Plerandra mackeei is an endemic tree of New Caledonia occurring in sclerophyllous forest. This species has suffered dry forest reduction and fragmentation. This is particularly linked to agriculture on the west coast. Today's main additional threats for Plerandra mackeei come from habitat degradation due to Rusa Deer (Rusa timorensis) and uncontrolled fires. Both its extent of occurrence (EOO) and area of occupancy (AOO) are estimated to be 8 km². The number of locations is estimated to be one. A continuing decline has been estimated in its quality of habitat, observed in the number of mature individuals and projected for the number of subpopulations. Using criteria B, Plerandra makeii is assigned a status of Critically Endangered (CR) B1ab(iii,iv,v)&2ab(iii,iv,v). Population size is estimated to be fewer than 50 with a continuing decline and two known subpopulations. Therefore, this species is also Critically Endangered using C2a(i) and D.While it is not currently included in a formally recognized protected area, Plerandra mackeei occurs in the Conservatoire Botanique de Tiéa, a 32.5 ha parcel located in an area that was previously private land managed by the Programme Forêt Sèche, but which was recently bought by North Province and is scheduled to become a permanent reserve in the near future.

Geographical area

Plerandra mackeei is an endemic tree of New Caledonia restricted to the west coast of Grande Terre in the region of Pouembout.

Population

Plerandra mackeei was originally known from a single specimen collected in 1972. It was rediscovered in 2014 by the botanist Dominique Fleurot who found a number of individuals in two subpopulations in the region of Pouembout. Population size is estimated to be around 15.

Habitat

Plerandra mackeei is found in sclerophyllous forest at an altitudinal range of 20-30 m, on black clay substrate. Tropical dry forests are probably among the worlds most endangered of all lowland tropical forests. Because of their propensity to become pastures and their susceptibility to fire, dry forests have been reduced dramatically, both in size as well as in quality. In New Caledonia, they have been extensively cleared for agricultural purposes for a century; what remains today are highly fragmented patches that have been estimated at 2% of the original area.

Threats

Tropical dry forests are probably among the worlds most endangered of all lowland tropical forests. Because of their propensity to become pastures and their susceptibility to fire, dry forests have been reduced dramatically, both in size as well as in quality. In New Caledonia, they have been extensively cleared for agricultural purposes or urbanization for a century; what remains today are highly fragmented patches that have been estimated at 2% of the original area. Uncontrolled fires sweep across the 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 have slowly transformed remnant patches of dry forest into scrubland dominated by Acacia spirorbis and Leucaena leucocephala, or Niaouli (Melaleuca quinquenervia) savannahs. Another main 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.

Conservation

Plerandra mackeei is not protected by local legislation. None of the subpopulations occur within a formal protected area, although dry forests benefit from a conservation programme managed by the Conservatoire des Espaces Naturels.One subpopulation occurs in the Conservatoire Botanique de Tiéa, a 32.5 ha parcel located in an area that was previously private land managed by the Programme Forêt Sèche, but which was recently bought by the Northern Province and is scheduled to become a permanent reserve in the near future. Both subpopulations are fenced against Rusa Deer.This species would benefit from further in situ and ex situ conservation actions (experimental nursery reproduction and in situ reinforcement).

Bibliography

Bouchet, P.; Jaffré, T. and Veillon J.-M. 1995. Plant extinction in New Caledonia: protection of sclerophyll forest urgently needed. Biodiversity and Conservation(4) , p.415-428.

Endemia.nc 2016. Faune et Flore de Nouvelle-Calédonie.

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..

Experts

Assessor(s): Tanguy, V.

Reviewer(s): Schatz, G.

Contributor(s): Barrière, R., Lowry, P., Fleurot, D., Vandrot, H., Butin, J., Barrabé, L.

Facilitator(s): Schatz, G.