Transfer dynamics of litter: Introduction to new vectors in the mobility of terrestrial litter

• There is little understanding of litter pathways from land to sea. • We theorise that movement of people has the potential to displace litter in an urban environment. • Nine littered items were tracked, three of which entered a nearby river through foot traffic. • Structural interventions within land pathways could stem the flow of litter from land to sea. • As litter moves, efficiency of anti-littering interventions at accumulation areas is questioned. Rivers are the primary contributor to marine plastics, transporting litter from inland sources through natural drainage systems. Despite an agreement among researchers that waste littered on land has the potential to enter river systems, there lacks specific quantification of the forces that facilitate transport. Although meteorological conditions (e.g. wind, rain) are considered factors, this exploratory study theorises that the influence of movement of individuals through an urban environment deserves investigation. To illustrate this hypothesis, litter items fitted with Global Positioning System (GPS) were released in an area of high foot traffic along the River Thames in Central London during a time of low meteorological influence. Point data were analysed through a Standard Deviational Ellipse (SDE) to quantify distance, speed and direction of travel of litter items under the sole influence of human movement. Of the 9 bottles distributed, 5 remained in the test site undisturbed by street cleansing staff. During this time, bottles travelled an average distance of 2.4 ms in directions consistent with the flow of foot traffic; two of which ultimately entering the river as a result of these forces. Although the study is limited, results imply proof of concept that passive anthropogenic forces contribute to riverine litter loads, calling into question public complicity when ignoring or kicking litter. It is suggested that packaging be designed with qualities that reduce transportability and the use of physical barriers along river edges be implemented as means to reduce the contribution of terrestrial litter to marine plastics.