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Tristan da Cunha

Last edited: Feb 7, 2022, 3:50 PM

About the territory

Tristan da Cunha is the most remote inhabited island in the world and is 2,778 km west of Cape Town at 37° 06’S and 12° 18’W. The island is volcanic and 98 km2 in area. It has one settlement, Edinburgh of the Seven Seas, which is the only inhabited part of the island. The Tristan Group also includes Nightingale, Inaccessible and Gough Islands. Nightingale Island has an area of 3.2 km2 and is 38 km southwest of Tristan at 37° 24’S and 12° 29’W. There are two associated small offshore islands, Stoltenhoff and Middle (or Alex) Islands as well as offshore islets and stacks. Inaccessible Island is 1.4 km2 in area and lies 40 km southwest of Tristan at 37° 18’S and 12°W. Gough Island is 350 km SSE of Tristan at 40° 21’S and 09° 53’W with an area of 65 km2. Whilst Nightingale and Inaccessible Islands are both uninhabited Gough Island contains a permanent meteorological station at Transvaal Bay. Average temperatures at Tristan range from 12°C in August-September to 19°C in February. Average annual rainfall is 1,681 mm. At Gough Island temperatures range between about 6°C and 17°C and average annual rainfall is over 3,000 mm.

Map of Tristan da Cunha

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 293.  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.

Biodiversity

The Kew database lists 53 species of native flowering plants for the Tristan 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.

Policy and legislation

Tristan da Cunha has an Environment Charter signed jointly with the UK Government. Guiding Principle 7 is to safeguard and restore native species, habitats and landscape features, and control or eradicate invasive species. Under the associated commitment 2 the government of Tristan Cunha will ensure the protection and restoration of key habitats, species and landscape features through legislation and appropriate management structures and mechanisms, including a protected area policy, and attempt the control and eradication of invasive species. Implementation progress was reviewed in 2007, 2010 and 2016, read the 2016 review report (external link).

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.

In 2020 new biosecurity legislation was developed for Tristan da Cunha, with provisions for pre-border, border and post-border regulation of invasive species.

A biosecurity policy was endorsed in 2016.

Invasive species and biosecurity

A total of 280 non-native species (marine and terrestrial) was recorded for Tristan da Cunha by the RSPB Stocktake (Churchyard et al 2014).

Taxon

Total species

Non-native species

Invertebrates

880

126

Vertebrates

199

4

Plants

826

150

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. 

Endemic tree ferns on the slopes of the volcano, Tristan main island; Introduced flax, Edinburgh of the Seven Seas settlement.

L-R: Endemic tree ferns on the slopes of the volcano, Tristan main island; Introduced flax, Edinburgh of the Seven Seas settlement.

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, and this is expected to take place in 2021. 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.

Biosecurity

In 2017 a biosecurity gap analysis (PDF) was completed. Overall biosecurity capacity is poor, with no facilities on the main island for inspections or treatments. Capacity for early warning and rapid response in the event of an incursion is particularly weak. With such a small population resources are identified as a major constraint on biosecurity activities.

Pest risk analysis is done on an ad hoc basis. Border operations vary depending on which island they are being applied to, with much higher standards imposed for Gough Island, a World Heritage Site for which there is a proposed mouse eradication programme being planned. Compliance is poor and inconsistent.

In 2018 a pathway analysis (PDF) was completed. Pathways of introduction are relatively few, there is no airport and access is via ship. Two fishing vessels, the MV Geo Searcher and MV Edinburgh, service the islands, visiting from Cape Town in South Africa up to nine times a year bringing passengers and cargo to Tristan Main Island. In addition, the South African research vessel, the SA Agulhas II visits once a year to service the weather station on Gough Island, dropping off passengers and cargo to Tristan Main Island. Local boats go from the main island to Nightingale and Inaccessible Islands up to a dozen times a year, during the summer season.

Horizon scanning was carried out in 2019, identifying a total of 57 new invasive species of concern which have the potential to arrive within the next 5 – 10 years; read a report on the horizon scanning (PDF).  

Projects

The South Atlantic Invasive Species project (SAIS) (external link) 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. In 2010 a SAIS Strategy and Action Plan (external link) was developed, and in 2015 a regional workshop was held in 2015 in Ascension Island to implement key actions.

Actions to eradicate various invasive plants from Gough and Inaccessible Islands have been funded by the Overseas Territories Environment Programme (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 Point area 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. 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). Fourteen OTEP funded projects (external link) were delivered in total between 2004 and 2014.

