Marine litter issues, impacts and actions

6 Knowledge Gaps

6.1 Micro plastics

Marine plastics have been shown to act as a vehicle for absorbing, transporting or releasing contaminants including PCB's, and a number of studies have shown this can be transferred to species through ingestion (in some cases selective ingestion). Thus the ingested micro plastics may prove a significant source for primary producers and input into and along the food chain, including to humans. The biological consequences of this are as yet, unclear.

The proliferation of marine litter particularly plastics provide additional opportunities for the dispersal of non-native, potentially invasive species. The type and size of debris can influence colonisation patterns and biota; however, uncertainties exist with regard to the potential extent of this issue with a warming climate and the resulting economic implications for Scotland and its maritime industries.

6.2 Monitoring

Beach cleans and the resulting monitoring tend to mostly occur on more popular, often urban or semi-urban beaches and as such the information available on the issues, types, levels, trends and impacts of marine litter are skewed because of this. To overcome this, a comprehensive picture of marine litter on Scotland's coasts including in rural and remote areas, is required to fully understand where the greatest issues lie, and regional differences and thus where resources are best aimed.

Information on the amounts and types of litter in the water column and on the sea bed is limited, due to the relatively limited monitoring studies focussed here. Based on estimations, however, there is a much greater amount here than on the coasts, yet efforts currently are more focussed on coastal cleaning than offshore. This is predominantly due to access and cost issues but also because it is much easier to feel affinity with an environment you are familiar with i.e. your local beach than the relatively unknown deep sea. This could be used as an advantage in any media campaigns as viewers become accustomed and desensitised by familiar images; the use of images out with their familiarity may act as more of a shock tactic.

Improved knowledge of litter sinks in terms of their location and size may allow for the predictions of the proximity of the source and local pathways including the future drift of suspended litter. This may be more suited to identification at the local scale, as frequently these sites are already known to local practitioners and field staff.

A comprehensive monitoring programme is required which is easily comparable spatially, both within Scotland and the UK but also at the EU level and temporally. This is fundamental for getting a clear idea of the scope of the issue but also for the evaluation of any management actions and legislation, in terms of their effectiveness. This should not, however, halt or preclude and current actions as the monitoring data from initiatives such as Beachwatch, KIMO's Fishing for Litter and the International Bottom Trawl Surveys ( IBTS), do to some extent show the scale of the problem and have identified key areas for focus based on amounts from a particular litter source such as land based sources.

The use of geospatial technologies and remote sensing could be better explored to make the most of limited resources for monitoring and assessment as well as data management and sharing.

6.3 Economic Impacts

Limited conclusive studies to date have been produced, either in the UK or internationally, on the full economic impacts of marine litter, including the potential cost of ghost fishing to the commercial fisheries industry. This may be a priority for any Strategy as cost implications on individuals and sectors are likely to work as strong deterrents for future inputs and as a driver for action on existing litter. In addition, it is necessary in objective setting to understand the cost (economic) of any action against the costs (in all senses) of taking no action, and which on that basis is the right course of action.

6.4 Social Impacts

Knowledge gaps exist regarding the social impacts of marine litter including the implications for ecosystem services (regulatory, provisioning, supporting and cultural). Despite a lack of research into the impact of marine litter on ecosystem services, it is highly likely that litter reduces the resilience of ecosystems, and hence the quality of ecosystem services they provide. Additional gap exist in the root cause of litter (marine and terrestrial); particularly in surveys that explore the social and behavioural aspects of society and marine litter generation and what forms of communication, media, governance and infrastructure are necessary to be effective not only in informing people of the impacts but to a sufficient level to change their behaviour.

Studies are required to evaluate the effectiveness of measures to prevent and reduce marine litter and to provide useful guidance to managers and decision makers for litter mitigation.

These gaps in knowledge hinder the ability to prioritize mitigation efforts and to assess the effectiveness of implementation measures. Where possible these gaps should be filled by joining forces with existing research programmes