Competing interests: Stephen Fletcher receives funding from the United Nations Environment Programme, the World Bank, the World Economic Forum, the Natural Environment Research Council (NERC), the Economic and Social Research Council, Aquapak, Defra, and the Flotilla Foundation. He is a member of the United Nations International Resource Panel and is the NERC agenda setting fellow for plastic pollution. Cressida Bowyer receives funding from the Medical Research Council, the Arts and Humanities Research Council, the NERC, the Sustainable Manufacturing and Environmental Pollution Programme, and the Flotilla Foundation.