Île d'Henderson
Country
United Kingdom of Great Britain and Northern Ireland (UK)
Inscribed in
1988
Criteria
(vii)
(x)
The conservation outlook for this site has been assessed as "significant concern" in the latest assessment cycle. Explore the Conservation Outlook Assessment for the site below. You have the option to access the summary, or the detailed assessment.
Située dans la partie orientale du Pacifique sud, l'île d'Henderson est parmi les rares atolls du monde à avoir conservé une écologie pratiquement intacte. Sa situation isolée permet d'y observer la dynamique de l'évolution insulaire et de la sélection naturelle, et elle est particulièrement remarquable pour ses dix plantes et ses quatre oiseaux terrestres endémiques. © UNESCO
Summary
2025 Conservation Outlook
Finalised on
11 oct 2025
Significant concern
Current state and trend of VALUES
High Concern
Overall THREATS
Overall PROTECTION and MANAGEMENT
Full assessment
Description of values
Raised and forested coral atoll of exceptional natural beauty
Criterion
(vii)
As an extremely remote and near-pristine island, Henderson Island is the world's only forested coral atoll with its landscape and ecology virtually intact, and with ongoing geological and biological processes (Pandolfi, 1995).
Exceptionally rich endemic flora
Criterion
(x)
Seven endemic species of flowering plants are found on a land area of only 43 km2 (Florence et al., 1995; Waldren et al., 1995).
Exceptionally rich endemic avifauna
Criterion
(x)
Four endemic species of land birds include Henderson crake (Zapornia atra), Henderson lorikeet (Vini stepheni), Henderson fruit dove (Ptilinopus insularis) and Henderson reed warbler (Acrocephalus taiti). The site also hosts one endemic seabird - the Henderson petrel (Pterodroma atrata) (Oppel et al., 2017; BirdLife International, 2016).
Exceptionally rich endemic invertebrate fauna
Criterion
(x)
Over half the island's 16 species of land snails (Preece, 1995) and about 30% of the 180 insect species may be endemic (Benton, 1995). Additional groups of invertebrates may show a similar level of endemism (Benton and Lehtinen, 1995), and a large proportion of the invertebrate fauna may not be described yet (Churchyard et al., 2016).
Important seabird nesting area (including of globally threatened species)
Criterion
(x)
The site hosts ca. 40,000 pairs of breeding seabirds (12 species), including ca. 20,000 pairs of the endemic and Endangered Henderson petrel (Pterodroma atrata) (Brooke, 1995a,b).
Rich terrestrial and coastal marine biota
Six vegetation communities of the island comprise 71 species of vascular plants, 20 of bryophytes and 30 of lichens (Waldren et al., 1995). Other noteworthy biodiversity includes fives terrestrial reptile species that may be native or may have been introduced by Polynesian settlers (Havery et al., 2017), and occasional nesting of green turtles (Chelonia mydas) (EN), regular occurrence of humpback whale (Megaptera novaeangliae), rich marine invertebrate fauna (including 29 species of coral) and coastal ichthyofauna (190 species, Lambrides and Weisler, 2015). The RSPB recorded 5 species of land crab in a 2024 expedition, including the Coconut crab (Birgus latro) (VU) (IUCN Consultation, 2024; Bond et al. 2024).
Pristine night sky
The Pitcairn Islands Group has been recognised as Mata ki te Rangi," or "Eyes to the Sky", becoming the first British Overseas Territory and one of only 15 places worldwide to be designated an International Dark Sky Sanctuary. This prestigious designation cements Pitcairn's commitment to preserving its untouched, multi-island environment for future generations, making it a beacon in the world of night sky conservation and international astro-tourism (Government of the Pitcairn Islands, 2024).
Evidence of Polynesian occupation
The first known settlers to the Pitcairn Islands were Polynesians and it is believed that Pitcairn and Henderson Islands were first colonised in about AD 900 and that the occupation of both islands lasted until about 1450. Therefore, the site is of significant archaeological interest with the Polynesian occupation lasting at least 600 years (Brooke et al., 2004).
Assessment information
In general, the uninhabited Henderson Island is well protected by its remoteness and hostile living conditions. An exception is the presence of the introduced Polynesian rat, which has a major negative impact on ground-nesting petrel species, and probably on endemic land birds, endemic invertebrate populations and likely plant communities also. The continued accumulation of plastic pollution on the North and East beaches of the island also threatens both the scenic and biological values of the site, however because few of the valuable macrofauna ingest plastic on the island, this threat can be considered low, especially in comparison to the biosecurity risk from visitors.
Recreational Activities
(Trampling and disturbance from tourism)
Inside site
, Localised(<5%)
Generally, the island is little visited, due to its extreme remoteness, however this remoteness (situated 193 km north-east of Pitcairn Island) also makes effective management of visitors to the World Heritage Site difficult (Government of Pitcairn Islands, 2021). There is evidence that visitors are accessing areas that are off limits to visitors (East Beach). Impacts of visitors are likely restricted to the coral reef, beaches, and vegetation along the beach fringe and the marginal areas of the coral plateau. Direct impacts by visitors in the interior plateau are unlikely. Although some damage to coral and vegetation may occur, and some disturbance to nesting birds, these are unlikely to significantly affect populations.
