Protected Areas and World Heritage Programme

NAME Plaine des Lacs

LOCATION 22^o15'S, 166^o55'E; about 50 km east of Nouméa and 10 km south of the Nouméa-Yaté road, Yaté Commune, near the southeastern tip of Grande Terre,

AREA About 5,000 ha.

ALTITUDE 200-260 m.

OVERVIEW A group of permanent freshwater lakes and marshes in depressions on a large plain surrounded by hills near the southeastern tip of Grande Terre. The area is of exceptional botanical and zoological interest, and supports many endemic species.

PHYSICAL FEATURES The Plaine des Lacs is a slightly undulating plain about 10 km long by 5 km wide, with altitudes varying between 260 and 240 m. The numerous depressions are occupied by permanent freshwater lakes, ponds and marshes, the largest lakes being Lac en Huit and Grand Lac. The plain is drained by the Riviere des Lacs, a tributary of the Yate, from its source in Lac en Huit across the northern edge of the plain. After the 10 m drop of Madeleine Falls (La Chute de la Madeleine), the river enters Yate Lake beyond its confluence with Pernod Creek which drains the exterior of the northwest slopes of the Plaine des Lacs. A narrow alluvial zone 1-5 m wide along the banks of the Riviere des Lacs is subject to flooding during high water. The geological substrate comprises peridotitic rocks which make up much of southern Grande Terre; the soils are ultrabasic ferric latosols and very poor in chemical elements except magnesium, iron and chromium. The deep horizons have concentrations of nickel and manganese that are higher than normal. In the lowest, central portions of the plain, the soils are more or less peaty.

The soils show a clear tendency toward induration in the form of fine ferruginous gravel, boulders of laterite or even solid laterite crusts several metres thick and completely impermeable.

The climate is tropical oceanic with an average annual rainfall of 2,500-3,000 mm and a mean annual temperature of between 22^o and 23^oC.

ECOLOGICAL FEATURES Freshwater marshes throughout the Plaine des Lacs are dominated by Xyris pancheri (Xyridaceae) and Schoenus brevifolius (Cyperaceae) (Dahl, 1980). In the Madeleine Falls area, the aquatic vegetation is poor in species, but includes a carnivorous species of Utricularia, a relatively rare aquatic fern Blechnum francii, and a species of Eriocaulon endemic to the south of Grande Terre (Jaffre, 1988). The narrow alluvial zone along the Riviere des Lacs supports a distinctive community dominated by the two gymnosperms Nageia (Decussocarpus) minor and Dacrydium guillauminii in a shrub layer 3-5 m high. D. guillauminii is known only from the banks of the Riviere des Lacs. A low discontinuous shrub layer in this alluvial zone comprises Melaleuca brongnartii, Xanthostermon aurantiacum, Homalium kanaliense, Pancheria communis and Cloezia aquarium. The herbaceous layer, which is absent on gravelly soil but continuous on alluvial soil, comprises the Cyperaceae Costularia xyridiodes, Schoenus brevifolius, Chorizandra cymbaria and Tricostularia guillauminii, and the Xyridaceae Xyris pancheri and X. neocaledonica (Jaffre, 1988). The dominant vegetation of drier ground is a semi-wet woody/herbaceous scrub with two endemic species of gymnosperms, an endemic fern and numerous lichens. Plant communities in the Madeleine Falls area have been described by Jaffre (1988) and are summarized in IUCN (1991).

LAND TENURE Owned by the French Government and the Territory. Concessions for mineral exploration have been granted, but no mining was in progress in 1991.

CONSERVATION MEASURES TAKEN A Special Botanical Reserve of about 400 ha (Reserve Speciale Botanique de la Chute de la Madeleine) was created along the Riviere des Lacs in 1990 (Resolution No.39-90/APS of 28 March 1990). This is located on the north-northwest edge of the Plaine des Lacs and is bordered in part by the Riviere des Lacs. Legislation prohibits the collection, removal, displacement or harvesting of any mineral or vegetation. Seven small protected areas, totalling 4,466 ha, have been established in the vicinity of the Plaine des Lacs. Together these constitute the Southern Special Botanical Reserve (Reserve Speciale Botanique du Sud), established by Resolution No.108 in May 1980. All mining activity is prohibited in these reserves (Order No.72-395/CG of 17 August 1972).

CONSERVATION MEASURES PROPOSED Dahl (1980) recommended the establishment of a reserve on the Plaine des Lacs to protect the lake fauna and marsh flora. More recently, it has been recommended that a Special Faunal and Floral Reserve be created to protect the entire plain.

LAND USE No information.

DISTURBANCES AND THREATS The growing numbers of visitors to the region have caused considerable damage; trees have been burned and broken, and rubbish has been dumped in the area. In the medium or long term, the principal threat comes from mining development (nickel, iron, chromium etc.) because of the potential mineral value of the region. Some mining activities began in the area in 1992.

HYDROLOGICAL AND BIOPHYSICAL VALUES No information.

SOCIAL AND CULTURAL VALUES The wetlands have some potential for tourism and conservation education. The region is of great interest to scientists and is becoming the object of intensive scientific study.

NOTEWORTHY FAUNA An endemic species of fish, Galaxias neocaledonicus, is known only from the Plaine des Lacs. It has been found in Lac en Huit and may also occur in the Madeleine Falls Special Botanical Reserve. This nocturnal species is believed to be a "living fossil" with Gondwanian affinities with New Zealand. Other aquatic species of scientific interest include two genera and three endemic species of freshwater snails, two species of shrimps, which are possibly endemic to the lakes, and a sponge. No information is available on the waterfowl.

NOTEWORTHY FLORA The Madeleine Falls area is exceptional for the diversity of its flora, the high concentration of gymnosperms and the presence of many rare species such as the aquatic fern Blechnum francii and an endemic carnivorous bladderwort (Utricularia sp.). Jaffre (1988) lists 168 species of phanerogam and ferns belonging to 53 families. About 95% of these are endemic to New Caledonia, and about 20% are endemic to the south of Grande Terre. The area is rich in lichens, many of which are apparently undescribed.

SCIENTIFIC RESEARCH AND FACILITIES Botanists from the Botanical Laboratory at ORSTOM carried out a survey of the vegetation and detailed inventory of the flora of the Madeleine Falls area in 1988 (Jaffre, 1988).

CONSERVATION EDUCATION The wetland is situated close to the small town of Yate, and could have some potential for conservation education.

MANAGEMENT AUTHORITY AND JURISDICTION Service des Forêts et du Patrimonie Naturel (SFPN), Direction du Développement Rurale Province Sud. Responsibility for management of the Madeleine Falls Special Botanical Reserve rests with the Service de l'Environnement et Gestion des Parcs et Reserves.

REFERENCES Dahl (1980); IUCN (1991); Jaffre (1988).

REASONS FOR INCLUSION 1a, 2a, 2b, 2d. A unique wetland; much the largest area of freshwater lakes and marshes in New Caledonia, with many endemic species.

SOURCE Association pour la Sauvegarde de la Nature Néo-Calédonienne.