Tropical forest

Tropical forests are forested ecoregions with tropical climates – that is, land areas approximately bounded by the tropics of Cancer and Capricorn, but possibly affected by other factors such as prevailing winds.

File:BorneoRainforest DSC 9267.JPG rainforest]]

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.{{cite journal | last1=Putz | first1=Francis E. | last2=Redford | first2=Kent H. | title=The Importance of Defining 'Forest': Tropical Forest Degradation, Deforestation, Long-term Phase Shifts, and Further Transitions | journal=Biotropica | publisher=Wiley | volume=42 | issue=1 | date=September 14, 2009 | issn=0006-3606 | doi=10.1111/j.1744-7429.2009.00567.x | pages=10–20| s2cid=83577100 }} There is no single scheme that defines what a forest is, in tropical regions or elsewhere.Anatoly Shvidenko, Charles Victor Barber, Reidar Persson et al. 2005 "Millennium Ecosystem Assessment." Ecosystems and human wellbeing: a framework for assessment Washington, DC: Island Press 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.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. The tropical domain has the largest proportion of the world's forests (45 percent), followed by the boreal, temperate and subtropical domains.{{Cite book|title=Global Forest Resources Assessment 2020 – Key findings|publisher=FAO|year=2020|isbn=978-92-5-132581-0|doi=10.4060/ca8753en|s2cid=130116768 }}

More than 3.6 million hectares of virgin tropical forest was lost in 2018.[https://www.theguardian.com/environment/2019/may/06/human-society-under-urgent-threat-loss-earth-natural-life-un-report Human society under urgent threat from loss of Earth's natural life. Scientists reveal 1 million species at risk of extinction in damning UN report] 6 May 2019 Guardian [https://www.dropbox.com/sh/yd8l2v0u4jqptp3/AACpraYjOYWpTxAFv5H-2vrKa/1%20Global%20Assessment%20Summary%20for%20Policymakers?dl=0&preview=Summary+for+Policymakers+IPBES+Global+Assessment.pdf&subfolder_nav_tracking=1]{{Cite web |title=World Lost 12 Million Hectares of Tropical Forest in 2018 |url=https://www.ecosystemmarketplace.com/articles/world-lost-12-million-hectares-tropical-forest-2018/ |access-date=2024-10-29 |website=Ecosystem Marketplace |language=en-US}}

History

The first tropical rainforests appeared during the Devonian, characterized mainly by Pseudosporochnalean and Archaeopteridalean plants.{{Cite journal |last1=Berry |first1=Christopher M. |last2=Marshall |first2=John E.A. |date=2015-12-01 |title=Lycopsid forests in the early Late Devonian paleoequatorial zone of Svalbard |url=https://pubs.geoscienceworld.org/gsa/geology/article/43/12/1043/131717/Lycopsid-forests-in-the-early-Late-Devonian |journal=Geology |volume=43 |issue=12 |pages=1043–1046 |doi=10.1130/G37000.1 |bibcode=2015Geo....43.1043B |issn=0091-7613}} 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.{{Cite web |title=Khan Academy |url=https://www.khanacademy.org/science/biology/ecology/biogeography/a/tropical-rainforest-biomes |access-date=2024-10-29 |website=www.khanacademy.org |language=en}}

Types of tropical forest

Tropical forests are often thought of as evergreen rainforests 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{{cite book | last=Van Der Hammen | first=Thomas | title=Tropical Forests and Climate | chapter=Palaeoecological Background: Neotropics | publisher=Springer Netherlands | location=Dordrecht | year=1991 | pages=37–47 | isbn=978-90-481-4147-0 | doi=10.1007/978-94-017-3608-4_4}} (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.

File:tropical_forests.tif

File:Tropical_Forests_2000_by_Major_Ecological_Domains.tif

File:Koppen-Geiger_Map_A_present.svg):

{{legend|#46A9FA|Aw—Tropical savanna climate.}}]]

