Plerandra polydactylis is an endemic tree of New Caledonia occurring in shrubland on ultramafic substrate ("maquis minier"). It is restricted to the ultramafic massifs on the west coast of the northern half of Grande Terre including on the Ile d'Art. There is an evident threat due to mining activities which impact the ultramafic massifs of north-west Grande Terre. Population size reduction cannot be assessed because of a lack of data. With an extent of occurrence (EOO) of 3,865 km², an area of occupancy (AOO) of 84 km² and 9-10 estimated locations, none of them occurring within a protected area, Plerandra polydactylis is assigned a status of Vulnerable with an observed and projected continuing decline of the area of occupancy, the quality of habitat, the number of sub-populations and the number of mature individuals. Population size cannot be estimated.

Geographical area

Plerandra polydactylis is an endemic tree of New Caledonia occurring in shrubland on ultramafic substrate ("maquis minier"). It is restricted to the ultramafic massifs on the west coast of the northern half of Grande Terre including on the Ile d'Art.

Population

Population size is unknown.

Habitat

Plerandra polydactylis species is found in low and middle altitude maquis (shrubland) on ultramafic substrate.

Threats

This species occurs on some ultramafic massifs threatened by mining activities and related threats. An important threat to biodiversity in New Caledonia comes from past, present and future mining activities. New Caledonia contains 20-30% of the world’s nickel resources. Intense mining activities since the late 19th century generated soil erosion (1.2% of bare ground mapped by SPOT5 in 2007). Based on the distribution of metal-rich soils and site accessibility, these threats are predictable and planned (rise in nickel production from 60,000 to 200,000 tonnes per year between 2013 and 2015). The west coast ultramafic massifs (such as the Tiebaghi dome, Mont Kaala, Ouazangou-Taom Mountains, Mont Koniambo, Mont Kopéto, Mont Paéoua and Mont Boulinda) are actively mined. These sites experience major impacts from mining activities and are not protected by local legislation.Another threat comes from Rusa Deer (Rusa timorensis), which was introduced in the 1880s and adapted extremely well to Caledonian habitats. Its population may have reached over 100,000 individuals into the wild. This rusa deer (Rusa timorensis) consumes a wide variety of plant species and causes severe damage to trees, which results in very little regeneration. Uncontrolled fires sweep across lowlands of New Caledonia each year, especially during the dry season (an average of 20,000 ha of land is burnt each year, with dramatic peaks of 70,000 ha). They contribute to habitat fragmentation and degradation of shrubland.

Conservation

Plerandra polydactylis species is protected by legislation (under the synonym Schefflera polydactylis) in Province Nord (code de l'environnement) but it does not occur in a gazetted protected area. It is however present in the "Tiébaghi conservatoire Ouest ; the zone du Vieux village de Tiébaghi" which has a label of archaeological heritage.This species would benefit from in situ and ex situ conservation actions.

Bibliography

Lowry, P. P. II; G. M. Plunkett; D. G. Frodin; C. Rodrigues Vaz; M. Gostel and A. N. Nicolas 2016. Revision of Plerandra A. Gray (Araliaceae). III. A taxonomic treatment of Plerandra subg. Dizygotheca..

L'Huillier L.; Jaffré T. and Wulff A. 2010. Mines et Environnement en Nouvelle-Calédonie : les milieux sur substrats ultramafiques et leur restauration.

Experts

Assessor(s): Tanguy, V.

Reviewer(s): Schatz, G.

Contributor(s): Lowry, P., Anquez, M., Amice, R., Birnbaum, P., Isnard, S., Vandrot, H., Gâteblé, G., Garnier, D., Fleurot, D., Cazé, H., Barrabé, L., Butin, J.

Facilitator(s): Schatz, G.