Henderson Island

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.

Henderson Island, which lies in the eastern South Pacific, is one of the few atolls in the world whose ecology has been practically untouched by a human presence. Its isolated location provides the ideal context for studying the dynamics of insular evolution and natural selection. It is particularly notable for the 10 plants and four land birds that are endemic to the island. © UNESCO

© Steffen Oppel
See all information

Summary

2020 Conservation Outlook

Finalised on
07 Dec 2020
Significant concern
The remote and uninhabited Henderson Island has so far been relatively well preserved, primarily because of the limited anthropogenic pressure. However, the biodiversity values of the island remain very highly threatened by rat predation and competition. The impact of rat predation on petrel chick mortality is extremely high. Other endemic land bird and invertebrate populations are also likely suppressed by rat predation, and the composition of native flora may be substantially altered due to rat predation of seeds and seedlings. 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. The endemic 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). A rat eradication programme was undertaken in 2011, but was not successful due to unknown reasons. Securing the status of Henderson island’s unique biodiversity critically depends on eradication of invasive rats (Dawson et al., 2015). The site is also at risk of potential future invasive alien species introductions, which could occur relatively easily through uncontrolled or poorly managed visitation and have a devastating effect on several key values of the island. The site would benefit from additional efforts to eradicate rats, as well as efforts to effectively enforce visitor regulations. The increasing accumulation of plastic debris along the beaches is a threat to the natural beauty of the island that will require action at global scales, and cannot be averted by site-specific mitigation measures. Site-specific measures to address the plastic debris, such as a beach ‘clean-up’ expedition in 2019, are likely to increase the risk of introducing further non-native species, while providing no lasting benefit to the conservation values of the site.

Current state and trend of VALUES

High Concern
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), 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). 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. 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. 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.

Overall THREATS

High Threat
The key threat to the World Heritage values of Henderson Island continues to be rat predation and competition and its effects on avifauna, invertebrates, and the wider ecological processes of the island. Possible future species introductions are also a significant threat. This implies that uncontrolled or poorly managed visitation, as the main invasive alien species vector, remains a potential threat to the site. The continued accumulation of plastic pollution on the beaches of the island threaten both the scenic and biological values of the site. 

Overall PROTECTION and MANAGEMENT

Some Concern
Henderson Island is generally sufficiently well-protected, primarily because of its remoteness, but would benefit from additional efforts to eradicate rats following the unsuccessful 2011 rat eradication programme, as well as efforts to effectively enforce 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. 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. 

Full assessment

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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 (Porzana atra) (VU: 5,755–12,749 in 2015; Oppel et al., 2016a), Henderson lorikeet (Vini stepheni) (VU: 554 - 3,014 in 2015; Lavers et al., 2016), Henderson fruit dove (Ptilinopus insularis) (VU: 4,476 - 10,072 in 2015; Lavers et al., 2016) and Henderson reed warbler (Acrocephalus taiti) (VU: 7,194 - 28,776 in 2015; Lavers et al., 2016). The site also hosts one endemic seabird - the Henderson petrel (Pterodroma atrata) (EN: 19,987 pairs in 2015; Oppel et al., 2017; BirdLife International, 2016).

Exceptionally rich endemic invertebrate fauna

Criterion
(x)
All 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).

