Located c.10 km east of Praslin, La Digue is the fourth-largest of the granitic islands. It is surrounded by beautiful sandy beaches, rocky coasts and a fringing coral reef. Traditional activities, including copra-production and fishing, were the basis of the economy until the tourism industry began in the 1970s. The western plateau (161 ha) was originally entirely covered with marshland and an extensive native forest of Calophyllum inophyllum and Terminalia catappa. Today, only 25% of its area retains indigenous woodland. Significant drainage has taken place, but an important wetland of reedbeds, small ponds and mangroves, Lanmar Soupap, remains. The rest of the plateau is now occupied by housing and tourism developments, coconut plantation and farmland. Little development has taken place on the hill, Nid d’Aigles, in the east of the island. Much drier than the plateau, it supports mixed woodland with both exotic and indigenous trees, small streams, large granite boulders and caves. The site includes La Veuve Special Nature Reserve.
See Box and Table 2 for key species. La Digue is the only island where Terpsiphone corvina is known to breed, all other populations historically present in other islands of the Praslin group having progressively disappeared (although a few birds have been reported on Marianne since 1997). Fifty-four of the 69 confirmed territorial pairs are concentrated on the western plateau, with the total population estimated to be 150–200 birds. There is a cave at 250 m on the hill with two small colonies of Collocalia elaphra (35–45 pairs). Important populations of Alectroenas pulcherrima (400–600 pairs), Hypsipetes crassirostris (2,000–4000 pairs) and Nectarinia dussumieri (1,500–3,000 pairs) also occur. Several hundreds of pairs of Streptopelia picturata picturata are also present, as well as small numbers of Phaethon lepturus and Gygis alba. The wetland regularly hosts several species of migrant and resident waterbirds,including 10–20 pairs of the rare Ixobrychus sinensis.
Non-bird biodiversity: Amphibians include one species of frog (Tachycnemis seychellensis) and three caecilians, all endemic to Seychelles. The western plateau marshes are a stronghold for the rare terrapins Pelusioscastanoides and P. subniger. The Seychelles sheath-tailed bat Coleura seychellensis silhouettae (CR) is present on La Digue and large numbers of the bat Pteropus seychellensis also occur.
Pressure/threats to key biodiversity
The small Special Reserve of La Veuve has been extended by 10 ha through a land acquisition programme conducted by the Ministry of Environment and Transport and financed by various sponsors, including the Dutch Trust Fund, the Environment Trust Fund, and private donors. A second phase to include the last remnants of native plateau forest is urgently needed. The main threats include continuing deforestation of the plateau for housing and tourism developments and illegal felling and ring-barking of trees. Invasion of the marsh by water lettuce (Pistia) and water hyacinth (Eichhornia) is also of concern, as is increased disturbance of the swiftlet colony by unauthorized visits.