The Mediterranean Sea is undergoing profound and potentially irreversible changes driven by climate change, scientists report. Warming waters, primarily caused by the burning of fossil fuels, are creating an environment conducive to hundreds of invasive species that are decimating native populations and altering coastal economies.
Scientists have identified the Mediterranean as a climate change "hot spot," with projections indicating a temperature increase of 2 to 6 degrees Celsius (3.6 to 10.8 degrees Fahrenheit) by 2100. Heat waves are expected to become more frequent and intense. The sea's enclosed nature prevents warmth from dissipating as it does in larger oceans, exacerbating this warming trend, according to Ronan McAdam, an oceanographer with the Euro-Mediterranean Center on Climate Change.
These warmer conditions have facilitated the proliferation of invasive species, such as the spotted puffer fish and the lionfish. The lionfish, first observed in the eastern Mediterranean in 2012, has rapidly expanded its range westward. Rabbitfish, which consume algae, are also contributing to habitat destruction. These species enter the Mediterranean primarily through the Suez Canal and are now spreading towards France and Spain.
The influx of invasive species has been accelerating since the early 2000s, coinciding with rising sea temperatures, according to the General Fisheries Commission for the Mediterranean. Ernesto Azzuro, a marine biologist with the Italian National Research Council, stated that about 1,000 invasive species have been identified in the Mediterranean, with 800 firmly established. This biodiversity loss is making the region "poorer" and "unsuitable for native species."
Coastal communities are already experiencing the consequences. In Cyprus, lionfish have supplanted native species like red mullet, diminishing the catch for local fishers. The shallows of the eastern Mediterranean have seen a 93% decline in their mollusk population. Along the Adriatic coast, once abundant mussel populations have nearly vanished due to sea temperatures that have occasionally exceeded 30 degrees Celsius (86 degrees Fahrenheit).
Beyond ecological impacts, some invasive species pose risks to human health. Puffer fish are toxic and potentially lethal if consumed, while lionfish possess venomous spines. To mitigate these effects, scientists are exploring strategies such as commercializing edible invasive species and incentivizing fishers to catch inedible ones for disposal.
While Azzuro noted that some invasive species, like the lionfish, can have economic benefits due to high market prices, not all are being exploited. The dusky spinefoot, for example, has seen significant population growth in Italian waters without being effectively commercialized.
Experts emphasize the need for global cooperation to reduce fossil fuel consumption, the primary driver of climate change. Piero Genovesi Papik, a zoologist with Italy’s Higher Institute for Environmental Protection and Research, stressed that while reversing the spread of invasive species is "too late," practical measures can mitigate their impact. These include enforcing international treaties to treat ballast water in ships and applying anti-fouling paint to ship hulls to prevent new species from hitching rides. Fishing policies are also being adapted to help native species, like mollusks less susceptible to the invasive blue crab, recover.
"In the coming years, I think that the challenge will be to restore, to find new ways to restore the environment," Papik said.