Assessment information

High Threat
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 landbirds and endemic invertebrate populations. 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.
Solid Waste
(Accumulation of plastic and other waste along coastline)
High Threat
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.
Recreational Activities
(Unregulated visitation by tourists)
Low Threat
Inside site
, Localised(<5%)
Generally, the island is little visited, due to its extreme remoteness. 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. However, 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).
Invasive Non-Native/ Alien Species
(Impacts of invasive species on avifauna, flora and invertebrate fauna)
Other invasive species names
Polynesian rat (Rattus exulans)
High Threat
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).
High Threat
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.
Invasive Non-Native/ Alien Species
(Impacts of invasive species on avifauna, flora and invertebrate fauna (further))
Other invasive species names
Black rat (Rattus rattus)
High Threat
Inside site
, Throughout(>50%)
The example of the rat predation effect on petrel populations (see above) shows that any species introduction, which might happen easily through unregulated 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 could be 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).
Mostly Effective
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). A 5-year management plan was published (Brooke et al., 2004), and implementation started in 2005, but an update was deferred until the rat eradication is completed. The Pitcairn government and the RSPB remain committed to restore Henderson Island and will likely aim at another rat eradication operation in the 2020s to restore the island’s ecosystem.
Some Concern
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 should be attempted in the 2020s. 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).
Highly Effective
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.
Data Deficient
The site is managed by Pitcairn Island Council according to Pitcairn Island OST planning (UNEP-WCMC, 2011), but no information about integration into formal planning is available.
Data Deficient
Not applicable - there is no permanent local population; island is only occasionally visited by Pitcairn Islanders and foreign research and conservation expeditions generally hire local staff.
Mostly Effective
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). However, there should be a requirement that all visiting cruise ships must be accompanied by a local ranger, and must have very stringent biosecurity controls in place.
Some Concern
Due to the Island's remoteness, no enforcement is possible. However, nor is it required given the little visitation that such remoteness affords. Concerns exist over the enforcement of biosecurity regulations. However, 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).
Mostly Effective
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.
Highly Effective
The only instance of use of the Island's natural resources is the previous harvest of miro by Pitcairn Islanders. However, harvesting was limited and considered sustainable, and now has not been practiced since 2004.  
Serious Concern
There is little on-site management needed once the threat of invasive rats 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, the lack of financing for another eradication attempt is of serious concern (IUCN Consultation, 2020).
Mostly Effective
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.
Data Deficient
Not applicable – due to the remoteness of the Island and limited number of direct stakeholders.
Mostly Effective
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. 
Some Concern
There is no regular systematic monitoring, but scientific expeditions in 2009, 2011, 2012, 2013, and 2015 provided some monitoring data to inform design and outcome of the rat eradication attempt. 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.
Mostly Effective
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 and 2015 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). As the cause of the 2011 eradication failure remains unknown, more research may be necessary to improve the chances of success of a second eradication attempt. 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).
Assessment of the effectiveness of protection and management in addressing threats outside the site
Some Concern
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 and invasive alien species introduction. 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 ranger. 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. 
Good practice examples
The eradication attempt in 2011 followed international best practice for rodent eradication operations on tropical islands (Keitt et al., 2015; Torr and Brown, 2012), and endemic avifauna was safeguarded by best practice during the operation (Oppel et al., 2016a).
Assessment of the current state and trend of World Heritage values
Deteriorating
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.

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.
Factors negatively affecting provision of this benefit
Invasive species
Impact level - High
Trend - Continuing
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.
Factors negatively affecting provision of this benefit
Invasive species
Impact level - High
Trend - Continuing
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 Henderson Island Restoration Programme aims to restore the island by eradicating invasive rats. Since the failed eradication attempt in 2011, the programme has focussed on research to understand the immediate response of the bird fauna (Bond et al., 2019), and rat ecology that may assist with a future eradication attempt (Oppel et al., 2019). Due to the remoteness of Henderson Island, the programme now supports experimental work on similar tropical Pacific islands to better understand the potential limitations to eradication attempts of invasive rats on tropical islands (Samaniego et al., 2020).
https://www.rspb.org.uk/our-work/conservation/projects/henderson-island-restoration-programme/

