Beach Litter Monitoring

Marine litter is any persistent, manufactured or processed solid material discarded, disposed of, abandoned or lost in the marine and coastal environment. It also includes items entering the marine environment via rivers, sewage outlets, storm water outlets and wind action.

Solid and liquid chemicals such as paraffin and oil, which are often recorded on beaches along with litter, are not included in this assessment.

The OSPAR indicator on beach litter is used to identify changes in the input of litter to the marine environment. The assessment is based on a time-series of abundance and type of litter items collected on a network of OSPAR survey sites.

According to the OSPAR beach litter monitoring guidelines, at each survey site all litter items on a 100-m stretch of coastline should be recorded four times a year using the OSPAR beach litter monitoring protocol (OSPAR 2010). However, due to limitations dictated by weather conditions, availability of manpower etc. not all survey sites included in this analysis have been surveyed as regularly as this for the whole period (Table a). On some survey sites, weather conditions prevent surveys in the winter survey period, other survey sites have only recently been added to the network of survey sites and surveys on other sites have been discontinued.

The data collected can be used to provide information on amounts, trends in abundance and sources of marine litter.

The surveys provide information on the magnitude of litter pollution in adjacent waters and coastal areas and can show spatial and temporal differences in litter pollution.

The litter on a given survey site may be generated locally at sea or on land, but may also arrive via ocean currents, rivers and wind drift from distant sources.

The litter recorded on the survey sites provides information on the frequency of individual litter types (e.g. plastic bags, metal cans), groups of litter types (e.g. single use plastics, fishing gear) and litter material categories (e.g. plastic, wood). This information helps to identify the sources of the litter and to some extent its level of threat to the marine environment (e.g. wood is not as harmful as plastic).

Spatial differences in litter composition can reflect regional differences in sources, which relate to differences in local or regional infrastructure and human activities. However, litter on the coastline can also originate from distant sources. Changes in composition can provide information on changes in sources as well as the effectiveness of measures (e.g. replacement of glass bottles by plastic bottles or, on the other hand, the introduction of recycling systems for plastic bottles).

Trends in total litter abundance or in the abundance of individual groups of litter types (e.g. fishing gear) generally provide information on changes in the level of pollution and on the effectiveness of measures introduced to reduce the input from different sources of marine litter. However, environmental factors such as climatic forces, prevailing winds and water currents can also influence deposition of litter on the coast at smaller and larger spatial scales. Environmental factors have not been taken into consideration in this assessment.

The litter encountered on beach litter survey sites can originate from human activities at sea such as shipping and fishing i.e. floating litter transported to and deposited on the coast by winds and water currents, or can be directly deposited on the coast by human activities such as touristism, recreation, or fly-tippers. A significant input of litter into the marine environment can also possibly be from items deposited inland on riverbanks or discharged directly or via storm-water drainage systems into rivers.

In the period between any two beach litter surveys, litter items that have been washed ashore by tides or deposited directly on to the beach may be buried, or removed by subsequent tides and winds. However, buried litter can also resurface during strong wave action and litter can be blown onto the beach from adjacent land or streets. Therefore, the amount of litter items recorded during any one survey will represent a steady state for litter deposited at that site.

In litter washed ashore, litter items that sink or disintegrate, dissolve or decay quickly in the marine environment are most likely to be under-represented compared to what we actually believe are littered at sea. The main category of litter found on beaches in the assessment period was ‘plastic and polystyrene’, which often floats and disintegrates extremely slowly in the marine environment. The main components of the other common litter categories all float and/or decay slowly (wood, bottles, jars, lightbulbs, paper cartons, tins and cans). The composition of litter recorded on beaches thus reflects its ability to reach the shore. Metal and glass are possibly under-represented because they are more likely to sink than items made of plastic, polystyrene, rubber and wood. Paper is also possibly under-represented because disintegrates more rapidly in water than the other items.

Although only a fraction of what is disposed of into the sea reaches the shore, the abundance of the items found can be used as an indication of the level of marine litter pollution in a given area, if it is assumed that the floating element of the litter represents a constant proportion of the total litter input. Surveys of litter items deposited on the seafloor (by recording litter caught in trawls during fish stock surveys) are used to identify trends in items that do not float (see OSPAR assessment of Composition and Spatial Distribution of Litter on the Seafloor ).

