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.

2. Approach to SEA

2.1. Background

2.1.1. A screening exercise was carried out by Marine Scotland to ascertain whether wild seaweed harvesting would be likely to result in significant environmental effects. Based on the evaluation against the screening criteria (Schedule 2 of the Act), Marine Scotland concluded that wild seaweed harvesting activities are likely to give rise to such effects unless they are undertaken in a sustainable manner. The screening report was submitted to the Consultation Authorities [2] in October 2015. All three agreed with Marine Scotland's view. Marine Scotland therefore concluded that SEA is required to ensure that such harvesting of wild seaweed in Scotland is sustainable, to assist decision making and to inform future policy.

2.1.2. The next step was to undertake a scoping exercise. The resulting Scoping Report, setting out the proposed approach to and scope of the SEA, was submitted to the Consultation Authorities in November 2015. All three provided helpful comments on the proposed scope and level of detail of the SEA, and the majority of these were taken into account in progressing the assessment.

2.1.3. Marine Scotland commissioned ABP Marine Environmental Research Ltd. ( ABPmer) to provide technical support to the SEA and to assist in the preparation of this Environmental Report.

2.1.4. Marine Scotland and ABPmer were assisted in the SEA by a Project Advisory Group, and we would like to thank the representatives of the following organisations for their participation and helpful contributions:

  • Scottish Natural Heritage;
  • Scottish Environment Protection Agency;
  • The Crown Estate;
  • Marine Scotland Science;
  • Marine Scotland Licensing Operations Team;
  • The Scottish Seaweed Industry Association;
  • Marine Alliance for Science and Technology for Scotland;
  • Scottish Environment Link;
  • Scottish Fishermen's Federation;
  • Comhairle nan Eilean Siar;
  • Scottish Coastal Forum; and
  • Natural History Museum, Department of Botany.

2.2. Scope of Harvesting Activities

Definition of Wild Harvesting

2.2.1. Wild seaweed and seagrass harvesting is defined as the picking, cutting, removal or gathering of seaweed or seagrass, either by hand or mechanically, and where there is a commercial reward and a sustained harvest. It is this activity that is included in the scope of this SEA. The traditional gathering of beach-cast seaweed by crofters is also included. The collection of seaweed/seagrass for personal use and the clearance of a single beach for environmental health reasons have been scoped out.

Geographic Scope

2.2.2. Wild harvesting activities are undertaken in Scottish territorial waters (0-12 nautical miles), including the intertidal zone and the coastal fringe of adjacent land, and it is not anticipated that future harvesting would be carried out beyond 12 nautical miles. Together these set the context for the geographic scope of the SEA.

Target Species

2.2.3. Maerl and seagrasses are not currently harvested in Scotland but have been included in the scope of the SEA for completeness, following the screening consultation, an information review and discussion.

2.3. Scope of the Assessment

2.3.1. The SEA focuses on the environmental effects of commercially harvesting wild seaweed and seagrass. One of the scoping responses included a request for the SEA to include an assessment of the effects of the end use(s) of harvested seaweed and seagrass. These concerns related to human health, i.e. through consumption of contaminated seaweed, and to the use of biofuel. However, widening the scope of the SEA in this way is not considered to be a proportionate approach. Such an approach would make the SEA more of a lifecycle analysis and would not be aligned with other marine SEAs. For example, the SEA of offshore wind, wave and tidal energy did not consider the end uses of the electricity that would be generated.

2.3.2. Schedule 3 of the Act sets out the environmental factors or topics that may be subject to SEA. The scoping exercise identified that the wild harvesting of seaweed and seagrass could affect the following:

  • Biodiversity, flora and fauna;
  • Climatic factors; and
  • Cultural heritage.

2.3.3. These topics have therefore been scoped into the SEA, with the remaining topics scoped out. The rationale for this approach is provided in Table 1 .

Table 1: Scoping In / Out of SEA Topics

SEA Topic


Reasons for inclusion / exclusion

Biodiversity, flora and fauna


Wild harvesting may affect biodiversity, including but not limited to: loss of habitat and/or shelter for a range of plants and animals, alongside loss of direct and indirect food sources. As well as detrital grazers and suspension feeders, this has consequences for higher trophic levels, e.g. mammals, birds and fish. This topic is scoped into the SEA.

There may also be disturbance of protected and other species (seals, otters, cetaceans, birds etc.) from harvesting and/or gathering activities in intertidal waters or on the shore, or from infrastructure construction such as buildings, access tracks, etc. Unless there are significant locational issues, these potential effects will be included in a guidance note for decision-makers and applicants.



