Which potentially invasive plants pose a future threat to protected sites in North West Wales?
In the UK, 51% of the nearly 3,500 plant species are non-native, with many more in gardens that may be capable of escaping into the wild. While most pose no threat, some become invasive non-native species (INNS), which can dramatically alter habitats, damage infrastructure, and negatively impact human health and recreation. Managing INNS is often costly, requiring extensive control efforts and site remediation. Overall, invasive species cost the UK economy almost £2 billion annually.
Climate change is expected to amplify these challenges by creating conditions more favourable for some non-native plants to become invasive while stressing native species and reducing habitat resilience. Identifying potential future invasive species is critical to mitigating their spread before they become significant problems.
This project, conducted for North Wales Wildlife Trust as part of their Garden Escapers Project, focuses on identifying non-native vascular plant species that could pose future threats to protected sites in North West Wales, including Sites of Special Scientific Interest (SSSIs), Special Areas of Conservation (SACs), Special Protection Areas (SPAs), and nature reserves. Launched in December 2024, the project is expected to conclude in autumn 2025.
The project is funded by the Nature Networks Programme. It is being delivered by the Heritage Fund, on behalf of the Welsh Government.
The work is divided into two key components:
Desk-Based Scoping Review
A geospatial data analysis will assess non-native plant species and protected sites within three target areas in North West Wales. The analysis will incorporate data on non-native plant records, protected sites, and potential sources of future invasive species, such as gardens and urban parks. Customised analytical functions are being developed to facilitate similar studies in other regions.Field Survey
Selected protected sites identified as being at high risk of invasive non-native plants will undergo habitat surveys. These surveys will focus on locating, identifying, and mapping non-native plants while assessing mapping habitats.
Desk-Based Scoping Review
The Desk-Based Scoping review involved analysis of over 16,000 plant records across 70 protected area boundaries and hundreds of potential non-native plant sources within the target areas. A suite of bespoke PostgreSQL/PostGIS functions performed this complex analysis in minutes, enabling rapid replication for any region. The analysis produced three key outputs:
Species Proximity: Identifies non-native plant species intersecting protected area boundaries or within five distance bands.
Potential Sources: Assesses sources of non-native plants relevant to each site, considering proximity and distance bands.
Habitat Network Links: Maps non-native species connected to protected areas via Cyfoeth Naturiol Cymru / Natural Resources Wales habitat networks.
In total, these amounted to 100,000+ rows of data, requiring further summarisation and interpretation. Two key approaches were used:
Automated Site Reports: R Markdown was used to generate standard reports for each site, compiling charts, lists, and tables into a single Word document. Smart logic adapted outputs based on the nature of the results, reducing the need for manual processing and minimising errors.
Normalised Potential INNS Score (npINNS): The site reports exceeded 300 pages, so the results were further summarised through the creation of a normalised potential INNS score (npINNS). To quantify risk, each factor contributing to non-native species presence was scored from 0 (lowest risk) to 1 (highest risk). A weighted sum produced an overall npINNS score for each site, aiding prioritisation.
The site reports and npINNS scoring tables fed into the final scoping review report, which outlined data sources, methodology, and findings. Crucially, it provided evidence-based recommendations for targeted field surveys in the next phase of the project.
Deliverables
The project will culminate in a comprehensive final report, supported by the outputs of the geospatial analysis and field surveys. These resources will provide a baseline to guide future restoration efforts and inform strategies and management options to prevent the spread of invasive non-native plants.
