Although Mohéli has large tracts of fertile land not yet cultivated, parts of Anjouan are so densely populated that farmers have been forced to extend cultivation to the higher slopes, leading to deforestation and soil erosion, especially when crops are cultivated on slopes without adequate terracing. Population growth has also increased the demand for firewood, threatening the remaining forest areas. Soil erosion is aggravated by lack of terracing. Comoros has about 0.2 cu mi of water, of which 47% is used for agricultural purposes, 48% is used in urban centers and for domestic purposes, and 5% is used in industry.
As of the mid-1990s, endangered species in the Comoros included the Anjouan sparrow hawk and Anjouan scops owl. Six of the 17 species of mammals in Comoros were endangered. Three types of birds in a total of 99 species and three plant species in a total of 416 were also endangered.