How much does marine litter weigh? A literature review to improve monitoring, support modelling and optimize clean-up activities
Umberto Andriolo, Gil Gonçalves
Abstract
The weight of marine litter has been marginally considered in comparison to counting and categorizing items. However, weight determines litter dynamics on water and coasts, and it is an essential parameter for planning and optimizing clean-up activities. This work reviewed 80 publications that reported both the number and weight of beached macro-litter worldwide. On average, a litter item weighed 19.5 ± 20.3 g, with a median weight of 13.4 g. Plastics composed 80% by number and 51% by weight of the global litter bulk. A plastic item weighed 12.9 ± 13.8 g on average, with a median weight of 9 g. The analysis based on continents and on water bodies returned similar values, which can be used to estimate litter weight on beaches from past and future visual census surveys, and from remote sensing imagery. Overall, this work can improve litter monitoring reports and support dynamics modelling, thereby contributing for environmental protection and mitigation efforts. • Analysis of 80 papers on beached litter abundance and weight over the past 24 years. • Around 3.4 million of items and a total weight of 27.9 tons were considered. • The median weight of an item varied from 8.6 g (Europe) to 19.6 g (Oceania). • On coasts, the median weight varied from 9.2 g (Atlantic) to 21 g (Pacific). • Plastics constituted 80% by number and 51% by weight of the global litter bulk.