Monomers leachate: the molecules bonded together to form plastics are called monomers. When plastic degrades, these monomers can leach and be ingested by biodiversity. Some of the monomers are hazardous, such as styrene which is the monomer of polystyrene. This impact has not been included in the valuation model due to its complexity and for lack of quantitative data.
STEP 2: BUILDING THE VALUATION MODEL ECONOMIC IMPACTS The main approach to value economic impacts generated by marine plastics is based on calculating the yearly revenue loss attributable to plastic litter. Fisheries and aquaculture According to Mouat et al., marine fisheries and aquaculture lose every year respectively 2% and 0.03% of their revenue.28 Trucost assumed that the same percentage of revenue loss was applicable at a global level. It was estimated that marine fisheries and aquaculture generated in 2009 revenue of approximately 52 and 1 billion 2012 US$.194 Considering that plastics comprise between 50% and 80% of marine waste, Trucost calculated that plastics were responsible for a yearly revenue loss of 794 and 7 million 2012 US$ for fisheries and aquaculture activities. Marine tourism Marine tourism includes seawater and freshwater angling, sailing and boating, water sports, and inland cruises. Studies estimated that beach litter in Sweden was responsible for a tourism decrease between 1 and 5%. Based on these numbers, Trucost assumed that 3% of global marine tourism revenue was lost because of marine litter. As result, Trucost calculated that plastic litter was responsible for a yearly revenue loss of 4 million US$. Clean-up cost To calculate the clean-up cost imposed by plastics litter on beaches, Trucost based its model on the number of volunteers estimated globally by the Ocean Conservancy.120 In 2012, more than 5 million volunteers helped clean beaches around the world. To put a value on the time spent by these volunteers on cleaning beaches, Trucost calculated the opportunity cost of their time, based on the global average income per capita per year and on the assumption that each volunteers dedicates half a day per year. As a result, the global opportunity cost of volunteers is 74 billion 2012 US$. While there could be a benefit to collection – volunteers becoming more aware of the environment for example – this has not been included in the analysis. To obtain the economic values per kilo, the annual values calculated must be divided by the quantity of plastics reaching the ocean every year. UNEP estimates that 6.4 million tonnes of litter enter the ocean every year – this figure is likely to be an underestimate, as it is based on research published in 1975.5 In 2013, a European Commission Green Paper suggested 10 million tonnes per year.16 No consensus exists today on this quantity which is highly complex to estimate. Trucost decided to use the figure which would give the more conservative result and based its calculation on a study done by Raveender Vannela in 2012, according to which 20 million tonnes of plastics reach the ocean every year.17 ECOLOGICAL IMPACTS Physical impacts: entanglement and ingestion According to the Secretariat of the Convention on Biological Diversity and the Scientifc and Technical Advisory Panel—GEF, the number of species with entanglement and ingestion records is 45% and 26% for marine mammals, 0.39% and 0.24% for fish and 21% and 28% for seabirds.6 To value these impacts, Trucost based its analysis on a contingent valuation, a survey-based economic technique where people are asked directly their willingness to pay for the preservation of an ecosystem good or service. This technique is often applied to capture non-use values such as the existence of species. Trucost applied a benefit transfer technique to a study done by Ressurreição A. et al., which assessed how much people would be willing to pay to avoid a loss of 10% and 25% of different categories of marine species.195 This study ignores the actual ecosystem services provided by each individual species. Yet, contingent valuations indirectly include the perceived services that these animals render to society. Chemical impacts As the only chemical impact considered, additive leachate is handled as per the valuation methodology described earlier in this appendix.
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