Within the OSPAR Beach Litter Monitoring Programme, litter has been counted on standard stretches of coastline (survey sites) since 2001 on the North-East Atlantic coasts of Belgium, Denmark (including beaches in Greenland and on the Faeroe islands), France, Germany, Iceland, Ireland, the Netherlands, Norway, Portugal, Spain, Sweden and the United Kingdom.

The surveys are carried out according to the OSPAR Guideline for Monitoring Marine Litter on the Beaches in the OSPAR Maritime Area (OSPAR Agreement 2010-02).

The standard length of a survey site is 100-m of coastline. The entire area from the waterline to the back of the beach is surveyed, with the back of the beach determined for example by the presence of a dune or a sea wall.

The beaches, on which the survey sites are situated, mainly comprise of sand or gravel and are exposed to the open sea. They are in most cases accessible to surveyors all year round for surveying and litter removal. However some sites, such as in the north of the OSPAR Maritime Area, are not accessible or not possible to survey during the winter survey period. The beaches have a minimum length of 100 m, are generally free of buildings all year round, and are (in most cases) not subject to litter collection activities (beach cleaning). National coordinators of the surveys have used expert judgement and local knowledge of coastal areas when selecting the survey sites. For example, in some countries local conditions do not allow for selection of beaches mainly comprising sand, and in some locations it is not possible to select beaches of 100 m in length.

The start and end points of the survey sites are marked clearly, to ensure that exactly the same site is monitored for all surveys.

According to the OSPAR beach litter monitoring guidelines, at each survey site all litter items should be recorded four times a year using the OSPAR beach litter monitoring protocol. However, due to limitations dictated by weather conditions, availability of manpower etc. not all survey sites included in this analysis have been surveyed as regularly as this for the whole period (see Table a). Some survey sites have only recently been added to the network of survey sites and surveys on other sites have been discontinued.

The survey periods are as follows: winter (between mid-December and mid-January), spring (April), summer (between mid-June and mid-July), and autumn (between mid-September and mid-October).

Data on the amount of litter on a survey site is recorded at the litter-type level. In total, there are 112 predefined litter types. Each item found on the survey site is allocated to one of the 112 litter types. Items comprise identifiable pieces of litter, including items such as plastic bottles, tetra-pak containers, metal drinks cans, and rubber gloves as well as unidentifiable fragments of litter objects. The litter types are assigned to specific categories according to the material from which they are made (e.g. plastic, wood, metal) or their use (e.g. medical, sanitary): Plastic / polystyrene (54 litter types), Metal (15 litter types), Paper and cardboard (9 litter types), Wood (9 litter types), Sanitary waste (6 litter types), Cloth (5 litter types), Rubber (4 litter types), Glass (3 litter types), Pottery/ceramics (3 litter types), Medical waste (3 litter types) and Faeces (1 litter type). The list of litter types with their unique OSPAR identification number and their allocation to material types, single-use-plastics and fishing gear is presented in Table b.

Paraffin and other chemicals, which although included in the litter database, are recorded using a different method than for litter items, are not analysed here.
During each survey for a given survey site the number of individual pieces of litter is recorded for each litter type. The survey forms allow for the registration of identifiable items, unknown items and litter fragments in different size categories. Litter items which do not fit into a definite litter type category, are registered under the litter types ‘other’ for the given material or use category. A short description of the litter types is included on the survey form. Multilingual photo guides are available to assist surveyors with the identification and categorisation of litter items. All litter items are normally removed from the beach during the survey.

The location and physical characteristics of survey sites are influent parameters in terms of litter deposition/ retention patterns as well as potential sources; for this reason the characteristics of a number of reference beaches are recorded in detail. This information includes the proximity of possible sources of marine litter to the beach, as well as other factors that could help explain the amount, type, and composition of marine litter found. This information is stored in the OSPAR Beach Litter Database.

