Non-native species are a major cause of the loss of
biodiversity globally and their impacts are especially severe on
the island ecosystems and species typical of our Overseas
Territories and Crown Dependencies. The biodiversity found in
the Territories contains many globally threatened and endemic
species and also populations of species whose abundance is of
regional or global significance.
This study was commissioned to investigate, through desk
study, the occurrence of non-native species in the Overseas
Territories and Crown Dependencies of the United Kingdom.
The review collated information gathered from the literature,
individual experts and organisations, both in the UK and in the
Territories or Dependencies themselves, and was guided by a
workshop at JNCC in January 2004 involving representatives of the
Foreign & Commonwealth Office, the Department for International
Development and the UK Overseas Territories Conservation
A minimum of 2261 non-native species is recorded as occurring
across the UK Overseas Territories & Crown Dependencies with a
total of >2900 records of occurrence overall. The review
showed that Bermuda has the unfortunate distinction of topping the
non-native species polls with 1139 species recorded – by contrast,
the South Sandwich Islands have none.
A number of species are recorded as causing problems in
several Territories. The study collated records of rats (Rattus
rattus, R. norvegicus and R. exulans) from
14 Territories and feral cats (Felis catus) and house mice
(Mus musculus) each from 11. The mimosa Leucaena
leucocephala is currently the most widely recorded introduced
plant species with records from 10 territories, followed by
Australian pine Casuarina equisetifolia from eight
Territories and lantana Lantana camara from six
Territories. However, it only takes the presence of a single
invasive species to have devastating consequences for some native
In general, the number of non-native species recorded from a
Territory is closely related to the amount of biological survey
work carried out there in recent years. The number of species
recorded in the database, therefore, does not necessarily reflect
the true numbers of introduced species in many Territories.
Numbers in most Caribbean Territories are likely to be far higher
than recorded here whereas numbers from the Falklands, Bermuda,
Gough Island, Ascension and St. Helena are based on recent
research. This review should, therefore, be seen very much as
work in progress. The low numbers of non-native species
recorded from the British Antarctic Territory and the South
Sandwich Islands are thought to be genuine.
This audit, the first of its kind, will help to inform any
measures aimed at eradicating, controlling and, more importantly,
preventing the future establishment of, non-native species and
conserving the native biodiversity they threaten.