In the South-West of the Indian Ocean, climate changes will probably induce more important cyclonic phenomenon. The small islands are often overwhelmed by those catastrophic situations whose human and material damages can be very severe. To illustrate the possible consequences of such a change, the article suggests to study the Comorian archipelago, situated in the Mozambique Channel. This group of islands, is thus composed of two neighbouring islands which allow comparison because the first one, Mayotte is a French organised territory while the other one, Anjouan, because of its political instability, is still in a low-developed situation. The specificity of these two islands is also that they are historically linked and deeply demographically interdependent. Beyond the differential of development, a real common management of cyclonic risk is necessary but still a long time coming. Many practices run counter to the durability of these populations settled on the coastal line.