Public Release: 

Excessive fishing prompted coastal ecosystems to collapse, but wise management now will help

University of North Carolina at Chapel Hill

(Embargoed) CHAPEL HILL - Looking back, before men began harvesting them in increasingly large and disruptive amounts, the worldwide abundance of sea creatures almost staggers the imagination.

In the Caribbean, instead of millions of tourists, tens of millions of sea turtles made their homes there. English seafarers in the 1800s reported herds of dugongs -- aquatic mammals resembling walruses -- composed of untold thousands of adults and juveniles extending four miles along the Australian coast. Reefs of living oysters once so flourished in the Chesapeake Bay, they could filter virtually all the bay's water in three days.

Whales, manatees, sea cows, monk seals, crocodiles, codfish, jewfish, swordfish, sharks, rays and other species are now functionally or entirely extinct in most coastal environments. As a result, "fantastic" coasts around the world have changed radically -- and for the worse, scientists say.

Evidence of what humans have lost and what might be done to restore at least part of the oceans' bounty is the subject of a ground-breaking paper appearing in the July 27 issue of the journal Science. Among 18 authors from the United States and Australia, are Drs. Jeremy B.C. Jackson, Ritter Memorial professor at Scripps Institution of Oceanography, and Charles H. Peterson, Alumni Distinguished professor of marine sciences at the University of North Carolina at Chapel Hill.

"At Jeremy's suggestion, we brought together for the first time historians, paleontologists, archaeologists, biologists and others to create a view into the past about marine systems that modern ecologists don't usually appreciate," Peterson said. "We looked closely at tropical coral reefs, kelp forests, rocky sub-tidal shores along warm and cold coastlines and estuaries worldwide using a large variety of records."

Among those were old accounts by sea captains, who sometimes were fine naturalists, Peterson said, and scientists commissioned by royalty. Even drawings by Mark Catesby, an 18th Century British naturalist, and Captain John Smith were part of the study.

"Our work demonstrates that what we view as pristine, natural systems are not at all pristine and natural," Peterson said. "In other words, the best of what we have today in the marine world has been radically transformed."

That transformation predated pollution and mechanical seafood harvesting and began thousands of years ago as humans exploited resources in coastal waters and became increasingly adept at removing the top link in the marine food chain -- sharks, turtles, whales and the largest fish species. Later, as those species declined, smaller species were eliminated from the systems to varying degrees, including oysters and other bivalves capable of filtering water and grazing down algal blooms.

"That had a tremendous negative effect on water quality," Peterson said. "We have diverted the natural passage of energy up through the system to large animals and diverted it instead downward to microbial production and microbial oozes. You can look at the Baltic Sea and the northern Gulf of Mexico, for example, and see huge dead zones resulting from the influx of excessive nutrients, a process called eutrophication."

Fossil records and traces of humans' impact along the world's coasts show that time lags of decades to centuries occurred between the beginning of overfishing and changes in ecological communities, the group wrote. That's because comparable unfished species took the place of exploited species until they too were overfished or died of epidemic diseases related to overcrowding. Historical accounts show the magnitudes of losses of large animals and oysters were "so great as to seem unbelievable based on modern observations alone."

Even pessimistic estimates of the global percentage of fish stocks that are overfished are almost certainly too low, the scientists said. Odds are good that that many more marine ecosystems could collapse soon.

"Place names for oysters, pearls and conches conjure up other ecological ghosts of marine invertebrates that were once so abundant as to pose hazards to navigation, but witnessed now only by massive garbage heaps of empty shells," they wrote.

The scientists did not write their paper, however, simply as a gloom and doom story, he said. Rather they hope it will serve as an appeal to use available information to help orchestrate a better future.

"We note opportunities for wise management to capitalize on components of the system that are still present and therefore could be conserved and restored," Peterson said. "Among these are native Pacific and East Coast oysters that are still found in patches and, if restored, would have a valuable impact on water quality and, simultaneously, create habitat for crabs, shrimp and fishes."

Promoting further development of aquaculture - growing and tending clams, oysters, scallops, and mussels also would have a huge public benefit in achieving better water quality and enhancing habitats for fish and shellfish, he said.

"The central point for successful restoration is that loss of economically important fisheries, degradation of habitat attractive to landowners and tourists and emergence of noxious, toxic and life-threatening microbial diseases are all part of the same standard sequence of ecosystem deterioration that has deep historical roots," the authors wrote.

"Responding only to current events on a case by case basis cannot solve these problems. Instead, they need to be addressed by a series of bold experiments to test the success of integrated management for multiple goals on the scale of entire ecosystems."

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Note: Peterson can be reached at 252-726-6841 or cpeters@email.unc.edu

Jackson's mobile number is 858-518-7613. A copy of the embargoed paper is available by calling 202-326-6440 or by contacting Science at scipak@aaas.org

Contact: David Williamson, 919-962-8596

By DAVID WILLIAMSON
UNC News Services

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