Searching for Shetland's lost seagrass: integrating historic records, community participation, and drone imagery to map change in seagrass distribution

Description

Accurate knowledge of changes in local seagrass abundance and distribution is important to inform marine management and provide a baseline for assessing the potential for restoration efforts. In the Shetland Islands, the regional marine planning process identified significant data gaps on the current status and distribution of seagrass habitats. To address these gaps, archival data and historic accounts were reviewed to identify changes in the distribution of seagrass across Shetland. Sites with evidence for the presence of subtidal Zostera marina (eelgrass) beds were surveyed to assess the current extent of eelgrass beds. Small Unmanned Aircraft Systems (UAS) were used to capture aerial images, which were manually assessed to identify subtidal features. Suspected seagrass bed locations were ground-truthed via paddleboard and snorkel surveys with photo and video transects carried out by community volunteers. This multi-method approach identified a period of high abundance of seagrass pre-1900s with evidence for the use of the dried eelgrass (or marlok or marlie in the Shetland dialect) for stuffing mattresses and as bedding for cattle continuing into the 1920s. Extensive loss and continued decline has occurred since this period, with only two remaining locations supporting eelgrass meadows at present. This project demonstrated the applicability of small, relatively inexpensive UASs to cost- and time-effectively survey remote and hard to access areas with complex coastlines. It also emphasised the importance of retaining access to detailed historic survey reports and local archival records if the species location records held in online repositories are to be used to assess change in seagrass distribution.

Period	11 Nov 2025
Event title	UK Seagrass Symposium 2025
Event type	Conference
Conference number	2
Location	Cardiff, United KingdomShow on map
Degree of Recognition	National