Aarhus University Seal / Aarhus Universitets segl

No. 359: Amounts, composition and trends in development of marine litter on Danish reference beaches

Feld L, Metcalfe RA & Strand J. 2019. Mængder, sammensætning og trends i udviklingen af marint affald på danske referencestrande. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 44 s. - Videnskabelig rapport nr. 359. http://dce2.au.dk/pub/SR359.pdf

Summary

This scientific report describes the amounts, composition and trends in development of marine litter, as registered through the national monitoring programme for marine litter during the period 2015-2019 at six Danish reference beaches. The monitoring data showed a large variation in the amounts and composition of the marine litter registered at beaches located in the different geographical regions, but also a considerable time-dependent variation between surveys performed at the same beach. The highest amounts of litter were registered at Skagen and Langerak beaches with 536 and 498 pieces of litter per 100 m beach length (median values excl. wax), respectively. The lowest amount of marine litter was registered at Roskilde Bredning, with 39 pieces of litter per 100 m beach length.

Marine litter items consisting of synthetic polymers/plastic comprised the main part (85.4 %) of the total amounts of marine litter in Denmark, with between 56 % and 94 % of the items registered at the six different beaches. The most frequent type of marine litter at all the six reference beaches was by far pieces of plastic, including foamed pieces of EPS/XPS with an unrecognizable origin (primarily fragments) in the size interval 2.5-50 cm. Among the next most frequent items were string and cord (< 1 cm diameter), other types of foamed plastic, machined wood (< 50 cm), crisp/sweet packets, and caps/lids from drinking bottles. Cotton bud sticks, cutlery/plates/straws, strapping bands, rope and tangled string/cord/nets comprised particularly a relatively large fraction of the marine litter at the beaches at Nordsøen/Skagerrak, while shotgun cartridges comprised a relatively large fraction of the litter at the inner fjord beaches Roskilde Bredning and Langerak in Kattegat.

In the new EU-directive on the reduction of the impact of certain plastic products on the environment, some specific single-use plastic (SUP) products are targeted by restrictions for placing on the market. At the Danish reference beaches, these specific SUP types comprised between 2 % and 12 % of the total amount of marine litter in the period 2015-2019. Similarly, SUPs that are covered by other types of regulation in the EU-directive comprised between 7 % and 13 % of the marine litter. Some marine litter types have been considered to have a higher risk of negative impact on marine animals, and these among others include pieces of string, cord and nets, in which animals can become entangled. Marine litter that is considered to have a higher potential of negative impact, comprised 18 % of the total marine litter registered in 2015-2019. Particularly at the beaches by Nordsøen/Skagerrak, a large fraction of the marine litter consisted of these higher potential risk litter types, which primarily is due to the relatively large amounts of litter from fishery and other maritime activities compared to beaches in the other regions.

For five out of six of the Danish reference beaches, the development in the amount of total marine litter and plastic litter showed a negative trend for the period 2015-2019, however, except for Skagen, this trend is not significant and thus the reduction can only be seen as a tendency. Though, exceptionally large amounts of litter were registered at Skagen during 2015, which may be due to accumulation of litter prior to the inclusion of the beach in the monitoring programme. If these data are left out of the analysis, the reduction at Skagen is not significant. Langerak only has a two-year monitoring history (2018-2019), and although an increasing (not significant) trend in the amounts of litter is seen, the small data material renders this trend analysis less robust.