Rodrigues Islets (6661)
Mauritius, Africa

Site overview

KBA status: confirmed

Year of last assessment: 2014

National site name: Rodrigues Islets

Central coordinates: Latitude: -19.7600, Longitude: 63.3880

System: marine, terrestrial

Elevation (m): 0 to 50

Area of KBA (km²): 2.22902

KBA classification: Regional

Legacy site: Yes

Site details

Site description: The site comprises 18 islets of over 1 ha extent (and some smaller stacks or rocks) that lie within the reef that surrounds the mainland of Rodrigues. This account concentrates on the three thought to have the most potential for rehabilitation and subsequent marooning for native Rodriguan birds and increases in seabird populations, based mainly on existing flora and fauna: Ile Cocos, Ile aux Sables and Crab Island. Cocos and Sables (usually reported as covering 14 ha and 8 ha respectively, although possibly larger) are almost identical coralline sand cay islets 1 km apart, about 4 km west of the western tip of Rodrigues. They support a mixture of trees (mainly exotic Casuarina equisetifolia), shrubs (especially Pisonia grandis), herbs and grasses typical of littoral zones, and are managed for ecological rehabilitation with small-scale controlled tourism (day visits currently only to Cocos). Crab, the largest of the 18 islets (44.5 ha), lies 400 m off the south-west coast of Rodrigues and rises to 50 m. It is partly basaltic and partly coralline, with terraces sloping to the south and east from a high escarpment. Its vegetation is a mixture of grasses, shrubs and trees, including several native (non-littoral) species. It is used as an animal-breeding centre. The other islets support only exotic grassland or scrub, with scattered native plants, on coralline rock or basalt; Frégate (12 ha) has native littoral vegetation and may warrant rehabilitation. Only two other islets (Cat and Gombrani) exceed 10 ha.

Rationale for qualifying as KBA: This site qualifies as a Key Biodiversity Area of international significance that was identified using previously established criteria and thresholds for the identification of Important Bird and Biodiversity Areas (IBAs) and for which available data indicate that it does not meet global KBA criteria and thresholds set out in the Global Standard. KBA identified in the CEPF Ecosystem Profile of the Madagascar and Indian Ocean Islands Hotspot (2014). Taxonomy, nomenclature and threat status follow the 2013 IUCN Red List. The following KBA trigger species occur at this site but are not yet available in WBDB, either because they have only been globally Red-List-assessed recently (in 2012-2013; global Red List category is given in brackets, where triggering the Vulnerability KBA criterion) or because they have not yet been globally Red-List-assessed (most of these taxa are nevertheless listed as valid in Catalogue of Life or Tropicos); many of the latter species may prove to be globally threatened, or are already listed as regionally or nationally threatened, and nearly all of the following species are also likely to be endemic to the Hotspot, often with very restricted known ranges, thus also triggering the Irreplaceability 1 KBA criterion: PLANTAE: Cynanchum guehoi; Dodonaea angustifolia; Mathurina penduliflora; Oldenlandia sieberi var congesta; Phyllanthus dumetosus; Sarcanthemum coronopus.

Additional biodiversity: See Box for key species. These islets have high potential for rehabilitation, which may include marooning of native landbird species. Cocos and Sables have seabird colonies dominated by Anous species; a single census (1998) estimated a total of 10,000–14,000 birds, but the annual total is likely to be much more. The same census revealed less than 1,000 pairs of A. stolidus and 4,000–6,000 pairs of A. tenuirostris, but ringing evidence suggests that much higher numbers nest during the course of a full year, and numbers may also increase as management continues. In 1998, Cocos and Sables also held Phaethon lepturus (a few pairs), Sterna fuscata (150 pairs in 1998), and Gygis alba (20 pairs; the only population in the Mascarene Islands), while Ile Frégate has a small colony of Puffinus pacificus. Cocos and Sables are also the main area on Rodrigues for migratory waders, although no more than 100 birds are generally present. Non-bird biodiversity: Plants: Sarcostemma odontolepis (R), Terminalia bentzoe rodriguesensis (V), Myoporum mauritianum (E), endemic Rodriguan palms.

Delineation rationale: Type 1 marine IBA: suitable for the seaward extension approach.

Habitats

Land use: nature conservation and research | tourism/recreation

Threats

Summary of threats to biodiversity at KBA: Cocos and Sables are both Nature Reserves. All Rodrigues islets were assessed in 1993 for rehabilitation potential, and Cocos, Sables and Crab were identified as the highest priorities. Rehabilitation may involve mammal eradication, weed control, translocation of birds and reptiles, revegetation and habitat and site manipulation, accompanied by control of access. Ile aux Sables is closed to visitors; landing there and on Cocos is controlled by the Forestry Division, and a warden is stationed on Cocos. Steps towards rehabilitation taken by 1998 included eradication of Mus musculus from Cocos and Sables (leaving these islets mammal-free), partial removal of exotic plants from Cocos and Gombrani, and introduction to Cocos of Rodriguan endemic palms threatened on the Rodrigues mainland by hybridization with Mauritian taxa. Threats or hurdles to rehabilitation remain: Crab has cats, Mus musculus, Rattus rattus and sheep; other islets have dogs and goats in addition; major problem weeds are Leucaena leucocephala and Lantana camara; human disturbance threatens the seabird colonies; and native wildlife on islets, especially any landbird populations introduced in future (if this is done), would be vulnerable to cyclones.

Additional information