Croton cordatulus is an endemic shrub of the northern part of Grande Terre in New Caledonia. This species is known from 4 subpopulations: Katépahié, Avangui, Cap Bocage and Koniambo. It is found in shrubland or in humid forest on an ultramafic substrate at an altitudinal range of 50-500 m asl. The main identified threats are ongoing mining activities and habitat damage by uncontrolled bushfires. Mining extraction projections for the coming 25 years could lead to a 50% reduction in the impacted subpopulations. Croton cordatulus is assessed as Endangered (EN) under criterion A4c with an inferred population reduction of more than 50% over three generations (75 years) starting in 1970 and projected to 2045; and under criteria B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v) with the number of threat-defined locations estimated to be four, a continuous decline of all concerned subcriteria and extent of occurrence (EOO) and area of occupancy (AOO) are respectively estimated to be of 1,514 km² and 16 km².

Geographical area

Croton cordatulus is an endemic shrub of the northern part of Grande Terre in New Caledonia. This species is known from four subpopulations: Katépahié, Koniambo, Avangui, and Cap Bocage.

Population

Population size is unknown. Croton cordatulus is quite common on the west coast, but elsewhere may go unnoticed because it occurs mostly as isolated plants. Mining extraction projections for the coming 25 years could lead to a 50% reduction in the impacted subpopulations and thus contribute to the potential reduction of the total population size.

Habitat

Croton cordatulus is found in shrubland or in humid forest on an ultramafic substrate at an altitudinal range of 50-500 m asl.

Threats

The main identified threats are ongoing mining activities at Cap Bocage and Koniambo and habitat damage by uncontrolled bushfires at the other locations. New Caledonia contains 20 - 30% of the world’s nickel resources and has experienced intense mining activities since the late 19th century which has 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 (there was a rise in nickel production from 60,000 to 200,000 tonnes per year between 2013 and 2015). Additionally, uncontrolled bushfires sweep across 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).

Conservation

Croton cordatulus is protected by legislation in Province Nord and Province Sud, but does not occur in any protected area. It is recommended to prospect the Kouaoua and Thio areas. This species would benefit from ex-situ and in-situ emergency conservation actions. It is proposed to monitor known subpopulations, and to preserve a viable population within delimited perimeters on Cap Bocage. It would be moreover advised to conduct propagation tests in order to assist future planting operations.

Bibliography

Wulff AS, Hollingsworth PM, Ahrends A, Jaffré T, Veillon J-M, L’Huillier L, et al. 2013. Conservation Priorities in a Biodiversity Hotspot: Analysis of Narrow Endemic Plant Species in New Caledonia.

Morat, P.; Jaffré, T.; Tronchet, F.; Munzinger, J.; Pillon, Y.; Veillon, J.-M. and Chalopin, M. 2012. Le référentiel taxonomique Florical et les caractéristiques de la flore vasculaire indigène de la Nouvelle-Calédonie [The taxonomic database « FLORICAL » and characteristics of the indigenous flora of New Caledonia]. Adansonia sér 3(34) , p.177-219.

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

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., Veillon, J., Amice, R., Barrière, R., Chambrey, C., Fleurot, D., Lannuzel, G.

Reviewer(s): Vandrot, H.

Contributor(s): Wulff, A.

Facilitator(s): Tanguy, V., Chanfreau, S.