Invasive species flood Mediterranean, 800 established as waters warm

Hundreds of invasive species are flooding the Mediterranean Sea and moving north toward France and Spain as climate change warms the waters, scientists reported in July 2026.

The spread has accelerated since the early 2000s, coinciding with rising sea temperatures, according to the U.N. General Fisheries Commission for the Mediterranean. The lionfish, first spotted in the eastern Mediterranean in 2012, has advanced rapidly westward. Rabbitfish strip algae from the sea floor, destroying habitats for native species, while the spotted puffer fish—called the 'worst invader'—is a voracious predator.

Biodiversity losses are severe. The eastern Mediterranean’s shallows have lost 93 percent of their mollusk population, said Ernesto Azzuro, a marine biologist with the Italian National Research Council. Along the Adriatic coast, almost all mussels have died off as sea temperatures in some years exceeded 30 degrees Celsius (86 degrees Fahrenheit).

The Mediterranean is a climate change 'hot spot,' expected to warm by 2 to 6 degrees Celsius (3.6 to 10.8 degrees Fahrenheit) by 2100, the Mediterranean Experts on Climate and Environmental Change estimate. Oceanographer Ronan McAdam of the Euro-Mediterranean Center on Climate Change explained that the sea’s enclosed basin traps heat, preventing it from dissipating.

Azzuro lamented, 'The Mediterranean of our grandfathers … is lost forever,' adding that many changes are irreversible.

Cyprus, because of its proximity to the Suez Canal, was first to feel the impact. Lionfish supplanted native red mullet, devastating local fishers. Rabbitfish further degrade ecosystems by consuming the algae that serve as habitat for many species.

His institute launched a campaign, 'Beware of those four,' to highlight health risks: the puffer fish is toxic if eaten, and lionfish spines can cause severe pain.

Zoologist Piero Genovesi Papik of Italy’s Higher Institute for Environmental Protection and Research said it is 'too late' to reverse the spread, but practical steps can soften the blow. Enforcing an international treaty to treat ship ballast waters could reduce new alien species by 95 to 99 percent, he said. Special hull paint can also deter hitchhiking organisms. Fishing policies are being amended to aid native species, for instance by cultivating mollusks less susceptible to the invasive blue crab. Azzuro suggested commercializing edible invasive species or paying fishers to catch inedible ones like the puffer fish for incineration.