Invasive Non-Native/ Alien Species
(Impacts of invasive species on avifauna, flora and invertebrate fauna)
Other invasive species names
Polynesian rat (Rattus exulans), Cocos nucifera
Inside site
, Throughout(>50%)
The impacts of rat predation on petrel chick mortality on Henderson Island have been estimated at 99% for Murphy’s petrel (Pterodroma ultima; Lavers et al., 2016), 60-80% for Henderson petrel (Oppel et al., 2017), and may be similarly high for Kermadec (Pterodroma neglecta) and Herald petrels (Pterodroma heraldica; Brooke, 1995a). Rat predation is likely to be responsible for a decrease of petrel abundance from an estimated 1 million pairs on the island before rat arrival to just 40,000 pairs (Brooke et al., 2010). This will have impacts on ecological processes of the island, as previously millions of seabirds would have provided a crucial nutrient source for the island’s ecosystem via their guano. Henderson petrel will also likely go extinct without intervention to eradicate the rats (Brooke et al., 2010), although the population may have been stable between 1991 and 2015 (Oppel et al., 2017). Landbird populations are also likely affected by rat predation, but the effect is difficult to quantify; as many as 25% of Henderson crake chicks are likely killed by rats (Jones et al., 1995). Similar effects of rat predation on native invertebrates and plants are likely to occur, but no data exist to quantify these effects. An attempt to eradicate rats in 2011 was not successful (Amos et al., 2016), and by 2015 rat populations had recovered to levels similar to those before the eradication attempt (Churchyard et al., 2013, Lavers et al., 2016, Bond et al., 2019b). With climate change induced sea level rise (see potential threat below) the neighbouring low-lying coral atolls of Ducie and Oeno may significantly reduce in size, or even disappear all together. As these are breeding sites for many seabirds these populations may move to Henderson Island as it is a raised atoll that will be less impacted by sea level changes. This status as a potential climate change refuge makes it even more important to remove rats from Henderson (IUCN Consultation, 2024; RSPB, 2024).
Coconuts: During a recent field visit to Henderson Island, it was discovered that although coconuts seem to be confined to areas previously mapped, there has been a significant expansion and the density of trees has increased (RSPB, 2024). This could impact the endemic flora and affect the aesthetic values of the site, however the degree to which this is the case is unclear.
Coconuts: During a recent field visit to Henderson Island, it was discovered that although coconuts seem to be confined to areas previously mapped, there has been a significant expansion and the density of trees has increased (RSPB, 2024). This could impact the endemic flora and affect the aesthetic values of the site, however the degree to which this is the case is unclear.
Garbage & Solid Waste
(Plastic pollution)
Inside site
, Localised(<5%)
On the North and East beaches on Henderson are deposits of large quantities of floating rubbish washed ashore by the sea. This pattern was already evident in the 1990s (Benton, 1995b), but has been amplified by the rapid increase in global production and discards of plastic materials. Parts of the eastern beach of Henderson resemble a rubbish dump, and waste has accumulated for decades and is buried by sand. In 2015, the total amount of plastic waste deposited on Henderson’s beaches was estimated at 37.7 million pieces weighing a total of 17.6 tonnes, with up to 30 items per square meter beach surface (Lavers and Bond, 2017) and therefore represents a high threat to the scenic and biodiversity values of the site. However, the high accumulation on beaches does not correspond to a high density of plastics in surrounding waters (Ryan and Schofield, 2020). Plastic bottles entrap 61,000 hermit crabs on Henderson (Lavers et al. 2020) and plastics influence sediment properties (Lavers et la. 2021) potentially affecting nesting green turtles (EN), which have temperature-dependent sex development.
During June 2022, Pulau School and the Island Administrator organised a school trip to the outer islands. During the trip, the 3 students undertook beach litter surveys on Acadia Island (Ducie), East Beach and North Beach (Henderson Island) and Oeno Island. Henderson Island was found to be the most impacted with an average of 87 pieces of litter along a 5m transect (Government of Pitcairn Islands, 2023). Nichols et al. (2021) showed that there has been a significant increase of microplastics samples in 2019 compared to 2015. Micro and nanoplastics were found at all sites on Henderson Island, which extrapolates to more than 4 billion plastic particles in the upper 5cm across the whole beech. The vast number of small particles on Henderson may make nearshore filter feeders susceptible to ingestion and subsequent detrimental impacts (Nichols et al., 2021). The beaches were cleared of some macroplastics by the Plastic Odyssey in February 2024 (IUCN Consultation, 2024), but plastic pollution was still widespread and evident on beaches in July 2024.
During June 2022, Pulau School and the Island Administrator organised a school trip to the outer islands. During the trip, the 3 students undertook beach litter surveys on Acadia Island (Ducie), East Beach and North Beach (Henderson Island) and Oeno Island. Henderson Island was found to be the most impacted with an average of 87 pieces of litter along a 5m transect (Government of Pitcairn Islands, 2023). Nichols et al. (2021) showed that there has been a significant increase of microplastics samples in 2019 compared to 2015. Micro and nanoplastics were found at all sites on Henderson Island, which extrapolates to more than 4 billion plastic particles in the upper 5cm across the whole beech. The vast number of small particles on Henderson may make nearshore filter feeders susceptible to ingestion and subsequent detrimental impacts (Nichols et al., 2021). The beaches were cleared of some macroplastics by the Plastic Odyssey in February 2024 (IUCN Consultation, 2024), but plastic pollution was still widespread and evident on beaches in July 2024.
Invasive Non-Native/ Alien Species
(Biosecurity risk from tourism)
Inside site
, Localised(<5%)
There is little appreciation of biosecurity among commercial boat operators bringing visitors to the island, and the greatest threat from visitors to the island is the potential introduction of non-native species (IUCN Consultation, 2020) (see Potential Threats below).
