Henderson Island (Pitcairn Islands)

"Henderson Island, a raised on the , is of great importance as one of the few examples of a Pacific island with intact lowland forest. It is also of biogeographic interest as it is practically the final island in a series of island chains, along which the fauna of has colonized, reaching back to . New collections of the non-flying terrestrial arthropod fauna were made on Henderson Island in 1991. In excess of 100 taxa are now known. There is a rich fauna (especially s), with many apparently endemic, some 26 species of spider, and nine species of (including three endemic to Henderson or nearby ). In addition , , , , , and are represented. The majority of the fauna is derived from the west, as expected, though many taxa appear to be introduced, some of them from the neotropics (e.g. and perhaps Hoplophorella stilifer)."

"The ecology of Henderson Island, a raised atoll near on the southern border of , still seems to be in its natural state. The birds include an endemic monotypic genus of flightless , an endemic species of , and endemic races of and . Its seabirds have not been adequately studied but are known to include a large population of the rare dark phase of the . The may be an endemic race with white feet. ... … it is now one of the few islands of its size in the warmer parts of the world still little affected by human activity, supporting a variety of endemic plants and animals and important seabird colonies in an area with few alternative sites."

"Henderson Island, located in the southeastern Pacific Ocean, is a fossil coral and is the world’s only raised atoll where the ecology is essentially intact, having been little degraded because of its extreme isolation and rough terrain. The surface is largely a plateau of reef rubble interspersed with areas of sharp coral pinnacles and with extremely rugged dissected ic round the edges. The central depression is the site of a fossil lagoon which formed before the island rose. The land is surrounded by high limestone cliffs which protect the island from storms. Its fossil corals record changes in and the over half a million years, and its isolation makes it an ideal site for studying the dynamics of island evolution and natural selection."

"Henderson is an elevated limestone island situated in 24"22'S and 128°20'W. Its nearest neighbours are , 200 km to the west-southwest; , 200 km to the west; and , 360 km to the east. It rises as an isolated conical mound from depths of ca 3.5 km, on a trend line which continues that of the and eastward to Ducie, and is presumably a reef-capped volcano. The island has a greatest length of 9.6 km and greatest width of 5.1 km, based on the ; its area is 37 sq km. It is usually said to rise about 33 m (100 ft) above sea level. ... The top of the island, as well as any land at the bases of the cliffs, is densely vegetated by tangled scrub and scrub-forest, but the central part of the depression and the makatea are more sparsely covered. In places, where the forest is taller and the canopy more complete, it is possible to walk freely for short distances. The tallest trees are ' , which in places rises as an emergent above the general canopy. The crowns of such emergents are conspicuously pyramidal or conical. The dried fallen leaves of Pandanus cover the ground in many places. The scrub and much of the scrub-forest is in many areas so dense and tangled that walking through it is impossible without the constant and vigorous use of a machete, and exhausting and slow even with the use of one. ... Fresh water is almost entirely absent. Slight dripping has been observed from the roofs of certain caves."

"In just over half a century products have revolutionized human society and have infiltrated terrestrial and marine environments in every corner of the globe. The hazard plastic debris poses to is well established, but mitigation and planning are often hampered by a lack of quantitative data on accumulation patterns. Here we document the amount of debris and rate of accumulation on Henderson Island, a remote, uninhabited island in the South Pacific. The density of debris was the highest reported anywhere in the world, up to 671.6 items/m2 ( ± : 239.4 ± 347.3 items/m2) on the surface of the beaches. Approximately 68% of debris (up to 4,496.9 pieces/m2) on the beach was buried <10 cm in the sediment. An estimated 37.7 million debris items weighing a total of 17.6 tons are currently present on Henderson, with up to 26.8 new items/m accumulating daily. Rarely visited by humans, Henderson Island and other remote islands may be sinks for some of the world’s increasing volume of waste."

"On the basis of field surveys from the north and north-west beaches, the vegetation of Henderson Island can be classified into 11 : 2 in littoral environments with sandy substrates, 4 on rocky coasts and 5 associated with the limestone plateau. Apart from the cutting of by , the communities are remarkably undisturbed, with only 5 adventive species recorded. ... The study of the vegetation communities of Henderson Island is of both great interest and importance. Henderson's vegetation is of interest in a regional context, first, , because of the island's remoteness in the south-east Pacific Ocean (Fosberg 1984) and secondly, because its floristic composition reflects a relatively rare stage in the continuum of vegetation types, controlled by increasing elevation above sea level, from the motus of sea-level atolls to the 'high' islands of Polynesia constructed from both volcanic rocks and limestones (Sachet 1985). In addition, Henderson's vegetation is of great significance to the wider debate on the structure and function of island ecosystems both past and present. As a result of the island's isolation, unsuitability for sustained human habitation and lack of economic phosphate deposits, the vegetation of Henderson Island has survived Polynesian and successive Western impacts (with only 5 introduced plant species) and provides an almost unique glimpse of the natural vegetation cover of a former atoll and lagoon well-raised above present sea level ... Furthermore, the continued removal of the natural vegetation communities of fragile tropical {[w|Island ecology|island ecosystems}} makes the field study of locations such as Henderson doubly important (Fosberg et al. 1983, Fosberg 1985b)."

"Situated at the extreme margin of the Indo-West Pacific biotic province, the four islands of the isolated Pitcairn Group hold interest for biogeographers and archaeologists alike. Human settlement may have been as early as the 8th century AD for the uplifted limestone island of Henderson, the most pristine island of its kind. An archaeological survey of the Pitcairn Islands is provided, while Henderson is examined in detail. Recent extensive excavations provide a record of change during 600 years of human occupation. Adaptation to the ecologically-marginal conditions is documented by artefacts, more than 150000 vertebrate bones, molluscs and subfossil plant remains recovered from stratigraphic contexts. The effects of prehistoric human occupation on the pristine environment are revealed by Polynesian plant and animal introductions, bird extinctions and range reductions, possible over-predation of marine molluscs, exploitation of sea turtles, and large-scale burning for swidden agriculture. The origin of human colonists is documented by analysing imported artefacts by geochemical characterization (x-ray fluorescence analysis). The human abandonment of Henderson, by the seventeenth century, is viewed in the context of prehistoric regional dynamics."

"Recent studies of island biotas have suggested that the is much greater than previously suspected. This impact resulted in the introduction of many new species and the extinction of many unique life-forms. Henderson Island, in the Pitcairn Group, has been found to be an excellent laboratory for the study of natural faunal turnover and the impact of people on the natural environment. This was principally due to the island's remote location and its limestone structure, which resulted in the excellent preservation of fossil remains. During the Sir Peter Scott Commemorative Expedition to the Pitcairn Islands, extensive excavations were undertaken resulting in the collection of 42213 bird bones. It was possible to identify 31%. Of the 31 taxa identified, four s appear to be vagrants, a surprisingly high number illustrating that the uncritical evaluation of fossil bird lists from other islands risks over-estimating the number of indigenous species. As a result of the arrival of Polynesian people during the first half of this millennium, half of Henderson's endemic landbirds became extinct, as did most of the small ground-nesting seabirds. The lower sea level during cold stages creates many temporary limestone ‘high’ islands. This results in many ‘former-atolls’ developing geological and ecological similarity to Henderson. Hence lower sea-level greatly facilitates the movement of flora and fauna between currently isolated oceanic ‘high’ islands."