Important aspects of microplastic pollution in the marine and coastal environment are its sources, distribution pathways, accumulation patterns, and its environmental impacts. In terms of mitigation of marine plastic pollution (MPP), the circular economy approach offers a solution to current governance challenges.

Authors

Kay Critchell, Anne Bauer-Civiello, Claudia F. Benham, Kathryn L.E. Berry, Lynne C. Eagle, Mark Hamann, Karen E. Hussey, Tyrone M. Ridgway

Highlights

• Microplastics are a major source of pollution in the ocean and the coastal environment, and managing marine plastic pollution currently represents a formidable environmental challenge.
• A circular economy approach, together with resource recovery and recycling, and clean-ups represents a viable long-term strategy for combating larger MPP.
• To effectively mitigate MPP, collaboration and commitment across sectors and societal scales, from the household to the global level will be necessary.

“… plastic pollution is one of the most ubiquitous and pressing contemporary threats to the world’s coastal and marine environments.”

RESEARCH BRIEF

This book chapter, which is part of a book on the future of coasts and estuaries, offers an overview of marine plastic pollution with a focus on microplastics, as a major source of pollution in the ocean and coastal environments. Firstly, the sources, distribution pathways, accumulation patterns, and environmental impacts of microplastics are reviewed. Then current governance challenges related to MPP are described. The authors particularly discuss the circular economy approach, using two case studies to illustrate its implications for waste management and for the reduction of plastic pollution in the oceans. Finally, the role of behavioural change within the range of measures to reduce MPP are assessed.

Microplastic pollution in the marine environment

The production and use of plastics has grown exponentially over the past century and much of it ends up as marine plastic pollution (MPP). Despite the recognition of microplastics as a significant component of MPP since the 1960s, there is a historical lack of research into microplastics and its impacts through, for example, ingestion.

As the sources of microplastics are diffuse, innovative economic, social and behavioural solutions are required. Although there is currently considerable knowledge on microplastics, and this knowledge is growing continually, policy and management efforts against microplastic pollution remain insufficient.

The main sources and dispersal pathways of microplastics in coastal and marine environments are accidental loss during manufacturing, microplastics from households and microplastics as the result of the breakdown of large plastics. Virgin pellets can be accidentally spilled during manufacture and transport; microplastic fibres from clothes and microbeads from cosmetics reach the marine environment through sewage or grey water systems with uncertain ecological effects; and microplastics are also produced by the breakdown of larger objects from land-based and oceanic sources.

Breakdown mechanisms include degradation through exposure to UV light and physical abrasion from waves and sediment movement. The magnitude and relative contribution of the sources of microplastics mentioned above remain largely unquantified.

Microplastic pollution in the coastal and marine environment

The mechanisms of plastics dispersal and accumulation in the marine environment depend to a large extent on freshwater and sewage discharge, as these are a major source of plastics. Dispersal and accumulation processes depend on both the chemical and physical properties of plastics, which determine their buoyancy, and on the characteristics of the riverine and oceanic environments where they are found. In rivers with strong flows, plastics can move downstream and enter the ocean instead of sinking to the riverbed.

However, in oceanic waters, many plastics are or become negatively buoyant and accumulate in benthic habitats where they are highly inaccessible. Buoyant plastics, on the other hand, are transported by wind and currents, while relatively small and less buoyant objects are unaffected by wind directly as they remain under the surface. Some plastics that arrive at coastal waters are then further dispersed and accumulated by the action of tides and waves.

Main challenges for predicting the dispersal and accumulation of plastics in the marine environment, specially at the local scale and on coasts, include: the coarse spatial resolution of hydrodynamic modelling, and that modelling, remote sensing and field-based research have focused on the ocean surface in particular areas of the world, while coastal waters remain understudied.

Research on MPP at local scales could be advanced by improving the knowledge on the sources of macro- and microplastics, as it is the central variable for local dispersion and accumulation. Finally, the accurate identification and quantification of microplastics on coastal environments require the refinement and conformity standardisation of sampling and laboratory techniques.

“Successfully mitigating plastic pollution requires a commitment to action at all societal scales, from the household, through to the community, national, and global levels.”

Governance challenges and current approaches

Some current responses to MPP as a global problem hint at opportunities for improved governance. Despite international commitments to mitigate MPP, the complexity and multiple facets of the problem and its diffuse and changing nature, make it challenging to tackle. The magnitude of MPP varies spatially and seasonally, and the composition of plastic products also evolves over time.

The embeddedness of plastics in society means that a multisectoral approach is necessary, while the global nature of MPP requires collaboration across scales and administrative boundaries, from local action to global coordination. A systemic approach, such as the circular economy is likely to be the necessary foundation of a long-term strategy to combat MPP.

A circular economy approach for marine plastic pollution

A circular economy approach for MPP should prioritise the phasing out of virgin plastics at the beginning of the supply chain. A variety of existing examples illustrate possible applications of this approach. In particular, a circular economy approach has multiple implications for waste management and ultimately to the reduction of MPP.

There is a need for a precautionary, integrated perspective within a circular economy approach, for example in the form of Integrated Solid Waste Management (ISWM). An underlying principle of ISWM is that responsibility for the effects of MPP should be shifted to producers. ISWM implies a hierarchy where preventative actions are top priority and curative actions, e.g. clean-ups, are lowest priority within a six R framework (reduce-redesign-remove-reuse-recycle-recover). Linked to this hierarchy, a staged approach to the implementation of ISWM where supporting infrastructure, investment incentives and behavioural change come first is probably the most effective strategy.

Although there are individual examples of potentially effective measures guided by ISWM, such waste management must be supported by legal mechanisms at all scales from the local to the global, underpinned by adequate research programs. Again, efforts to reduce MPP as implied by a circular economy approach need to refocus from mitigation and clean-up to prevention.

As mentioned above, measures aimed at preventing MPP require cross-sectoral and multilevel initiatives. These may be legislation, economic instruments, co-management and voluntary initiatives (including education and awareness campaigns), and technological innovation together with improvement of infrastructure.

“The changes required for a circular economy are likely to extend well beyond plastic pollution into the very heart of modern work and life.”

Extended Producer Responsibility and Behavioural change

Two case studies of governance efforts based on the circular economy approach to mitigate MPP are presented: 1) the banning of microbeads in the United Kingdom, the United States, Canada and Australia, and the European experience with the introduction of extended producer responsibility (EPR). EPR is defined here as “a regulatory intervention that extends a producer´s responsibility for a product to the postconsumer stage of the product´s life cycle.”

While international experience with the banning of microbeads has shown mixed results due to the existence of legal loopholes, EPR interventions can be regarded as mainly successful and producing positive side effects, such as technological innovations.

Policy regarding behavioural change to combat MPP must shift from a focus on information provision to a focus on the motives of behaviours. Early successes point at strategies that use this kind of social marketing complemented with legislation.

The full book chapter is available here.