Wild harvesting activities would not result in e.g. significant increases and/or decreases in human population numbers, changes to in- or out-migration, etc. These topics are scoped out of the SEA.

Human health


Wild seaweed harvesting activities have health and safety implications for harvesters using certain harvesting methods, but these are issues for the sector under the appropriate health and safety at work legislation. Harvesting activities would not result in significant changes to air, noise, water quality, or land quality (contamination).

Human health issues around the human consumption of seaweed have been scoped out of the SEA (see Section 2.3.1 for the rationale).

Soil, geology and hydrodynamic processes


Potential impacts on coastal geodiversity interests include sediment processes; changes to sedimentation rates and patterns, changes to water movement and changes in coastal accretion. These impacts are scoped into the SEA and reported under "climatic factors"..


Wild seaweed harvesting activities would be unlikely to result in levels of detritus higher than those that would occur naturally as part of seaweed growth cycles, and would therefore not result in increased detritus on the seabed (which would have potential for smothering and changes in benthic chemistry). These topics are scoped out of the SEA

Water quality, resources, ecological status


Activities are likely to affect the ecological status of water bodies, through their effects on biodiversity, and ecological status is therefore scoped into the SEA. This topic has been assessed and reported under "biodiversity, flora and fauna", in the interests of proportionality.


Wild seaweed harvesting activities would not result in increased discharges to the aquatic environment, or require significant increases in water consumption. Water quality is scoped out of the SEA.



Wild harvesting activities would be unlikely to result in emissions to air, other than those from vessels used for gathering and/or harvesting activities. It is unlikely that such vessels would make a significant contribution to existing vessel emissions. We therefore consider that wild seaweed harvesting activities would not result in significant changes to atmospheric emissions, and have scoped air quality out of the SEA.

Climatic factors


Wild harvesting activities would not result in increased/ decreased emissions of greenhouse gases and these are scoped out of the SEA. The role of seaweed/seagrass in carbon cycling, providing carbon sinks and providing coastal/flood defence is scoped into the SEA.

Material assets


The role of kelp beds as spawning and nursery areas for (commercial) fish and invertebrates is scoped into the SEA and reported under "biodiversity, flora and fauna".

The role of seaweed in providing coastal defences ( e.g. through wave energy absorption), carbon sinks and carbon cycling is scoped into the SEA and reported under "climatic factors".

The traditional gathering of beach-cast seaweed, e.g. by crofters is scoped into the SEA and reported under "cultural heritage".

Cultural heritage


Wild harvesting activities, particularly those using dredging methods, have the potential to affect underwater marine archaeological features. This topic is scoped into the SEA.

Gathering beach-cast Laminaria and other species is a traditional activity by crofters and others, and could be affected by commercial harvesting. Such harvesting may also affect the ability of cast seaweed to provide coastal erosion protection and, therefore, protection of historic environment features vulnerable to such erosion.

Landscape/ seascape


The construction and/or operation of supporting infrastructure may have local effects on landscape and/or seascape. However, these issues are likely to arise at all sites, at the local level, and will be considered accordingly. These issues are therefore scoped out of the SEA.

2.3.4. The activity of harvesting of wild seaweed and seagrass also has the potential to give rise to contamination ( e.g. spills from vessels), disturbance of coastal and intertidal species ( e.g. by the construction of infrastructure such as access tracks), and effects on landscape from such infrastructure. There may also be disturbance of protected and other species ( e.g. seals, otters, cetaceans etc.). There are also concerns about the potential introduction and/or spread of invasive non-native species during hand or mechanical harvesting, through the discharge of ballast water or use of equipment where such species are inadvertently present.

2.3.5. These issues could arise at most sites around the coast. Marine Scotland considers that, although these issues are important at project and/or activity level, there are well-known measures for the control and/or management of such issues. They have therefore been scoped out of the SEA with the agreement of the Consultation Authorities. However, these issues will be included in a guidance note for decision-makers and applicants, along with the necessary mitigation measures (see Section 9 ).

2.3.6. An SEA of seaweed aquaculture was undertaken and an Environmental Report published for consultation in August 2013 alongside a draft Seaweed Policy Statement [3] . The scope of this SEA therefore does not include the environmental effects of seaweed aquaculture, given that the previous work is relatively recent and that, as yet, no monitoring results are available from pilot seaweed farms.

