NatureScot Research Report 1286 - Seagrass restoration in Scotland - handbook and guidance

NatureScot. “NatureScot Research Report 1286 - Seagrass Restoration in Scotland - Handbook and Guidance.” Accessed December 13, 2021. NatureScot Research Report 1286 - Seagrass restoration in Scotland - handbook and guidance | NatureScot.

Global declines in seagrass beds along with a growing appreciation for the value of such habitats has stimulated an interest in seagrass restoration in a number of countries and regions. Seagrass beds occur along the British coastline and successful seagrass restoration projects in Wales along with a push towards net zero have stimulated enthusiasm for trials to begin in Scotland.

This handbook has been developed by NatureScot in collaboration with Scottish Government (Marine Scotland) and Project Seagrass to inform and guide potential seagrass restoration projects in Scotland and to ensure all appropriate policy, licensing and monitoring aspects have been considered. NatureScot is Scotland’s nature agency and have a role in assessing human activities in the Scottish marine environment. NatureScot also provide advice to ensure that natural features are maintained and enhanced. Marine Scotland is a directorate of the Scottish Government. Marine Scotland manages Scotland’s seas and freshwater fisheries along with delivery partners NatureScot and the Scottish Environment Protection Agency (SEPA).

This handbook aims to provide an evidence-led approach to guide seagrass restoration proposals in Scotland. While guidance exists for other countries, for example the USA (Fonseca, 1998), Sweden (Moksnes et al., 2021), the Indian Ocean (UNEP, 2020), no equivalent is currently available for Scotland. A seagrass restoration handbook has been developed by the Environment Agency for the UK (Gamble et al., 2021) which provides further information.

Restoration may not be the most appropriate action for conservation management of seagrass at certain sites and priority should be to protect and promote recovery of existing seagrass beds. Where restoration is considered appropriate, this handbook can help guide projects and ensure all relevant aspects are considered.

Seagrass beds are a Priority Marine Feature (PMF) in Scotland and a protected feature in a number of marine protected areas (e.g. Special Areas of Conservation – SACs, Nature Conservation Marine Protected Areas and Sites of Special Scientific Interest - SSSIs). Restoration attempts that take place within a protected area should consider if and how the various activities (e.g. seed collection, planting, monitoring) could affect protected features of that site (and in some cases adjacent sites).

We highlight how seagrass restoration proposals should outline the potential risks and benefits of the project and clearly state the aims, objectives and timescales, including how success of the project will be measured. The handbook also provides background on policy, legislation and licensing considerations within Scotland and the roles that NatureScot and Marine Scotland can play in supporting projects with appropriate advice on a case-by-case basis.

It is important to fully assess project feasibility and site suitability (chapter 3) at an early stage. Chapters 4 provides background and guidance on seagrass restoration techniques as well as tips for seed collection and storage. A robust monitoring plan should be set out from the start, including data review, habitat suitability assessments and baseline monitoring (see chapter 6 for more information).

NatureScot have developed a Marine Enhancement Guidance Framework to assess enhancement and restoration proposals and provide guidance on aspects such as licensing, monitoring, biosecurity and planning. The level of assessment and licensing requirement will depend on the scale and location of the proposed project. Further information can be found in the Marine Enhancement Framework Guidance and report which should be used alongside this handbook.

This handbook highlights many of the knowledge gaps in our understanding of seagrass restoration, however, there are broad guiding principles to that have emerged from existing work globally. The guidance provided here therefore focusses around guiding practitioners to follow such guiding principles in order to shape projects appropriate to the local environmental, biological and social setting.

Key recommendations

  • There exists a critical need for projects to conduct feasibility studies and surveys in order to design restoration that can have a high chance of success. Studies have shown that in some areas, seagrass beds are often unviable at locations where they have existed in the past. It is thought that when a seagrass bed is lost, the entire ecosystem can shift to unsuitable conditions for the species to thrive. Seagrass beds stabilise the sediment, therefore when they disappear, resuspension can increase, and water quality degrades. Algal mats can then take over and reduce the light available, further hampering the potential for seagrass to grow. There are also other problematic processes driven by the underlying condition of coastal seas such as eutrophication and the overabundance of green shore crabs due to loss of predators. Seagrass restoration projects should assess site suitability before planting to ensure optimal ecosystem functioning and ensure local conditions will not inhibit recovery even if initial assessment indicates suitability. This should involve reviewing historic data, making use of habitat suitability models, and monitoring physical and biological parameters in the area that has been selected.
  • It is important to understand the status of existing seagrass beds in a proposed area and the cause of any declines in bed condition or extent. If the pressure causing the decline persists, then it is likely that any restoration efforts will fail. Causes of seagrass decline can range from coastal development, eutrophication, disease, fishing, aquaculture, trampling or changes in hydrodynamics. Seagrass planting should not go ahead if known pressures continue to affect the proposed area of restoration.
  • Seagrass beds naturally change over time - an individual bed will show considerable variation in extent and density throughout the year and between years. Events such as storms, algae blooms or unusually high summer temperatures can wipe out a seagrass bed. Therefore, even with thorough research and planning, restoration trials can fail. Scale is important, with large-scale seagrass restoration trials more likely to succeed. There may be a threshold size whereby a bed becomes self-sustaining. However, seagrass restoration research and trials are at a very early stage in Scotland and further research is required into the specific conditions required for seagrass on different parts of the coast. Small-scale test planting and trial plots should be used before large-scale seagrass restoration efforts are attempted.
  • Biosecurity implications in terms of accidental transfer of diseases and invasive non-native species should be a consideration for any seagrass restoration proposal and discussed with NatureScot and Marine Scotland.
  • A range of seagrass restoration techniques exist which largely fall into seed-based methods or adult transplants. The appropriateness of each technique will depend on the environmental conditions at a given site. Seed-based methods have been developed in recent years (e.g. the BoSSLine method – see Seed planting options section) to maximise success in some locations, however mixed methods of transplants and seeds have been found to be appropriate in many locations. Seeds should be sourced (where possible) from local beds to reduce biosecurity risks and may increase the chance of successful adaptations to the local environment.
  • Restoration plans should consider connectivity of seagrass beds in the area and potential changes in connectivity over time. A changing climate may require future consideration of mixed populations or ‘pre-adapted’ donor beds to support increased ecosystem resilience. However, knowledge in this research field is weak.
  • Monitoring is an important factor to include in any seagrass restoration proposal – this should include baseline measurements of physical and biological environment, test planting and long-term monitoring.
  • Effective evaluation of a seagrass restoration project requires reference beds, i.e. natural unaffected seagrass beds that are as close to the restoration area as possible. This is very important for demonstrating whether changes observed at the restoration site are due to conditions at the planting site or methods used in the restoration, or to natural variations in seagrass between years or wider impacts (e.g. pollution or changes to hydrodynamics).
  • Further research and site-specific studies on seagrass ecosystem functions and services are required in Scottish waters, particularly where there is an interest in restoring seagrass beds as a nature-based solution for carbon storage, coastal erosion and flooding protection, and biodiversity. Projects that aim to restore ecosystem functions and services related to seagrass beds will need to include appropriate controls in the monitoring design and consider the likely timescales for such processes to reflect natural seagrass habitats.