Plastic debris in the marine environment is widely documented, but the quantity entering the ocean from waste generated on land is unknown. By linking worldwide data on solid waste, population density and economic status, a recent global study estimated the mass of land-based plastic waste entering the ocean in 2010 to be between 4.8 to 12.7 million tons -- that was nine years ago.
This estimate is just a snapshot of a single year but plastics, often used just once, are designed to be durable and can potentially remain in the ocean for years before breaking down or sinking. Plastic marine debris ranges from microscopic pieces - either intentionally manufactured for products such as soap, creams, gels and toothpaste or broken down by sunlight, wind and currents - to larger waste items such as bags, cigarette filters, balloons, bottles, caps, or straws which are the most visible form of plastic pollution. Plastic debris has been detected in all major marine environments worldwide, from shorelines and surface water down to the deepest parts of the ocean, even at the bottom of the Mariana Trench.
A 10-year study on the loggerhead turtle showed that 35 percent of the specimens analyzed had ingested debris, which were almost all plastic. In a study carried out in the Mediterranean, 18 percent of tuna and swordfish had plastic debris in their stomachs as did 17 percent of blackmouth catsharks in the Balearic Islands, most of which was cellophane and PET.
The threat is growing. By using a mixture of literature surveys, oceanographic modeling and ecological models, Wilcox et al. explored the risk of plastic ingestion to 186 seabird species globally. Their models indicate that today, 90 percent of the world's seabirds have fragments of plastic in their stomachs compared to only 5 percent in 1960. Impacts were found to be greatest at the southern boundary of the Indian, Pacific and Atlantic Oceans, a region thought to be relatively pristine. If action is not taken to reduce the flow of plastics into the sea, their models predict that plastic will be found in the digestive tracts of 99 percent of all seabird species by 2050.
