UK's Overseas Territories at ongoing risk from wide range of invasive species

A new study has for the first time predicted which invasive species could pose a future threat to the UK's ecologically unique Overseas Territories.

The 14 Territories—many of them small, remote islands such as St Helena and Pitcairn—are home to species found nowhere else in the world. This makes them extremely vulnerable to biological invasions—in the oceans or on land—which could lead to the extinction of these endemic species or irrevocably change their unique ecosystems.

Researchers at the UK Centre for Ecology & Hydrology (UKCEH) and Durham University, working in partnership with communities on the Overseas Territories, assessed thousands of potential invasive non-native species, to predict which are most likely to arrive and impact these environments within the next 10 years.

The resulting research, published in the journal Conservation Letters, provides a reference for authorities, conservation ecologists and the public to guide them in preventing these invasive non-native species from becoming established and causing ecological and economic damage.

UKCEH ecologist Professor Helen Roy, who led the work, says, "These Territories are exceptionally biodiverse. St Helena, for example, has over 400 invertebrates found nowhere else in world—it is simply unique. We hope that this study draws attention to these Overseas Territories and the inspiring people on them who are working so hard to protect their incredible wildlife and habitats."

To produce the list, experts from each UK Overseas Territory collaborated with the wider project team of experts from around the world to predict which invasive non-native species were likely to arrive, establish and impact on biodiversity, ecosystems, human health and the economy within the next 10 years. The report also examines how the species are most likely to arrive, with shipping containers identified as a key route for many animal species.

Gibraltar and Saint Helena are threatened by biological invasion from the greatest number of species overall. St Helena is most at risk from a high number of plant species, while the Falkland Islands and Tristan da Cunha are threatened by the most marine invasive non-native species.

One of the invasive non-native species that could pose a threat to many of the UK Overseas Territories is the green mussel (Perna viridis). It can 'hitchhike' around the world on ships and boats, and form dense colonies in places where it establishes outcompeting other species by, for example, reducing levels of phytoplankton—a key component of aquatic ecosystems.

Other invasive non-native species that present a major threat to many UK Overseas Territories include the little fire ant (Wasmannia auropunctata), the brown rat (Rattus norvegicus), and the mesquite tree (Prosopis juliflora) .

Dr. Wayne Dawson of Durham University said, ""The knowledge and experience of local experts was central to identifying the non-native species that pose the highest threats to each Territory, and it was a great privilege to work with a wide range of contributors on the project."

Ecologists and other experts on the UK Overseas Territories are aware of the challenges of invasive non-native species and in many cases have robust biosecurity measures in place, but Professor Roy hopes that the report will draw attention to their vital work.

Professor Roy added: "Preventing the introduction of invasive non-native species is key, because management of species that have established and spread is often extremely expensive and in some cases there are no options available. We hope that this list will help inform action, including supporting biosecurity activities, to safeguard the wildlife in these precious places."

The paper, "Horizon scanning for potential invasive non-native species across the United Kingdom Overseas Territories" is published in Conservation Letters, a journal of the Society for Conservation Biology.