Land-based discharges of human-made debris comprise the largest source of marine debris
in oceans world-wide (nearly 80%).

The Plastic Debris, Rivers to Sea Project seeks to minimize the land-based discharges of marine debris. Just like ocean-based marine debris, land-based discharges of human-made debris are comprised mostly of plastics.

The threat and impacts of marine debris have long been ignored. Perhaps it is the perceived vastness of ocean and lack of visibility of marine debris to most people that has allowed society to dismiss the problem as a serious threat. However, recent research demonstrates that quantities and impacts of marine debris are significant and increasing. The Algalita Marine Research Foundation’s investigation of plastic in the North Pacific Central Gyre of the Pacific Ocean showed that the mass of plastic pieces was six times greater than zooplankton floating on the water’s surface. This study is one of many that demonstrate that our oceans have become the virtual garbage can for the developed and developing world.(1) 

Most of the marine debris in the world is comprised of plastic materials. The average proportion varies between 60 to 80% of total marine debris.(2) In many regions, plastic materials constitute as much as 90 to 95% of the total amount of marine debris.(3)

Nearly 80% of marine debris comes from land-based sources.(4) Most of the land-based debris is conveyed to oceans via urban runoff through storm drains. The main sources of plastic and other types of anthropogenic (human-made) debris in urban runoff include: litter (mostly bags, packaging and single-use disposable products), industrial discharges, garbage transportation, landfills, construction debris, and debris from commercial establishments and public venues.

In November 2003, the Algalita Marine Research Foundation (AMRF) received a grant from the California State Water Resources Control Board (SWRCB) to implement a project designed to assess and begin to reduce sources of plastic debris and other discarded materials in urban runoff. This project, titled Plastic Debris, Rivers to Sea, is being implemented with the help of the California Coastal Commission.


(1) C.J. Moore, S.L. Moore, M.K. Leecaster, and S.B. Weisberg,  A Comparison of Plastic and Plankton in the North Pacific Central Gyre, Marine Pollution Bulletin, 13 February 2004.

(2) Gregory, M.R., Ryan, P.G. 1997. Pelagic plastics and other seaborne persistent synthetic debris: a review of Southern Hemisphere perspectives.. In Coe, J.M., Rogers, D.B. (Eds.), Marine Debris- Sources, Impacts, Solutions. Springer-Verlag, New York, pp.49-66.

(3) United Nations Environment Programme: www.marine-litter.gpa.unep.org

(4) Faris, J. and Hart, K., Seas of Debris: A Summary of the Third International Conference on Marine Debris, N.C. Sea Grant College Program and NOAA, 1994, title page.


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