It’s extremely difficult to gauge the total amount of plastic waste in our oceans. There have been a number of scientific studies seeking to estimate the volume or total weight of the plastics by measuring the amount in a given area and extrapolating for the whole. But these estimates involve a number of uncertainties, firstly because the researchers only collect random samples and can only project the total amount.
Secondly, it’s extremely difficult to estimate the total amount because the litter stems from various sources, not all of which can be measured in detail. It is blown out to sea from landfills and sewage treatment plants; it is washed out into coastal waters from canals and rivers, or dumped directly into the ocean. All this is supplemented by waste from ships and fishing nets. In order to estimate the total amount, the microplastics, plastics floating on the surface and those that sink to the ocean floor would all need to be taken into account. Not only is such a task difficult from a technical perspective, the lack of international standards means that different countries’ figures on litter production often can’t be compared.
Accordingly, a team of researchers recently chose to pursue a different approach, using production data to calculate how much litter is produced worldwide. Their conclusion: every year, between 4.8 and 12.7 million tonnes of the plastic waste produced on land eventually reach the ocean.