Tristan da Cunha

The Conservation Ordinance for Tristan da Cunha, published in 2006, includes some references regarding non-native species. Section 3 (1) (e) prohibits the import of any kind of organism not native to Tristan da Cunha without a permit. Section 3 (1) (f) includes some restrictions on the liberation, dissemination or escape of plants or organisms not native to Tristan. Section 4 (4) places restrictions on transporting native organisms between the different islands of the Group. Section 4 (5) prohibits the release on any island or islet specimens of any native organism that was not originally derived from that island or islet.

The JNCC database lists 172 non-native species for the Tristan da Cunha Group. Of this 112 species are invertebrates, 119 plant species and six vertebrates.

Problems with invasive non-native species

A number of introduced plants are regarded as invasive and causing significant problems (eg New Zealand Flax Phormium tenax, Procumbent Pearlwort Sagina procumbens, a grass Holcus lanatus and Kikuyu Grass Pennisetum clandestinum). The impacts of introduced invertebrates on native species are largely unknown but there are concerns about some of the parasitic wasps (eg Ichneumon insulator, Meloboris helminda) and their impact on native flightless Noctuid moths.

Black rats Rattus rattus are a major agricultural and food storage pest on Tristan and are regarded, along with cats, as being responsible for the massive reduction in the numbers of some breeding seabirds on the Island and reductions in some of the landbird species. Perhaps the most publicised problem with an invasive species has been that of House Mouse Mus mus on Gough Island where not only are they having a major impact on the invertebrate fauna, plant population dynamics and nutrient cycling but are now known to have evolved into a major predator of Procellariform seabird chicks including the endemic Tristan Albatross and Atlantic Petrel.

Priority invasive non-native species and actions

Cats were eradicated from Tristan da Cunha in 1974.

The Management Plan for the Gough Island and Inaccessible Island World Heritage Site has actions against non-native species as a key component. In particular there are current ongoing programmes to eradicate Sagina procumbens from Gough Island and to eradicate New Zealand Flax and other invasive plants from Inaccessible Island. The RSPB is also developing plans for the eradication of house mice from Gough Island. Investigating the impacts and potential feasibility of eradicating Ichneumon insulator from Inaccessible Island is considered a priority. The Management Plan also sets out actions to develop and implement an overall biosecurity plan for the islands.

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