A Horizon Scan of research priorities to inform policies aimed at reducing the harm of plastic pollution to biota.

Plastic pollution in the oceans is a priority environmental issue. The recent increase in research on the topic, coupled with growing public awareness, has catalyzed policymakers around the world to identify and implement solutions that minimize the harm caused by plastic pollution. To aid and coordinate these efforts, we surveyed experts with scientific experience identified through their peer-reviewed publications. We asked experts about the most pressing research questions relating to how biota interact with plastic pollution that in turn can inform policy decisions and research agendas to best contribute to understanding and reducing the harm of plastic pollution to biota. We used a modified Horizon Scan method that first used a subgroup of experts to generate 46 research questions on aquatic biota and plastics, and then conducted an online survey of researchers globally to prioritize questions in terms of their importance to inform policy development. One hundred and fifteen experts from 29 countries ranked research questions in six themes. The questions were ranked by urgency, indicating which research should be addressed immediately, which can be addressed later, and which are of limited relevance to inform action on plastics as an environmental pollutant. We found that questions relating to the following four themes were the most commonly top-ranked research priorities: (i) sources, circulation and distribution of plastics, (ii) type of harm from plastics, (iii) detection of ingested plastics and the associated problems, and (iv) related economies and policy to ingested plastics. While there are many research questions on the topic of impacts of plastic pollution on biota that could be funded and investigated, our results focus collective priorities in terms of research that experts believe will inform effective policy and on-the-ground conservation.

Significant plastic accumulation on the Cocos (Keeling) Islands, Australia.

For over 60 years, our oceans have been a reservoir for exponentially increasing amounts of plastic waste. Plastic has been documented at all levels of the marine food web, from the deepest oceanic trenches to the most far-flung beaches. Here, we present data on the presence of significant quantities of plastic on the remote Cocos (Keeling) Island group, located 2,100 km off the northwest coast of Australia. From our comprehensive surveys of debris on the beach surface, buried, and beach-back vegetation, we estimate there are 414 million anthropogenic debris items, weighing 238 tonnes, currently deposited on the Cocos (Keeling) Island group. Of the identifiable items, ~25% were classified as disposable plastics, including straws, bags, and toothbrushes. Debris buried up to 10 cm below the surface is estimated to account for 93% (~383 million items) of all debris present on Cocos, the majority of which (~60%) is comprised of micro-debris (2-5 mm). In the absence of meaningful change, debris will accumulate rapidly on the world's beaches. Small, buried items pose considerable challenges for wildlife, and volunteers charged with the task of cleaning-up, thus preventing new items from entering the ocean remains key to addressing this issue.