Despite knowledge of the role played by rivers, there are no global estimates of the amount of man-made debris reaching the ocean at river mouths. Therefore, of the estimated 4.8 to 12.7 million tonnes of litter which enter the marine environment in 2010 from land-based sources within a 50 km-wide coastal zone (Jambeck et al., 2015), the proportion delivered by rivers is unknown. Debris originating more than 50 km inland from the coast would also need to be added to the figures above. The quantity and composition of anthropogenic debris delivered by a particular river also depends on the intensity and character of the socio-economic activities and population density in the river basin. The implementation of environmental protection and waste treatment measures may help to reduce the leakage of debris. The distribution and extent of impervious surfaces (built-up areas) in watersheds has been used as a proxy for the input of plastic debris through watercourses, as it is directly related to both urbanization and runoff volume (Lebreton et al., 2012).
From collection: Marine Litter Vital Graphics
GRID-Arendal and Maphoto/Riccardo Pravettoni