Year of compilation: 2006
Non-bird biodiversity: The flora of Pitcairn includes 80 species of native vascular plants, of which ten, two ferns and eight angiosperms, are endemic. Fifty one of the native vascular plants are threatened. Particular concern attaches to the endemic Coprosma benefica, known from only 11 individuals, and the endemic fern Angiopteris chauliodonta, restricted to small and fragmented populations. Other species (e.g. Cyclophyllum barbatum, Psydrax odoratum) are becoming rare as they are utilised by the Islanders. Their populations could be enhanced by nursery propagation (see conservation issues). Several species are poorly dispersed on Pitcairn (e.g. Coprosma, Psydrax, Xylosma suaveolens) due to the lack of a frugivorous bird to disseminate fruit.Eight of Pitcairn's 26 species of extant land snail are endemic; three survive only in small remnants of native vegetation around one hectare in extent. If rose-apple or Lantana were to invade these remnants and create an understory inimical to these taxa, they would probably become extinct.
While the rose-apple has not yet invaded the southern flank of Pitcairn, this will probably happen in due time if not prevented. Ideally, the best pockets of native vegetation should be weeded periodically, for example in Faute Valley and Tautama. Funding for the labour involved is required. Consideration should also be given to protecting at least parts of these areas from goats by fencing. Other important pockets of native vegetation (e.g. Brown's Water, home to a high number of endemic and threatened species) should be protected from road encroachment.The large tracts of rose-apple growing over Pitcairn are of little wildlife value. In the long-term, it would be ideal if this introduced invasive species could be replaced by native and, especially, threatened species. To this end, seedlings grown in the nursery could be planted out in small areas where the rose-apple had been cleared. This general methodology will perhaps need refining in the light of experience, but is certainly to be preferred to wholescale clearance of rose-apple. Since little grows underneath rose-apple, such clearance would undoubtedly be accompanied by loss of topsoil and erosion. The ideas are now being tested in a project run by Trinity College, Dublin and funded by the Foreign and Commonwealth office, London.Since the Pitcairn Reed-warbler appears able to co-exist with Pacific rats Rattus exulans and with feral cats, and to live in a variety of altered and disturbed habitats, there appears no immediate cause for concern. This would change were other rat species to reach Pitcairn. In 1997 and 1998, two attempts to eradicate rats were made using hand distribution of poison baits. If successful, the eradication would have contributed to human welfare, allowed the recolonisation of Pitcairn by surface-nesting seabirds, and reduced the risk that Oeno (see that island's account) would be re-invaded by rats. While the attempts certainly reduced the rat population to a very low level, with immediate evident benefits to the Islanders' fruit and vegetable crops, neither attempt was entirely successful. Inevitably, it is impossible to be certain about the reason(s) for failure, but there is wide agreement that, in the event of a third attempt, the period of monitoring by dedicated personnel after the main bait distribution should be lengthened to several months. There is a population of free-ranging goats on Pitcairn. When numbers increase beyond about 100, the situation at the time of writing, their impact on the vegetation and erosion visibly escalate. Regular culling appears justified.
BirdLife International (2023) Important Bird Areas factsheet: Pitcairn Island. Downloaded from http://www.birdlife.org on 04/02/2023.