School Email Exchange

Is it accurate that 80% of all debris is from land-based sources?

Posted on November 10 2012

Question submitted by Trinity-Pawling School

This statistic is frequently cited, but we are unaware of the primary source and data that went into this estimate.  It is not well-understood how much of marine debris originated from sources on land, although we do know that there are many routes for waste to enter the ocean from land, such as by rivers, sewage and wastewater outflows, runoff, beaches, wind transport, and catastrophic events such as hurricanes, floods, or tsunamis.  Marine sources include dumping (intentional or not) from vessels at sea or at-sea platforms, lost shipping containers, and lost fishing or aquaculture gear.  All of these sources are very difficult to quantify.

On this expedition, of the large "macroplastic" items that we recovered, about 50% are thought to have originated from a marine source (e.g. fishing floats or buoys).  Other items, including some with Japanese characters on them, appear to have become debris as a result of the 2011 tsunami in Japan (e.g. refrigerator, small boat, child's toy).  In general, unless the debris is recognizable and has some identifying characteristic that indicates whether its primary use is on land or at sea, it is impossible to determine its origin, let alone the pathway that it took to reach the ocean gyre.

This is an example of the kind of floating macrodebris that we've been seeing.  This one has Japanese characters on it.

The origin of these floating pieces of Styrofoam (upper left) and other plastic is difficult to determine without identifying markings.

If we can identify the major sources of input into the ocean, we know where to focus efforts to educate the public and work for legislation or other policy changes to address the problem.