The site comprises the central ridge and upper slopes of the island of Mwali, occupying the interior of the western two-thirds of the island above 500 m. The ridge is higher than 700 m for about 8 km of its length, between Mlédjélé in the east and the Chalet St Antoine in the west; the highest part being Mzé Koukoulé (790 m). Numerous small valleys extend to the coast on either side of the ridge. Habitation is restricted to the coast, except on the deforested Djandro Plateau in the east of the island. This site contains the catchments of the towns Fomboni (the island capital), Nioumachoua and Miringoni.The major habitat is mixed montane forest, rich in epiphytes and pteridopytes, but distinct from that of Ndzuani and Ngazidja. Low, poorly stratified cloud-forest dominates the ridges. In less exposed sites, a more diverse, stratified forest with a 30–40 m canopy and emergents up to 48 m is found. Dry evergreen forest survives only above Miringoni. Underplanted forest forms a mosaic with intact forest above c.600 m, but dominates below this level. Thickets of exotic Syzygium jambos also occur, especially along riverbanks, where they may be mixed with other shade-bearing exotics and native species. Other abundant, invasive exotics are Lantana camara and Clidemia hirta, but not yet (1996) Psidium cattleianum. Forest plantations (Pterocarpus indicus, Eucalyptus robusta, Tectona grandis) exist in small areas, and these trees are also widely scattered. A survey in 1983 reported 1,553 ha of intact forest and 1,904 ha of underplanted forest. The area of intact forest has certainly declined by a further several hundred hectares since then; an estimate of 1,145 ha was made in 1996. The main forest-use is cutting of trees and associated conversion for agriculture. Non-timber forest products are also harvested (such as fruits of Tambourissa spp.).
Mwali supports a unique forest bird community, including two Mwali-endemic species: the newly-described, threatened Otus moheliensis (common in intact forest, less so in underplanted forest), and the Near Threatened Nesillas mariae. Six other restricted-range species and one seabird also breed, of which one, Columba pollenii, is near-threatened. Twelve Mwali-endemic and seven Comoro-endemic subspecies are also present, along with the near-threatened, but non-endemic, Circus maillardi (found in all habitats). Most of the threatened and restricted-range species are associated with the intact forest and are fairly common in it, although all have been seen outside it (some even at sea-level). Puffinus lherminieri breeds in forest at this site.
Non-bird biodiversity: Evergreen forest is likely to be rich in Mwali- and Comoro-endemic species. Mammals: Pteropus livingstonii (CR; endemic to Ndzuani and Mwali, Mwali population c.60), Rousettus obliviosus (LR/nt; Comoro-endemic species), Eulemur mongoz (VU; introduced, but very important population on Mwali). Reptiles: six Comoro-endemic species: Lycodryas sanctijohannis, Paroedura sanctijohannis, Phelsuma v-nigra, Amphiglossus johannae, Mabuya comorensis, Typhlops comorensis. Butterflies: one Mwali-endemic and four Comoro-endemic species (three shared only with Ndzuani).
BirdLife International (2019) Important Bird Areas factsheet: Mont Mlédjélé (Mwali highlands). Downloaded from http://www.birdlife.org on 19/04/2019.