The Pitcairn Islands Group comprises Pitcairn Island, Henderson Island, which are volcanic islands, Ducie and Oeno which are flat atolls. Pitcairn Island is the only inhabited island and is at latitude 25o 04’ South and longitude 130o 06’ West. It is about 2 170 km east-southeast of Tahiti. The islands’ administrative capital is in Aukland, New Zealand, 5310 km away.

Pitcairn Island covers a total area of about 5.1 km2 and has a population of around fifty. Henderson Island covers about 49 km2 in area and is 193 km northeast of Pitcairn Island. Oeno Island is a coral atoll, 143 km northwest of Pitcairn Island. The atoll has a diameter of 5km but a total land area of just 0.69 km2. Ducie Island is 470 km east of Pitcairn Island and covers 4 km2. Average annual rainfall on Pitcairn is 1800mm and temperatures range from 10oC to 43oC. The rainy season is during November to March with July and August being the driest months.

The islands were settled by the Polynesians for a number of centuries but they were no longer present when the group was discovered by Europeans. In 1606 a Portuguese sailor, Pedro Fernandes de Queiros, discovered the islands group although it is unclear which islands he actually landed on. Pitcairn Island was found by HMS Swallow in July 1767. In 1790 mutineers from the Bounty and some of their Tahitian companions settled on Pitcairn and burnt the ship there. Alcoholism, murder and disease reduced the numbers significantly. Contact was re-established after HMS Briton and HMS Tagus sent a party ashore in September 1817. The island became a British colony in 1838. By the mid 1850s the community was outgrowing the island and in 1856 the entire population of 193 people were transferred to Norfolk Island. However, subsequently, over forty returned to Pitcairn Island. After peaking at 233 in 1937, the population has declined, mainly as a result of emigration to New Zealand. Henderson, Oeno and Ducie were incorporated into the Pitcairn Islands Group in 1938.

Much of the information on biodiversity comes from the inter-disciplinary Sir Peter Scott Commemorative Expedition to Henderson Island, 1991-92.

According to the Kew online herbarium database (quoting the PhD thesis of Kingston, 2001) there are 367 plant species, with 147 native to these islands and neighbouring French Polynesia and and a further 19 endemic to the Pitcairn Island Group. There is a high level of endemism amongst the insect fauna on Henderson Island and half the molluscan species are thought to be endemic, at least to sub-species level. Fish endemicity is regarded as low. There are no native species of reptile, amphibian or mammal. Henderson Island is regarded as being of great ornithological importance. All four land birds there (Henderson Crake (Porzana atra), Henderson Fruit-Dove (Ptilinopus insularis), Henderson Lorikeet (Vini stepheni), Henderson Reed-warbler (Acrocephalus taiti) ) are endemic and there is one endemic bird species, Pitcairn Reed-warbler (Acrocephalus vaughani), on Pitcairn Island. Most, if not all of the world population of Henderson’s Petrels (Pterodroma atrata) and over 90% of the world population of Murphy’s Petrel (Pterodroma ultima) nest in the Group.

There is no specific legislation regarding invasive species in the Pitcairn Islands.

The JNCC database contains 276 introduced species for the Pitcairn Island Group. This includes over 250 plant species, 11 invertebrates and 10 vertebrates.

Pacific rats (Rattus exulans) are regarded as a major threat, particularly to breeding birds although they may also be implicated in the extinction of some land snail species. In 1997 rats were eradicated from Ducie and Oeno. Introduced invasive plant species such as Rose-apple (Syzgium jambos), (Lantana camara) and (Passisflora maliformis) are posing a threat to endemic plant species some of which have a limited range and low numbers.

Two fruit flies (the Queensland fruit fly (Bactrocera tryoni) and a Mediterranean fruit fly (Ceratitis capitata) damage fruit trees.

Although rats have been eradicated from Ducie and Oeno there is a continuing threat of reintroduction from Pitcairn Island where two eradication attempts have failed. Eradication of rats on Henderson Island is currently underway. Baiting of the island with rat poison took place during 2011 but follow up monitoring indicates that this has not been successful. Future efforts will also look at improving biosecurity in order to prevent introduction of rats from elsewhere.

An introduced fruit fly (Ceratitis capitata) that is a pest of Citrus is subject to management through the annual issue of insect pheromone traps by the Conservation Officer. The aim is to reduce the number of male fruit flies available for breeding.

Updates on the project to eradicate rats from Henderson Island can be followed at www.rspb.org.uk/ourwork/projects/details/241934-henderson-island-restoration-project , or through the blog posts below:

Science expedition to Henderson Island to investigate invasive rats: Part 1
Science expedition to Henderson Island to investigate invasive rats: Part 2
Science expedition to Henderson Island to investigate invasive rats: Part 3

The latest issue of the Henderson Island Newsletter is now available here.

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.

JNCC – Invasive species in the UK Overseas Territories and Crown Dependencies
http://jncc.defra.gov.uk/page-4080

Kew RBG – UKOTS Online Herbarium
http://dps.plants.ox.ac.uk/bol/UKOT/Home/Index