The software package litteR was used to analyse abundance, top items and trends in the results of the OSPAR beach litter surveys. litteR calculates mean and median values for abundance at the individual survey site level. Abundances were calculated for total abundance, which includes all litter types on the OSPAR list i.e. also plastic fragments, abundance of material categories, Single-Use-Plastic items, fishing gear and individual litter types.

To provide abundance values for groups of survey sites, the mean of the mean abundance values was calculated. R (Wilcoxon-Test) was used to test the significance of differences between sub-regional abundances.

The number of survey sites, as well as the number of surveys, has increased since the start of the monitoring programme in 2001 (Figure a). Despite an overall increase in the number of survey sites, the specific sites used and the number of surveys undertaken per year at those sites, have varied. Nevertheless 68% of the survey sites supplied data for at least four of the six years covered for the calculation of abundance and composition.

Threshold values for the abundance of litter items on OSPAR beach litter survey sites are presently being developed by the Technical Group Marine Litter of the European Union. The lack of threshold values for litter abundance means that the results on total abundance, abundance of Single-Use-Plastics, Fishing Gear, material categories or individual litter types cannot be evaluated at present. However, trends in the abundance of litter on the OSPAR survey sites are used to give an indication of the present situation in comparison to the OSPAR Intermediate Assessment 2017.

Assessment of abundance and composition 2012-2017

Overall abundance of litter

Abundance of litter items and their composition have been calculated using data for the period April 2012 to January 2018. This includes OSPAR beach litter data for a six year assessment period from the spring survey in 2012 to the winter survey in 2017/18.
The present distribution of survey sites and the mean total abundance of litter items per 100m at these sites are presented in Figure b and the availability of survey data is presented in Table a.

The mean[1] number of litter items per survey (100m of coastline) was 966. The mean number items in the plastic/polystyrene material category was 835/survey (100m).

A number of litter items in the material categories rubber and cloth/textile as well as in the use categories sanitary and medical are made of artificial polymer material. Examples of litter items, which are a major component of beach litter on OSPAR survey sites, are cotton-bud-sticks, which are included in the sanitary category, despite being mainly made of plastic, and cigarette butts, which are included in the category paper & cardboard, although they are made of synthetic fibers. This is done to link the litter types to their sources, with the ultimate aim of enabling the development of suitable litter reduction measures. When just these two litter types are considered to belong to the plastic/polystyrene material category, then about 90% of litter items recorded on OSPAR beach litter survey sites are made of artificial polymers and all other material categories each make up only 2% or less of the total amount of litter recorded on the survey sites (Figure 2).

Differences in abundance and composition of litter between regions

Mean abundance for total abundance, Single Use Plastics, fishing gear and a selection of litter types are presented in Figures 3-10. Due to high variability in abundance between sites the differences between regions are not always significant. Significant differences in the abundance of litter items for a selection of different litter categories and types are presented in Table 3 (Note: The Wider Atlantic region only includes one survey site with a total of eight surveys in two consecutive years).

The mean total abundance of litter items/survey varies greatly between OSPAR regions (Figure 3), especially between the northern North Sea and all other regions, the differences are only significant for Arctic survey sites, which have less litter than survey sites in all other regions, and between survey sites in the northern North Sea, which have a higher total abundance than those on the coast of the Celtic Sea. The mean number of plastic & polystyrene items/survey is also significantly higher in the northern North Sea than in the Celtic Seas (Figure 4). The number of Single Use Plastic items (Figure 5) is significantly lower on sites in the Arctic Seas than in all other sub-regions (Table 3).

In general the abundance of litter generally considered to be sewage (cotton-bud-sticks) (Figure 6) or tourist related (cigarette butts (Figure 7), crisp & sweet packaging (Figure 8)) is less abundant on Arctic Seas survey sites than on sites in all other regions. This is also the case for the litter types caps & lids (Figure 9) and plastic drinks bottles & containers (Figure 10). The sites on the southern North Sea coasts have significantly less cotton-bud-sticks than the sites in the northern North sea and Celtic Seas as well as the sites in the region Bay of Biscay & Iberian Coast. Cigarette butts occur in high numbers (>25/100m) on North Sea sites in the British Isles, on French sites in the southern North Sea and on Portuguese, French and Spanish sites in the region Bay of Biscay and the Iberian coast. Rubber balloons, which make up a large proportion of the items recorded under the category rubber, are significantly more abundant on North Sea sites than on sites in the region Bay of Biscay & Iberian coast and significantly more abundant on northern North Sea sites than on sites in the southern North Sea and Celtic Seas (Figure 11). Especially high abundances of rubber balloons are recorded on the Scandinavian sites in the northern North Sea.

