Reducing the threat of invasive non-native species on St Helena

UKCEH scientists co-organised a workshop with experts on St Helena as part of a project assessing risks posed by invasive non-native species in the UK Overseas Territories...

Invasive non-native species (INNS) pose a threat to the biodiversity and unique ecosystems of each of the UK Overseas Territories (UKOTs). Funded by Darwin Plus, we are currently working with each of the UKOTs to compile inventories of INNS. The project aims to enhance the availability of information on INNS and, in the long term, provide a template for a constantly evolving database of INNS, reviewing the threats they pose to each UKOT and considering the needs for monitoring and reporting.

This will allow experts to determine appropriate mitigation strategies to minimize the threat of INNS to people and nature.

Experts from a wide range of organisations attended our workshop in January 2024: St Helena Government (Environment, Natural Resources & Planning, Environmental Management, Project Management Office), St Helena National Trust, St Helena Research Institute, RSPB, students, and local farmers and land users.

The on-the-ground knowledge of the local experts was expansive. They provided a crucial insight into the most pressing concerns to the preservation of St Helena’s biodiversity, recognising the interconnections and dependencies of people and nature. There are many established non-native species widespread across St Helena and understanding the magnitude of their impacts to inform prioritisation of management is critical, particularly in the context of rapidly changing climates, to ultimately ensure the biodiversity can prosper.

One INNS discussed extensively was Whiteweed (Austroeupatorium inulifolium). This species was originally introduced as an ornamental plant and has spread extensively across the island via wind and vector (human/vehicle/bird) dispersal. It dominates the vegetation in many areas of the island and is thought to increase the risk of soil erosion. Another species highlighted was the New Zealand flax (Phormium tenax). The Flax industry was integral to St Helena’s economy in the 1900s until the 1960s, when the use of synthetic fibres and high shipping cost made it unviable. Due to the historic areas being used as flax plantations, Flax is widespread across St Helena and competes with native and endemic plant species. Experts stressed the importance of regular surveying of the distribution of Whiteweed and Flax and targeted removal to prevent further spread.

Seeing the breadth of different landscapes on St Helena was a particular highlight of the visit, especially an insightful tour around the island with Julie Balchin, Biosecurity Officer for the St Helena Government, and hiking to Blue Point and Peak Dale. The landscapes were breath-taking and diverse, highlighting the range of habitats found on such a small expanse of land. In Peak Dale we walked through an area which had many of the endemic Gumwood (Commidendrum robustum) present and on the way back drove past an area abundant with She cabbage (Lachanodes arborea). These unique and beautiful endemic plants highlight the need to work towards reducing the threat of invasive non-native species.

One project of particular significance on St Helena is the St Helena Cloud Forest Project, which is a highly collaborative multi-year project working to implement the Peaks Management Plan for St Helena’s ‘Peaks National Park’. This globally significant area, which is mostly made up of natural forest, holds over one sixth of the UK’s total endemic biodiversity (approximately 250 unique species). Previously a popular hiking spot, access to the area has recently been restricted (in 2022) due to the confirmed presence of the tree disease Phytophthora which is spread through movement of plants, mud, water and represents a significant threat to endemic tree species on the Peaks. 

Throughout the workshop experts highlighted the extensive work they do on the Peaks. The St Helena National Trust carries out invertebrate surveys and the St Helena Government removes invasive non-native species and preserves the St Helena seed bank while complying with the strict biosecurity measures currently in place. Their work and dedication to the preservation of St Helena’s native biodiversity is inspiring.

During the workshop, we collaboratively reviewed the database of non-native species being compiled through Darwin Plus 175 and considered ways in which the information could be updated and used. Through discussions, it became evident that the biggest concern to participants was raising awareness about invasive non-native species present on the island and highlighting the biosecurity measures that people could take to minimize their spread. 

There are already many amazing schemes in place to increase understanding about invasive non-native species including school packs developed by St Helena National Trust and posters developed by the St Helena Government. Additional approaches to engagement were discussed including utilizing local media resources and continued work with local schools.
 
Another suggested measure was the development of a policy brief to highlight the evidence of the growing and major threat of biological invasions and ultimately support the ongoing management of invasive alien species and restoring habitats. And project coordinator, Professor Helen Roy was pleased to highlight the factsheet on islands developed from the recent IPBES assessment report on invasive alien species and their control, which Helen co-chaired. 

Climate change

Climate change is another concern for the island, manifesting so far through unpredictable weather patterns. During the workshop, we mapped out the different ways in which climate change might directly and indirectly affect the spread, establishment or impact of the INNS of most concern.  

We hope that the information systems and resources we develop with our inspiring partners on St Helena will play a part in addressing the threat biological invasions pose to this incredible island. We are extremely appreciative of the time and expertise that has been given so far and are looking forward to our ongoing collaborations. 

Thank you to everyone for making us so welcome. Particular thanks to Julie Balchin for her support and guidance including in the co-development of the workshop programme.

Megan Williams

Related links

Learn more about the project: Enhancing monitoring and prevention of invasive non-native species across UKOTs