Entrecasteaux: Up to 400 Green Turtle Nests in a Single Night Reveal a Refuge Under Climate Pressure

Entrecasteaux, more than two days’ voyage from Nouméa, hosts an exceptional reproduction of green turtles. Access is forbidden to protect these isolated beaches, but the climate is now altering their incubation conditions. Research initiated since 2025 aims to measure this risk before it transforms this refuge.

Entrecasteaux protects isolated beaches where green turtle nesting reaches a rare scale

The Entrecasteaux atolls lie north of Grande Terre, far from inhabited areas. UNESCO listed this ensemble as a World Heritage Site in 2008, and protection has progressed further since. Since January 1, 2024, regulation places the entire area in full reserve.

Huon, Surprise, Fabre et Le Leizour accueillent les principales plages de ponte de l’archipel. Le Parc naturel de la mer de Corail estime qu’environ 47 000 femelles viennent pondre chaque année. Cependant, une trace ne correspond pas toujours à une tortue différente.

At Huon, nesting nights can approach 400 nestings without representing 400 different turtles

Between November and February, the Huon beach changes its appearance from the tracks left during the night. Scientists count about 200 nocturnal nestings, with peaks near 400. In parallel, the WWF notes up to 600 nestings during the seasonal peak.

Those figures, however, describe different phenomena. A montée sur la plage can end without a nest if the female abandons her site. Furthermore, the same turtle may return to nest roughly two weeks later during the season.

The long runs of fieldwork have revealed the site’s real scale. Between 1988 and 2021, teams accumulated 1,456 counting nights at Entrecasteaux. Depending on the seasons, researchers estimate between 5,513 and 103,511 nesting activities.

The Megafauna program measures nest warmth and the rapid evolution of Entrecasteaux beaches

Since 2025, the Megafauna program tracks turtles across two successive breeding seasons. Teams count the tracks, monitor the emergences, and retrieve the thermometers they buried in the nests. Thus, these data should clarify reproductive success and the male-to-female ratio.

Temperature plays a direct role during egg incubation. Warmer nests favor females, while cooler temperatures favor males. Moreover, excessive heat can kill embryos and reduce the hatching success.

Researchers also monitor the shape of islets with drones. In 2026, they used a first-time LiDAR to map the relief precisely. Thus, they measure erosion, accretion, and areas threatened by submersion.

The turtles depart Entrecasteaux on journeys over 1,000 kilometers, greatly widening the protection challenge

The reserve protects reproduction, but not the entire life cycle. After nesting, some females reach Australia, Papua New Guinea, or other New Caledonian sectors. These migrations sometimes exceed 1,000 kilometers and connect several zones of the Coral Sea.

The green turtle has been listed since October 2025 as Near Threatened on the IUCN Red List. Its global population has increased by about 28% since the 1970s. However, Entrecasteaux remains exposed to warming, erosion, and rapid transformations of its beaches.