The Bermuda Islands are covered with low hills of insignificant height to affect the local air masses. Therefore, it is assumed that the major control of the climate of Bermuda are the local ocean currents, the Florida and Gulf Stream currents. The warm Gulf Stream waters, which curl around Bermuda on the west and north, are important in keeping the temperature of the marine environment high enough to allow the existence of coral reef fauna, which is essentially tropical in nature.