What are ecosystems?

An ecosystem is a community of organisms, including humans, in conjunction with their nonliving environment.   Ecosystems involve complex interactions between organisms, their environment, and the processes that drive the system.  Ecosystems are both complex and continuously changing. Humans and human institutions, beliefs and practices are integral parts of the ecosystem.

In the mid-1980s, Dr. Kenneth Sherman of NOAA’s National Marine Fisheries Service and Dr. Lewis Alexander of the University of Rhode Island pioneered the concept of large marine ecosystems (LMEs). Sherman, Alexander, and several others recognized that large areas of the oceans function as ecosystems, and that pollution from air, land, and water and overexploitation of living resources, along with natural factors, influenced the varying productivity of these ecosystems. NOAA and international partners have defined 64 LMEs around the world. Although expansive, with most greater than 200,000 km2 (77,220 mi2), each LME has a distinct bathymetry, hydrography, and biological productivity that supports and connects all organisms within the system. The LME concept uses an EBM approach to help assess, manage, and recover regional marine areas.  Click here for more information on the U.S. regional ecosystems and EBM activities being undertaken in each region.