More than 40 percent of the world’s oceans are heavily affected by human activities, and few if any areas remain untouched, according to the first global-scale study of human influence on marine ecosystems. By overlaying maps of 17 different activities, such as fishing, climate change, and pollution, researchers have produced a composite map of the toll that humans have exacted on the seas.

The work, published last month in Science and presented at a press conference at the American Association for the Advancement of Science meeting, was conducted at the National Center for Ecological Analysis and Synthesis (NCEAS) at UC Santa Barbara. It involved 19 scientists from a range of universities, NGOs, and government agencies.

The study synthesized global data of human impacts on marine ecosystems ranging from sea grass beds to the deep ocean. Past studies have focused largely on single activities or single ecosystems.

“This project allows us to finally start to see the big picture of how humans are affecting the oceans,” said lead author Ben Halpern, assistant research scientist at NCEAS. “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 influence on the ocean varies dramatically across various ecosystems. The most heavily affected areas include coral reefs, sea grass beds, mangroves, rocky reefs and shelves, and seamounts. The least impacted ecosystems are soft-bottom areas and open-ocean surface waters.

The study reports that 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. The least affected areas are largely near the poles (see map).

“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 Carrie Kappel, a principal investigator on the project and a post-doctoral researcher at NCEAS.

Despite a complicated process to quantify and compare how different human activities affect each marine ecosystem process, the authors acknowledge that their maps are still incomplete. Many human activities are poorly studied or lack good data.

This study provides critical information for evaluating where certain activities can continue with little effect on the oceans, and where other activities might need to be stopped or moved to less sensitive areas. Management and conservation of the oceans is turning toward marine protected areas and ecosystem-based management.

“The message for policy makers seems clear to me: conservation action that cuts across the whole set of human impacts is needed now in many places around the globe.” said Andrew Rosenberg, a professor at the University of New Hampshire who was not involved with the study.

“There is definitely room for hope,” added Halpern. “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.”

—Nancy Baron/SeaWeb & COMPASS