for National Geographic News
Overfishing that took place hundreds if not thousands of years ago is a
key culprit in the collapse of coastal marine ecosystems today, an
international group of researchers reports.
Up until now,
scientists have tied the current collapse of the world's coastal
ecosystems almost entirely to recent human impacts—pollution,
increased nutrient runoff, and climate change.
By looking at historical evidence, the researchers were able to draw a picture of ancient oceans teeming with life in an abundance heretofore unimagined.
The picture today is dramatically different: dying coral reefs, dwindling populations of marine mammals, fish, and shellfish, shrinking seagrass beds, increased invasions of alien species, noxious algal blooms, and more virulent and frequent outbreaks of disease.
This current state of affairs can be attributed at least in part to the actions of aboriginal coastal populations, say the authors of the two-year study, which was published August 3 in Science.
"Up until now weve been attributing the collapse of coral reef ecosystems to pollution and global warming," said co-author Karen Bjorndal, a marine ecologist at the University of Florida's Archie Carr Center for Sea Turtle Research. "While that's certainly a factor and something society must address, ecosystem collapse was set in motion long before modern activities contributed."
The authors hope their work will help reorient current conservation and restoration practices away from quota systems and no-fishing zones to a more broad-based ecosystem approach.
"We need to change the way we think about our coastal seas—not pristine, but damaged, and equally not hopeless, but salvageable," said co-author Roger Bradbury of the Australian National University in Canberra.
Long-Term Domino Effect
In their report, the authors note that large marine vertebrates—whales, manatees, dugongs, sea cows, monk seals, crocodiles, codfish, jewfish, swordfish, sea turtles, sharks, and rays—are now functionally or entirely extinct in most coastal marine ecosystems.
They found that the depletion of these species through overfishing and overharvesting sets off a domino effect that can have impacts even centuries later.
To draw a picture of what marine ecosystems looked like eons ago, the 19 researchers who contributed to the study examined marine sediment evidence from about 125,000 years ago, archaeological information from early human coastal settlements some 10,000 years ago, and European trade records from the 15th century to the present.
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