Comoran waters are the habitat of the coelacanth, a rare fish with limblike fins and a cartilaginous skeleton, the fossil remains of which date as far back as 400 million years and which was once thought to have become extinct about 70 million years ago. A live specimen was caught in 1938 off southern Africa other coelacanths have since been found in the vicinity of the Comoro Islands.

Several mammals are unique to the islands themselves. The macao, a lemur found only on Mahoré, is protected by French law and by local tradition. Another, Livingstone's fruit bat, although plentiful when discovered by explorer David Livingstone in 1863, has been reduced to a population of about 120, entirely on Nzwani. The world's largest bat, the jet-black Livingstone fruit bat has a wingspan of nearly two meters. A British preservation group sent an expedition to Comoros in 1992 to bring some of the bats to Britain to establish a breeding population. Humboldt's flycatcher is perhaps the best known of the birds native to Comoros. .

Partly in response to international pressures, Comorans in the 1990s have become more concerned about the environment. Steps are being taken not only to preserve the rare fauna, but also to counteract degradation of the environment, especially on densely populated Nzwani. Specifically, to minimize the cutting down of trees for fuel, kerosene is being subsidized, and efforts are being made to replace the loss of the forest cover caused by ylang-ylang distillation for perfume. The Community Development Support Fund, sponsored by the International Development Association (IDA --a World Bank affiliate--see Glossary) and the Comoran government, is working to improve water supply on the islands as well.

The climate is marine tropical, with two seasons: hot and humid from November to April, the result of the northeastern monsoon, and a cooler, drier season the rest of the year. Average monthly temperatures range from 23° C to 28° C along the coasts. Although the average annual precipitation is 2,000 millimeters, water is a scarce commodity in many parts of Comoros. Mwali and Mahoré possess streams and other natural sources of water, but Njazidja and Nzwani, whose mountainous landscapes retain water poorly, are almost devoid of naturally occurring running water. Cyclones, occurring during the hot and wet season, can cause extensive damage, especially in coastal areas. On the average, at least twice each decade houses, farms, and harbor facilities are devastated by these great storms.

Data as of August 1994