Syzygium laxeracemosum is an endemic shrub restricted to the valley of Tontouta on Grande Terre in New Caledonia. A single population is known. It is found in shrubland on an ultramafic substrate at an altitudinal range 50-150 m asl. Recurrent bushfires and on-going mining activities in the valley contribute to the degradation of the habitat, especially to erosion. Myrtle's rust is a potential supplementary threat. Its extent of occurrence (EOO) and area of occupancy (AOO) are both estimated to be of 16 km² with an estimation of one location. Syzygium laxeracemosum is therefore assessed as Critically Endangered (CR) with criteria B1ab(iii,v) with a continuing decline of habitat quality and number of mature individuals.

Geographical area

Syzygium laxeracemosum is an endemic shrub restricted to the valley of Tontouta on Grande Terre in New Caledonia.

Population

This species, a prostrate shrub, is discreet and is considered as rare.

Habitat

It is found in shrubland on an ultramafic substrate at an altitudinal range 50-150 m asl.

Threats

Recurrent bushfires and on-going (and past) mining activities in the valley (Tomo and Vulcain by SMGM, Opoué by SLN) contribute to the degradation of the habitat, especially to erosion. Some individuals are directly impacted by the mine Gallieni/Vulcain. 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). New Caledonia contains 20-30% of the world’s nickel resources. Intense mining activities since the late 19th century have 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). This species could be impacted by the myrtle's rust, which was declared in 2013 in New-Caledonia. It seems the rust has a predilection for riverbanks species.

Conservation

Syzygium laxeracemosum is protected by legislation in Province Sud. It does not occur in any protected area. This species would benefit from emergency in-situ and ex-situ conservation measures. Research is needed to enhance knowledge of the species' distribution and allow the monitoring of the population. It seems this species is recalcitrant to seed banking but it shows good germination in plant nurseries. In terms of protection, while it seems difficult to propose perennial measures as long as the valley will be exploited, it is proposed to carry anti-erosive measures and to protect some areas of the valley of Tontouta. It is moreover recommended to gather mining actors to get an inventory of protection measures already implemented and to try to launch a collaboration between institutions (DIMENC and DENV) and mining operators (SLN, Ballande, SMGM) in order to preserve the Tontouta flora.

Bibliography

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

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.

Experts

Assessor(s): Tanguy, V., Veillon, J., Amice, R., Cazé, H., Chambrey, C., Dubreuil, M., Fleurot, D., Garnier, D., Lagrange, A., Lannuzel, G., Leborgne, T., Letocart, D., Letocart, I., McCoy, S., Villegente, J.

Reviewer(s): Maura, J.

Contributor(s): Wulff, A.

Facilitator(s): Tanguy, V.