A “hotspot” of biodiversity (18% of the world’s known marine species live in 0.3% of the world’s ocean volume), the Mediterranean is also a “hotspot” of global warming. This region is recording a 20% rise in temperature faster than anywhere else on the planet. To the extent that the basin is now flirting with an increase of 1.5 ° C since the beginning of the industrial era, a mark that the signatory states to the Paris Agreement tend not to exceed. What are the implications for ecosystems? WWF has been studying the fate of the biological life of the closed sea for many years and for that purpose it collects all the scientific studies conducted in this particular marine environment. This last report confirms a massive phenomenon: the Mediterranean is becoming a tropical sea. To avoid this, WWF asks this 30% of its area is classified as a marine protected area. The Our sea antiquity can be cured as we have suggested in No. 892 (since June 2021) Science and the future.
The Eastern Mediterranean is changing the climate
Near the Suez Canal, the eastern waters of the basin form the first colonization area of species from the Red Sea and the Indian Ocean. But it is very difficult to come up with evidence that populations are changing due to the warming of waters that have “taken” 0.4 ° C since the beginning of the industrial age. A study by the University of Vienna published on January 6, 2021 Proceedings of the Royal Society B cited in the report provides scientists with a new tool to assess changes in the marine environment. Researchers examined the corpses of shells found on benthos, the seabed of the Israeli continental shelf. And they compared the species they belonged to with those currently living in those areas.
Amazing result: only 5 to 12% of the species once present still lived there. For Paolo Alban, the researcher who conducted this research, “the complete absence of common Mediterranean species and the significant presence of alien species make this marine environment unrecognizable compared to other sites in the Mediterraneane “.
In turn, vegetation also undergoes profound transformations. The arrival of two species of herbivorous fish from the Red Sea and the Indian Ocean, cut tail rabbit fish (Siganus luridus) and a rabbit with a striped belly (Siganus rivulatus), strongly modifies the environment. These two fish greedily attack algae forests and degrade these ecosystems, turning them into low-vegetation areas or even sterile areas. According to the WWF, pastures have biomass 44 times lower than the previous algae environment. These carbon sinks can thus become net emitters of greenhouse gases.
What to do ? For WWF, fishermen must play a major role in controlling invasive species (unfortunately rabbits are poisonous and inedible) and conserving indigenous species populations through sustainable management of their numbers.
Invasive species are very destructive
The rabbit is blacklisted as an invasive species. But that is only part of the problem. There are 986 new arrivals throughout the Mediterranean. 126 fish are mostly from the Suez Canal. A study conducted in the marine protected area of Gokovo (Turkey) showed that 98% of herbivorous fish were rabbits. Where shoals of these fish are longer than 15 inches, large seagrass falls, 65% algae and 40% local biodiversity.
Progress of avalanche fish (Mile Pterois) is also spectacular. Caught for the first time in Israel in 1991, this carnivore with huge poisonous ears is now found all the way to Italy and Tunisia. Its hunting is all the more effective because the species encounters fish and crabs in the Mediterranean that do not know this predator and therefore do not know how to avoid it. It is difficult to limit its spread because today it is present in large numbers in at least 2/3 of the pools. According to the WWF, fishermen could be encouraged to target Mile Pterois whose meat is good to eat. Another solution is to encourage the recovery of brown grouper populations – overfished for decades – that love lion fish.
Jellyfish are multiplying
Fishermen see this: more and more jellyfish are present in their nets. And tourists fear their increasing presence near the beach, so much so that in recent years, beach managers in Spain, France and Italy are setting up safety nets. Rising temperatures favor native species such as those from the Suez Canal. But nutrient intakes from coastal agricultural areas also facilitate their spread. Finally, reducing the number of their natural predators, tuna, turtles and sharks increases their chances of survival. WWF recognizes this: the problem can no longer be solved in the short term unless the industrial use of the collagen of these gelatinous bodies is found. In the long run, the return of predators and the reduction of land pollution could restore balance to the marine environment.
Posidonia, gorgonians, large ridges in danger
1500 hectares of carbon are stored on one hectare of Posidonia. Five times more than the rainforest! This flowering plant that has decided to return to the marine environment can be of great benefit in the fight against climate change. Unfortunately, it is endangered while oxygenating the waters and providing a habitat that is visited by 20% of the marine species that use it as nurseries. Human pressure has been the main one responsible for the disappearance of 30% of meadows over the last fifty years, especially due to the anchorage of numerous pleasure boats where Posidonia is most prevalent, north of the basin, along the rivers Spain, France and Italy. The main action, therefore, is to protect the seagrass bed by prohibiting tying where they are found. This is what was imposed by a French decree published in December 2020. Another idea is to promote replanting (with a lot of patience, because it takes half a century to renovate a meadow), and especially by charging for the service. . The costs would actually be borne by companies or activities that want to offset CO2 emissions. The process is underway near Andalusia and in the Calanques National Park, on the outskirts of Marseille.
A WWF report points to the fate of two other emblematic species of the Mediterranean: the gorgonian and the great mother-of-pearl. Huge seabed lace, gorgonians are essential elements of many animal and plant species. In addition to their sensitivity to rising temperatures, they are also threatened by the increasing force of storms that destroy these fragile structures. The large mother-of-pearl is an immeasurable mold longer than a meter for the most spectacular individuals who are today classified as at risk of extinction. Since 2016, the parasite has affected this shell, which has been protected at the European level since 1992 and further weakens the population. It is urgent for the WWF to save the emblematic species of the Mediterranean.