Study Finds Humans' Effect on Oceans Comprehensive
Friday, February 15, 2008
Human activities are affecting every square mile of the world's oceans, according to a study by a team of American, British and Canadian researchers who mapped the severity of the effects from pole to pole.
The analysis of 17 global data sets, led by Benjamin S. Halpern of the National Center for Ecological Analysis and Synthesis in Santa Barbara, Calif., details how humans are reshaping the seas through overfishing, air and water pollution, commercial shipping and other activities. The study, published online yesterday by the journal Science, examines those effects on nearly two dozen marine ecosystems, including coral reefs and continental shelves.
"For the first time we can see where some of the most threatened marine ecosystems are and what might be degrading them," Elizabeth Selig, a doctoral candidate at the University of North Carolina at Chapel Hill and a co-author, said in a statement. "This information enables us to tailor strategies and set priorities for ecosystem management. And it shows that while local efforts are important, we also need to be thinking about global solutions."
The team of scientists analyzed factors that included warming ocean temperatures because of greenhouse gas emissions, nutrient runoff and fishing. They found that the areas under the most stress are "the North and Norwegian seas, South and East China seas, Eastern Caribbean, North American eastern seaboard, Mediterranean, Persian Gulf, Bering Sea, and the waters around Sri Lanka."
Some marine ecosystems are under acute pressure, the scientists concluded, including sea mounts, mangrove swamps, sea grass and coral reefs. Almost half of all coral reefs, they wrote, "experience medium high to very high impact" from humans.
Overall, rising ocean temperatures represent the biggest threat to marine ecosystems.
Pew Environment Group Managing Director Joshua Reichert, whose advocacy organization has launched a campaign to preserve several of the oceans' most ecologically rich regions by creating three to five marine reserves over the next five years, said the study demonstrates that human activity has already transformed "what had been viewed as the Earth's last great bastion of nature."
Reichert added that while it made sense that coastal areas close to dense populations had suffered the most, the scientists' most significant finding was that human effects are reaching even isolated regions.
"As the result of more sophisticated technology and fishing gear that's been able to reach farther underneath the surface . . . we're reaching the remote areas of the sea," Reichert said. "They were off bounds. They're not anymore."
One of the unusual aspects of the new map is its geographic precision. Selig worked with John Bruno, a University of North Carolina marine sciences professor, and Kenneth Casey, a researcher at the National Oceanic and Atmospheric Administration, to create a grid of local ocean temperature variation in which each block measures just 1.5 square miles. Previous data sets spanned areas of nearly 20 square miles.