The site covers the south-western part of the island, south of a line linking Powell Point and ‘The Buoys’ in the south-east and Horse Pasture Point in the north-west, via Clifford Arboretum in the interior, together with Egg Island (79 m), Speery Island (120 m) and all other offshore islets, stacks and rocks. All four vegetation zones on the island are represented. Below 350 m, c.25% of the area, the landscape is arid with large-scale erosion, dominated by Suaeda, Lantana and Carpobrotus. This gives way to pasture and non-indigenous woodland, up to 500 m, dominated by Pennisetum, Cynodon and Digitaria, with Acacia and Pinus. Above 500 m lies ‘moist’ and ‘semi-moist’ grassland, woodland (dominants include Agrostis, Pennisetum and Stenotaphrum, with Podocarpus, Acacia and Pinus) and flax Phormium tenax plantations. At High Peak is a small remnant native thicket of endemic Dicksonia ferns and Melanodendron cabbage trees. The coast is dominated by imposing sea cliffs, rising mainly to between 300 m and 570 m. High Peak (798 m), in the far north-east, is the highest point. Egg Island, off the north-west lee side, is a mass of pale bedded lavas with an apparent dip towards the south-west, while nearby Peaked Island (32 m) is a sharp pyramid of scoriaceous slag. Speery Island is a spectacular steep-sided, jointed monolithic pipe of paler alkaline trachyte, whilst neighbouring Salt Rock (40 m) is a remnant of a wide basaltic dyke. The remaining islets and stacks are basaltic. Vegetation (shrubs, grasses, weeds) has been noted only on Lighter Rock, Ladies Chair, Egg Island, Peaked Island and Thompson’s Valley Island, all in the lee. Lichens have been found at the summit of Egg Island. The heaviest guano deposits are on Egg, Peaked and Speery Islands. In the south, the Speery Island group of outliers is much more exposed and, but for Speery Island itself, has not been visited by ornithologists and may therefore harbour unrecorded seabirds. Included in the IBA are three important breeding sites for Charadrius sanctaehelenae, i.e. at Broad Bottom, Southern Pastures and Man and Horse. There is an important fossil site at Sandy Bay.
See Box and Table 2 for key species. Although as many as 45 bird taxa have been recorded, there are now only seven known species of breeding seabirds and 11 species of resident landbirds, i.e. Oceanodroma castro, Phaethon aethereus, Sula dactylatra, Alectoris chukar, Phasianus colchicus, Gallinula chloropus, Charadrius sanctaehelenae, Sterna fuscata, Anous stolidus, A. minutus, Gygis alba, Columba livia, Geopelia striata, Acridotheres tristis, Foudia madagascariensis, Padda oryzivora, Estrilda astrild and Serinus flaviventris. Sula leucogaster may also breed. Speery Island has the highest seabird breeding diversity in the IBA with, probably, seven species. There are also records of non-breeding visitors and vagrants with fewer than five records. The former include Diomedea exulans, Pterodroma mollis, Oceanites oceanicus, Fregetta grallaria, Fregata sp., Ardea cinerea, Bubulcus ibis, Ciconia ciconia, Calidris alba, Stercorarius parasiticus, S. pomarinus and Sterna paradisaea. The site requires further study.
Non-bird biodiversity: As with North-east St Helena (SH003), the endemic invertebrates are of particular importance.
BirdLife International (2020) Important Bird Areas factsheet: South-west St Helena. Downloaded from http://www.birdlife.org on 14/08/2020.