The Mediterranean Sea is undergoing a major ecological transformation due to climate change. Waters are warming rapidly, facilitating the arrival of exotic species that disrupt natural balances. This phenomenon, closely observed by scientists and divers, could extend to the entire Mediterranean basin in the coming decades.
High temperatures recorded at depth, sometimes reaching nearly 30°C (86°F), have become common in certain areas like the Turkish coast. Murat Draman, a diving instructor, reports dramatic changes: where waters were around 25°C (77°F) twenty years ago, they now approach 32°C (90°F) at the surface. This thermal increase paves the way for species originating from the Red Sea and tropical Atlantic Ocean, which migrate via the Suez Canal and Strait of Gibraltar, to gradually colonize the Mediterranean.
A lionfish, an invasive species typically living in tropical seas.
Image Wikimedia Among these newcomers, the lionfish stands out for its danger and devastating impact. This voracious predator, lacking natural predators in the Mediterranean, proliferates rapidly and decimates local small fish populations. Diving observations reveal an alarming increase in their numbers, signaling a profound disruption of food chains and marine biodiversity.
Scientists like Professor Gil Rilov warn about the speed of this invasion, accelerated by the recent widening of the Suez Canal and ongoing warming. Many native species have already disappeared from the eastern Mediterranean, serving as a warning for the rest of the basin. Models predict expansion toward the north and west, with scenarios ranging up to complete tropicalization by the end of the century.
Faced with this threat, conservation measures are being considered to protect sensitive marine areas. The absence of natural predators against invasive species like the lionfish makes the situation particularly critical.
Ocean warming
Global climate change is causing rising ocean temperatures, affecting marine currents and marine life. Warmer waters alter natural habitats, forcing some species to migrate to cooler latitudes or disappear if they cannot adapt.
This phenomenon is particularly visible in the Mediterranean, where warming is faster than the global average. Satellite data and in situ measurements confirm an upward trend over several decades, with recent heat records being broken.
Consequences include melting polar ice, sea level rise, and water acidification, which affect corals and other marine organisms. Understanding these mechanisms is vital to predict future changes and develop adaptation strategies.
Invasive species and their impacts
An invasive species is an organism introduced into a new environment where it did not evolve naturally, often with negative effects on the local ecosystem. These introductions can occur through human activities, such as maritime transport or artificial canals.
In the Mediterranean, the opening of the Suez Canal in 1869 allowed many Red Sea species to enter. With warming waters, their establishment and spread are facilitated, threatening native biodiversity.
Ecological impacts include competition for resources, predation on local species, and habitat alteration. For example, the lionfish consumes large quantities of small fish, unbalancing trophic networks. Managing these invasions requires continuous monitoring and sometimes targeted interventions.