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Last updated on April 20, 2014 at 8:28 EDT

Human Activity Heavily Impacting World’s Oceans

February 14, 2008

More than 40 percent of the world’s oceans are heavily impacted by human activities, such as overfishing and pollution, leaving only four percent relatively unspoiled, according to a new study that provides a first of its kind map that shows the damaging effects of human activities across the world’s oceans.

According to the new map, 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, while the least affected areas are near the poles.

The research revealed that no areas of the ocean are completely untouched by human activities.   Roughly one-third are heavily impacted, and the most heavily affected environments are the continental shelves, rocky reefs, coral reefs, seagrass beds and seamounts.

Coral reefs house more than 25 percent of all marine life and protect against wave erosion.  Seagrass beds are nursery grounds for young fish and mangroves, which grow in coastal habitats and also help ward off erosion.

In performing their study, researchers examined17 different types of human activities, including climate change, fishing, land-based pollution, commercial shipping and other activities, and then analyzed their effects on marine ecosystems, continental shelves and the deep ocean. 

The team measured three areas of human-induced climate change, including sea surface temperature changes, UV radiation, and ocean acidification. These measures were found to be among the most important factors in determining the global impacts.

To create the map, the researchers compiled the data and fed them into a model that assigned a single value to each square kilometer of the ocean, reflecting the overall impact of all the human-induced changes at work in that particular spot.

“This project allows us to finally start seeing the big picture of how humans are affecting the oceans,” said Dr. Benjamin Halpern of the National Center for Ecological Analysis and Synthesis (NCEAS) at the University of California Santa Barbara.  Dr. Halpern is lead author of the study “A Global Map of Human Impact on Marine Ecosystems”.

He explained that while previous studies have focused on how a single type of human activity affects the ocean, or the condition of only one marine ecosystem, the new research looks at many different types of human activities and all marine ecosystems simultaneously, therefore presenting a more thorough, global picture of the oceans’ health.

The research is expected to be a useful tool for developing strategies for conserving the ocean’s resources.

Despite their vastness, the study revealed the oceans are far from a pristine wilderness.  But, “there is definitely room for hope,” Halpern said. “With targeted efforts to protect the chunks of ocean that remain pristine, we have a good chance of preserving these areas in good condition.”

“Whether one is interested in protecting ocean wilderness, assessing which human activities have the greatest impact, or prioritizing which ecosystem types need management intervention, our results provide a strong framework for doing so,” said Kimberly Selkoe, also of NCEAS and a principal investigator on the project.

“The extent of human influence was probably more than any of us expected,” said Dr. Kenneth Casey with the National Oceanic and Atmospheric Administration’s (NOAA) National Oceanographic Data Center in Maryland, one of the study’s co-authors.

He explained that red areas on the map indicate the most heavily impacted regions.  He said the new map, which visually highlight the ocean trouble spots, are tools for the world’s decision-makers to assess the real impact of human activities on marine ecosystems and help identify ways to reduce the threats.

Dr. Casey added that the study 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.”

The study, “A Global Map of Human Impact on Marine Ecosystems”, will appear in the 15 February issue of the journal Science.  

An abstract of the report can be viewed here.

The high-resolution maps can be viewed at:
http://www.nodc.noaa.gov/SatelliteData/Cortad/

On the Net:

www.noaa.gov