Beach litter

Understanding beach litter in Scotland

In Scotland, tides, winds and coastal currents are very active. The combination of these results in some effects that alter the average loadings of litter on beaches. The oceanographic effects mean that average beach loadings increase up the west coast of Scotland, reset to a base value north of Scotland, and then increase again down the east coast (see Turrell, 2019b for full details).

The oceanographic processes are influenced by the direction of the prevailing wind relative to the beach in question, as well as by the nature of the water body the beach is located within. The technical analysis that supports the pilot indicators (Turrell, 2018; Turrell, 2019a) suggested that beaches within harbours, sea lochs, estuaries and embayments have different litter loadings than beaches lying along open coasts. For this reason, indicators have been estimated using surveys only from open coast foreshores. 

Owing to the complex effect of natural processes, total beach loadings must be viewed in the context of where a particular beach lies along our coasts. The SBLPI look at trends within a sub-region of the coast rather than absolute values. They also use a relative scale that is the same for all litter categories and for all sub-regions (i.e. values normalised to have a mean of zero, and a standard deviation of one over the period 2008-2017).

The natural variability of the amount and composition of beach litter described above can result in large day to day, month to month, and even year to year, variations. The trends presented here are influenced not just by the size of the source of the items entering the sea, but also this natural variability.

Subsets of the 118 beach litter categories were grouped to create 25 Scottish Beach Litter Performance Indicators (SBLPI, Table a) that were used to assess the state of litter on beaches, as well as judge the success of policies in reducing sources of marine plastics and litter (Turrell, 2019a). Indicators were classed as: “Priority One” if they measured changes in litter items subject to current or developing Scottish Government policies and strategies; “Industry” if they related to litter items that might be traced back to specific marine industries; “Other” if none of the above. Using the MCS surveys, these pilot indicators were selected based on:

• Availability of data in the MCS/OSPAR beach survey databases;
• Relevance to industry sectors that the Scottish Government may influence through dialogue/legislation;
• Relevance to specific litter items that the Scottish Government may influence through policies/legislation/publicity campaigns;
• Relevance to specific litter items of concern to the Scottish public;

Subsets were grouped to give 25 Scottish Beach Litter Performance Indicators (SBLPI), which were used to assess the MCS beach litter surveys. Indicators marked by an asterix can include additional (but similar) litter items as well as the target item owing to the nature of the MCS survey recording protocols. Further details of what litter items are contained in each category and the corresponding OSPAR beach litter description can be found in Turrell (2019a).

There are two types of SBLPI: sub-totals that sum a range of litter categories together and specific items, which target individual marine litter items. Inclusion or exclusion of litter categories in the performance indicators that use sub-totals is somewhat arbitrary. For example, in the sub-total category “Marine Related”, which tries to capture litter from marine sources (shipping, offshore industries, fishing vessels) other than identifiable fishing gear, includes the litter category “8 Engine oil containers and drums <50 cm”. Obviously these could also come from land-based sources. However, a judgment has been made based on the likelihood of land versus marine sources.

An arbitrary number of 4 surveys per year was set as the minimum needed in any sub-region for that year to be valid, and a minimum of 5 valid years within the 10 year period for a sub-region to be included in the analysis. There were sufficient data for an assessment of the SBLPI for five of the fifteen coastal sub-regions (Figure 2); Clyde, Orkney, Moray Firth, East Coast (North) and Forth (including Forth harbours). There were insufficient surveys to estimate the SBLPI for Solway, Malin Shelf, Firth of Lorn, Atlantic, South Minch, North Minch, Inner Moray Firth, Cromarty/Dornoch, Firth of Tay and East Coast (South). There are no data for Shetland. The Da Voar Redd Up is Shetland’s annual beach clean but the data are recorded in a different way to that of the Marine Conservation Society therefore could not be used here.

Using the beach location (latitude and longitude), each beach was examined using the satellite images contained in Google maps. The location of each survey with respect to principal sea areas around Scotland’s coasts was determined, as was the nature of the surveyed foreshore. Foreshores were categorised as beaches, bays, sea lochs or harbours. A bay was defined as relatively short foreshores having semi-enclosing adjacent coastlines extending out to sea for distances approximately equal to or greater than the foreshore length itself. Sea lochs are glacially-cut fjords, and are well identified and named in Scotland. Harbours were defined as foreshores within industrial areas with man-made substrates and/or retaining structures. 

The east coast of Scotland has a much simpler morphology than the west coast. Whereas the west coast has island chains, peninsulas and glacially-cut fjords, the east coast has no offshore islands of any size, and has linear coasts devoid of fjords.

While foreshores on the east coast predominantly face east, a few major embayments disrupt this general trend, specifically the Dornach, Cromarty, Tay and Forth Firths, and the inner Moray Firth (a firth in Scotland is a large embayment or channel, normally navigable in some way). 

Foreshores on the west coast can face in any direction, owing to the complex topography. For this reason west coast beaches and bays had a further parameter added, determined from the satellite images, namely the direction they face (the exposure). A beach recorded as having an exposure to the SW would experience winds directed perpendicularly onshore for winds blowing from the south west. Initial analysis of the data showed that beaches and bays on the west coast, outside the Clyde sea area, predominantly faced westwards, with a minority facing east.

Water body types

For the purpose of this analysis, all data from harbours were excluded from regional assessments, except for Forth harbours which were included as an example of litter levels within harbours. Forth harbours were selected as they have the most available data. Other sites rejected were within river channels or at landward extremes of estuaries, where marine deposition of litter could be augmented by riverine sources. On the west coast, all surveys on foreshores with an exposure towards the north, northeast, east, southeast or south were excluded from the analysis as these are not representative of foreshores facing into the prevailing wind (Turrell, 2019b). These included many on the eastward, and hence sheltered, side of islands and peninsulas.