2.4. Reasonable Alternatives

2.4.1. The Act requires the assessment of reasonable alternatives. The reasonable alternatives that have been identified are:

  • Do nothing, i.e. continue with the existing licensing/leasing arrangements for all future commercial harvesting activities;
  • All commercial wild harvesting activities to require a marine licence;
  • Using a combination of existing arrangements and marine licensing depending on the scale of the harvesting activity;
  • Stop all commercial harvesting activities.

2.4.2. The implications of these alternatives are discussed in Section 10 .

2.5. Assessment Methodology and Reporting

2.5.1. The potential environmental effects of harvesting have been assessed using the key questions set out in Table 2. These were developed at the scoping stage and are based on consideration of the ecological functions and ecosystem services provided by wild seaweed and seagrass ( Section 4.4 ); a review of the existing environment ( Section 5 ); the potential effects of wild harvesting ( Section 6 ) and the environmental protection objectives ( Appendix B ). They also take account of the comments received from the Consultation Authorities.

2.5.2. The key questions enable the assessment to focus not only on environmental topics, but also on the interactions and inter-relationships between them. They also enable the identification of measures for mitigation and/or enhancement and requirements for monitoring.

2.5.3. The results of the assessment are structured in a narrative style, centred on exploring the issues that the key questions raise. This approach provides explanatory text to support the findings of the assessment, and records the evidence used in reaching its conclusions and recommendations.

Table 2 Key Questions

Section(s) of Environmental Report ( ER)


Which species are most likely to be exploited by wild harvesting activities?

Table 4: Page 39


What is the nature of the resource, based on existing information? i.e.:

What are the target species? Identify living, beach-cast, calcified seaweeds and seagrass

What amount/biomass is available for harvesting?

Appendix C: Page 178


Where around the Scottish coast is it located?

Section 3.2 Page 21


What ecological functions and ecosystem services do these seaweeds/seagrasses provide? How do these vary with location? The relative importance of locations should be considered in this context.

Section 3.10: Page 34;
Section 4.4: Page 61;
Section 5: Page 77


Would wild harvesting activities affect these ecological functions, both those of coastal margins and marine ecosystems, including but not limited to:

Would loss of habitat and/or shelter for other species be permanent? How would the scale and duration of habitat loss relate to the sensitivity (resistance and resilience) of any impacted species?

How would loss of feeding grounds affect higher trophic levels?

How would loss of direct and indirect food sources affect suspension feeders and others?

Would this be related to season?

Can adverse effects be mitigated?



Would wild harvesting activities affect these ecosystem services, both those of coastal margins and marine ecosystems, including but not limited to:

Adverse effects on coastal defences? Adverse effects on fish spawning and nursery grounds? Seaweed's role in the carbon cycle, including its function as a carbon sink?

Loss of physical modification, e.g. wave damping? An increase in wave scour?

6.2, 7.5


Would wild harvesting/gathering activities affect historic environment assets?

Section 8


Can wild harvesting activities be undertaken in a sustainable manner?

Section 12


Are there any geographic areas/locations of particular environmental/ecosystem service sensitivity? (Please note that this includes ecological services for the coastal margins as well as marine ecosystems.)



Could the harvesting of wild seaweed be undertaken in such a way as to maintain the environmental quality and resources which support material assets such as fish nursery grounds/ coastal defences?

Section 12


Are there potential cumulative environmental effects from wild harvesting, including but not limited to aquaculture, renewables, coastal defence works, coastal realignment, etc.?

Section 11

2.6. Building on Previous Assessments

2.6.1. An SEA of seaweed cultivation was undertaken and an Environmental Report published for consultation in August 2013, alongside a draft Seaweed Policy Statement ( http://www.gov.scot/Publications/2013/08/6786). The SEA included a high-level assessment of the potential environmental effects of wild seaweed harvesting, but was not detailed enough to inform decision making and the information is also out-of-date.

2.6.2. The current SEA has built on, and updated, existing information collected through the SEA for seaweed cultivation. Information from other sources including, but not limited to, the National Marine Plan for Scotland and the SEAs of the Marine Protected Areas has also been used to inform this SEA. Information provided by respondents to previous consultations was also taken into account.

2.7. Identifying Monitoring Proposals

2.7.1. Proposals for monitoring will be provided in the Post Adoption Statement. These will focus on the significant environmental effects identified in Sections 6, 7 and 8 of this report. Where possible, existing data sources and indicators will be linked with relevant indicators, to minimise resourcing requirements for additional data collection.


Back to top