Marine Debris Project Final Report 2014

Part VSources, Distribution and Fate of Marine Debris5. OverviewMarine debris is recognized as an increasingly important global issue that affects the environment andeconomics and can negatively impact wildlife, tourism, fishing and navigation. It has remained difficult todevelop a synoptic description of the overall threat of marine debris to ecological systems. This uncertaintyis due to three causes: an absence of a national map of the distribution of marine debris, comparativeinformation on exposure of wildlife across taxa and regions, and a clear understanding of the effects ofexposure to debris. This project provided an initial step in addressing this uncertainty by identifyingavailable information on debris and developing preliminary analysis of its sources and distribution at anational scale.5.1 Estimating quantities and sources of marine debris at a continental scaleThe loss of plastic into the environment, and the oceans in particular, has effects on economic productivity,aesthetic values, and appears to be driving biodiversity losses. Plastic comes in a wide variety of shapes andsizes, from derelict industrial fishing nets that are kilometers long and can weight many tons, to beveragecontainers and other consumer items, to small fragments used as abrasives and from breakdown of largeritems. Larger items represent a hazard to shipping, leading to fouling of propellers and water intakes.Estimates from a large study in Scotland suggest fouling rates of one event per vessel per year, andtogether with snagging and fouling of gear and contamination of catches, this costs the industryapproximately 5% of its total revenue (Mouat et al. 2010). Beaches, harbors, and other sites that generaterevenues from users are also significantly impacted. Removal of marine litter costs harbors in the UK €2.4million each year, with substantially higher costs in other parts of Europe (Mouat et al. 2010). Coastaltourism is also significantly affected, and municipalities incur substantial costs to reduce these impacts.Municipalities in the Belgium, the Netherlands, and the UK spend between €10 and 20 million per year toreduce coastal debris (Mouat et al. 2010). A single period of heavy rainfall in South Korea during July 2011increased coastal debris, resulting in a 63% decrease in tourism and lost revenue of $33 million (Jang et al.2014). Similar results were observed in a US study of debris on the US east coast in 1987-1988, witheconomic losses estimated between $379 and $1,598 million (Ofiara and Brown 1999). In fact, thereappears to be a direct relationship between marine debris and stated aesthetic values, with a study inSouth Africa suggesting that residents and tourists would not visit a beach with more than two litter itemsper meter (Ryan 1990).22 | Understanding the effects of marine debris on wildlife