Plastic Mythbusters

Is it true that 80% of plastics in the ocean comes from land, 20% from the sea?

Uncertain V4

This claim is uncertain. We could find no credible scientific source to back up this claim. The percentage of land- and sea-based plastic inputs into the ocean has not yet been calculated on a global level and therefore remains unknown. Scientific studies show that the ratio of land versus ocean-based plastics can differ strongly depending on the specific location and the scientific metric used.

Detailed information

Researchers who surveyed plastics on the surface of the Great Pacific Garbage Patch between California and Hawaii found that half of the items came from activities at sea such as nets, traps, ropes, and floats used in the fishing industry. Fishing nets alone made up 46 percent of the total weight.

On Arctic beaches, data collected by citizen scientists showed that even more of the plastics that washed up came from fisheries - over 80 percent.

However, these studies only counted objects floating on the ocean surface or washing up on beaches and shorelines. Part of the waste sinks down the water column, some of it sinks to the bottom of the ocean, which can be thousands of meters deep. These hidden plastics are hard to find and count, which poses an additional challenge when trying to understand the sources on land and in the ocean.

To get a global picture, a team of scientists recently compiled a database of millions of macro-debris items - larger than a few centimeters - from different aquatic environments across the world, including rivers, shorelines the open ocean and the seafloor. 80 percent of these items were plastic, and most of them were connected to the take-away consumer industry. This includes plastic bags, bottles, wrappers, cutlery and containers for food and beverages. Fishing activities made up the second-largest proportion of ocean debris with 22 percent. This includes synthetic ropes, buoys and nets, which were especially prevalent in open ocean waters.

“Our global analysis clearly points to consumer activities as the main sources of marine litter”, the authors concluded, “followed by sea-based activities." However, their analysis only includes macroplastics and not microplastics. In addition, they omitted important polymer types such as polyvinyl chloride (PVC) and polyethylene terephthalate (PET), which account for 40 percent of the ocean plastics.

Many items such as food packaging, cleaning products or bin bags, cannot be attributed with certainty to either land- or sea-based sources, as they are used in households and on ships, which makes an accurate source attribution difficult.

The metric that is used can also lead to different results. For example, mass-based metrics often conclude a higher importance of heavy fisheries-related debris (seabased sources) than count-based metrics.

In conclusion, the results between different studies still differ widely. The exact proportion of plastic entering the ocean from land- versus from sea-based activities thus remains uncertain.

Expert check

Thanks toMelanie Bergmann of Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) for scientific fact-checking.

Updated on: October 31, 2023