UKCEH scientists organised a workshop in Gibraltar 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 Overseas Territories (UKOTs). Funded by Darwin-Plus, we are currently working with each of the UKOTs to compile individual lists of these INNS. The project aims to enhance the availability of information on these species and, in the long term, to provide a template for a constantly evolving database of INNS, reviewing the threats they pose to each UKOT. This database could allow experts to determine appropriate mitigation strategies to minimize the threat of these INNS to biodiversity and ecosystems.

The latest UKOT we had the pleasure of visiting was Gibraltar. Despite its relatively small size (5km x 1.2km), Gibraltar is steeped in military history and showcases a unique blend of both British and Spanish culture. It is used as a migratory pathway for many birds, insects, and marine species, and has two Special Areas of Conservation: The Rock of Gibraltar and the Southern Waters of Gibraltar, which contain endemic flora and fauna.

Experts from a wide range of institutes attended our workshop in June 2023: Wildlife (Gibraltar) Ltd, Gibraltar Botanic Gardens, University of Gibraltar, HM Government of Gibraltar, Gibraltar Natural History Society, Joint Services Health Unit, and Enalia Physis. The local terrestrial and marine knowledge of the experts was invaluable and extremely impressive; they provided a rich source of information on the various threats that INNS pose to Gibraltar’s biodiversity. A series of presentations made it clear that a number of INNS now call Gibraltar home, and are negatively impacting the native wildlife.

After a vote, we found INNS of particular concern included the macroalgae Rugulopteryx okamurae, Asian tiger mosquito Aedes albopictus, and perennial plant Oxalis pes-caprae.

Asian tiger mosquito

Asian tiger mosquito Aedes albopictus, an invasive non-native species of concern. Photo by James Gathany, CDC.

Oxalis pes caprae flowers

Perennial plant Oxalis pes-caprae, another invasive non-native species of concern in Gibraltar. Photo by Robert Flogaus-Faust (CC BY 4.0)

A particular highlight of the visit was the field day, which provided us with a firsthand view of the local habitats and wildlife. Keith Bensusan (Wildlife Gibraltar Ltd, Gibraltar Botanic Gardens) acted as our guide on The Rock and through the local Botanical Gardens. We took regular stops whilst climbing the face of The Rock for Keith to point out the amazing flora and fauna native to the territory, such as the Wild Olive tree Olea europaea and the Barbary macaque Macaca sylvanus.

While walking through the Botanic Gardens we managed to attract a trail of invasive feral chickens Gallus gallus domesticus, which followed us throughout the tour to the final stop - the laboratory building which house the Gibraltar Botanic Gardens entomology collection. The collection was remarkable, displaying a vast array of entomology orders in pristine condition.

Encountering a Barbary macaque on in the Gilbraltar Nature Reserve

Encountering a Barbary macaque on The Rock

Trees in Gilbraltar Botanic Gardens

Gibraltar Botanic Gardens

Later the same day, University of Gibraltar PhD students Amy Swift and Xavier Villar-Buzo took us out on a snorkeling tour of the beautiful Sandy Bay, which lines the eastern side of The Rock.

Amy highlighted the presence of the invasive macroalgae Rugulopteryx okamurae which has almost completely monopolized Sandy Bay, resulting in a huge reduction in the biodiversity of marine flora and fauna in the area. She stressed the importance of regular surveying and subsequent removal of the microalgae in order to monitor and prevent its spread.

Sandy Bay, Gilbraltar viewed from above on The Rock

View of Sandy Beach from The Rock

Group with snorkeling gear on Sandy Beach, Gilbraltar

Snorkeling in Sandy Bay reveals how an invasive macroalgae Rugulopteryx okamurae has caused a huge reduction in the biodiversity of marine flora and fauna in the area

Over the course of the workshop it became evident that the establishment of a Gibraltar-specific biodiversity portal incorporating both historic and current data resources in a standardized format would be extremely beneficial to the participants. This data could then be used to inform fine scale distribution maps of INNS, allowing for the visualization of the extent of their distribution across the territory. Further to this, these maps could be used to identify which areas may benefit from further monitoring or mitigation strategies.

In addition, during the workshop Jakovos Demetriou (Enalia Physis, JSHU) presented to the participants the Cyprus Database of Alien Species (CyDAS), a database created, supplemented and maintained during Darwin Plus projects 056,088 and 124. The presentation highlighted the structure and importance of databases on non-native and INNS as similar databases are being prepared for all UKOTs under DPLUS175.

The importance of engagement, outreach events and resources to raise local public awareness of invasive non-native species was also highlighted. Methods of engagement discussed included: the promotion of iNaturalist; the production of postcards describing locally found INNS; holding citizen science events; utilizing local media resources; working with local schools; and creating an interactive biodiversity platform.

It was evident that local students and researchers alike have a strong affiliation with the fauna and flora native to Gibraltar and are really invested in trying to conserve and safeguard the unique biodiversity and ecosystems as far as possible. We hope that the information systems and resources we develop with our inspiring partners on Gibraltar will play a part in addressing the threat biological invasions pose to the area.

Group photo of 20 workshop participants in front of the University of Gibraltar sign
Workshop participants at the University of Gibraltar

We are extremely appreciative of all the time and expertise that has been given so far and we are looking forward to our ongoing collaborations. Particular thanks to Keith Bensusan, Rhian Guillem and Darren Fa (and his affiliated students) for their support and guidance including co-developing the workshop programme.

Written by Megan Williams, Emily Williams and Jakovos Demetriou