Cumulative Ocean Impacts Mapped Off U.S. and Mexican Shores

May 27, 2009


Most efforts to alleviate harmful effects to beleaguered ocean waters tend to focus on just one or two causes at a time, such as overfishing or sewage dumping. But in real life, scores of factors interact, sometimes in unexpected ways, to create the status quo.

In order to better understand the total picture, researchers from California and Hawaii have analyzed 25 factors and developed a map that reflects the relative cumulative magnitude of their effects on the waters extending for about 250-350 miles off the shores of Washington, Oregon, California, and the Baja Peninsula. They announced their final results on May 11, 2009, following early online publication April 17, 2009, in the journal Conservation Letters:

  • "Mapping Cumulative Human Impacts to California Current Marine Ecosystems": Release (includes numerous contacts) and journal article.

This project builds on a similar map developed for the world's oceans that was published Feb. 15, 2008, in the journal Science. The new map reflects refinements of the method, but generally meshes well with the

earlier product, suggesting that the global information could be useful if you are covering other ocean areas.

For the latest effort, the researchers found that climate change, fishing, and commercial shipping are among the major culprits.

The cumulative effects are greatest in some areas you might expect, such as immediately offshore from major cities, and lowest in some other expected areas, such as immediately offshore from many stretches of Baja. But there are a number of potential surprises, such as the major degradation of the waters close to shore and hundreds of miles off the shores of Washington and Oregon, and in some near-shore areas off of Baja. In contrast the cumulative degradation of some of the waters off California shores is lower than you might expect.

The researchers hope that the map and its underlying information will help spur more comprehensive efforts to address the multiple sources of ocean degradation. For journalists, the information may serve as a useful tool for better understanding of the big picture, and the relative impacts that each of the many individual forces are having on specific ocean areas of interest to your audience.