tight against its coasts, swelling human populations have shaped the ecological character of the Mediterranean Sea almost as much as it has formed their cultural and political identities.

Most of the Mediterranean Sea experiences little to no tide. But at the Gulf of Gabes in Tunisia, the waters have a range of up to 2m. “It is at the crossroads of the eastern and western basin in the Mediterranean,” says Prof Nejla Bejaoui, a researcher at the University of Carthage in Tunis.

“It receives water from the Atlantic through the Strait of Gibraltar and from the Red Sea through the Suez Canal. There is, therefore, a mixing of waters and a very important variety of species of ecological interest,” she adds.

In the 19th century the area was a rich fishing ground to the extent that there was fierce conflict over sponges and octopus. Fishing has been perhaps the most enduring human influence on the Mediterranean Sea, explains Daniel Faget, professor of history at the University of Marseilles.

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“The first traces of the exploitation of fish resources date back to the Neolithic period... Classical Greece, then the Roman period, saw a significant development of fisheries thanks to the improvement of navigation and port infrastructures, the development of a distribution market, and the diffusion of new fishing techniques,” he adds.

Fishing intensified in the 16th century, expanding from the coasts of Provence and Catalonia with new techniques like the sardine – a net designed to catch small fish. “For the first time, the supply of fresh fish exceeded the immediate consumption capacity of the population,” Faget says. “To preserve the fish, salting workshops were developed everywhere from Spain to Italy, controlled by the urban bourgeoisie.”

The dragnet was another innovation that preceded the modern trawler and ushered in the reality of bycatch: fish caught unintentionally and discarded as waste. With more intensive techniques came a decline in fish numbers.

“Modern paintings, of Italian or Iberian origin, reflect the first effects of overexploitation on the coastal strip: the sturgeon, well represented in the 16th century, gradually disappeared from the canvases of the masters,” Faget notes.

Invasive species

In 2020, the UN Food and Agriculture Organisation reported that 75 per cent of commercial fish species were overexploited in the Mediterranean Sea. In addition to this crisis of decline, an influx of non-native species has released a new set of problems on the Mediterranean, Bejaoui explains.

Perched at the bottleneck between Sicily and North Africa, the Gulf of Gabes has become a frontier for the invasion of alien species on both its flanks. “Invasive species have entered the Mediterranean from both the Atlantic and the Red Sea,” she says, disrupting the local ecology and causing havoc for fishers.

Blue crabs began to appear in 1993, proliferating over the next 20 years and competing with indigenous species for space and food. Octopus were the only real predator of the crabs but there weren’t enough of them to control the population.

Blue crabs disrupted the collection of clams by fisherwomen; they shredded nets and the fish within them. They were a source of dismay for communities to the extent that fishers came to name the crab “Daesh” – the Arabic term for the Islamic State.

While there was no local demand for blue crabs in Tunisia, they are sought after throughout Asia, the United States and Australia. So fishers upended the catastrophic invasion and turned it into a lucrative business by trapping crabs and exporting them.

The adaptation of Tunisian fishers is an example of the evolving nature of human relationships with the Mediterranean. It is a response to concurrent crises that affect both marine ecology and coastal society, Faget suggests. The good news is “[fishers are] increasingly adopting a systemic vision of the environment, the good health of each of the living compartments being the guarantee of the good health of their own activity.”

This is an important move but it has not always been the case. For marine mammals, especially dolphins and seals, interaction with fisheries has been one of the greatest existential threats.

The Mediterranean monk seal was once distributed from the Bosphorus to the Strait of Gibraltar and around the west African coast. The earliest records exist in Homer’s Odyssey, where they are found dosing on sun-drenched beaches. But human pressures drove these charismatic animals into caves as far back as the first millennium.

“The species was largely killed by fishermen that were aggravated by the seals damaging their nets, taking fish,” says Dr Joan Gonzalvo, director of the Ionian Dolphin Project with Tethys Research Institute.

Gonzalvo started working with the monk seal when he noticed their increasing numbers during his research trips in western Greece. “The seals, in a way, were shaking a flag. We started to see them more often than before”.

By photographing seals at a distance, from boats and drones, he and his team identify and track the behaviours of individuals within the Ionian Sea.

A small increase in numbers spells cautious hope for the monk seal, he points out. “Increasing in number in the Greek islands, this area might have a buffer effect by, let’s say, ‘exporting’ individuals that occasionally move to recolonise what used to be the former range of the species”.

He attributes this largely to a changing perspective among fishers: “I guess a little bit of a shift in the attitude of fishermen, either because they have come to terms with the idea that they are sympatric species sharing the same area and have to live together. But also, less naively perhaps, there are laws and strong fines for those who kill seals or dolphins.”

Gonzalvo is optimistic but the monk seal has a long way to go before reaching a point of safety. In the confines of the Mediterranean, competition for space is an ongoing problem and new threats arise with a barrage of tourism.

“Our curiosity as tourists to see pristine places [means that] some caves aren’t safe anymore for seals because people, of course they go inside, so part of the conservation is also to educate people,” he underlines. His organisation distributes information on respectful interactions with marine mammals and engages tourists to record sightings of animals.

There is a marked change in monk seal behaviour when tourism drops off, Gonzalvo says. “Actually we see now that in places where there has been the establishment of a marine protected area, or where in the winter months there has been no presence of boaters or tourists, it’s not rare to see monk seals on a beach. Obviously for a marine mammal that is warm blooded . . . they will be more comfortable in a dry and sunny beach than in a wet and humid cave,” he adds.

The plight of the monk seal has been ongoing for generations. If there is a chance to recover from the impacts of humankind, it might deliver hope for seemingly overwhelming challenges elsewhere. They include the threat from phosphogypsum, a run-off from fertiliser production, that is spilling into the Gulf of Gabes in Tunisia, while drilling for oil and gas is planned for the Ionian Sea; the bastion of the monk seal.

The Mediterranean is under attack from all fronts, but is still has much to hold on to. Gonzalovo highlights the importance of protecting the marine ecology of the Mediterranean, not just for its own sake, but for that of the coastal civilisations that surround it. The monk seal is emblematic of the point at which the Mediterranean Sea finds itself – teetering in a balance that could go either way.

“The Mediterranean monk seal is very strongly related to the Mediterranean character, culture and heritage, in a way, so if we are not capable of protecting this iconic species then there is little hope for other species,” he says.

The identities of the Mediterranean and its peoples are bound in a history where each has determined, to a certain extent, the fate of the other.

It is their interdependence that emphasises the need for a sustainable relationship as they move forward.