The Northern Islets
There are 6 northern islets which are very important for their biodiversity, especially seabirds (Pigeon Rock and Serpent Island), reptiles (Round Island and Flat Island), and remnant populations of coastal species and palm-rich forest (e.g. Round Island, Ilot Gabriel, Gunner’s Quoin). All of these islets are now free from rats. The main reason for this rich biodiversity is due to their relative isolation.
Another well known northern islet is ile d’Ambre. This islet is near the coast, thus easily accessible by everyone. It has suffered lots of degradation and thus lost its native biodiversity which are still present on neighboring islets.
Round Island and Serpent Island
The most northerly of the offshore islands are Round Island which is not round, and Serpent Island which does not have any serpents. These are two of the most important islands for biodiversity as neither ever had any rats on them.
Round Island is of exceptional biological importance because:
1. It is the largest area, and the only relatively large island in the Mascarenes free of introduced mammals and reptiles; it is also one of the very few remaining elevated topical islands in the world that is rodent-free. Following the eradication of goats in 1979 and rabbits in 1986 the palm-rich forest is coming back, with the help of restoration planting.
2. It is the largest area of native vegetation, and only relatively large island in the Mascarenes, free of major woody weed species.
3. It supports the last remnants of a palm rich forest once characteristic of the northern plains of Mauritius.
4. It is home to at least ten threatened native plant species such as Palmiste bouteille (Hyophorbe lagenicaulis), vacoas (Pandanus vandemeerschii) and Latanier bleu (Latania loddigesi), including nine taxa endemic to Mauritius, and is potential habitat for many threatened plant species that could be introduced or reintroduced.
5. It is home to possibly eight taxa of native reptiles including six that are endangered: two geckos, two skinks and two primitive boa snakes. All of these taxa are endemic to the Mascarenes and five now occur only on Round Island.
6. It is the only known breeding ground in the Indian Ocean for the rare Round Island petrel and an important breeding site for three other species of seabird.
These biological values were under threat as a result of over 150 years of modification by introduced rabbits and goats. The eradication of goats in 1979 and rabbits in 1986 saved much of the remaining biota of Round Island from destruction and has facilitated the possibility of the restoration of the island to a condition more like that of the nineteenth century.
Serpent Island is an important seabird colony with almost no vegetation. This barren rock is home to sooty terns (Sterna fuscata), brown noddy (Anous stolidus) and lesser noddy (Anous tenuirostris) terns etc. and a tarantula that has yet to be described scientifically.
Flat Island, Ilot Gabriel & Pigeon Rock
These three islets to the north of Mauritius have important values for biodiversity, history and tourism.
Pigeon Rock National Park is a volcanic plug, rising vertically out of the sea and is a seabird colony.
Ilot Gabriel Nature Reserve is a small island with coastal sand dune vegetation. Much of the island is covered by Baume de l’Ile Plate (Psiadia arguta), the only place where this plant grows.
Flat Island Nature Reserve is separated from Ilot Gabriel by a narrow lagoon rich in marine life. It is the largest of the northern islets (253ha). In spite of its degraded nature, the islet is home to two species of reptile unique to this island; it is used as a breeding site for sea birds, and also has remnant populations of some plant species that once formed part of the palm-rich forest. The islet was used a quarantine station during the 19th century and the remaining infrastructure is of historical and cultural interest. Today, the island is a popular day-trip destination for tourists to enjoy the quiet beaches and lagoon.
Gunner’s Quoin National Park
Gunner’s Quoin is shaped like a whale. The palm-rich forest is very degraded by prune malgache (Flacourtia indica), but it is important for several native species, including Gagnebina pterocarpa (acacia indigène), Lomatophyllum tomentorii (mazambron marron), and Dicliptera falcata (last recorded in 1858, and thought extinct until rediscovered in 2005). The island is also used by seabirds for breeding.
Ile d’Ambre National Park
Situated to the north east of the mainland, Ile d’Ambre is a popular weekend destination for Mauritians. The island is badly degraded, although it still has some Latanier bleu (Latania loddigesi) and mangrove forests remaining.