Total human impact on oceans mapped
Thursday February 14 2008
Fishing, climate change and pollution have left an indelible mark on virtually all of the world's oceans, according to a huge study that has mapped the total human impact on the seas for the first time. Scientists found that almost no areas have been left pristine and that more than 40% of the world's oceans have been heavily affected.
"This project allows us to finally start to see the big picture of how humans are affecting the oceans," said Ben Halpern, assistant research scientist at the University of California, Santa Barbara, who led the research. "Our results show that when these and other individual impacts are summed up, the big picture looks much worse than I imagine most people expected. It was certainly a surprise to me."
Human impact is most severe in the North Sea, the South and East China Seas, the Caribbean, the Mediterranean, the Red Sea, the Gulf, the Bering Sea, along the eastern coast of North America and in much of the western Pacific.The oceans at the poles are less affected, but melting ice sheets will leave them vulnerable, researchers said.
Different ecosystems have been affected to differing degrees: the study found that almost half of the world's coral reefs have been heavily damaged. Other areas of concern are seagrass beds, mangrove forests, seamounts, rocky reefs and continental shelves. Soft-bottom ecosystems and the open ocean fared best, but even these were not pristine in the majority of locations. (clip)
To make the map, scientists compiled global data on the impacts of 17 human activities including fishing, coastal development, fertiliser runoff and pollution from shipping traffic. They divided the ocean into 1-square-kilometre cells and worked out which human activities might have touched each particular cell.
For each cell, the scientists allocated an impact score to look at the degree to which human activities affected 20 types of ecosystem. Around 41% had medium high impact to high impact scores. A small fraction, 0.5% but representing 2.2m square kilometres (850,000 square miles), were rated very highly affected. (clip)
Halpern said that the map should act as a wake-up call. "Humans will always use the oceans for recreation, extraction of resources, and for commercial activity such as shipping. This is a good thing.
Our goal, and really our necessity, is to do this in a sustainable way so that our oceans remain in a healthy state and continue to provide us with the resources we need and want."
Somehow, that statement reminds me of something Miss Higgins, my kindergarden teacher might have said.
"Now children, we don't want to piss and s#it on everything or else we'll have a real mess won't we."
In fairness, I guess it's more complicated than that. Who could have guessed that sunscreen kills coral reefs?
Or that fertilizer and warming makes giant dead zones.
"A massive dead zone off Louisiana is created each spring by a slurry of nutrient-rich farm runoff and sewage that flows out the Mississippi River, causing algae to bloom riotously, die and drift to the bottom to decompose. Bacteria then take over. In the process of breaking down the plant matter, they suck the oxygen out of the seawater, making it unable to support most forms of sea life.
Off Oregon, the dead zone appears to form because of changes in atmospheric conditions that create the oceanic river of nutrient-rich waters known as the California Current.
The California Current along the West Coast and the similar Humboldt Current off Peru and Benguela Current off South Africa are rarities. These powerful currents account for only about 1% of the world’s oceans but produce 20% of the world’s fisheries." clip
Crab fisherman were the first to take note of Oregon's dead zone. Al Pazar recalls his alarm in 2002 when he pulled up his traps and found something seriously amiss."It was a good amount of crabs," Pazar said. "But they were dead, or dying or very, very weak. Those that we managed to keep alive didn't survive for long."
The good news is this.
"Scientists say seafood caught in low-oxygen zones is not harmful to eat."
Some people think that Waterworld was just a bad movie.
Others probably think that Soylent Green was too.
They'll be much worse as realities.
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