Ecological problems in coastal waters are nothing new?they began thousands of years ago when primitive peoples fished so heavily that marine environments became ecologically unbalanced and remain that way today.
By examining ancient garbage mounds, sediment deposits and archeological records, scientists found that excessive hunting of sea mammals, turtles and fish upset delicate webs of life on a scale never before realized. The report uses research from dozens of coastal ecosystems from North America, Europe, Asia and Australia.
The disruptions unleashed population explosions of the species that were not eaten, contributing to the conditions that strain oceans today, the research team reported in a study in the journal Science. ?What we?re finding is a number of the crises that our marine ecosystems are facing today can be traced back thousands of years in some cases, and hundreds of years in others, to when human beings first began affecting those ecosystems,? says co-author Karen Bjorndal.
In America, overfishing reached its peak in the Colonial and modern eras, but it became a problem long before the arrival of Europeans, ?contrary to romantic notions of the supposedly superior ecological wisdom of non-Western and pre-Colonial societies,? the paper states.
The scientists reconstructed fishing patterns over time through a variety of means. They read historic accounts, including one from the Chesapeake Bay describing a long cannon, used to blast large fish, that was ?clearly visible in over 30 feet of water.? They sifted through refuse mounds in the Caribbean and Maine, which are filled with the remains of fish leftovers, thrown away thousands of years ago.
The over-harvesting of fish can be compared to Stone Age hunting practices, which drove dozens of species to extinction, with one major exception. ?On the land, as we killed off the giant mammals and destroyed the ancient forests, we replaced with a new suite of farmed species. In the coastal seas, we took out animals and replaced them with nothing,? according to co-author Roger Bradbury of Australia.
The disappearance of predators and other key links in the ocean food chain set off a series of events that have indirectly lead to ecological instability in our age, such as toxic algae blooms, dead zones and outbreaks of disease. In the Chesapeake Bay, for instance, vast reefs of oysters once flourished, acting as natural filters in an estuary that harbored alligators, gray whales, giant sturgeon and hammerhead sharks. But after Native and Colonial Americans picked the reefs clean, nothing prevented choking waves of algae from turning the bay into a murky and biologically impoverished mess.
Land and sea hunting differed in another crucial way, which could be the key to the restoration of damaged water ecosystems. Only a handful of coastal species, like the Steller’?s Sea Cow in the North Pacific and the Caribbean monk seal, were driven to complete extinction as result of human harvesting. While depleted, populations of species such as green sea turtles, sea otters and others have managed to cling to survival with enough numbers to bring about their revival, if they?re given a chance.
In our era, pollution and high-tech fishing techniques have increased pressures on the deep. But marine conservation practices that take into account the long-term biographies of coastal ecosystems could help restore them. ?We need to change the way we think about our coastal seas; not pristine, but damaged, and equally not hopeless, but salvageable, Bradbury says. ?Our research points the way.?
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