The most widespread top-litter types (on > 50% of sites) are Plastic-polystyrene-fragments, string-cord (diameter <1cm), caps-lidsand crisp & sweet packaging. Other widespread top-litter types (on 25-50% of sites) are plastic drinks bottles & containers, rope (diameter >1cm), food-containers, other-wood <50cm, cotton-bud-sticks and nets-pieces-of-net <50cm. Cotton-bud-sticks were among the top litter items on 22%, rubber balloons on 15% and small and large plastic bags each on 19%  of survey sites (see also Table 4). Small and medium-sized plastic fragments as well as caps and lids were widespread top-litter types on survey sites in all regions, whereas cotton-bud-sticksare less widespread on sites in Arctic Waters (only on 6% of sites) and the southern North Sea (9%) and drinks bottles & containers as well as food containers are less widespread on Arctic Waters sites (each 6% of survey sites).

The most widespread top-litter types for the OSPAR regions are presented in Table c. Three litter types, the two plastic and polystyrene fragments categories less than 50cm in size, and plastic string less than 1cm in diameter, are under the top items found on 50% or more of all survey sites in all regions. Caps & lids are under the top items on 50% or more of sites in all regions except Arctic Waters, where they are top items on 28% of sites. Cotton-bud-sticks are widespread top items on at least 40% of sites in the Greater north Sea north, the Celtic Seas and the Bay of Biscay/Iberian Coast regions, whereas cigarette butts are only widespread top items in the Bay of Biscay/Iberian coast region.

There are significantly more cigarette butts, Single Use Plastics and crisp/sweet packaging on survey sites on tourist beaches and significantly more sanitary items on survey sites near (≤10km) to wastewater inflow. Significant differences in the abundance of fragments in relation to the nearness (≤10km) of river inflow or significant differences in the abundance of strapping bands, fishing gear, injection gun cartridges in relation to nearness (≤10km) of shipping activities could not be detected. However, the information in the OSPAR database on the nearness of rivers and shipping to survey sites is at present only limited to a few survey sites.

Assessment of trends

Trends in abundance of litter items for litter types, groups of litter types and material categories have been calculated using data for the period December 2009– January 2018. This includes the results from 33 survey periods from the winter survey period 2009/2010 to the winter survey period 2017/18.

Significant trends in total abundance of litter items could be detected for a third (n=42) of all survey sites. Significant reductions in total abundance of litter items occurred on 23% of survey sites, ranging from 16% of sites in the Bay of Biscay & Iberian coast region to 41% of sites in the Celtic Seas. Significant increases in the total abundance of litter items were recorded for 9% of the survey sites, ranging from 3% in the southern North Sea to 19% in the Bay of Biscay & Iberian coast region.

Significant trends in the number of of litter items for material categories could be detected for 11% (n=14) (medical, ceramic/pottery) to 31% (n=40) (plastic/polystyrene) of all survey sites. The majority of significant trends in material/use categories and groups of litter types (Single-Use-Plastics, fishing gear) on survey sites are decreasing ones.  This is also the case at an OSPAR regional level, with the exception of the Bay of Biscay & Iberian coast, where  sites with increasing trends for total abundance (n=6), sanitary (n=6) (mainly cotton-bud-sticks), cloth/textiles (n=5) and paper/cardboard (n=4) (mainly cigarette butts) are more common.

The most reductions in abundance of litter items were recorded for the plastic/polystyrene category, with declines in litter abundance recorded on 27 (21%) of the survey sites in the OSPAR area.

