Europa is an island in the southern Mozambique Channel, 350 km west-south-west of Morombe, Madagascar. It is one of the least modified coralline islands in the western Indian Ocean and was formed from the progressive filling of an ancient atoll which appeared 90,000 years ago. It is composed of a central lagoon largely surrounded by mangrove Rhizophora mucronata; shrubland, bushland and thicket, dominated by Psiadia altissima, Suriana maritima and/or Pemphis acidula; Euphorbia stenoclada dry forest; Sclerodactylon macrostachyum grassland; halophile vegetation (Arthrocnemum indicum) and a fringing beach- and dune-system rising to 12 m, the highest land on the island. In all, 33–46 angiosperm species occur. Eighteen people live on the island in shifts of 45 days; three occupy a meteorological station, and 15 are military servicemen.
See Box for key species. Europa holds a diverse and very large population of breeding seabirds, with five species occurring in globally significant numbers, and it is also the only known breeding site outside Madagascar and Aldabra for the globally near-threatened Ardeola idae (up to 15 pairs in 1996). Additional nesting waterbird and seabird species are Fregata minor (700–1,100 pairs; the second largest colony in the western Indian Ocean), Puffinus lherminieri (50–100 pairs; probably of the subspecies P. l. bailloni, previously thought to be endemic to the Mascarene Islands), Egretta dimorpha (abundant breeding resident) and Sterna caspia (10–15 pairs). The seabird community appears to be biogeographically isolated from others in the region as it shows several unique features, including the presence of an endemic subspecies, Phaethon lepturus europae. Three landbird species are present, of which one, the abundant Zosterops maderaspatanus voeltzkowi, is an endemic subspecies. A wide range of migrant and vagrant species have been recorded.
Non-bird biodiversity: The island is a nesting site for the sea-turtle Chelonia mydas (EN), and Eretmochelys imbricata (CR) and Caretta caretta (EN) are also present. There are two endemic lizard subspecies (Mabuya comorensis infralineata and Cryptoblepharus boutonii bitaeniatus). Overall, the coral island ecosystem is one of the finest in the Indian Ocean.
Pressure/threats to key biodiversity
Europa has received little attention from the scientific or conservation communities, yet it seems hardly more damaged than the much more famous Aldabra atoll (Seychelles). It was made a Nature Reserve in 1975. Classification as a Strict Nature Reserve by Arrêté Ministériel is needed to improve the site’s protection (see ‘Conservation infrastructure and protected-area system’). Seabirds suffer from predation by introduced Rattus rattus and by two landbirds Tyto alba and Corvus albus, which are probably native, but which have populations maintained at high levels by human and exotic rodent populations. Further threats to native ecosystems are browsing by introduced goats Capra hircus (which number over 300), invasion by exotic plants (Agave sisalana and Furcraea foetida are already present, others may arrive) and animals (further introductions are a danger), fires and occasional human disturbance. To date, conservation activities include experimental eradication of Rattus rattus from a small islet to test the effect on seabird nesting success, control of Corvus albus, waste control, and monitoring of vegetation and seabird distributions.