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We're destroying our oceans
15/02/2008 12:03 - (SA)
Mira Oberman
Chicago - Nearly every corner of the world's oceans have been damaged in some way by human activity and some 41% of those waters are heavily affected, a study released on Thursday has found.
Coastal areas are polluted by runoff. Oyster beds and fisheries are disappearing. Floating islands of trash the size of small states clutter what used to be open water. Birds and whales are struck by ships which leave a trail of oil and waste in their wakes.
But the biggest damage is from climate change, according to the first global-scale study of human influence on marine ecosystems which will be published in Science magazine.
"It's got broad, intense impacts," said study co-author Kim Selkoe, a researcher with the University of Hawaii.
Significant increases in water temperatures have already been observed in the North Atlantic between 1995 and 2005 and global warming is projected to further raise temperatures to varying extents elsewhere.
These higher temperatures increase plankton levels, and change the species composition at higher levels on the food chain. It also leads to high rates of disease and changes in ocean circulation, Selkoe said.
The oceans are also becoming more acidic as they absorb carbon dioxide and plants are being affected by increased ultraviolet radiation.
"The other really surprising thing to me was that our fishing data showed 80% of the world's ocean is fished," Selko said.
Nowhere left to hide
"There's nowhere left for the fish to hide... fishing boats are just really everywhere."
While subsistence fishing has a limited impact on ocean ecologies, high-impact commercial fishing dumps millions of pounds of unwanted dead fish, birds and mammals back into the ocean. This has threatened many species of turtles, birds, whales, and dolphins with extinction.
Shipping traffic is the third largest culprit because there is simply so much of it.
"When you look at the map of the ship traffic, it's just a solid coverage of the world's oceans," she said.
"The fuel gets spilled, there's noise pollution which is disturbing to whales and such... which has a major affect on the ecosystem."
Shifting shipping lines away from sensitive areas like coral reefs and continental shelfs could significantly reduce the impact on ocean life, she said.
The most heavily affected waters in the world include large areas of the North Sea, the South and East China Seas, the Caribbean Sea, the east coast of North America, the Mediterranean Sea, the Red Sea, the Persian Gulf, the Bering Sea, and several regions in the western Pacific.
Just 3.7% of the ocean is considered to be a very low-impact area and the bulk of this is found near the poles where seasonal or permanent ice limits human activities.
"Unfortunately, as polar ice sheets disappear with warming global climate and human activities spread into these areas, there is a great risk of rapid degradation of these relatively pristine ecosystems," said co-author Carrie Kappel, a researcher at the National Centre for Ecological Analysis and Synthesis.
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