"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 worlds coasts show that time lags of decades to centuries occurred between the beginning of overfishing and changes in ecological communities, the group wrote. Thats 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 ecosy
Contact: David Williamson
University of North Carolina at Chapel Hill