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.

12. Summary and Conclusions

12.1. Introduction

12.1.1. The wild seaweed harvesting sector has indicated its aspiration to develop industrial-scale harvesting around Scotland. The aim of this SEA is to assess the potential environmental effects of wild harvesting of seaweeds and seagrasses and in turn inform future regulation.

12.1.2. Seaweeds and seagrasses are important resources which may be harvested sustainably. However, sustainable management is not straightforward. Both seaweeds and seagrasses have complicated life histories. Failure to take account of this in the management of harvesting operations could have adverse consequences for these habitats ( SNH, 2016). Damage to growing areas of individual plants can affect regeneration and the removal of target species by harvesting will impact the ecological structure and function of these habitats and also the ecosystem services that they provide.

12.2. Harvesting

International experience of large scale harvesting

12.2.1. Although not straightforward, sustainable commercial scale harvesting of certain species is possible and is taking place in other countries, such as Norway and Chile where annual live extractions of kelp by trawlers reaches 200,000 tonnes (Vasquez, 2008; Vea & Ask, 2011; Smale et al., 2013; Burrows et al., 2014a). The ability to sustainably remove such quantities at these locations has been attributed to the rapid recruitment and growth of kelps, the species associated with the kelp beds, and the implementation of appropriate and functional management of the resource (Smale et al., 2013).

Vulnerability of Maerl and Seagrass

12.2.2. The SEA has identified that the sustainable extraction of maerl is not possible and that harvesting of maerl should be prohibited ( Section 9 ). Although the evidence indicates that the sustainable harvesting of seagrass might be possible, the seagrass beds found in Scotland are typically small ( Section 3.2 ) and unlikely to support wild harvesting activities. The commercial harvesting of seagrass should therefore also be prohibited.

Small Scale harvesting

12.2.3. Current small scale ( i.e. artisanal) hand cutting or picking of wild seaweed in Scotland managed through existing regulation is unlikely to result in significant adverse environmental impacts. However, management will need to take account of species and location as well as scale and for the cumulative impacts of small harvesting operations, the sensitivity of particular location and the future expansion of the industry. It is recognised that there is a risk that small seaweeds (namely green and red seaweeds) could be completely cleared from an area by these small scale harvesting activities. However, there is no information available on what would be considered a significant volume of removal for these small seaweeds and therefore at this stage in the absence of evidence it is not possible to propose an accurate threshold for triggering regulation of these activites.

12.2.4. Although small scale harvesting activities are currently not regulated under marine licensing, operators will still need to continue to consult SNH in the context of a number of legislative duties. These include advice on the need for an HRA, mitigating against disturbance to wildlife under the Wildlife and Countryside Act 1981, the need for a SSSI consent under the Nature Conservation (Scotland) Act 2004, European Protected Species ( EPS), impacts on features of MPAs and management of the risks associated with invasive non native species.

Consequences of large scale harvesting

12.2.5. The SEA has confirmed that significant adverse effects can occur as a result of large scale ( i.e. industrial) mechanised harvesting of seaweeds (namely kelps and wracks). These primarily relate to impacts on the ecological function of these important habitats (namely ecological interactions, food web dynamics and production) as well as on the ecosystem services that they provide (including coastal protection and carbon sequestration), and that these impacts may be further exacerbated in the future with the predicted effects of climate change. Such harvesting also has the potential to affect cultural heritage (namely underwater heritage assets and the collection of beach-cast seaweeds by crofters). Potential issues include but are not limited to:

  • Loss of habitat and/or shelter for a range of plants and animals, alongside loss of direct and indirect food sources. This has consequences for detrital grazers and suspension feeders, as well as higher trophic levels, e.g. mammals, birds and fish;
  • Loss of nursery grounds for juvenile invertebrates and fish, with consequences for higher trophic levels and commercial fish stocks;
  • Loss of the physical modification effects of seaweed, e.g. wave damping, which may result in increases in coastal erosion and/or flooding events;
  • Loss of carbon stores and sinks provided by some seaweed species; and
  • Loss of or damage to cultural heritage assets and reduction in resource available to crofters.

12.2.6. Many of these effects are likely to be site specific and will depend on a range of factors, including the species to be harvested, the harvesting method, the amount taken, the timing (season) of harvest, the harvesting location and its environmental context, and the time allowed for regeneration prior to harvesting again. Harvesting practices, most notably the extent and scale of harvesting ( i.e. frequency of harvesting, the proportion of a seaweed community harvested, and the proportion of an individual plant harvested) and the species harvested have been identified as key factors in ensuring plant regeneration and recovery of harvest areas, and ensuring the sustainability of the resource and the biodiversity it supports.

Cumulative Effects in an expanded industry

12.2.7. Although there is no evidence that small scale artisanal hand cutting or gathering of living and beach-cast seaweeds at discrete locations have significant environmental effects, there is the potential for significant cumulative effects as a result of multiple harvesting activities. However, we do not know what the cumulative effects of a large number of small-scale activities being undertaken within the same geographic location or the cumulative effects of potential small scale harvesting operations in conjunction with large scale industrial operations would be. These would need to be considered in the cumulative assessments of individual licence applications.


12.2.8. One way to help manage and mitigate these potential cumulative effects would be to create a public register of seaweed harvesting activities. This would provide a record of the harvesting activities that are being undertaken or are proposed to be undertaken. It is recognised that there could be issues regarding commercial confidentiality and also issues concerning how it would be administered. Although Marine Scotland is unlikely to be able to resource the management of such a register, it may be possible for industry to take forward such an initiative as a form of self-regulation.

12.2.9. Following the conclusion of a consultation, Marine Scotland intends to prepare a guidance note to assist licence application. This will include information on key issues associated with wild harvesting that have been identified in the SEA. It will also include information on issues that fall outside the scope of the assessment but will need to be considered at the project-level by industry (see Sections 2.3.4 and 2.3.5 ). A link to the risk matrix that has been developed as part of this SEA will also be provided together with a link to the evidence base ( Section 9 and Appendix E ). This matrix will be managed and periodically updated by Marine Scotland in light of any new evidence to ensure that it is based on the best available scientific information.

12.2.10. GIS data layers that have been created as part of this SEA, namely the distribution of the current seaweed and seagrass resource, will be included on Marine Scotland's National Marine Plan interactive ( NMPi) site [31] .


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