According to a model study recently published in Nature Geosciences, 95% of the initial global total amount of floating plastic in the ocean in 2020 was composed of plastic fragments larger than 2.5 centimeters, which may have lasted longer than previously expected.
In the past, it was estimated that there were approximately 250 million kilograms (250000 tons) of plastic pollutants on the global ocean surface, but it is expected that the amount of plastic pollution entering the ocean each year is much greater than this number. People believe that the reasons for this difference may be overestimation of the amount of plastic input from land and rivers, unknown processes that remove most of this type of plastic from the ocean surface, or fragmentation and degradation.
To explore the reasons for this difference, scientists at the Ulrich Research Center in Germany have incorporated global plastic pollution observation data into a numerical model that tracks how plastic particles migrate and transform in the ocean. The team estimates that there were 3.2 million tons of floating plastic in the ocean in 2020. About half of the 470000 to 540000 tons of plastic entering the ocean in 2020 came directly from fishing activities, while the rest came from coasts and rivers. 95% of the floating plastic was larger than 2.5 centimeters, with microplastics accounting for only a small proportion.
Research has shown that compared to past estimates, the total amount of plastic is higher but the input is lower, indicating that some processes for removing marine plastic have not been missed. But the lifespan or survival time of this type of plastic is very long, and only 10% of the plastic may degrade or sink within two years.
The team estimates that the amount of floating plastic input into the ocean is increasing at an annual rate of 4%, highlighting the need for urgent action to reduce marine plastic pollution. (Reporter Zhang Mengran)