There is a high threat of additional invasive alien species introductions to the island, which might have adverse effects on all or parts of its biodiversity. Furthermore, there is evidence that climate induced changes including sea level rise, rising sea surface temperature, increased frequency and intensity of extreme weather events will potentially have significant impacts on the site's values, altering the island's land and sea ecosystems. Furthermore, in combination with potential climate-induced species population shifts from neighbouring islands, the threat from invasive alien species is enhanced, as Henderson Island will be a key climate refuge for nesting birds and the effect of rat predation would be detrimental.
Invasive Non-Native/ Alien Species
(Impacts of invasive species on avifauna, flora and invertebrate fauna (further))
Inside site
, Throughout(>50%)
The example of the rat predation effect on petrel populations (see above) shows that any species introduction, which might happen through visitation, may lead to major impacts on the native flora and fauna, and hence on the island’s ecosystem, landscape and beauty. The high degree of endemism in all taxonomic groups present makes the island's community extremely vulnerable to invasive alien species. Although the island is rarely visited, there is little appreciation of biosecurity among commercial boat operators bringing visitors to the island, and very little regulation or enforcement of regulation. In 2015, a biological expedition likely introduced some non-native plants, but the invasion was contained. Although the risk is very small that further species are introduced, the potential consequence of the introduction of other mammalian predators or highly invasive plants could be catastrophic (IUCN Consultation, 2020).
Changes in Physical & Chemical Regimes, Changes in Temperature Regimes
(Extreme weather events, sea level rise, increase in surface temperature)
Inside site
, Throughout(>50%)
Outside site
Although climate change projections are regional at best and there are no downscaled projections for the Pitcairn Islands, it is to be expected, that climate change is one of the biggest threats the environment faces during the next century. Pressures such as increases in air and sea surface temperatures, increased ocean acidity and sea level rise are all likely to negatively impact the marine environment within the Pitcairn Islands MPA and the ecosystem on Henderson Island. Changes to the ocean climate will impact species, ecosystems, food webs and dependent communities in the Pitcairn Islands (Johnson et al., 2021).
Increase in frequency and intensity of extreme weather events: In the tropical Pacific Ocean cyclones are becoming stronger (IPCC, 2019) and the proportion of intense tropical cyclones (category 4-5) versus weaker cyclones (category 1-2) has increased substantially in the last 40 years (Holland and Bruyere, 2014). Deep-ocean swells from extra-tropical cyclones frequently reach Pacific islands and these are more likely to impact the Pitcairn Islands, but no assessment on these impacts has been conducted for the region to date (Johnson et al., 2021).
Increase in sea surface temperature: Sea surface temperature is projected to increase by >3 Degrees Celsius by 2100 in the Pacific region (Asch et al., 2018), producing cascading effects on sea level, dissolved oxygen levels, net primary productivity and pH (IPCC, 2019).
Sea level rise: Sea level rise across the Pacific region has been recorded as being around 6 cm since 1960. By 2100, sea levels around the Pitcairn Islands could have risen by up to 140 cm according to some recent models, endangering many of the low-lying areas (Government of Pitcairn Islands, 2021). Climate change induced sea level rise means the neighbouring low-lying coral atolls of Ducie and Oeno may well significantly reduce in size, or even disappear altogether. These are breeding sites for many seabirds and the obvious place for them to move to would be Henderson as it’s a raised atoll that will be far less impacted by sea level changes. This status as a potential climate change refuge makes it even more important to remove rats from Henderson. Nesting turtles at East Beach on Henderson Island and nesting bird populations on the three uninhabited islands will be threatened during over-washing events and the lagoons, which provide safe nursery grounds for juvenile fish and other species, would be exposed to increased wave action (Government of Pitcairn Islands, 2021; IUCN Consultation, 2024).
Increase in frequency and intensity of extreme weather events: In the tropical Pacific Ocean cyclones are becoming stronger (IPCC, 2019) and the proportion of intense tropical cyclones (category 4-5) versus weaker cyclones (category 1-2) has increased substantially in the last 40 years (Holland and Bruyere, 2014). Deep-ocean swells from extra-tropical cyclones frequently reach Pacific islands and these are more likely to impact the Pitcairn Islands, but no assessment on these impacts has been conducted for the region to date (Johnson et al., 2021).
Increase in sea surface temperature: Sea surface temperature is projected to increase by >3 Degrees Celsius by 2100 in the Pacific region (Asch et al., 2018), producing cascading effects on sea level, dissolved oxygen levels, net primary productivity and pH (IPCC, 2019).
Sea level rise: Sea level rise across the Pacific region has been recorded as being around 6 cm since 1960. By 2100, sea levels around the Pitcairn Islands could have risen by up to 140 cm according to some recent models, endangering many of the low-lying areas (Government of Pitcairn Islands, 2021). Climate change induced sea level rise means the neighbouring low-lying coral atolls of Ducie and Oeno may well significantly reduce in size, or even disappear altogether. These are breeding sites for many seabirds and the obvious place for them to move to would be Henderson as it’s a raised atoll that will be far less impacted by sea level changes. This status as a potential climate change refuge makes it even more important to remove rats from Henderson. Nesting turtles at East Beach on Henderson Island and nesting bird populations on the three uninhabited islands will be threatened during over-washing events and the lagoons, which provide safe nursery grounds for juvenile fish and other species, would be exposed to increased wave action (Government of Pitcairn Islands, 2021; IUCN Consultation, 2024).
Involvement of stakeholders and rightsholders, including indigenous peoples and local communities, in decision-making processes
There is no permanent local population and the island is only very occasionally visited by Pitcairn Islanders and foreign research and conservation expeditions generally hire local staff. Regarding the wider setting, local communities are strongly involved in the environmental conservation of the Pitcairn Islands and the Pitcairn Islanders are proud custodians of the MPA (Government of Pitcairn Islands, 2024).
