Unprecedented study also finds fish teeming in fully protected areas
Washington, D.C. — 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, an unprecedented study of the Mediterranean concludes.
Research by an international team of scientists designed to measure the
impact of marine reserves found that the healthiest places were in well-enforced
marine reserves; fish biomass there had recovered from overfishing to levels
five to 10 times greater than that of fished areas. However, marine “protected”
areas where some types of fishing are allowed did not do better than sites that
were completely unprotected. This suggests that full recovery of Mediterranean
marine life requires fully protected reserves, the scientists write in a paper
published Feb. 29, 2012, in the journal PLoS ONE.
“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 authors made hundreds of dives over three years off Morocco, Spain,
Italy, Greece and Turkey, 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. The result is information on the Mediterranean at an
While the level of protection was the most important factor in determining
the biomass of fish, the health of the algal forests that support the fish
depended on other factors, the authors write. Recovery of formerly abundant
algal forests takes longer than recovery of fish. “It’s like protecting a piece
of land where the birds come back faster than the old trees,” Sala said.
The study also provides the first baseline that allows evaluation of the
health of any Mediterranean site at the ecosystem level — not only its fish but
the entire ecological community. The trajectory of degradation and recovery
found by the authors allows for evaluation of the efficacy of conservation at
the ecosystem level for the first time.
“Recovery of Mediterranean marine ecosystems should be a poster child for
conservation of the ocean, given the beauty and importance of the area to so
many people,” said Dr. Andrew Rosenberg, Chief Scientist for
Conservation International and co-author of the paper. “Our study
provides important guidance on how to begin on that path to recovery.”
Sala believes the results about fully protected marine reserves give reason
for hope in waters well beyond the Mediterranean. “If marine reserves have
worked so well in the Mediterranean, they can work anywhere,” he said.
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
A series of marine reserves that shelter slivers of the sea allows certain
ecosystems to recover and their all-important 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 one square
kilometer can generate jobs and a tourism revenue of 10 million euros, a sum 20
times larger than earnings from fishing.”
“Without marine reserves, fishing has no future,” said fisherman Miquel
Sacanell, who fishes near the Medes reserve.
The research was supported by Spain’s National Research Council, the Pew
Charitable Trusts, the Oak Foundation, the Lenfest Ocean Program and the
National Geographic Society.
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