A two-year project (Defra CR 0492), was carried out by CABI in January 2011, looking at the impact of invasive non-native species in the UK Overseas Territories in the South Atlantic and the potential for biological control. Read details of this project and the final report (external link).

Tristan has received a number of Darwin Initiative funded projects, listed below. For more information read the project reports (external link):

The project ‘Tackling invasive non-native species in the UK Overseas Territories’ was implemented between 2016 and 2020 to strengthen biosecurity in the OTs, funded by the UK government Foreign and Commonwealth Office’s Conflict, Stability and Security Fund (CSSF). Tristan da Cunha benefitted from a number of activities to strengthen its biosecurity, including: pathway analysis, horizon scanning, pathway action planning, legislative support for drafting biosecurity legislation, access to online learning, and technical support. Read further details.

The Blue Belt Programme seeks to enhance long-term sustainable marine protection strategies for the UKOTs, and provides £20 million of funding over 4 years (2016 to 2020), also funded by CSSF and delivered by the Centre for Environment, Fisheries and Aquaculture Science (Cefas). The Programme is assisting Tristan with scientific research towards the declaration of a marine protection strategy in 2020 that allows for the sustainable development of the Tristan fisheries. In March-April 2019, the Blue Belt Programme and the British Antarctic Survey (BAS) led a marine survey around Tristan da Cunha and St Helena. The survey, known as Discovery 100, took place on board the RRS Discovery and was a follow up to the 2018 survey on the RRS James Clark Ross. The aim of the survey was to improve understanding of the different marine ecosystems present within Tristan da Cunha and St Helena. Blue Belt also funded the refurbishment of the fishery patrol vessel Wave Dancer in 2020. Read reports and further information (external link).

Tristan da Cunha was involved in the CSSF project ‘Natural Capital in the Caribbean and South Atlantic Overseas Territories’ from 2016 to 2019, and delivered to seven OTs by the Joint Nature Conservation Committee (JNCC). The programme of work involves mapping and valuing the participating OTs natural capital assets through integrating ecological data, satellite data, Geographic Information Systems (GIS) and economic assessments. Read project details and reports (external link)

Useful information

Information for visitors

Before travelling please ensure all items are clean, free from organic materials such as mud, faeces, seeds and invertebrates:

  • Check your footwear, outdoor clothing and day packs to make sure they are clean and free from weed seeds, mud, invertebrates and plant material. If possible we recommend that you travel with new outdoor clothing and equipment. Shake out or vacuum all the compartments and pockets before you pack.
  • If you have been camping, check that your tent and other equipment is clean, dry and free of dirt and invertebrates such as ants and spiders. Shake it out before you pack it up for travel and ensure no soil remains on tent pegs.
  • If you have been hiking, visiting a wilderness area, farm or zoo, make sure your footwear and clothes are clean and free from seeds, mud and faeces. Check boot soles for mud between the treads, Velcro fastenings for seeds and plant material, and shake out or vacuum pockets to remove any dirt and plant material.
  • If you are carrying golf, fishing or other sports and outdoor equipment with you, make sure they are clean, dry and free from dirt and any live creatures.

Advice for visitors (external link) 
Biosecurity measures for visiting vessels (external link) 

Contact

Conservation Department, 

Tristan da Cunha

Edinburgh of the Seven Seas 

South Atlantic Ocean TDC 1ZZ

Official Enquiries: tdcenquiries@tdc-gov.com

Tristan Agriculture: agriculture@tdc-gov.com

Documents

  • Barnsley, S., Cary, E., Pienkowski, M. and Wensink, C. (Eds) (2016).  Review of performance by 2016 of UK Overseas Territories and Crown Dependencies in implementing the 2001 Environment Charters or their equivalents and moving towards the Aichi Targets and Sustainable Development Targets. UK Overseas Territories Conservation Forum, April 2016.
  • Churchyard, T., Eaton, M., Hall, J., Millett, J., Farr, A., Cuthbert, R. and Stringer, C.  (2014). The UK’s wildlife overseas: a stocktake of nature in our Overseas Territories.  Sandy, UK: RSPB.
  • Edgar, P. (2010). The Amphibians and reptiles of the UK Overseas Territories, Crown Dependencies and Sovereign Base Areas: Species Inventory and Overview of Conservation and Research Priorities. Bournemouth, UK: Amphibian and Reptile Conservation.
  • 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.

Websites