A composite map of the toll exacted by humans on the seas showed that more than 40 percent of the world's oceans are heavily affected by fishing, climate change and pollution, the University of California, Santa Barbara said in a release.

The study, conducted by an international group of scientists at the university's National Center for Ecological Analysis and Synthesis, synthesized global data on human impacts to a number of marine ecosystems.

The findings were presented at the American Association for the Advancement of Science meeting in Boston.

The most affected waters 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 report said.