Legal framework
The legal framework is mostly effective through the Local Government Regulations Part IV, which provide for wildlife protection and fishery management, and the Lands and Administration of Estates Ordinance that applies restrictions on possession, occupation and transference of land (UNEP-WCMC, 2011). The Marine Conservation Regulations were signed into law in October 2022, controlling how human activities within the Coastal Conservation Areas will be managed. This includes ensuring that fishing by local communities is sustainable (Government of Pitcairn Islands, 2023).
The territory’s 2024 Biosecurity Ordinance (Governor of the Islands of Pitcairn, Henderson, Ducie and Oeno, 2024) provides further regulations to protect the island. Ideally there should be a requirement that all visiting cruise ships must be accompanied by a local government employee, however, this is more difficult in practice.
The territory’s 2024 Biosecurity Ordinance (Governor of the Islands of Pitcairn, Henderson, Ducie and Oeno, 2024) provides further regulations to protect the island. Ideally there should be a requirement that all visiting cruise ships must be accompanied by a local government employee, however, this is more difficult in practice.
Governance arrangements
The Council of Regional Organisations in the Pacific brings together several regional inter-governmental agencies, of which the most relevant in this context are the Pacific Community (SPC) and the Secretariat of the Pacific Regional Environment Programme (SPREP). The SPC is the principal scientific and technical organisation supporting development in the Pacific region. It is an international organisation established by treaty (the Canberra Agreement) in 1947 and is owned and governed by its 26 members including all 22 Pacific Island countries and territories; the Pitcairn Islands are a member of the SPC. The SPC’s main focus is on major cross-cutting issues, such as climate change, disaster risk management, food security and human rights. SPREP is the region’s key inter-governmental organisation for environment and sustainable development. The purposes of SPREP are to promote cooperation in the South Pacific Region and to provide assistance in order to protect and improve the environment and to ensure sustainable development for present and future generations. The administration of the islands' affairs lies with the Commissioner based at the Pitcairn Islands Office in Auckland. On Pitcairn Island, the Pitcairn Island Council is responsible for the local government and administration of internal affairs within the group. The Island Council comprises: the Island Mayor (elected every three years), the Island Secretary, Chairman of Internal Affairs Committee, four officers (elected annually) and two advisers, one appointed by the governor and one by the elected members. In the past there were two Pitcairn Island posts that dealt with environmental matters, those of Conservation Officer and Quarantine Officer (Smyth, 2008). However, since then there has been a rearrangement of roles in the Pitcairn Government and there are now also various biosecurity-related roles.
Integration into local, regional and national planning systems (including sea/landscape connectivity)
The site is managed by Pitcairn Island Council according to Pitcairn Island OST planning (UNEP-WCMC, 2011) and the management of Henderson Island is integrated into the local, regional and national planning systems. For example, the WH values and objectives for the site have been integrated into the Pitcairn Islands MPA Management Plan and the 2008 Pitcairn Islands Environment Management Plan. Furthermore, the site's protection is well integrated in the environmental protection of British Overseas Territories and is monitored as part of the UK Overseas Territories and Crown Dependencies in implementing the 2001 Environment Charters or their equivalents (Barnsley et al. 2016).
Boundaries
The boundaries of the site are appropriate for the protection of its World Heritage values. However, the adjacent coastal marine areas are not included in the World Heritage site's boundaries. In September 2016, a fully protected marine reserve was established surrounding the Pitcairn archipelago, thus formally protecting the marine areas around Henderson Island. Along with the Pitcairn Islands MPA Management Plan 2021-2026, there is a strong management framework in place to protect the adjacent coastal marine areas.
Overlapping international designations
N/A
Implementation of World Heritage Committee decisions and recommendations
Most of the previous World Heritage Committee requests and recommendations have been addressed to some extent (UNESCO, 2010, 2012). No Decisions have been taken by the Committee regarding this site in recent years.
Climate action
Data collected during the Operation Redfish Expedition was analysed to work out the resilience of the corals within the MPA to a changing climate. The images collected from the seabed were analysed to look at things such as coral cover, coral size, number of different species, number of herbivorous fish and number of top predators (sharks). The reefs around the Pitcairn Islands are currently some of the best examples of unimpacted corals in the world (The Pitcairn Islands Marine Protected Area Annual Review 2022-2023). Expeditions going forward will be able to use this data to identify changes in the reef caused by climate change. This can be used as an early warning system to inform new management or mitigation measures to protect the habitat. However, there is no specific climate action integrated within the current management plan for Henderson Island.
Management plan and overall management system
The management system is generally sufficient. A rat eradication operation was conducted in 2011, but the operation failed to eradicate every rat on the island (Amos et al., 2016). The Pitcairn Government and the RSPB remain committed to restore Henderson Island and, following an experimental expedition in the middle of 2024 will possibly hold another rat eradication operation in 2028 to restore the island’s ecosystem.
The 2021-2026 Management Plan for Pitcairn Islands MPA (Government of the Pitcairn Islands, 2021) includes a specific objective on enhancing the understanding and appreciation of the Henderson Island WH site, since the Henderson Island World Heritage Site Management Plan 2004–2009 has not been revised since first being published. To address outstanding priority management actions, these are included within the MPA Management Plan. Along with the 2005 Henderson Island Management Plan, the 2008 Pitcairn Islands Environment Management Plan (Smyth, 2008) also forms the management framework, setting out ten key objectives based on the Environment Charter guiding principles for managing the environment of the Pitcairn Islands. Furthermore, management experiences are shared across stakeholder responsible for managing sites with similar environments and challenges e.g. Inaccessible Island. More recently, the Island Council of Pitcairn formally adopted the first Territorial Invasive Species Strategy and Action Plan (TISSAP) (Government of the Pitcairn Islands, 2024).
