The Humid Tropics

Abstract

There should be little difficulty in defining the humid tropics, for most authorities are agreed that this is the region where evergreen rain forest is the climax vegetation, a formation type which requires constantly high temperatures and a large annual rainfall evenly distributed throughout the year. Yet in practice there is considerable dispute about the limits of the humid tropics. On the margins of the true rain forest there is an increasing proportion of deciduous trees, and botanists differ on the boundary between the rain forest and semi-evergreen forest. Over much of the humid tropics the primary forest has been cleared and burned for cultivation, and the climax vegetation destroyed. Whilst the rain forest nominally requires abundant rainfall without a dry season, most parts of the humid tropics have one or more months when rainfall is less than the potential evapotranspiration.