Tropical Montane Cloud Forests: Montane cloud forests on remote islands of Oceania: the example of French Polynesia (South Pacific Ocean)

Small, isolated patches of tropical montane cloud forest (TMCF) are found in many remote islands of the Pacific region (Oceania). French Polynesia comprises 37 high volcanic islands and islets, all located at more than 5000 km from the nearest continents. TMCFs are found on 12 of them (Huahine, Moorea, Raiatea, Tahaa, and Tahiti in the Society Islands, Fatu Hiva, Hiva Oa, Nuku Hiva, Tahuata, Ua Huka, and Ua Pou in the Marquesas Islands, and Rapa in the Austral Islands), with a total area of up to 8000 ha. Their current individual extent ranges from less than 20 ha (Huahine, Rapa, Tahaa) to c. 1000 ha (Hiva Oa, Nuku Hiva) and more than 5000 ha (Tahiti), the other islands having less than 100–200 ha each. TMCFs are located between 300–400 m.a.s.l. and up to 1600–1800 m.a.s.l. (Tahiti), but are more often found above 800–900 m.a.s.l. They are generally located on the upper slopes of valleys, on high-elevation plateaux, and in gullies and ridges below the summits, with annual rainfall ranging between 3000 and 8500 mm. TMCFs are floristically the most diverse of all plant communities in French Polynesia, with the highest endemism and number of biological types. Between 60% (Moorea, Tahiti, and Rapa) and more than 70% (Raiatea, Hiva Oa, Ua Pou, and Ua Huka) of the endemic vascular plant species are found in the TMCFs, and between 25% (Moorea and Rapa) and 50% (Hiva Oa, Nuku Hiva, and Ua Pou) of these endemics are restricted to these habitats. The TMCFs of the different archipelagos of French Polynesia share many common genera of flowering plants with other Polynesian island groups (e.g. Cook Islands, Samoa, Hawaiian Islands). Current threats include road construction, hydro-electricity development, grazing or trampling by feral ungulates (pigs, goats) and invasion by alien plant species, especially the tree Miconia calvescens in Tahiti and Moorea. Habitat conservation and invasive pest management is urgently needed to save the TMCFs in French Polynesia which still remain unprotected.