Bioregion: Seychelles & Comoros Tropical Islands (AT5)
Ecoregion Size (1000 ha):
States: Federal Islamic Republic of the Comoros
Frequent cyclones and volcanic activity pose a constant threat to the wealth of wildlife which find a home in the forests of the Comoros archipelago. Mount Karthala (2,361 m), an extremely active volcano dominating the largest of the four islands, Ngazidja, erupts every 10 to 20 years. Due to the range of climates experienced on these islands, there are a number of distinct microhabitats supporting many endemic species, including four strict endemic species of bird: Cormoro scops-owl, Grande Comore flycatcher, Grande Comore drongo, and Mount Karthala white-eye.
The ecoregion covers the Comoros Islands which are found approximately 300 km from northern Madagascar and about 300 km from the mainland of East Africa. The islands of Ngazidja (1,146 km2), Mwali (211 km2), and Nzwani (424 km2) comprise the Federal Islamic Republic of the Comoros, and Mayotte (374 km2) is a French dependency.
The Comoros Islands have a maritime tropical climate. The rainy season is from November to April when the predominant northerly winds off the Indian Ocean bring moist, warm air to the region (average of 25°C). From May to September southerly winds dominate the region bringing cooler (approximately 18°C) and drier air. The central, higher elevation areas of the islands are cooler and wetter, receiving over 5,000 mm per annum on some uplands, than the coastal regions, with the driest coastal areas receiving around 1,000 mm rain per annum.
The soil consists of laterite, which is rich in minerals but very poor in humus material, and is subject to extreme erosion. Semi-deciduous forests once covered the lowlands of the Comoros islands, while montane evergreen moist forests can be found at above 800 m elevation, with dominant plant species such as Ocotea comoriensis, Khaya comorensis, and Chrysophyllum biovinianum. Plant species are also represented by major families including Sapotaceae, Ebenaceae, Rubiaceae, Myrtaceae, Clusiaceae, Lauraceae, Burseraceae, Euphorbiaceae, Sterculiaceae, Pittosporaceae, and Celastraceae.
There is huge flora diversity and high endemism on these islands: of the approximately 1000 native plant species, 30 percent are endemic to the Comoros, including the endangered palm, Ravenea hildebrandtii. Most flora has affinities with those of Africa and Madagascar. There are also many introduced species of plants.
Almost all of the endemic avifauna species are found in the forest areas or the montane heathlands. Three species of bird are threatened with extinction: the Mayotte drongo, Anjouan scops-owl, and the Mohéli scops-owl. Of the native mammals present on these islands, two species of fruit bats are strictly endemic including the Livingstone’s fruit bat which is endemic to Ndzuani and Mwali. Other mammals include the mongoose lemur - introduced from Madagascar. The nine endemic reptiles include the Comoro flapnose chameleon, Comoro day gecko, snake-eyed skink, Comoro worm snake, and Mayotte chameleon.
In the past, most of these islands were covered by forest, however, little intact forest now remains on Ndzuani and Mayotte and much of the remaining forest on Mwali and Ngazidja is badly degraded except at higher elevations where the terrain is rugged or otherwise unproductive. Although considerable progress has been made to create conservation laws in the Comoros, none of the remaining forest areas are effectively protected. The protected areas include Massif du Mt Ntringui and Bimbi peninsula on Ndzuani, Pointes et Plages de Saziley et Charifou on Mayotte, and Lake Dziani Boudouni, a Ramsar wetlands site. More recently, the Coelacanth Marine Park was established on the southern end of Ngazidja.
Much of the natural vegetation has already been destroyed and clearance for agricultural land is still proceeding. Wildlife exploitation includes the poaching of green sea turtles for local consumption and the collection of day geckoes for the pet trade. Currently, the Seychelles flying fox is eaten occasionally by some but not all ethnic groups, while the Livingstone fruit bat is less consumed due to its rarity and its reduced threat to crops. However, as food resources become scarcer due to a growing population, the local taboos against eating bats may disappear.
The islands’ biodiversity also suffer from introduced plant and animal species including the small Indian mongoose, the Indian civet, feral domestic cats, and rats which may have severe effects on bird populations. Introduced exotic plants, for example Lantana camara, out-compete or severely impact native plant species. Cyclones bring strong winds, which can affect fruit bat populations, topple trees, and cause landslides. These effects are exacerbated by deforestation and logging that open forest areas and increase their exposure to wind. Deforestation also results in increased erosion of topsoil and the silting of reef ecosystems.
The priority conservation actions for the next decade will be to: 1) establish protected areas to conserve critical habitats, for example, Livingstone fruit bat roost sites; 2) promote sustainable agricultural practices to reduce the impact of deforestation; and 3) develop reforestation and water management programmes.
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