Chapter 2. Forest and Terrestrial Biodiversity of Mauritius 2.1 Overview of Biodiversity Mauritius has an area of 1,865 km2, of which 30% is considered forested. The area of good quality native forest, (i.e. that with more than 50% native plant cover, Page & d’Argent 1997), is estimated to cover less than 2% of the island (NEAP 1999, MWF unpublished, Fig.2.1). The rest consists of plantation forestry, deer-ranches or highly degraded vegetation invaded by alien plant and animal species. As a result Mauritian biodiversity is amongst the most threatened in the world.
Figure 2.1 Forest cover in Mauritius (Page and d’Argent, 1997)
Fifteen vegetation types have been classified (Vaughan & Wiehe 1937), varying 13
in species composition and structure, and ranging from coastal sand dune vegetation to cloud forest. Remnants of some vegetation types are concentrated in the Black River Gorges National Park in the south west, the Bambous Mountain Range in the south east and the Moka-Port Louis Ranges in the North West. There are also some isolated mountains which are important e.g. Corps de Garde, Trois Mamelles and Le Morne Brabant, and several offshore islands with remnants of coastal and mainland diversity. Table 2.1: Native diversity of selected groups in Mauritius, with respective total number of extinctions. Numbers in brackets indicate the number of endemic species. Number of native species Angiosperms1 Mammals2 Birds2 Reptiles2 Butterflies3 Snails4 671 (311) 5 (2) 30 (24) 17 (16) 37 (5) 125 (81) % species endemic 46% 40% 80% 94% 14% 65% Number of extinct species 77 (42) 2 (1) 18 (15) 5 (5) 4 (1) 43 (36) Number of extant species 594 (269) 3 (1) 12 (9) 12 (11) 33 (4) 82 (45)
1. Page & D’ Argent, 1997; 2. Cheke, A. S. & Hume, J. P. in press; 3. Williams,1989; 4. Griffiths & Florens in prep. 2.1.1 Flora There are 671 species of indigenous flowering plant recorded in Mauritius, of which 311 are endemic (Mauritius has eight endemic plant genera), and 150 are endemic to the Mascarene Archipelago (Page & d’Argent, 1997; Strahm, 1994). 77 of these indigenous species are classified as extinct. Of the extant flowering plant species, about 35% are already classified as threatened as per IUCN criteria (Bachraz & Tezoo, 1997). The most recent study of lower plants estimates that there are 207 taxa consisting of 89 genera of mosses and 59 genera of hepatics (Tixier & Gueho, 1997). There are about 200 species, subspecies and varieties of pteridophytes, of which 13 species are endemic, and 40 are extinct (Bachraz, 2000). 2.1.2 Fauna 24 of the 52 native species of forest vertebrate that were known to have occurred on Mauritius and adjacent islets are now extinct, including the Dodo (Raphus cucullatus), a giant parrot (Lophopsittacus mauritianus) and two species of giant tortoise (Cylindrapsis spp.). Many of the extant species are threatened. Mammals – The only native mammals are bats. Of the three species of fruit bat (Pteropus niger, P subniger and P.rodricensis) known to have occurred, only one (the Mauritian fruit bat P. niger) remains and is still locally common. P. subniger is extinct. P.rodricensis still occurs on Rodrigues. There are two native insectivorous bat species (Taphosus mauritianus & Mormopterus acetabulosus) that are also found on Reunion and mainland Africa (IUCN, 2003). Birds - Twelve species of land bird have so far escaped extinction (Table 2.1). Of these, 14
nine are threatened according to the IUCN Red List (2003). Species recovery programmes have saved three of these species from probable extinction: The Mauritius Kestrel (Falco punctatus) was once the rarest falcon in the world due to DDT poisoning with only four birds known in 1974. The kestrel population is now estimated to be 800 birds. The Echo Parakeet (Psittacula eques echo) is the last surviving parrot in the Mascarenes. It was considered the rarest parrot in the world, with only about 12 individuals known in 1987 due to nest predation by invasive...
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