A new study has indicated that more than 40 percent of the world's oceans are heavily impacted by human activities, including overfishing and pollution.
Conducted by researchers from the National Oceanic and Atmospheric Administration (NOAA), the study combined 17 data sets of different human activities - from fishing and fertilizer run-off, to commercial shipping and pollution - and analyzed their effects on marine ecosystems, continental shelves and the deep ocean.
The results revealed that the most heavily affected waters include the East Coast of North America, North Sea, South and East China Seas, Caribbean Sea, Mediterranean Sea, Red Sea, Persian Gulf, Bering Sea and areas off the western Pacific Ocean.
The least affected areas were determined to be near the poles.
According to Dr. Kenneth Casey from NOAA's National Oceanographic Data Center in Silver Spring, Maryland, three measures of human-induced climate change were examined by the research team, including changes in sea surface temperatures, UV radiation, and ocean acidification.
These measures were found to be among the most important factors in determining the global impacts.
According to the study, the ecosystems most at threat are: coral reefs, which house more than 25 percent of all marine life and protect against wave erosion; seagrass beds, which are nursery grounds for young fish and mangroves, which grow in coastal habitats and also help ward off erosion.
"The extent of human influence was probably more than any of us expected," said Casey, explaining that red areas on the map indicate the most heavily impacted regions.
Casey added that the study and map - designed to visually highlight the trouble spots in the oceans - are tools for the world's decision-makers to assess the real impact of human activities on marine ecosystems and help identify ways to lessen the threats.
"This project allows us to finally start seeing the big picture of how humans are affecting the oceans," said the study's lead author, Dr. Ben Halpern of the National Center for Ecological Analysis and Synthesis at the University of California - Santa Barbara.
According to Casey, the study has established the framework for routinely assessing the state of marine ecosystems in the future.
"As we compile more and better data, they can be fed back into the study to see where things stand," he said.