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:
Temperature profile, which is relatively even in equatorial rainforest or with a cooler season towards subtropical latitudes;
Precipitation levels and seasonality, with strong dry seasons significantly affecting flora (e.g. the predominance of lianas);{{cite journal |last1=Chen |first1=Ya-Jun |last2=Cao |first2=Kun-Fang |last3=Schnitzer |first3=Stefan A. |last4=Fan |first4=Ze-Xin |last5=Zhang |first5=Jiao-Lin |last6=Bongers |first6=Frans |date=September 29, 2014 |title=Water-use advantage for lianas over trees in tropical seasonal forests |url=https://epublications.marquette.edu/cgi/viewcontent.cgi?article=1782&context=bio_fac |journal=New Phytologist |publisher=Wiley |volume=205 |issue=1 |pages=128–136 |doi=10.1111/nph.13036 |issn=0028-646X |pmid=25264136 |doi-access=free}}
Elevation affects the above, often creating "ecological islands" with high endemism (e.g. Mount Kinabalu in the Borneo rainforest).{{Cite journal | doi=10.1038/nature14949| pmid=26266979| title=Evolution of endemism on a young tropical mountain| journal=Nature| volume=524| issue=7565| pages=347–350| year=2015| last1=Merckx| first1=Vincent S. F. T.| last2=Hendriks| first2=Kasper P.| last3=Beentjes| first3=Kevin K.| last4=Mennes| first4=Constantijn B.| last5=Becking| first5=Leontine E.| last6=Peijnenburg| first6=Katja T. C. A.| last7=Afendy| first7=Aqilah| last8=Arumugam| first8=Nivaarani| last9=De Boer| first9=Hugo| last10=Biun| first10=Alim| last11=Buang| first11=Matsain M.| last12=Chen| first12=Ping-Ping| last13=Chung| first13=Arthur Y. C.| last14=Dow| first14=Rory| last15=Feijen| first15=Frida A. A.| last16=Feijen| first16=Hans| last17=Soest| first17=Cobi Feijen-van| last18=Geml| first18=József| last19=Geurts| first19=René| last20=Gravendeel| first20=Barbara| last21=Hovenkamp| first21=Peter| last22=Imbun| first22=Paul| last23=Ipor| first23=Isa| last24=Janssens| first24=Steven B.| last25=Jocqué| first25=Merlijn| last26=Kappes| first26=Heike| last27=Khoo| first27=Eyen| last28=Koomen| first28=Peter| last29=Lens| first29=Frederic| last30=Majapun| first30=Richard J.| display-authors=29| bibcode=2015Natur.524..347M| s2cid=4447746| url=}}
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).{{Cite journal |doi = 10.1659/mrd.0875|title = The Dynamics of Secondary Forest Landscapes in the Lower Mekong Basin|journal = Mountain Research and Development|volume = 27|issue = 3|pages = 232–241|year = 2007|last1 = Heinimann|first1 = Andreas|last2 = Messerli|first2 = Peter|last3 = Schmidt-Vogt|first3 = Dietrich|last4 = Wiesmann|first4 = Urs|s2cid = 102490131| url=https://boris.unibe.ch/25546/ }}
Soil characteristics (also subject to various classifications): including depth and drainage.Schulte, A, Ruhiyat D (Eds.) (1998) Soils of Tropical Forest Ecosystems: Characteristics, Ecology and Management. Springer, 204 pp.

=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):

Extent of tropical and sub-tropical -

File:Biome map 03.svg|coniferous forest regions

File:Biome map 02.svg|dry forest regions

File:Biome map 01.svg|moist forest regions

Threats

File: Logging Bulletwood Berbice-Guyana JK.JPG, Guyana]]

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.{{Cite journal |doi = 10.1098/rstb.2019.0116|title = Climatic and local stressor interactions threaten tropical forests and coral reefs |journal = Philosophical Transactions of the Royal Society B|volume = 375|pages = 20190116|year = 2020|last1 = França |first1 = FM|last2 = Benkwitt |first2 = CE|last3 = Peralta |first3 = G |last4 = Robinson |first4 = JPW|last5 = Graham|first5 = NAJ |last6 = Tylianakis |first6 = JM|last7 = Berenguer |first7 = E |last8 = Lees |first8 = AC|last9 = Ferreira |first9 = J|last10 = Louzada |first10 = J |last11 = Barlow |first11 = J|issue = 1794 |pmid = 31983328 |pmc = 7017775 }} All tropical forests have experienced at least some levels of disturbance.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

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".{{cite journal | url=https://doi.org/10.1038/s41559-021-01417-z | doi=10.1038/s41559-021-01417-z | title=Mapping the deforestation footprint of nations reveals growing threat to tropical forests | year=2021 | last1=Hoang | first1=Nguyen Tien | last2=Kanemoto | first2=Keiichiro | journal=Nature Ecology & Evolution | volume=5 | issue=6 | pages=845–853 | pmid=33782576 | bibcode=2021NatEE...5..845H | s2cid=232420306 }}

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.[http://www.cifor.org/publications/pdf_files/factsheet/6552-factsheet.pdf Gaveau DLA (2016) What a difference 4 decades make: Deforestation in Borneo since 1973 CIFOR (retrieved 29 October 2017)] 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.[http://www.cifor.org/publications/pdf_files/OccPapers/OP-155.pdf Pham TT, Le ND, Vu TP, Nguyen HT, Nguyen VT (2016) Forest land allocation and payments for forest environmental services in four northwestern provinces of Vietnam: From policy to practice CIFOR (retrieved 29 October 2017)]