Tropical dry forests are one of the most threatened parts of the earth’s environment. This forest type typically experiences an annual hard dry season. The average rainfall is sufficient enough to promote growth of trees, but these tree and plant species must be able to withstand periods of low precipitation and moisture. During the driest months, these species will drop their leaves much in the same manner that northern deciduous forest species lose their leaves in the fall and winter. Dry forests occur most commonly on low islands or on the lee side of mountainous islands and on coastal areas of low relief.