Tropical forests are forested landscapes in tropical regions: i.e. land areas approximately bounded by the tropic of Cancer and Capricorn, but possibly affected by other factors such as prevailing winds.
Some categories of tropical forest types are difficult. While forests in temperate areas are readily categorised on the basis of tree canopy density, such schemes do not work well in tropical forests. There is no single scheme that defines what a forest is, in tropical regions or elsewhere. Because of these difficulties, information on the extent of tropical forests varies between sources. However, Tropical Forests are extensive, making up just under half the world’s forests.
Types of tropical forest
Tropical forests are often thought of as evergreen rainforests and moist forests, however in reality only up to 60% of tropical forest is rainforest (depending on how this is defined - see maps). The remaining tropical forests are a diversity of many different forest types including: seasonally-dry tropical forest, mangroves, tropical freshwater swamp forests (or "flooded forests" such as the Várzea of the Amazon), dry forest, open Eucalyptus forests, tropical coniferous forests, savanna woodland (e.g. Sahelian forest), and mountain forests (the higher elevations of which are cloud forests). Over even relatively short distances, the boundaries between these biomes may be unclear, with ecotones between the main types.
The nature of tropical forest in any given area is affected by a number of factors, most importantly:
- Geographical: location and climatic zone (see sub-types), with:
- Precipitation levels and seasonality, with strong dry seasons significantly affecting flora (e.g. the predominance of lianas);
- Temperature profile, which is relatively even in equatorial rainforest or with a cooler season towards subtropical latitudes;
- Elevation affects the above, often creating "ecological islands" with high endemism (e.g. Mount Kinabalu in the Borneo rainforest).
- Historical: prehistoric age of forest and level of recent disturbance (see threats), changing primary (usually maximum biodiversity) into secondary forest, degenerating into bamboo forest after prolonged swidden agriculture (e.g. in several areas of Indo-China).
- Soil characteristics (also subject to various classifications): including depth and drainage.
The Global 200 scheme
- Tropical and subtropical moist broadleaf forests,
- Tropical and subtropical dry broadleaf forests,
- Tropical and subtropical coniferous forests.
Extent of tropical and sub-tropical -
A number of tropical forests have been designated High-Biodiversity Wilderness Areas, but remain subject to a wide range of disturbances, both natural and anthropogenic. All tropical forests have experienced at least some levels of disturbance.
A study in Borneo describes how, between 1973 and 2018, the old-growth forest had been reduced from 76% to 50% of the island, mostly due to fire and agricultural expansion. A widely-held view is that placing a value on the ecosystem services these forests provide may bring about more sustainable policies. However, clear monitoring and evaluation mechanisms for environmental, social and economic outcomes are needed. For example, a study in Vietnam indicated that poor and inconsistent data combined with a lack of human resources and political interest (thus lack of financial support) are hampering efforts to improve forest land allocation and a Payments for Forest Environmental Services scheme.
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