Comoros - Mayotte




Ashley Brown, Conservation Science Program, WWF-US, Washington, DC, USA




Roger Safford, BirdLife International, Cambridge, UK

Major Habitat Type

Oceanic Islands

Drainages flowing into

Indian Ocean

Main rivers to other water bodies

Streams originate in forested highlands, dropping precipitously to flow through the coastal plain before reaching the ocean. There is also one crater lake, Dziani Boundouni, located in the southeast portion of Mohéli Island, and two natural lakes on Mayotte: Dziani Karehani and Dziani Dzaha (crater) (Louette 1999).



The Comoros Islands are located in the Indian Ocean northwest of Madagascar in the Mozambique Channel and cover about 2,171 km2 (Mittermeier et al. 1999). From west to east, the islands include Grande Comore (Njazidja), Mohéli (Mwali), Anjouan (Ndzuani), and Mayotte (Maore), among others. Mayotte is a French territory while the other islands form the Republique Fédérale Islamique des Comores. The volcanic, mountainous Comoros Islands have a depauperate freshwater fauna that inhabits the lakes and streams of the ecoregion. 


On Grande Comore, the youngest and largest island, the soil is thin and rocky and there are no valleys or permanent watercourses. The 2,361 m high Karthala Volcano on Grande Comore is still active, erupting every 10 to 20 years (Henkel & Schmidt 2000).

Freshwater habitats

Whereas Mohéli and Mayotte both possess streams and other water bodies, including crater lakes, the islands of Grande Comore and Anjouan possess few freshwater habitats. Mayotte, the oldest of the islands, has many meandering streams that flow from the highland rainforests of the island, in addition to the two lakes Dziani Karehani and Dziani Dzaha. On Mohéli, the freshwater, but sulphurous Dziani Boundouni, has frequent upwellings due to subterranean volcanic activity (Wetlands International 2002). 

Terrestrial habitats

Tropical rainforest remains in a few places at high altitudes (500 to 1,900 m asl), especially on Karthala and dry forest, mangroves, baobabs and Indo-Pacific scrub grow in parts of the lowlands (Stuart et al. 1990; Sayer et al. 1992). On lava flows, lichens, ferns, other herbaceous vegetation, and woody plants grow in succession (Henkel & Schmidt 2000). Thirty-three percent of the plant species in Comoros are endemic (Mittermeier et al. 1999). However, many plant species have been introduced to the islands. In 1979, out of 1,000 plant species identified from the Comoros, about 500 had been introduced by man (Henkel & Schmidt 2000).

Justification for delineation

The Comoros Islands comprise this ecoregion, which hosts a diversity of brackish and freshwater fish, dragonflies, caddisflies, waterbirds, and frogs. All of the freshwater fish of the islands are from secondary families. The Miocene volcanic origin of the islands and the fact that they have never been joined with a continent explain the lack of primary fish families (Louette 1999).

Level of taxonomic exploration

Low for fish, Medium for Odonata


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