Most ecosystems of the tropical and subtropical latitudes are seasonally stressed by drought (Schimper, 1898; Köppen, 1931; Murphy & Lugo, 1986). Research on population and ecosystems dynamics, and conservation efforts, however, rarely address these ecosystems, but rather concentrate on what is usually understood as tropical wet forest or rain forest. There has been enormous scientific and public attention directed toward documenting the effects of destruction of wet forests on soil fertility, biotic diversity, and global biogeochemistry. These concerns are certainly justified as the rates of forest and species loss accelerate. In contrast, relatively little attention has been given to forests subject to prolonged dry seasons (Ridpath & Corbett, 1985), and to their changing status. Degradation and conversion of ‘dry forest’ is far more advanced than that of wet forest: only a small fraction remains intact (Murphy & Lugo, Chapter 2; Sampaio, Chapter 3; Menaut, Lepage & Abbadie, Chapter 4; Rundel & Boonpragob, Chapter 5; Gentry, Chapter 7), and the area explicitly conserved is hardly perceptible. This is unfortunate because the forests with prolonged annual drought occupy more area than wet forests, have been of greater use to humans, and are still poorly known over most of their distribution.
The extent of forest in the drier tropics, and even its character, are difficult subjects for debate and research. Particularly in Africa, India and Asia, the relations between savannas, woodlands and dry forests (of various leaf habits) are notoriously complex (Furley, Proctor & Ratter, 1992). Savannas and their degradation are certainly priority subjects of tropical and global ecology, but as with wet forests, they are well studied compared with dry forests.