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 tropical forest types are difficult to categorize. While forests in
temperate areas are readily categorized on the basis of
tree canopy density, such schemes do not work well in tropical forests.[1] There is no single scheme that defines what a forest is, in tropical regions or elsewhere.[1][2] 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.[3] The tropical domain has the largest proportion of the world's forests (45 percent), followed by the boreal, temperate and subtropical domains.[4]
More than 3.6 million hectares of virgin tropical forest was lost in 2018.[5]
History
The original
tropical rainforests, which covered the planet's land surface, were the type of flora that covered Earth. Other canopy forests expanded north-south of the equator during the
Paleogene epoch, around 40 million years ago, as a result of the emergence of drier, cooler climates.
The tropical forest was originally identified as a specific type of
biome in 1949.
Types of tropical forest
Tropical forests are often thought of as
evergreenrainforests[2] and moist forests, but these account for only a portion of them (depending on how they are defined – see maps). The remaining tropical forests are a diversity of many different forest types including:
Eucalyptus open forest,
tropical coniferous forests,
savanna woodland (e.g.Sahelian forest), and
mountain forests[6] (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 forests in any given area is affected by several factors, most importantly:
Geographical: location and
climatic zone (see sub-types), with:
Soil characteristics (also subject to various
classifications): including depth and drainage.[10]
The Global 200 scheme
The Global 200 scheme, promoted by the
World Wildlife Fund, classifies three main tropical forest habitat types (
biomes), grouping together tropical and sub-tropical areas (maps below):
A number of tropical forests have been designated
High-Biodiversity Wilderness Areas, but remain subject to a wide range of disturbances, including more localized pressures such as habitat loss and degradation and anthropogenic climate change.
Studies have also shown that ongoing climate change is increasing the frequency and intensity of some climate extremes (e.g. droughts, heatwaves and hurricanes) which, in combination with other local human disturbances, are driving unprecedented negative ecological consequences for tropical forests around the world.[11] All tropical forests have experienced at least some levels of disturbance.[12]
Current deforestation in the biodiversity hotspots of North of South America, sub-Saharan Africa, South-East Asia and the Pacific, can be attributed to export of commodities such as: beef, soy, coffee, cacao,
palm oil, and timber; there is a requirement for "strong transnational efforts ... by improving supply chain transparency [and] public–private engagement".[13]
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.[14] 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.[15]
^
abPutz, Francis E.; Redford, Kent H. (September 14, 2009). "The Importance of Defining 'Forest': Tropical Forest Degradation, Deforestation, Long-term Phase Shifts, and Further Transitions". Biotropica. 42 (1). Wiley: 10–20.
doi:
10.1111/j.1744-7429.2009.00567.x.
ISSN0006-3606.
S2CID83577100.
^
abAnatoly Shvidenko, Charles Victor Barber, Reidar Persson et al. 2005 "
Millennium Ecosystem Assessment." Ecosystems and human wellbeing: a framework for assessment Washington, DC: Island Press
^D'Annunzio, Rémi, Lindquist, Erik J., MacDicken, Kenneth G. 2017 "Global forest land-use change from 1990 to 2010:an update to a global remote sensing survey of forests Forest Resource Assessment Working Paper 187" FAO, Rome.
^Robin L. Chazdon 2003 "Tropical forest recovery: legacies of human impact and natural disturbances" Perspectives in Plant Ecology, Evolution and Systematics 6/1,2, pp. 51–71