References

№References
1
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.
2
Benton, T.G. & Lehtinen, P.T. (1995) Biodiversity and origin of the non-flying terrestrial arthropods of Henderson Island. Biological Journal of the Linnean Society, 56, 261-272.
3
Benton, T.G. & Spencer, T., eds. (1995) The Pitcairn Islands: Biogeography, ecology and prehistory. Academic Press, London.
4
Benton, T.G. (1995) Biodiversity and biogeography of Henderson Island's insects. Biological Journal of the Linnean Society, 56, 245-259.
5
Benton, T.G. (1995b) From castaways to throwaways - marine litter in the Pitcairn Islands. Biological Journal of the Linnean Society, 56, 415-422.
6
BirdLife International (2016) IUCN Red List for birds. BirdLife International (2016) IUCN Red List for birds. Available at: http://datazone.birdlife.org/quicksearch?qs=Henderson. Accessed on 21 Dec 2016.
7
Bond, A.L., Brooke, M. de L., Cuthbert, R.J., Lavers, J.L., McClelland, G.T.W., Churchyard, T., Donaldson, A., Duffield, N., Forrest, A., Harrison, G., Mackinnon, L., Proud, T., Skinner, A., Torr, N., Vickery, J.A., and Oppel, S. (2019). Population status of four endemic land bird species after an unsuccessful rodent eradication on Henderson Island. Bird Conservation International 29, 124-135.
8
Bond, A.L., Churchyard, T., Cuthbert, R.J., Donaldson, A., Duffield, N., Forrest, A., Havery, S., Lavers, J.L., MacKinnon, L., McClelland, G.T.W., Kelly, J., Proud, T., Skinner, A., Torr, N., Vickery, J.A. and Oppel, S. (2019b). 'Recovery of introduced Pacific rats (Rattus exulans) following a failed eradication attempt on subtropical Henderson Island, South Pacific Ocean'. In: C.R. Veitch, M.N. Clout, A.R. Martin, J.C. Russell and C.J. West (eds.) Island invasives: scaling up to meet the challenge. pp. 167-174. Gland, Switzerland: IUCN.
9
Brooke, M.de L. (1995a) The breeding biology of the gadfly petrels Pterodroma spp. of the Pitcairn Islands: characteristics, population sizes and controls. Biological Journal of the Linnean Society, 56, 213-231.
10
Brooke, M.de L. (1995b) The modern avifauna of the Pitcairn Islands. Biological Journal of the Linnean Society, 56, 199-212.
11
Brooke, M.de L., Cuthbert, R.J., Harrison, G., Gordon, C., & Taggart, M.A. (2013) Persistence of brodifacoum in cockroach and woodlice: Implications for secondary poisoning during rodent eradications. Ecotoxicology and Environmental Safety, 97, 183-188.
12
Brooke, M.de L., O'Connell, T.C., Wingate, D., Madeiros, J., Hilton, G.M., & Ratcliffe, N. (2010) Potential for rat predation to cause decline of the globally threatened Henderson petrel Pterodroma atrata: evidence from the field, stable isotopes and population modelling. Endangered Species Research, 11, 47-59.
13
Churchyard, T., Proud, T., Brooke, M.de L., O'Keefe, S., Warren, P., & Rodden, M. (2013). Henderson Island Trip Report 2013. Royal Society for the Protection of Birds, Sandy, UK.
14
Cuthbert, R.J., Brooke, M.de L., & Torr, N. (2012) Overcoming hermit-crab interference during rodent-baiting operations: a case study from Henderson Island, South Pacific. Wildlife Research, 39, 70-77.
15
Dawson, J., Oppel, S., Cuthbert, R.J., Holmes, N., Bird, J.P., Butchart, S.H.M., Spatz, D.R., & Tershy, B. (2015) Prioritizing islands for the eradication of invasive vertebrates in the United Kingdom overseas territories. Conservation Biology, 29, 143-153.
16
Florence, J., Waldren, S., & Chepstow-Lusty, A.J. (1995) The flora of the Pitcairn Islands - a review. Biological Journal of the Linnean Society, 56, 79-119.
17
Havery, S., Oppel, S., Cole, N., & Duffield, N.D. (2017) Density of three skink species on Henderson Island estimated with hierarchical distance sampling. Herpetological Conservation and Biology, 13, 507–516.
18
Jones, P., Schubel, S., Jolly, J., Brooke, M.de L., & Vickery, J. (1995) Behaviour, natural history, and annual cycle of the Henderson Island rail Porzana atra (Aves: Rallidae). Biological Journal of the Linnean Society, 56, 167-183.
