Low densities of macroplastic debris in the Pitcairn Islands Marine Reserve

Beaches on Henderson Island, one of the Pitcairn Islands in the central South Pacific, have been reported to have some of the highest standing stocks of stranded plastic recorded. Surveys of floating debris at sea show that this is not related to high densities of plastic in the area. Only 19 macroplastic items were observed during 905 km of at-sea transects (0.5 items·km^-2; 135 g·km^-2). This low density confirms previous microplastic surveys which show that the Pitcairn group lies west of the South Pacific Gyre. Plastic loads on beaches at other islands in the Pitcairn group are not exceptional. The east coast of Henderson Island appears to be particularly effective at accumulating drifting debris, but many small plastic fragments on these beaches probably result from degradation in situ, so removing macroplastics will reduce the formation of microplastics.

Significant range extensions for two fish species at Pitcairn Island, South Pacific

A baited videographic survey at Pitcairn Island has significantly extended the known range for two reef-fish species: blue-lined triggerfish Xanthichthys caeruleolineatus and greater amberjack Seriola dumerili, with an additional minor extension noted for giant trevally Caranx ignobilis. This highlights the importance of further research in this remote, poorly studied island group and provides evidence supplementing the understanding of oceanographic patterns in the South Pacific.

The real bounty: marine biodiversity in the Pitcairn Islands

In 2012 we conducted an integrated ecological assessment of the marine environment of the Pitcairn Islands, which are four of the most remote islands in the world. The islands and atolls (Ducie, Henderson, Oeno, and Pitcairn) are situated in the central South Pacific, halfway between New Zealand and South America. We surveyed algae, corals, mobile invertebrates, and fishes at 97 sites between 5 and 30 m depth, and found 51 new records for algae, 23 for corals, and 15 for fishes. The structure of the ecological communities was correlated with age, isolation, and geomorphology of the four islands. Coral and algal assemblages were significantly different among islands with Ducie having the highest coral cover (56%) and Pitcairn dominated by erect macroalgae (42%). Fish biomass was dominated by top predators at Ducie (62% of total fish biomass) and at Henderson (35%). Herbivorous fishes dominated at Pitcairn, while Oeno showed a balanced fish trophic structure. We found high levels of regional endemism in the fish assemblages across the islands (45%), with the highest level observed at Ducie (56% by number). We conducted the first surveys of the deep habitats around the Pitcairn Islands using drop-cameras at 21 sites from depths of 78 to 1,585 m. We observed 57 fish species from the drop-cams, including rare species such as the false catshark (Pseudotriakis microdon) and several new undescribed species. In addition, we made observations of typically shallow reef sharks and other reef fishes at depths down to 300 m. Our findings highlight the uniqueness and high biodiversity value of the Pitcairn Islands as one of the least impacted in the Pacific, and suggest the need for immediate protection.

The plant communities and environmental gradients of Pitcairn Island: the significance of invasive species and the need for conservation management

Quantitative surveys of the vegetation of south-east Polynesian Islands are rarely undertaken owing to time and logistical restrictions; however they are fundamental in determining the conservation status of fragile island ecosystems. The aim of the research was to document quantitatively the vegetation of Pitcairn Island by investigating whether clearly definable plant communities existed on the island, and the underlying environmental gradients influencing these communities. Initially, 10 x 10 m quadrats were taken from all areas of the island, with environmental parameters recorded for each quadrat. The vegetation was then mapped from high altitude vantage points. Two-way indicator species analysis was used to identify distinct plant communities, and canonical correspondence analysis was used to determine the underlying environmental gradients. The vegetation consists of 14 plant communities: four coastal, six forest, two fernland and two scrub communities. Large areas are covered by non-native scrub vegetation, and by monospecific Syzygium jambos (rose-apple) plantations. Less than 30 % of the island is covered by native forest, and these areas are limited to remote valleys. Fernlands also cover large areas, including both eroding areas and ridge tops. Coastal vegetation comprises rock and cliff communities with limited strand vegetation. The major environmental gradient affecting the composition of the plant communities is altitude, but anthropogenic influences also have a large effect, owing to forest clearance and introduced species. The light environment is affected by the canopy species, and determines what ground flora can develop. Identification of distinct plant communities has allowed for a system of nature reserves to be suggested, which conserve all of these plant communities and a significant proportion of the threatened plant species.

Pitcairn Island: fertility and population growth, 1790-1856

The hybrid English-Tahitian community which lived on Pitcairn Island between 1790 and 1856 exhibited a high population growth (3% overall). Unlike some other isolated groups, they did not live long lives (expectation of life at birth was 50.4 years overall for both sexes combined), but infant mortality, at 5.5% of births is lower than might have been expected. The level of marital fertility on Pitcairn was extremely high, higher even than for the Hutterites. Although births outside marriage were uncommon, brides were frequently pregnant at marriage. Age at first marriage changed markedly in response to changes in the community. There is some evidence that premarital sex became more frequent, possibly as an adjustment to Tahitian behavioural norms within the community's English religious ethic.