The 2021-2026 Management Plan for Pitcairn Islands MPA (Government of the Pitcairn Islands, 2021) includes a specific objective on enhancing the understanding and appreciation of the Henderson Island WH site, since the Henderson Island World Heritage Site Management Plan 2004–2009 has not been revised since first being published. To address outstanding priority management actions, these are included within the MPA Management Plan. Along with the 2005 Henderson Island Management Plan, the 2008 Pitcairn Islands Environment Management Plan (Smyth, 2008) also forms the management framework, setting out ten key objectives based on the Environment Charter guiding principles for managing the environment of the Pitcairn Islands. Furthermore, management experiences are shared across stakeholder responsible for managing sites with similar environments and challenges e.g. Inaccessible Island. More recently, the Island Council of Pitcairn formally adopted the first Territorial Invasive Species Strategy and Action Plan (TISSAP) (Government of the Pitcairn Islands, 2024).
Law enforcement
Due to the Island's remoteness, no on-island enforcement is possible nor is it required given the little visitation that such remoteness affords. Two Biosecurity officers are responsible for the Pitcairn Islands and having a ranger on the island may indeed pose a risk of further species invasions and decrease the site’s protection and natural values as an uninhabited island almost untouched by human development (IUCN Consultation, 2020). Access to the Pitcairn Islands group requires a licence issued by the Governor (through the Pitcairn Island Administration office in Auckland) in consultation with the Island Council (Brooke et al. 2004). MPA management falls under the remit of the Environmental, Conservation & Natural Resources Division (ECNRD). This Division exercises general oversight of the preservation and conservation of the natural environment including biosecurity, quarantine, natural resource management (land, water, fisheries, etc.), management of the plant nursery, promotion of local agricultural production and export, eco-trail maintenance, land court and surveyors, environmental supervision of the outer islands and liaison with international environmental organisations. Enforcement sanction decisions under the Compliance & Enforcement Strategy are the responsibility of the Attorney General’s office and New Zealand Police
Sustainable finance
There is little on-site management needed once the threat of invasive rats and coconuts can be eliminated, given the lack of human population and the islands remoteness and there is no permanent operational budget for the management of the site. However, various funding streams have supported the site’s management and the protection of the surrounding seascape. The UK Overseas Territories Fund run by John Ellerman Foundation has supported the branding and communication strategy for the Pitcairn Islands MPA and has supported marine conservation and research. Darwin Plus, also known as the Overseas Territories Environment and Climate Fund, provides funding for environmental projects in UK overseas territories and fellowships for nationals of UK overseas territories to gain technical and scientific expertise and broaden their knowledge and experience of environmental projects. Although, the lack of financing for another eradication attempt was of serious concern in the last Outlook site assessment (IUCN Consultation, 2020), Darwin Plus funding has been secured to support the preparations for a rodent-free Pitcairn Islands 2022-2025 (RSPB, 2024). However, no funding has yet been secured to enable another rodent eradication operation on Henderson Island.
Staff capacity, training and development
Currently there is no management presence on site, with a part-time manager currently stationed off-site. However, off-site management is appropriate for this site, despite the requirement for the manager to accompany visitors in order to enforce biosecurity and other measures necessary for the conservation of the site's Outstanding Universal Value. Training has been carried out by Cefas to train the Natural Resources Division and MPA Officer on how to sample and identify marine invasive non-native species (IUCN Consultation 2024).
Education and interpretation programmes
During June 2022, Pulau School and the Island Administrator organised a school trip to the outer islands. During the trip, the 3 students undertook beach litter surveys on Acadia Island (Ducie), East Beach and North Beach (Henderson Island) and Oeno Island (Government of Pitcairn Islands, 2023).
Following the 2019 Henderson Island Expedition, the artist Mandy Barker displayed her artwork, created using plastic collected on the expedition in an art gallery of New Zealand to raise awareness of plastic pollution (Government of Pitcairn Island, 2023).
A leaflet was developed to communicate the marine biosecurity guidance to visiting vessels and tourists. The Blue Belt Programme also worked with the RSPB to design an interpretation board. This highlights the importance of biosecurity for the Pitcairn Islands, and the many pathways that invasive species can be transported to the islands and surrounding waters (Government of Pitcairn Islands, 2023).
Following the 2019 Henderson Island Expedition, the artist Mandy Barker displayed her artwork, created using plastic collected on the expedition in an art gallery of New Zealand to raise awareness of plastic pollution (Government of Pitcairn Island, 2023).
A leaflet was developed to communicate the marine biosecurity guidance to visiting vessels and tourists. The Blue Belt Programme also worked with the RSPB to design an interpretation board. This highlights the importance of biosecurity for the Pitcairn Islands, and the many pathways that invasive species can be transported to the islands and surrounding waters (Government of Pitcairn Islands, 2023).
Tourism and visitation management
Tourist numbers are very limited. Nonetheless, a visitor guide and code of conduct was published in 2007. The remoteness and risk of invasive alien species introduction do not favor large-scale tourism promotion, and is therefore not a management priority.
The Government of Pitcairn Islands ‘Guide for Visiting Vessels’ also states that landing is to be on North Beach only; East Beach and North-West Beach are off limits to visitors. This is difficult to enforce, and it has been noted that there are often footprints in the sand, even on East Beach. In order to encourage visitors to remain on North Beach, an eco-trail within the woodland at the back of North Beach is to be established. The eco-trail will be located and constructed in such a way to minimise any impacts to the environment following scientific advice. This will provide visitors with information about the important habitats and species they are seeing and will remind them of responsible behaviour as outlined in the code of conduct. The trail will also reduce the likelihood of visitors venturing into areas that are prohibited, protecting sensitive species such as breeding birds (Government of Pitcairn Islands, 2021). Due to the evidence of visitors accessing areas they should not and the high associated biosecurity risk and further threat from trampling on the site's biodiversity, visitor management should be a priority, even though the total numbers are low.
