The world’s oceans may cover about 70 percent of the earth’s surface, but scientists at UCSB’s National Center for Ecological Analysis and Synthesis say almost half of those seas are affected heavily by human activity. The results of their work were published in the Feb. 15 issue of the journal Science.

To reach their conclusion, the researchers, from various universities as well as government and nongovernment agencies, studied global data on human impacts to marine ecosystems. Prior to this study, most of the focus has been on single ecosystems, or certain activities within a given region.

“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 NCEAS and the study’s lead author. “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.”

By collecting and quantifying data on different human activities and their impact on the different kinds of marine ecosystems, as well as data on the locations of these systems and their condition, the scientists were able to score the effects of factors like fishing, pollution and climate change on marine ecosystems around the world.

The results? The North Sea, the South and East China seas, the Caribbean, the Mediterranean, the United States’ East Coast, the Bering Sea and the Persian Gulf are among the most heavily affected. The least affected are the areas around the poles, although, according to NCEAS researcher Carrie Kappel, global warming and the subsequent loss of ice sheets, along with the spread of human activity to those areas may result in degradation of these relatively pristine areas. The most affected ecosystems include coral reefs, rocky reefs, mangroves and seagrass beds. The least affected are soft-bottom areas and open ocean surface waters.

The maps are not complete, say the researchers, owing to lack of data, but as more information is incorporated into the study, they say the results are likely to be even less encouraging.

According the Halpern, there is still room for hope.

“With targeted efforts to protect the chunks of the ocean that remain relatively pristine, we have a good chance of preserving these areas in good condition,” he said.

With the information provided by the study, assessments can be made that will inform decisions on which activities can be continued, and which ones may have to be moved, or stopped altogether. Currently the Southern California coastal and marine region is being evaluated for marine protected areas, a network of sites mandated by the California Marine Life Protection Act, which aims to protect marine ecosystems along the state’s coast.

“Humans will always use the oceans for recreation, extraction of resources, and for commercial activity such as shipping,” Halpern said.  “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 the resources we need and want.”