Disentangling beach litter pollution patterns to provide better guidelines for decision-making in coastal management

Understanding the factors affecting the quantity and composition of street litter: Implication for management practices

Some urban areas have more litter than others. Understanding the reason for this is important not only for dealing with urban littering but also for marine water quality because approximately 80% of the world's marine litter originates on land. This study aimed to better understand the quality and quantity of litter on sidewalks along with the sampling site's socio-economic attributes to better discern why some areas have more/different litter than others and what, if any, are the implications for a more tailored waste management strategy. We surveyed twice each of the 35 sites we selected from the Lower Passaic River watershed and the related Harbor Estuary within New Jersey, U.S.A. A total of 28,431 litter items were recorded with a total mass and volume of 245.8 kg and 4.7 m³, respectively. Floatable items accounted for 66% of all objects collected. Cigarette butts were the most numerous among all items (28%) and represented 43% of the total floatable items, the remaining 57% being represented by potentially recyclable items such as plastic, rubber, and Styrofoam. Stepwise linear regression was used to explore the relationship between the litter collected and various predictors. Among others, the results suggest the importance of strategically placing collection bins around properties with relatively lower assessed values, outdoor smoking areas, close to schools, and places where people predominantly walk to their destination. Possible management strategies include prohibiting single use plastic bags, limiting foam food ware, public education, and outreach.

Willingness to pay for cleaning up beach litter: A meta-analysis

At the global level, the UN 2030 Agenda for Sustainable Development Goal 14 calls for action to significantly reduce marine litter pollution by 2025. To understand the non-market benefits of removing marine litter, researchers have conducted numerous studies on Willingness to Pay (WTP) for reductions in beach litter. This paper estimates the overall effect size of WTP for a worldwide dataset of 63 primary studies over 22 years by applying a meta-regression technique to assess the variability in WTP estimates. The results show an annual mean effect size of $US0.71 (or $US35.29) per person for a 1 % (for a corresponding 50 %) reduction in all types of beach litter. The observed heterogeneity is associated with WTP elicitation methods, beach attributes, geographic locations, and per-capita income. This study yields valuable information for policy makers to develop cost-effective policies and recommends standardised measurements to benchmark changes in marine litter pollution.

Operational use of multispectral images for macro-litter mapping and categorization by Unmanned Aerial Vehicle

The use of Unmanned Aerial Systems (UAS, aka drones) has shown to be feasible to perform marine litter surveys. We operationally tested the use of multispectral images (5 bands) to classify litter type and material on a beach-dune system. For litter categorization by their multispectral characteristics, the Spectral Angle Mapping (SAM) technique was adopted. The SAM-based categorization of litter agreed with the visual classification, thus multispectral images can be used to fasten and/or making more robust the manual RGB image screening. Fully automated detection returned an F-score of 0.64, and a reasonable categorization of litter. Overall, the image-based litter density maps were in line with the manual detection. Assessments were promising given the complexity of the study area, where different dunes plants and partially-buried items challenged the UAS-based litter detection. The method can be easily implemented for both floating and beached litter, to advance litter survey in the environment.