The Government of Pitcairn Islands ‘Guide for Visiting Vessels’ also states that landing is to be on North Beach only; East Beach and North-West Beach are off limits to visitors. This is difficult to enforce, and it has been noted that there are often footprints in the sand, even on East Beach. In order to encourage visitors to remain on North Beach, an eco-trail within the woodland at the back of North Beach is to be established. The eco-trail will be located and constructed in such a way to minimise any impacts to the environment following scientific advice. This will provide visitors with information about the important habitats and species they are seeing and will remind them of responsible behaviour as outlined in the code of conduct. The trail will also reduce the likelihood of visitors venturing into areas that are prohibited, protecting sensitive species such as breeding birds (Government of Pitcairn Islands, 2021). Due to the evidence of visitors accessing areas they should not and the high associated biosecurity risk and further threat from trampling on the site's biodiversity, visitor management should be a priority, even though the total numbers are low.
Sustainable use
The only instance of use of the Island's natural resources is the previous harvest of miro and tao by Pitcairn Islanders. However, harvesting was limited and considered sustainable, and now has not been practiced since 2004. According to the Marine Conservation Regulations (2016) residents of Pitcairn are allowed to fish in the territorial seas around Henderson, Oeno and Ducie Islands without a permit, provided that fishing is for consumption during the period of stay on the relevant island, is by an attended line and is conducted during that trip, is by an attended line and is conducted in accordance with any Marine Conservation Regulations and Fisheries Management Plan (Government of Pitcairn Islands, 2021).
Monitoring
There is no regular systematic monitoring, but scientific expeditions in 2009, 2011, 2012, 2013, 2015 and 2024 provided some monitoring data to inform the design and outcome of the rat eradication attempt (IUCN Consultation, 2024; RSPB, 2024). Further monitoring expeditions may be required in preparation for another eradication attempt, and follow-up monitoring of such an attempt would be necessary to assess the response of native biodiversity to the management intervention. There is currently no monitoring of the breeding seabird populations on Henderson Island nor of the green turtles which nest on East Beach, however according to the MPA Management Plan, a key objective is to establish such monitoring programmes.
Research
Research expeditions in 1991/1992 provided much of the knowledge about the island’s ecosystem (Benton and Spencer, 1995), further expeditions were undertaken in 2009 and 2011 (Torr and Brown, 2012), and expeditions in 2013, 2015 and 2024 provided more information on bird populations and rat ecology following the failed eradication attempt (Churchyard et al., 2013; Lavers et al., 2016; Bond et al., 2019b; Oppel et al., 2019). The cause of the 2011 eradication failure remains unclear, and an expedition in 2024 collected data to inform the design of a future rat eradication attempt and improve its chances of success. In 2019, a brief research expedition to the island focussed on plastic accumulation and did not yield insights relevant to the core biodiversity values or threats of the site (IUCN Consultation, 2020). The Pitcairn Government, Plastic Odyssey and RSPB all conducted expeditions in 2024 (IUCN Consultation, 2024).
In February 2024, Pitcairn opened a marine science base, which serves as a hub for studying humpback whales, green turtles, seabirds and coral reef ecosystems. Additionally, it will accommodate visiting scientists and support climate change research (Government of the Pitcairn Islands, 2024).
Pitcairn Islands MPA Research and Monitoring Plan will be published soon. However, to what extent this will impact the on-land monitoring and research on Henderson Island is unclear.
In February 2024, Pitcairn opened a marine science base, which serves as a hub for studying humpback whales, green turtles, seabirds and coral reef ecosystems. Additionally, it will accommodate visiting scientists and support climate change research (Government of the Pitcairn Islands, 2024).
Pitcairn Islands MPA Research and Monitoring Plan will be published soon. However, to what extent this will impact the on-land monitoring and research on Henderson Island is unclear.
Effectiveness of management system and governance in addressing threats outside the site
Addressing the threat of predation by the invasive Polynesian rat requires funding and additional research/management, but a single successful eradication could remove this threat. Besides the existing invasive rat threat, all conceivable potential threats would originate from outside of the island, particularly through uncontrolled visitation, invasive alien species introduction and climate change. A permanent ranger presence would likely exacerbate the risk of invasive species as considerable infrastructure would be required to establish adequate habitation on this extremely remote island. To effectively enforce visitor regulations (including the 2007 Code of Conduct), visitors should be required to undergo rigorous biosecurity procedures and be accompanied by a government official. The issue of marine debris accumulation on the island, which is impacting the values under both criteria for which the site is listed, is an issue which cannot be sustainably managed on-site.
Effectiveness of management system and governance in addressing threats inside the site
The rat eradication operation in 2011 was unsuccessful (Amos et al., 2016), but the failure was not due to poor planning or poor execution (Torr and Brown, 2012). The cause for the failure is poorly understood, but surviving rats are still susceptible to the toxin used in 2011 (Amos et al., 2016) and a new eradication operation will be attempted in the late 2020s following the ongoing Darwin Plus project by the RSPB: ‘Inhabited Territory restoration: completing preparations for a rodent-free Pitcairn Islands’. Supplementary research on a similar island indicates that rats can be successfully eradicated even when they are breeding and when coconut and other food is abundant (Samaniego et al., 2020) though some questions remain about the relative feasibility of such an operation on large, tropical islands. Additionally, there are efforts to reduce plastic pollution to the site's beaches, although the source from overseas cannot be addressed through the site's management. Along with other recent developments like the Pitcairn Island MPA Management Plan and the Biosecurity Ordinance, there are considerable efforts from the management perspective to maintain the site's and its surrounding land and seascape's values.
