Tristan da Cunha
- About Tristan da Cunha
- Invasive species data & legislation
- News & activities
- Documents, useful links & contacts
The islands were originally discovered by the Portuguese Admiral Tristao da Cunha in 1506 en-route to Cape Town. The first recorded landing of Tristan was by the Dutch in 1643 and there were two subsequent Dutch expeditions before they abandoned the idea of using it as a permanent supply base. In 1816 the UK formally took possession of the island when HMS Falmouth established a garrison there. The next year a small group led by Thomas Glass settled the island permanently. They were joined by others over the years, including five female volunteers from Saint Helena, and by 1832 the population had risen to 34. Various travails and periods of isolation meant that when a communications base was established during World War Two the island experienced a major transformation. This brought new buildings and some cash into the economy. Between the war and 1961 Tristan experienced a booming economy due to the establishment of a successful fishing industry to exploit the crawfish and the agreement to the establishment of a meteorological base on Gough Island by the South African Government. As part of the lease agreement for Gough the RMS Agulhas makes an annual supply visit to Tristan from Cape Town.
During October 1961 a volcanic eruption led to the entire population of 264 islanders and 26 expatriates being evacuated, firstly to Cape Town and then to Southampton in the UK. Although initially the UK Government assumed that the evacuation would be permanent the islanders pressed for repatriation. After a favourable report from a Royal Society expedition in 1962 the islanders returned to re-establish the settlement in late 1963.
The population Of Tristan da Cunha is now about 260. The economy is based on traditional subsistence farming and fishing supplemented by royalties from the commercial crawfishing industry, the sale of stamps and coins and income from limited tourism.
The Kew database has 53 species of native flowering plants for the Group of which 28 species and 4 sub-species are regarded as endemic. There are also 38 species of ferns and clubmosses, of which 15 species and 2 subspecies are regarded as endemic. Seven of the endemic species are restricted to one island in the Group, mainly Gough Island. Terrestrial invertebrates are less well studied although over a hundred species have been recorded, including eight that are endemic to Gough Island and another 14 endemic to the Group. Only eight species of freshwater invertebrates are known. At least 79 species of littoral invertebrates have been recorded and 20 coastal species of fish. The Tristan rock lobster (Crawfish) Jasus tristani is a major element of a local commercial fishery which brings income to the Islands.
There are no native reptiles, amphibians or land mammals. The islands are of major ornithological significance and contains 14 species of global concern. There are six endemic land birds; the Inaccessible Rail Atlantisia rogersi, Tristan Thrush Nesochicla eremita, Tristan Bunting Nesospiza acunhae and Grosbeak Bunting Nesospiza wilkinsi are endemic to the main Tristan group whilst the Gough Moorhen Gallinula comeri and Gough Bunting Rowettia goughensis are endemic to Gough Island. Four species of breeding seabirds are endemic to the islands – the Tristan Albatross Diomedea dabbenena, Atlantic Yellow-nosed Albatross Thalassarche chlororynchos, Spectacled Petrel Procellaria conspicillata and Atlantic Petrel Pterodroma incerta.
A South Atlantic Invasive Species Strategy and Action Plan agreed by the Governments of Ascension Island, Saint Helena, Tristan da Cunha, the Falkland Islands and South Georgia and the South Sandwich Islands was published in October 2010. This set out a number of strategic aims for the South Atlantic Overseas Territories in order to develop effective prevention and response measures for invasive species and thus reduce damage to their natural heritage, communities, livelihoods and options for future development. Key actions are grouped under five objectives: (A) Building awareness and support; (B) Co-ordination, co-operation and capacity-building; (C) Prevention; (D) Monitoring, early detection and rapid response; (E) Control, management and restoration.
In 1995 Gough Island and the surrounding waters out to three nautical miles was declared a World Heritage Site and the site was extended to include Inaccessible Island and the surrounding waters out to 12 nautical miles in 2004. In October 2010 a Gough and Inaccessible Island World Heritage Site Management Plan was produced by the RSPB and Tristan Conservation Department.
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.
The Annual Ratting Day took place on 23 April 2012. A total of 1009 rats were caught. Details and photos of event can be found at www.tristandc.com/newsratting.php.
The South Atlantic Invasive Species project (SAIS) was undertaken during the period December 2006 to December 2009. It was funded by the Ninth European Development Fund and carried out by the RSPB in partnership with the Governments of Ascension Island, Saint Helena, Tristan da Cunha, the Falkland Island, South Georgia and the South Sandwich Islands, Falklands Conservation and the Saint Helena National Trust. The overall goal of the SAIS project was to enhance the economic prosperity and quality of life of the people of the UK Overseas Territories (OTs) in the South Atlantic through the reduction of the threat that invasive species pose to the native biodiversity of the South Atlantic UKOTs.
A new two-year project (Defra CR 0492), being carried out by CABI and started in January 2011, is looking at the impact of invasive non-native species in the UK Overseas Territories in the South Atlantic and the potential for biological control. Details of this project can be found at www.cabi.org/?page=1017&pid=9748&site=170.
Actions to eradicate various invasive plants from Gough and Inaccessible Islands have been funded by OTEP during the period 2007-2012 (eg OTEP TDC 403 Managing alien plants on the outer islands of Tristan da Cunha; OTEP TDC 802 Clearing alien plants from Tristan da Cunha and Gough Island). A further project (OTEP TDC 404 Restoration of the Sandy Pointarea by the eradication of the Logan Berry plant, Tristan da Cunha) involved removing invasive loganberry plants but also raising the awareness of alien plants amongst the young people of Tristan. Details of these projects can be found at www.ukotcf.org/otep/awards.htm.
OTEP has funded work looking into the potential for eradicating rodents on Gough Island (eg TDC 502 Control of alien mice and plants at Gough Island World Heritage Site and TDC 601 Preparations for the eradication of mice and Sagina from Gough Island). Defra is now funding a Darwin Initiative project (Ref: 18-017 – Developing knowledge to eradicate house mice from UK OT Islands) which aims to test the feasibility of eradicating house mice from Gough Island, undertake research on the Falkland Islands and South Georgia on the impact of mice, and to create the capacity to undertake mice eradication operations on all three UK OTs. More information and projects reports can be found at http://darwin.defra.gov.uk/project/18017/.
Proctor, D. and Fleming, L. V., eds. (1999). Biodiversity: the UK Overseas Territories. Peterborough, UK: JNCC.
Sanders, S. M., ed. (2006). Important Bird Areas in the United Kingdom Overseas Territories. Sandy, UK: RSPB.
Varnham, K. (2006). Non-native species in UK Overseas Territories: a review. Peterborough, UK: JNCC Report No. 372.