The site comprises the whole of Green Mountain situated just off-centre of Ascension Island. Green Mountain has the highest elevation in Ascension peaking at 859 m. To the north and west the land forms a gently sloping plain with volcanic vents. The site includes two vegetative zones, the middle zone (330 m – 600 m) extensively covered with shrubs and grasses and the humid zone (above 600 m) which is extensively covered in introduced vegetation in some areas amounting into cloud forest.
See table for key species. This inland site is important for one of the 11 resident seabird species, Gygis alba. The other species of Oceanodroma castro, Phaethon aethereus, P. lepturus, Sula dactylatra, S. sula, S. leucogaster, Fregata aquila, Onychoprion fuscata, Anous stolidus and A. minutus breed on Boatswainbird Island, Letterbox Peninsula, the Wideawake Fairs and also the coastal cliffs and rock stacks. Puffinus lherminieri is present in the area, and although not confirmed, it is possible that this species may be breeding on Green Mountain (Ratcliffe et al., 2009). There are five resident landbirds, all introduced; Francolinus afer (introduced 1851), Acridotheres tristis (introduced 1879 and 1880), Passer domesticus (introduced 1985 onwards, Georgetown only), Estrilda astrild (introduced 1860) and Serinus flaviventris (introduced 1890). There are also records of non-breeding visitors and vagrants with fewer than five records. The former include Bubulcus ibis, Gallinula chloropus, Arenaria interpres, Apus apus, Hirundo rustica, and Delichon urbica. In the fossil record, two species are known, an extinct night heron Nycticorax nov. sp. and the extinct flightless rail Atlantisia elpenor.
Non-bird biodiversity: There is a long list of invertebrates, including historic records of endemic pseudoscorpions Apocheiridium cavicola and Allowithius ascensionis. Yellow and purple land-crabs Johngarthia lagostoma occur throughout the main island, returning to the sea to breed each year. Other than some of the invertebrates, all land animals are introduced and includes Equus asinus, Oryctolagus cuniculus, Liolaemus wiegmannii and Hemidactylus mercatorius. The indigenous flora of Ascension Island is minimal with approximately 25 vascular plants, and 7 endemics.. There are 77 recorded species of bryophytes on Ascension, of which 15 are believed to be endemic to the island. The many introduced plants include Acacia, Alpinia, Araucaria, Bambusa, Buddleia, Erythrina, Eucalyptus, Ficus, Grevillia, Juniperus, Mangifera, Musa, Olea, Pinus, Podocarpus and Psidium. In the humid zone some of this introduced vegetation has amounted to cloud forest.
BirdLife International (2020) Important Bird Areas factsheet: Green Mountain. Downloaded from http://www.birdlife.org on 02/04/2020.