Henderson Island is generally sufficiently well-protected, primarily because of its remoteness. There are efforts to initiate a new rat eradication programme and with the Pitcairn Islands MPA Management Plan, which includes objectives related to the WH site, there is a strong management framework in place to coordinate the conservation of the Pitcairn Islands land and seascape. The Biosecurity Ordinance of 2024 is another welcome development that is expected to improve the enforcement of visitor regulations (including the 2007 Code of Conduct), i.e. through the requirement for visitors to undergo rigorous biosecurity procedures and be accompanied by a ranger. However, currently there is no funding to eradicate invasive species already present, and there is no effective management in place to prevent further introductions, which is of concern. The issue of marine debris accumulation on the island, which is impacting the values under both criteria for which the site is listed, is an issue which cannot be sustainably managed on-site and therefore the management of the site cannot be assessed on it's treatment of this issue.
Raised and forested coral atoll of exceptional natural beauty
Low Concern
Trend
Deteriorating
Integrity of the site's ecosystem and landscape has been stable. However, increasing amounts of solid waste in the Pacific Ocean are deposited on Henderson Island owing to ocean current patterns, leading to increasing quantities of plastic rubbish that adversely affect the natural beauty of the island. The presence of invasive Pacific rats is also having negative effects on the island’s flora, fauna and ecosystem function.
Exceptionally rich endemic flora
Data Deficient
Trend
Deteriorating
No abundance, reduction or loss of endemic flora has been reported and no new threat factors have arisen since the site's inscription on the World Heritage List. Nevertheless, the lack of reporting is likely a function if there being little data collection ongoing due to the remoteness of the site. Rats are likely to affect relative abundance of endemic flora through consumption of most palatable seeds, which was inferred by the abundance of seedlings emerging in study plots following the temporary reduction of the rat population after the 2011 eradication attempt (Churchyard et al., 2013; Lavers et al., 2016). Pandanus tectorius, which may or may not be a natural species (Waldren et al., 1999), may outcompete endemic flora, but quantitative data on the extent of Pandanus cover is not available. Cocos nucifera (coconut) is an invasive species on many islands, and forms dense monospecific stands along parts of the beaches of Henderson, but is mostly absent from the coral plateau. Regarding the possible expansion of coconut - existing stands have been mapped in 2015 and 2024 and there is an indication that there has been an expansion and increase in the density of trees (Lavers et al., 2016; RSPB, 2024), which could negatively impact the endemic flora and affect the aesthetic value of the site.
Exceptionally rich endemic avifauna
High Concern
Trend
Deteriorating
Most endemic bird species have been negatively affected by rat predation and competition and a continuous slow decline with a potential to lead to extinction of one species (Henderson petrel, Pterodroma atrata) has been inferred (Brooke, 1995a; Brooke et al., 2010). The impacts of rat predation on petrel chick mortality on Henderson Island have been estimated at 60-80% for Henderson petrel (Oppel et al., 2017). Bird monitoring after the 2011 rat eradication attempt indicated a slight recovery of the Henderson reed warbler and the Henderson fruit dove during the phase when the rat population was temporarily reduced, suggesting that populations of these species may be suppressed by rat predation (Bond et al. 2019). However, confounding factors such as a drought that may have naturally lowered baseline population estimates in 2011 complicate this assessment. 2024 data seem to indicate that the Henderson Fruit Dove population might be low in 2024, but it is unclear whether this was a temporary or permanent state (IUCN Consultation, 2024).
Exceptionally rich endemic invertebrate fauna
Low Concern
Trend
Data Deficient
The invertebrate fauna of Henderson Island is relatively little studied and may be particularly vulnerable to invasive alien species, but no abundance reduction or loss of endemic invertebrates has been reported, in part due to the lack of data collected. However, while no research has been carried out, rats are likely to be significantly affecting overall abundance and community structure of endemic invertebrate fauna (IUCN Consultation, 2020). Plastic debris entraps 61,000 hermit crabs, potentially influencing beach invertebrate communities and nutrient cycling (Lavers et al. 2021).
Important seabird nesting area (including of globally threatened species)
High Concern
Trend
Deteriorating
Among the nine breeding seabird species, Henderson petrel (Pterodroma atrata) and other Pterodroma spp. have been particularly threatened by rat predation (Brooke, 1995a), and a continuous slow decline with a potential to lead to extinction has been inferred (Brooke et al., 2010). The impacts of rat predation on petrel chick mortality on Henderson Island have been estimated at > 99% for Murphy’s petrel (Pterodroma ultima; Lavers et al., 2016), 60-80% for Henderson petrel (Oppel et al., 2017), and may be similarly high for Kermadec (Pterodroma neglecta) and Herald petrels (Pterodroma heraldica; Brooke, 1995a). Rat predation is likely to be responsible for a decrease of petrel abundance from an estimated >1 million pairs on the island before rat arrival to just 40,000 pairs (Brooke et al., 2010). This will impact on ecological processes of the island, as previously millions of seabirds would have provided a crucial nutrient source for the island’s ecosystem via their guano. However, an expedition in 2015 provided some reassurance that the decline of Henderson petrels may not be as rapid as previously feared (Oppel et al., 2017). No robust data exist on population sizes or trends of other seabird species.
