Wild seaweed harvesting: strategic environmental assessment - environmental report

Investigates the sustainability and potential environmental impacts of wild seaweed and seagrass harvesting, maerl extraction and removal of beach-cast seaweed.

8. Cultural Heritage

8.1. Introduction

8.1.1. Throughout human history the coastal environment around Scotland has provided food, defence and a means for trade and communication. As a result, a wide range of archaeological features are located along the coast and in the marine environment. These include the remains of ships and aircraft lost at sea, harbours, lighthouses and other structures relating to transport and trade by sea and the remains of human settlement. Due to sea level rise, previously terrestrial sites may now be located in the marine environment. This is particularly noticeable on the coasts of the Orkney and Shetland where numerous Neolithic and Mesolithic structures are now below sea level (Historic Scotland, n.d. a).

8.1.2. While many heritage features lie wholly within the marine environment, numerous features are also located in coastal areas. It is believed that there as many as 38,000 historic and unprotected sites of interest in marine and coastal environments around Scotland (Scottish Government, 2011). Managed and accessible coastal or marine heritage sites are much fewer in number, with 97 currently existing in Scotland. These include World Heritage Sites (St Kilda and Heart of Neolithic Orkney), coastal properties in care of Historic Environment Scotland, maritime and coastal heritage museums, and designated wreck sites (Scottish Government, 2011). Protected wrecks (protected places and controlled sites) under the Protection of Military Remains Act 1986 (Designation of Vessels and Controlled Sites) Order 2012 are shown in Figure 26.

8.1.3. Historic Environment Scotland ( HES) is directly responsible for safeguarding the Scottish historic environment, including marine and coastal features. One mechanism whereby HES can provide protection to marine archaeological sites is through the designation of Historic Marine Protected Areas ( HMPA). These areas are designated under the Marine (Scotland) Act 2010 for the purpose of preserving marine historic assets of national importance, including but not limited to significant historic shipwrecks, remains relating to important fleet anchorages, battle sites or navigational hazards (where multiple wrecks and other features exist) and submerged prehistoric landscapes (if structural or artefact-based evidence is identified on the seabed). Currently there are seven designated HMPAs around Scotland ( Figure 27). These are (Historic Scotland, n.d. b):

  • Drumbeg (Sutherland, Highland);
  • Mingary (Ardnamurchan, Highland);
  • Kinlochbervie (Sutherland, Highland);
  • Campania (Firth of Forth, Fife);
  • Out Skerries (Shetland);
  • Dartmouth (Morvern, Highland); and
  • Duart Point (Mull, Argyll and Bute)

8.1.4. There is also one proposed HMPA, Iona, located in the Clyde ( Figure 27).

Figure 26: Location of protected wrecks in Scotland

Figure 26: Location of protected wrecks in Scotland

Figure 27: Location of designated and proposed HMPA

Figure 27: Location of designated and proposed HMPA

8.1.5. Other forms of statutory designation protecting cultural heritage sites around the coast of Scotland are afforded to listed buildings, scheduled monuments and war graves through the Historic Environment Scotland Act 2014 and the Protection of Military Remains Act 1986 (Historic Scotland, n.d. c).

8.1.6. In addition to designated heritage assets, there are many undesignated/uncertain/unknown assets. There is a significant data gap associated with these, particularly in relation to underwater heritage assets.

8.1.7. The protection afforded to designated coastal and marine archaeological sites tends to prevent direct human disturbance. However, the environment can also pose a serious threat to the conservation of these sites and undesignated/uncertain/unknown assets. Coastal erosion is a major issue for archaeological sites in many areas around Scotland (Historic Scotland, n.d. d). Sea level rise and the increased frequency of storm events associated with climate change are likely to worsen the situation; endangering coastal and marine archaeological sites (see Section 4.4).

8.1.8. In addition to archaeological features, the cultural tradition of crofting has been carried out for hundreds of years in Scotland ( SNH, 2012). Crofters play a key role in maintaining the machair [28] and other wildlife through traditional practices. These include using natural fertilizers such as seaweed, namely kelp ( Laminaria sp.). Large quantities are washed up by the winter storms and collected fresh from the beach when the winds and tides allow ( RSPB Machair LIFE+, 2014a). Seaweed is then left in piles for several weeks to decompose which concentrates the nutrients and reduces its volume for spreading. Rotten seaweed is spread on the machair during late winter/early spring before it is cultivated. Seaweed helps to bind the sandy soils and its use allows for a wide range of arable and fallow wildflowers to grow because they are not engulfed by more vigorous plants boosted by artificial fertiliser.

8.1.9. The use of these natural fertilisers adds bulk, improves fragile soils and increases productivity. The Crofters (Scotland) Act 1993 (as amended) gives crofters access to reasonable use of seaweed under Common Grazings regulations. This is largely confined to the gathering of beach-cast Laminaria spp. and other mixed species for spreading on machair land in the Western Isles ( SNH, 2012). Little information is available about the extent or size of such gathering from beaches (The Scottish Government, 2013). However, the extent of spreading on the machair has been estimated between 2011 and 2013 to be a total of 317ha in the Uists and Berneray in the Western Isles ( RSBP Machair LIFE+, 2014b).