The regional overviews of significant trends in total abundance and the OSPAR material/use categories are presented in Tables 5, d, e and f. The significant trends at a survey site level for total abundance are presented in Table 5. The significant trends at a survey site level for Single-Use-Plastics and Fishing Gear are presented in Tables d and e. Examples of significant trends are presented in the Figures b-p.

Figures b - p Trend graphs for a selection of beaches with significant trends in total abundance (TA) and in Single Use Plastics

Magnitude of reductions in the number of litter items/100m

The average annual reduction in total abundance in the period December 2009 – January 2018 on sites with significant trends (n=30) was 85 litter items/100m. The average increase in abundance on sites with significant trends (n=12) was 25 litter items/100m. However, three survey sites with less than ten surveys had very high reductions in litter items. If these sites are removed from the calculation the average annual reduction in total abundance in the period December 2009 – January 2018 on sites with significant trends (n=27) was 16 litter items/100m.

The survey sites which supplied the data used in the analysis of beach litter for the OSPAR regions are situated on beaches, which are very variable in their topography, geography, proximity to point sources and human use, all of which can influence the amount of litter deposited on the beach. Although the beaches surveyed are generally sandy, several other beach types are included in the OSPAR Beach Litter Monitoring Programme. These include rocky, boulder and shingle beaches as well as beaches with different levels of pebble, rock and shingle as well as vegetation coverage. Physical characteristics of the survey site influence deposition and retention levels of litter, for example sandy bays on rocky coasts have the potential to accumulate and retain more litter than long open sandy beaches. Furthermore, water currents, weather conditions and prevailing wind conditions, have a significant influence on deposition and retention of litter and thus litter abundance. OSPAR Beach Litter monitoring assesses the litter deposited on the survey sites from diverse sea-based and land-based sources. The importance of the different sources can vary between OSPAR sub-regions, but also between survey sites within a sub-region, depending on their location. Urban beaches, for example, tend to have land-based sources of litter and rural beaches tend to have sea-based sources. Within OSPAR there is no classification between urban and rural beaches. However we do have some information on the distance to the nearest town, river, shipping route and wastewater outlet as well as information on whether the beach is used for tourists or not (simple yes/no). This information was used to analyse the data for survey sites used by tourists and those not used by tourists, those near to rivers, shipping routes and wastewater outlets and those further away. Significant differences in the abundance of fragments in relation to the nearness of river inflow and significant differences in the abundance of strapping bands, fishing gear and injection-gun cartridges in relation to nearness of shipping could not be detected. However this was certainly due to the fact that there is generally only information available in the database for a small selection of survey sites. Significantly more cigarette butts, SUPs and crisp/sweet packaging could be detected on tourist beaches and significantly more sanitary items on beaches near (10km) to wastewater inflows because this information was available and usable for a larger sample of survey sites. The distribution of different types of beaches e.g. urban and rural could not be fully taken into consideration when comparing the litter abundance, composition and trends in this assessment. Their distribution across regions might affect the results if it is much skewed. Differences in the topography, geography of the beaches was not considered at all in this analysis and needs to be considered in future assessments. A further related aspect that needs to be considered in future assessments is the effect of changes in the number and distribution of survey sites on the data summarised for the OSPAR area and the OSPAR regions. Although in this analysis the greater majority of survey sites were assessed constantly throughout the six year assessment period surveys on some sites were discontinued after the first couple of years and some sites were added toward the end of the period. The analysis of trends on a survey site basis, however, helps to combat this problem.

In the future the effects of weather phenomenon, such as the North Atlantic Oscillation (NAO), should be analysed to assess their influence on abundance and trends in the beach litter data set.

Schulz, M., van Loon, W., Fleet, D. M., Baggelaar, P. and van der Meulen, E. (2017) OSPAR standard method and software for statistical analysis of beach litter data. Mar Pollut Bull, 122, 1-2, pp. 166-175

Schulz, M., Walvoort, D. J. J., Barry, J., Fleet, D. M. and van Loon, Willem M. G. M. (2019) Baseline and power analyses for the assessment of beach litter reductions in the European OSPAR region. Environ Pollut. 248, pp. 555-564

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