Assessment of the current state and trend of World Heritage values
Deteriorating
Most endemic bird species have been negatively affected by rat predation and competition and a continuous slow decline with a potential to lead to extinction of one species (Henderson petrel, Pterodroma atrata) has been inferred, although the population may have been stable between 1991 and 2015. Land bird populations are also likely affected by rat predation, but the effect is difficult to quantify; as many as 25% of Henderson crake chicks are likely killed by rats. Rat predation is likely to be responsible for a decrease of petrel abundance from an estimated 1 million pairs on the island before rat arrival to just 40,000 pairs. This will impact on ecological processes of the island, as previously millions of seabirds would have provided a crucial nutrient source for the island’s ecosystem via their guano. Similar effects of rat predation on native invertebrates and plants are likely to occur, but no data exist to quantify these effects. No abundance, reduction or loss of endemic flora has been reported and no new threat factors have arisen since the site's inscription on the World Heritage List. Nevertheless, the lack of reporting is likely a result of the limited data collection that is occurring due to the remote nature of the site. However, rats are likely to affect relative abundance of endemic flora through consumption of most palatable seeds, which was inferred by the abundance of seedlings emerging in study plots following the temporary reduction of the rat population after the 2011 eradication attempt. The integrity of the site's landscape has been stable. However, increasing amounts of solid waste in the Pacific Ocean are deposited on Henderson Island owing to ocean current patterns, leading to enormous and increasing quantities of plastic rubbish that adversely affect the natural beauty of the island. Nevertheless, clean up missions have significantly reduced the macroplastic debris though this is a temporary measure with significant financial and carbon costs.
Assessment of the current state and trend of other important biodiversity values
Good
Stable
No deterioration of the other natural values of the site and no emerging factors that would make a negative trend likely have been reported since inscription.
Assessment of the current state and trend of other important values
Good
Stable
No deterioration of the other important values of the site and no emerging factors that would make a negative trend likely have been reported since inscription.
Additional information
Collection of genetic material
The island may serve as a reservoir of genetic material of miro and tau stocks for the future (UNEP-WCMC, 2011) and may hold genetic resources of global importance among its endemic biota.
Importance for research
As one of the few nearly pristine raised coral atolls, the site has generated significant scientific knowledge since discovery (Benton and Spencer, 1995) and could provide a reference for the ecological restoration of other islands in the wider South Pacific if rats can be successfully eradicated.
Invasive rats may limit certain aspects of research, but the presence of rats, the temporary suppression, and the development of techniques for successful eradication also provide interesting opportunities for applied research (Amos et al., 2016; Brooke et al., 2013; Cuthbert et al., 2012; Oppel et al., 2016a; Oppel et al., 2016b; Oppel et al., 2019).
The nature conservation benefits of this remote and uninhabited site exceed other types of benefits significantly, although there are also additional minor and potential benefits. As one of the few nearly pristine raised coral atolls, the site has generated significant scientific knowledge since discovery (Benton and Spencer, 1995) and could provide a reference for the ecological restoration of other islands in the wider South Pacific if rats can be successfully eradicated.
| № | Organization | Brief description of Active Projects | Website |
|---|---|---|---|
| 1 | Royal Society for the Protection of Birds (RSPB), The Pitcairn Environmental, Conservation & Natural Resources Division | This project addresses outstanding questions around the feasibility of removing Pitcairn’s rodents and provide final technical inputs regarding Henderson. Continuous community consultation, pre-operational mapping and non-target species mitigation research will empower fully-informed local decisions to proceed with eradication delivery, potentially enabling the first rodent-free inhabited Overseas Territory. | |
| 2 | Pitcairn Islands Community, Cefas and University of Edinburgh | During February 2023, Operation Redfish took place. This scientific research expedition, jointly funded by the Government of Pitcairn Islands and the Blue Belt Programme, visited 40 Mile Reef as well as the outer islands of Oeno and Henderson. Members of the Pitcairn Island community were joined by scientists from Cefas and the University of Edinburgh. The scientists used baited remote underwater video systems (BRUVs), dropdown video, eDNA sampling and carbonate chemistry sampling to better understand the deep reefs and seamount ecosystems within the MPA. Analysis of the data collected is now taking place with findings expected soon. |
See Pitcairn Islands MPA Annual Review 2022-2023
|
| 3 | Government of Pitcairn Islands, Pitcairn Islands Community | Although not focussed on the land-based biodiversity of Henderson Island it is a community-led branding and communications strategy for the MPA as a whole which will likely have positive knock on effects for raising awareness of Henderson Island. |
https://protect.blue/portfolio/pitcairn-mpa-a-community-project
|
| 4 | Plastic Odyssey | Project to remove some of the macroplastic on Henderson's beaches by an organised beach clean-up in 2024 with removal of the collected plastic for safe disposal elsewhere. Removal of macroplastic may prevent the breakdown of macroplastic into microplastic, which could eventually be ingested by fish or filter feeders (Ryan and Schofield 2020). |
https://henderson.plasticodyssey.org/
|
References
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Amos, W., Nichols, H.J., Churchyard, T., & Brooke, M.de L. (2016) Rat eradication comes within a whisker! A case study from the South Pacific. Royal Society Open Science, 3, 160110.
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| 3 |
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| 4 |
Benton, T.G. & Spencer, T., eds. (1995) The Pitcairn Islands: Biogeography, ecology and prehistory. Academic Press, London.
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| 5 |
Benton, T.G. (1995) Biodiversity and biogeography of Henderson Island's insects. Biological Journal of the Linnean Society, 56, 245-259.
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| 6 |
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| 7 |
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| 8 |
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| 9 |
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| 10 |
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| 12 |
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| 13 |
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| 14 |
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| 17 |
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| 18 |
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| 25 |
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| 26 |
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| 27 |
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