Hundreds of invasive marine species are spreading through the Mediterranean as rising sea temperatures make the region increasingly hostile to native fish – and more welcoming to tropical arrivals.
Scientists warn the transformation is accelerating, particularly in the eastern Mediterranean where species entering through the Suez Canal are displacing local populations and damaging fishing livelihoods.
The Mediterranean Experts on Climate and Environmental Change describes the region as a climate hotspot, with sea surface temperatures projected to rise by up to several degrees by the end of the century.
Many native species are already approaching their heat tolerance limits as marine heatwaves become more frequent, longer and more intense. At the same time, warmer conditions allow species from the Red Sea and other tropical waters to survive and expand westwards.
Lionfish, rabbitfish and the toxic silver-cheeked puffer fish are among the most damaging arrivals.
The puffer fish preys on native species, destroys fishing gear and contains a toxin that can be fatal if eaten. Rabbitfish can strip underwater habitats of vegetation while lionfish consume large numbers of smaller fish.
The UN’s General Fisheries Commission for the Mediterranean has recorded more than 900 non-indigenous species across the Mediterranean and Black Sea, with around 700 found in the eastern Mediterranean.
The Mediterranean contains between 4% and 18% of the world’s identified marine species despite accounting for less than 1% of the global ocean surface.
Many invasive species entered through the Suez Canal while others arrived through ballast water, ship hulls and the Strait of Gibraltar.
MedECC warns invasive species are already affecting biodiversity, fisheries and other ecosystem services. Warming, pollution, habitat damage and overfishing are combining to reduce the ability of native populations to recover.
The economic threat is also growing for coastal communities built around traditional catches. Some governments are paying fishermen to remove invasive species, while researchers are exploring whether edible varieties such as lionfish and blue crab, can be turned into commercial products.
However, scientists say removing established populations completely is no longer realistic.
Measures including tighter ballast-water controls, monitoring ship hulls, targeted fishing and faster detection could slow further introductions.
That extraordinary biodiversity is now being reshaped by warming at a speed many native species cannot match.
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