8.1.10. It is worth noting also that there is an ancient breed of sheep in North Ronaldsay (Orkney) that played a key role in the cultural development of North Ronaldsay in the 1800s. This breed of sheep is confined to the seashore by the drystone dyke encircling the island, and survives on a diet of seaweed to which it has become adapted (The Orkney Sheep Foundation, 2016).

8.2. Effects of Harvesting on Cultural Heritage

8.2.1. Terrestrial archaeological features ( e.g. monuments, light houses) will not be affected by seaweed or seagrass harvesting which take place in the marine environment and along the coastal fringe. Any potential indirect effects on the land ( e.g. access) would be managed under the existing Town and Country Planning system. Terrestrial heritage features are therefore scoped out of the SEA.

8.2.2. Wild harvesting activities have the potential to affect underwater archaeological features. These include shipwrecks, prehistoric landscapes and war graves (see Section 8.1). The potential effects on these heritage features are discussed below in relation to the broad groups of seaweeds and seagrasses.


8.2.3. Although trawling/sledging/dredging methods used to harvest kelp are designed to avoid physical disturbance of the seabed (see Table 5), the removal of entire plants by these devices could disturb the seabed and any underwater heritage features that may be associated with it. Kelps do not have roots. Instead, they secure themselves onto substrate made of rock or cobble by their holdfasts. They are therefore unlikely to be attached to archaeological features that comprise softer material, for example submerged landscapes or wooden shipwrecks. They may, however, be attached to archaeological features comprising harder material such as the metal hulls of shipwrecks. Overall, the likelihood of this method of harvesting affecting underwater archaeological features (either designated or undesignated/uncertain/unknown) is considered to be low. In the interests of best practice, however, it would be advisable for operators to avoid areas of known charted wreck sites and archaeological features.

8.2.4. Other methods of harvesting kelp that involve hand or mechanical cutting methods will not disturb the seabed and will therefore not impact cultural heritage features.


8.2.5. The primary means of harvesting maerl is by dredging. Maerl does not have roots but accumulates subtidally as dense beds of calcareous material. The extraction of maerl by dredgers would therefore disturb the underlying seabed and potentially any associated archaeological features (either designated or undesignated/uncertain/unknown). Furthermore, the recoverability of maerl is very low given their very slow growth rates. Therefore, depending on the nature of the underlying substratum (hard versus soft), the removal of maerl could lead to an increase in the potential for erosion (see Section 6.3) and exposure of any underlying cultural heritage features. Maerl harvesting is therefore considered a significant risk for cultural heritage.

Other Groups of Seaweed

8.2.1. Harvesting other groups of seaweed involves hand or mechanical cutting methods that are considered to be non-invasive. These will therefore not impact cultural heritage features.


8.2.2. Although not common practice, any trawling/sledging/dredging of seagrass beds would result in the uprooting of this plant. In contrast to kelps, seagrasses have roots and occur on soft substrate, typically sandy or muddy sediment. The complete removal of these plants is therefore more likely to disturb any underlying cultural heritage features (either designated or undesignated/uncertain/unknown) that might be present. Furthermore, the regeneration of areas where seagrass is harvested using these methods would be slow and could lead to an increase in the potential for erosion (see Section 6.3). This in turn could result in the exposure of cultural features. This activity has been assessed as a medium risk to high risk on a site by site basis.

8.2.3. Other methods of harvesting seagrass that involve hand or mechanical cutting methods will not disturb the seabed and will therefore not impact cultural heritage features.


8.2.4. Harvesting beach-cast seaweed may affect the ability of cast seaweed to provide coastal erosion protection and, therefore, protect underlying historic environment features that are vulnerable to such erosion. Overall, harvesting beach-casts in areas where the coastline is soft ( e.g. beaches) could increase the potential for coastal erosion although the evidence in support of this is limited. However, the degree of erosion would be small and unlikely to be of a magnitude that would expose any underlying archaeological features (either designated or undesignated/uncertain/unknown).

8.2.5. Mechanical gathering of beach-casts involves the use of large vehicles such as tractors or JCBs which could also disturb the shore. These vehicles can leave tracks on beaches and result in some minor disturbance of the surface layer of the sediment. The depth of penetration by the tyres, however, is very small (of the order of a few centimetres) and therefore unlikely to affect any cultural heritage features.

8.2.6. Harvesting beach-cast seaweed also has the potential to reduce the availability of this resource for crofters. The degree of effect on this cultural tradition will depend on the scale of harvesting. Small scale (artisanal) hand gathering is unlikely to be an issue whereas large scale mechanical harvesting could be more of an issue. It will therefore be important for crofters to be consulted prior to any large scale harvesting of beach-cast kelp to ensure that any potential interactions are avoided or minimised (see Section 6.6).


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