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Report: Ancient fishing linked to modern crisis

By Richard Stenger

(CNN) -- Ecological upheavals in coastal waters began thousands of years ago as primitive peoples massacred the denizens of the sea, leaving marine environments susceptible to the escalating pressures of contemporary times, according to a new report.

Examining ancient garbage mounds, sediment deposits and archeological records from four continents, scientists found that excessive hunting of sea mammals, turtles and fish upset delicate webs of life on a scale never before realized.

The disruptions unleashed population explosions of opportunist species and lethal epidemics against less fortunate ones, and contributed to the conditions that strain oceans in modern times, the scientist team reported in a study to appear Friday 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," said co-author Karen Bjorndal.

Fishy garbage from the past

An interactive map of species affected by overfishing  

In America, while overfishing reached its peak in the Colonial and modern eras, 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 stated.

In contrast to the narrow geographic and chronological focus of many studies, the report draws on the research of dozens of coastal ecosystems from North America, Europe, Asia and Australia.

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 "clearly visible in over 30 feet of water." They sifted through refuse mounds in the Caribbean and Maine, chock full of fish leftovers thrown away thousands of years ago.

Alligators in the Chesapeake

The over-harvesting was akin to Stone Age hunting, which drove dozens of beasts to extinction, with two major exceptions, the time detectives concluded.

"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," said co-author Roger Bradbury of Australia.

Colonial-era sea hunters placed added pressures on North Atlantic coastal waters  

The disappearance of predators and other key links in the food chain set off a succession of events that have indirectly lead to ecological instability in our age, such as toxic algae blooms, dead zones and outbreaks of disease, according to the report.

In the Chesapeake Bay, vast reefs of oysters once flourished, acting as natural filters in an estuary that harbored alligators, Grey whales, giant sturgeon and hammerhead sharks.

But with Native and Colonial Americans picking the reefs clean, nothing prevented choking waves of algae from turning the bay into a murky and biologically impoverished mess, the scientists said.

Glimmer of hope in the water

In the Caribbean, dwindling numbers of grazing green sea turtles no longer keep turtle grass in check, making the underwater forests vulnerable to periodic plagues, which in turn threaten a hot of species dependent on the plant.

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.

Baskets of cod and haddock, which have been fished extensively for centuries
Baskets of cod and haddock, which have been fished extensively for centuries  

While depleted, populations of species such as green sea turtles, sea otters and others have managed to cling to survival with enough numbers to allow their revival, the scientists said.

Pollution and high-tech fishing techniques have escalated the 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. Our research points the way," Bradbury said.

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