In one of the most comprehensive looks yet at the oceans, researchers say that humans have "strongly" fouled 41 percent of the high seas with everything from storm water runoff to shipping waste and that only small polar regions are still untouched.
"Almost half of the oceans are in a fairly degraded state, based on what we found," said Benjamin Halpern, the report's lead author and a marine biologist at the California-based National Center for Ecological Analysis and Synthesis. "There isn't a spot on the planet that hasn't been touched by humans."
Most studies of the oceans' health have focused on one or two signals, such as the loss of coral reefs or the decline of fish stocks.
But the report, being published today in the journal Science and presented at a scientific conference this week in Boston, is designed to summarize how humans are affecting the 70 percent of the planet covered by the seas.
The results might be used by Maryland scientists to compare conditions in the Atlantic off Ocean City, or the Chesapeake Bay, with other waters, experts say.
"I think it shows the problems we see in the bay are not just local," said James Carton, chairman of the University of Maryland's Department of Atmospheric and Oceanic Science.
The findings also highlight the need to focus restoration efforts on overall health of waterways -- such as the bay -- rather than on any individual species, they said.
"You just can't manage fisheries alone or try to just manage nutrient runoff or invasive species by themselves. You have to think of them in a more comprehensive context," said Donald F. Boesch, a professor of marine science and president of the University of Maryland Center for Environmental Science.
The international team of 19 researchers looked at impacts from 17 human activities, including commercial fishing, runoff from development, invasive species, industrial pollution, oil rigs and the effects of climate change.
Their sources included satellite imagery, United Nations reports on fisheries harvests, estimates of commercial shipping wastes and runoff from pesticide use.
"None of the information has been pulled together in this comprehensive a format before," Halpern said.
"The oceans are in trouble, in a lot of areas and in a lot of ways," said Andrew Rosenberg, a professor of natural resources at the University of New Hampshire who wasn't involved in the study but who reviewed it.
Only 3.7 percent of the oceans have seen little or no impact from human activity and they lie near the North and South poles, the researchers say. The most polluted areas are along the Atlantic's eastern seaboard, as well as in the North Sea, Caribbean, Red Sea, Bering Sea, the Persian Gulf and the China seas.
The report is intended to sound an alarm to environmental groups and governments about the plight of the oceans, Halpern said.
"Hopefully, this is a wake-up call showing what our impacts are on the oceans and what can be done to minimize them," he said.
There have been previous alarms. A $5 million report by the Pew Ocean Commission in 2003 called for restoring coastline ecosystems, improving the way fisheries are managed and cracking down on sources of pollution.
But experts say Halpern's report goes further.
"This changes how we view the oceans by showing how widely scattered our impacts are," said Boris Worm, a marine biologist at Dalhousie University in Halifax, Canada. Worm was co-author of a widely publicized report in 2003 that predicted a collapse of the world's fisheries by mid-century if human impacts continue at their current pace.
The biggest impacts in the deep oceans are from climate change and commercial fishing, Halpern said. Along coastal areas, the major culprits are shoreline development, wastewater discharge and sediment runoff, he said.
The most severely troubled waters lie within dozens of miles of most coastlines. It is there that impacts from land- and ocean-based activities show up, such as the depletion of fish stocks from commercial fishing and sediment runoff from coastal development.
Industrial fishing fleets equipped with sonar and global positioning systems have fished the seas to the point that about 90 percent of the worldwide stocks of tuna, cod and other large fish have disappeared, experts say.
The oceans also are a final destination for much of the greenhouse gas produced by smokestacks, cars and trucks. The seas become a repository for nitrogen in fertilizers used by farmers and gardeners and for the mix of sediment and runoff from shoreline development, said Lisa Suatoni, ocean scientist for the Natural Resources Defense Council.
The trapping of carbon dioxide, nitrogen oxide and other greenhouse gases in Earth's atmosphere also has increased temperatures of the Chesapeake Bay by an average 1.4 to 2 degrees Fahrenheit since the 1950s and increased global sea surface temperatures about 1.2 degrees Fahrenheit in the past 100 years, experts say.