19
Keitt, B., Griffiths, R., Boudjelas, S., Broome, K., Canwell, S., Millett, J., Pitt, W., & Samaniego-Herrera, A. (2015) Best practice guidelines for rat eradication on tropical islands. Biological Conservation, 185, 17-26.
20
Lambrides, A.B.J. & Weisler, M.I. (2015) Assessing protocols for identifying Pacific island archaeological fish remains: The contribution of vertebrae. International Journal of Osteoarchaeology, 25, 838-848.
21
Lavers, J.L. & Bond, A.L. (2017) Trashing paradise: exceptional and rapid accumulation of anthropogenic debris on one of the world’s most remote and pristine islands. Proceedings of the National Academy of Sciences of the USA, submitted.
22
Lavers, J.L., McClelland, G.T., MacKinnon, L., Bond, A.L., Oppel, S., Donaldson, A.H., Duffield, N.D., Forrest, A.K., Havery, S.J., & O’Keefe, S. (2016). Henderson Island expedition report: May-November 2015. Royal Society for the Protection of Birds, Sandy, UK.
23
Oppel, S., Bond, A.L., Brooke, M.de L., Harrison, G., Vickery, J.A., & Cuthbert, R.J. (2016a) Temporary captive population and rapid population recovery of an endemic flightless rail after a rodent eradication operation using aerially distributed poison bait. Biological Conservation, 204, Part B, 442-448.
24
Oppel, S., Lavers, J., Donaldson, A., Forrest, A., McClelland, G., Bond, A., & Brooke, M. (2017) Population status, breeding success and ecology of the Henderson Petrel after a failed rat eradication on Henderson Island. Emu, 117, 151–159.
25
Oppel, S., Lavers, J.L., Bond, A.L., & Harrison, G. (2016b) Reducing the primary exposure risk of Henderson crakes (Zapornia atra) during aerial broadcast eradication by selecting appropriate bait colour. Wildlife Research, 43, 298-303.
26
Oppel, S., McClelland, G.T.W., Lavers, J.L., Churchyard, T., Donaldson, A., Duffield, N., Havery, S., Kelly, J., Proud, T., Russell, J.C. and Bond, A.L. (2019). 'Seasonal variation in movements and survival of invasive Pacific rats on sub-tropical Henderson Island: implications for eradication'. In: C.R. Veitch, M.N. Clout, A.R. Martin, J.C. Russell and C.J. West (eds.) Island invasives: scaling up to meet the challenge. pp. 200-208. Gland, Switzerland: IUCN.
27
Pandolfi, J.M. (1995) Geomorphology of the uplifted Pleistocene atoll at Henderson Island, Pitcairn group. Biological Journal of the Linnean Society, 56, 63-77.
28
Preece, R.C. (1995) Systematic review of the land snails of the Pitcairn Islands. Biological Journal of the Linnean Society, 56, 273-307.
29
Samaniego, A., Griffiths, R., Gronwald, M., Holmes, N.D., Oppel, S., Stevenson, B.C., & Russell, J.C. (2020) Risks posed by rat reproduction and diet to eradications on tropical islands. Biological Invasions 22, 1365–1378.
30
Torr, N. & Brown, D. (2012). Henderson Island restoration project post-operational report. Royal Society for the Protection of Birds, Sandy, UK.
31
UNEP-WCMC (2011) Henderson Island, UK. In UNEP-WCMC World Heritage Information Sheets. Available at: https://www.unep-wcmc.org/resources-and-data/world-heritage…. Accessed 21 Dec 2016.
32
Waldren, S., Florence, J., & Chepstow-Lusty, A.J. (1995) A comparison of the vegetation communities from the islands of the Pitcairn group. Biological Journal of the Linnean Society, 56, 121-144.
33
Waldren, S., Weisler, M.I., Hather, J.G., & Morrow, D. (1999) The non-native vascular plants of Henderson Island, South-Central Pacific Ocean. Atoll Research Bulletin, 463, 1-20.

Henderson Island, which lies in the eastern South Pacific, is one of the few atolls in the world whose ecology has been practically untouched by a human presence. Its isolated location provides the ideal context for studying the dynamics of insular evolution and natural selection. It is particularly notable for the 10 plants and four land birds that are endemic to the island. © UNESCO

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