Oceanographer Enric Sala, a National Geographic explorer-in-residence, encounters an endangered dusky grouper. (Photo: Josep Clotas)
Parts of the Mediterranean have become barren: study
Friday, March 02, 2012, 23:30 (GMT + 9)
Continued overfishing and the introduction of invasive species from the Red Sea have made some portions of the Mediterranean Sea barren, tells an unprecedented study.
An international team of scientists found that the healthiest ecosystems were located well-enforced marine reserves, where fish biomass had bounced back to levels five to 10 times greater than in fished areas. However, marine protected areas (MPAs) where some types of fishing are allowed did not allow for this recovery, suggesting that full recuperation of Mediterranean marine life requires fully protected reserves.
The findings were published this week in the journal PLoS ONE.
|National Geographic Explorer-in-Residence Enric Sala
"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 team made hundreds of dives over three years off these countries and Morocco, setting up transects to count fish and collect samples of plants and animals on the seafloor in 14 MPAs and 18 open-access sites, gathering data at an unprecedented scale.
While fishing levels were the chief factor in determining the biomass of fish, the health of the algal forests depended on other factors and their recovery takes longer.
"It's like protecting a piece of land where the birds come back faster than the old trees," Sala said.
The study also gives the first baseline that allows evaluation of the health of the entire ecological community at any Mediterranean site and of the efficacy of conservation at this level for the first time.
Sala believes the results give reason to support reserves in waters across the globe.
"If marine reserves have worked so well in the Mediterranean, they can work anywhere," he said.
|Trawlers in the Mediterranean (Photo: Oceana/Juan Cuetos)
The Mediterranean, whose resources support hundreds of millions of people, suffers from overexploitation, habitat loss, pollution, rising sea surface temperatures due to climate change and more than 600 invasive species.
Marine reserves that shelter slivers of the sea permit some ecosystems to pick up and their predators to eventually reappear.
"The protection of the marine ecosystems is a necessity as well as a 'business' in which everyone wins," Sala said. "The reserves act as savings accounts, with capital that is not yet spent and an interest yield we can live off. In Spain's Medes Islands Marine Reserve, for example, a reserve of barely 1 sqkm can generate jobs and a tourism revenue of EUR 10 million, a sum 20 times larger than earnings from fishing."
By Natalia Real