Tropical Rain Forests

Rainforests are vegetation types dominated by broad-leaved trees that form a dense upper canopy (layer of foliage) and contain a diverse array of vegetation. Contrary to common thinking, not all rainforests occur in places with high, constant rainfall; for example, in the so-called “dry rainforests” of northeastern Australia the climate is punctuated by a dry season, which reduces the annual precipitation. Nor are all forests in areas that receive large amounts of rainfall true rainforests; the conifer-dominated forests in the extremely wet coastal areas of the American Pacific Northwest are temperate evergreen forest ecosystems. Therefore, to avoid conveying misleading climatic information, the term rainforest is now preferred over rain forest.
This section covers only the richest of rainforests—the tropical rainforests of the ever-wet tropics.
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Tropical rainforests grow mainly in three regions: the Malesian botanical subkingdom, which extends from Myanmar (Burma) to Fiji and includes the whole of Thailand, Malaysia, Indonesia, the Philippines, Papua New Guinea, the Solomon Islands, and Vanuatu and parts of Indochina and tropical Australia; tropical South and Central America, especially the Amazon basin; and West and Central Africa (see biogeographic region). Smaller areas of tropical rainforest occur elsewhere in the tropics wherever climate is suitable. The principal areas of tropical deciduous forest are in India, the Myanmar–Vietnam–southern coastal China region, and eastern Brazil, with smaller areas in South and Central America north of the Equator, the West Indies, southeastern Africa, and northern Australia.
The flowering plants (angiosperms) first evolved and diversified during the Cretaceous Period about 100 million years ago, during which time global climatic conditions were warmer and wetter than those of the present. The vegetation types that evolved were the first tropical rainforests, which blanketed most of the Earth's land surfaces at... [continues]

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