A new, unprecedented study has concluded that centuries of overexploitation of fish and other marine resources — as well as invasion of fish from the Red Sea — have turned some formerly healthy ecosystems of the Mediterranean Sea into barren places.
Unsurprisingly, the researchers found that the healthiest places were in well-enforced marine reserves, where fish biomass had recovered from overfishing to levels 5-10 times higher than in fished areas. More importantly, scientists found that "protected" areas where some fishing was allowed did not do better than sites that were completely unprotected, suggesting that full recovery of Mediterranean marine life requires fully protected reserves.
"We found a huge gradient, an enormous contrast. In reserves off Spain and Italy, we found the largest fish biomass in the Mediterranean," said National Geographic Explorer-in-Residence Enric Sala, the paper’s lead author. "Unfortunately, around Turkey and Greece, the waters were bare."
The study, published last month in the journal PLoS ONE, is a result of hundreds of dives over three years throughout the Mediterranean, setting up transects to count fish and take samples of plants and animals living on the seafloor in 14 marine protected areas and 18 open-access sites.
Often called the "cradle of civilization," the Mediterranean is home to nearly 130 million people living on its shores, and its resources support countless millions more. A variety of pressures keep the organisms that live in the sea in a permanent state of stress. "It’s death by a thousand cuts," said Enric Ballesteros of Spain’s National Research Council and coauthor of the study. Among them are overexploitation, destruction of habitat, contamination, a rise in sea surface temperatures due to climate change and more than 600 invasive species. On the southwest coast of Turkey, for example, an invasive fish from the Red Sea called the dusky spinefoot has left Gokova Bay’s rock reefs empty.
The full press release is available at the National Geographic Society.