Succulent woodlands and spiny thickets occur in the semi-arid south-southwestern portion of Madagascar. Spiny bushes and trees are dominant in these areas with a few plant families including the dogbanes (Apocynaceae), spurges (Euphorbiaceae), and leguminous trees and shrubs (Fabaceae, Leguminosae). The region is characterized by its dry tropical climate with a rainy season that extends from November to April with a mean average rainfall of approximately 750 mm (29.5 in) and yearly total rainfall ranges between 575 mm (23 in) and 1330 mm (52 in) per year. Much of the area is threatened by unintentional wildfires and intentional burning to clear land for agriculture.