![Koppen-Geiger_Map_A_present](https://upload.wikimedia.org/wikipedia/commons/2/23/Koppen-Geiger_Map_A_present.svg)
The tropics are the regions of
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
surrounding the
Equator. They are defined in
latitude
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...
by the
Tropic of Cancer
The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted tow ...
in the
Northern Hemisphere at N and the
Tropic of Capricorn
The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point at the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reac ...
in
the
Southern Hemisphere at S. The tropics are also referred to as the tropical zone and the torrid zone (see
geographical zone
The five main latitude regions of Earth's surface comprise geographical zones, divided by the major circles of latitude. The differences between them relate to climate. They are as follows:
# The North Frigid Zone, between the North Pole at 90 ...
).
In terms of climate, the tropics receive sunlight that is more direct than the rest of Earth and are generally hotter and wetter as they aren't affected as much by the
solar seasons. The word "tropical" sometimes refers to this sort of climate in the zone rather than to the geographical zone itself. The tropical zone includes deserts and snow-capped mountains, which are not tropical in the climatic sense. The tropics are distinguished from the other climatic and biomatic regions of Earth, which are the
middle latitudes
The middle latitudes (also called the mid-latitudes, sometimes midlatitudes, or moderate latitudes) are a spatial region on Earth located between the Tropic of Cancer ( latitudes 23°26'22") to the Arctic Circle (66°33'39"), and Tropic of Cap ...
and the
polar regions
The polar regions, also called the frigid zones or polar zones, of Earth are the regions of the planet that surround its geographical poles (the North and South Poles), lying within the polar circles. These high latitudes are dominated by floa ...
on either side of the equatorial zone.
The tropics constitute 40% of Earth's surface area and contain 36% of Earth's
landmass
A landmass, or land mass, is a large region or area of land. The term is often used to refer to lands surrounded by an ocean or sea, such as a continent or a large island. In the field of geology, a landmass is a defined section of continenta ...
. , the region was home also to 40% of the world's
population
Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using a ...
, and this figure was then projected to reach 50% by 2050. Because of
global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
, the weather conditions of the tropics are expanding with areas in the subtropics,
having more extreme weather events such as heatwaves and more intense storms.
These changes in weather conditions may make certain parts of the tropics uninhabitable.
Etymology
The word "tropic" comes via
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
from
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
(), meaning "to turn" or "change direction".
Astronomical Definition
![axial_tilt_vs_tropical_and_polar_circles](https://upload.wikimedia.org/wikipedia/commons/4/40/Axial_tilt_vs_tropical_and_polar_circles.svg)
The tropics are defined as the region between the
Tropic of Cancer
The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted tow ...
in the
Northern Hemisphere at N and the
Tropic of Capricorn
The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point at the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reac ...
in the
Southern Hemisphere at S;
these latitudes correspond to the
axial tilt
In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orb ...
of the Earth.
The Tropic of Cancer is the Northernmost latitude from which the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
can ever be seen
directly overhead, and the Tropic of Capricorn is the Southernmost.
This means that the tropical zone includes everywhere on Earth which is a
subsolar point at least once during the
solar year
A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky of a celestial body of the Solar System such as the Earth, completing a full cycle of seasons; for example, the time f ...
. Thus the maximum latitudes of the tropics have equal distance from the equator on either side. Likewise, they approximate the angle of the
Earth's axial tilt. This angle is not perfectly fixed, mainly due to the influence of the moon, but the limits of tropics are a geographic convention, and their variance from the true latitudes is very small.
Seasons and climate
![Monthly zonal mean precipitation](https://upload.wikimedia.org/wikipedia/commons/3/33/Monthly_zonal_mean_precipitation.png)
"Tropical" is sometimes used in a general sense and feeling for a
tropical climate
Tropical climate is the first of the five major climate groups in the Köppen climate classification identified with the letter A. Tropical climates are defined by a monthly average temperature of 18 °C (64.4 °F) or higher in the cool ...
to mean warm to hot and moist year-round, often with the sense of lush vegetation.
Many tropical areas, however, have both a dry and a wet season. The
wet season
The wet season (sometimes called the Rainy season) is the time of year when most of a region's average annual rainfall occurs. It is the time of year where the majority of a country's or region's annual precipitation occurs. Generally, the sea ...
, rainy season or green season is the time of year, ranging from one or more months, when most of the average annual
rainfall
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
in a region falls. Areas with wet seasons are disseminated across portions of the tropics and
subtropics, some even in
temperate
In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...
regions. Under the
Köppen climate classification
The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, notabl ...
, for
tropical climate
Tropical climate is the first of the five major climate groups in the Köppen climate classification identified with the letter A. Tropical climates are defined by a monthly average temperature of 18 °C (64.4 °F) or higher in the cool ...
s, a wet-season month is defined as one or more months where average precipitation is or more. Some areas with pronounced rainy seasons see a break in rainfall during mid-season when the
intertropical convergence zone or
monsoon trough
The monsoon trough is a portion of the Intertropical Convergence Zone in the Western Pacific,Bin WangThe Asian Monsoon.Retrieved 2008-05-03. as depicted by a line on a weather map showing the locations of minimum sea level pressure, and as such, ...
moves poleward of their location during the middle of the warm season;
[J . S. 0guntoyinbo and F. 0. Akintola (1983)]
Rainstorm characteristics affecting water availability for agriculture.
IAHS Publication Number 140. Retrieved on 2008-12-27 typical vegetation in these areas ranges from moist
seasonal tropical forest
Seasonal tropical forest, also known as moist deciduous, semi-evergreen seasonal, tropical mixed or monsoon forests, typically contain a range of tree species: only some of which drop some or all of their leaves during the dry season. This tropic ...
s to
savannahs.
When the wet season occurs during the warm season, or
summer,
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
falls mainly during the late afternoon and early evening hours. The wet season is a time when
air quality
Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different types ...
improves, freshwater quality improves and vegetation grows significantly due to the wet season supplementing flora, leading to crop yields late in the season. Floods and rains cause rivers to overflow their banks, and some animals to retreat to higher ground.
Soil
Soil, also commonly referred to as earth or dirt
Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty.
Common types of dirt include:
* Debri ...
nutrients are washed away and erosion increases. The incidence of
malaria
Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
increases in areas where the rainy season coincides with high temperatures. Animals have adaptation and survival strategies for the wetter regime. The previous dry season leads to food shortages into the wet season, as the crops have yet to mature.
However, regions within the tropics may well not have a tropical climate. Under the
Köppen climate classification
The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, notabl ...
, much of the area within the geographical tropics is classed not as "tropical" but as "dry" (
arid
A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most ...
or
semi-arid
A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi- ...
), including the
Sahara Desert
, photo = Sahara real color.jpg
, photo_caption = The Sahara taken by Apollo 17 astronauts, 1972
, map =
, map_image =
, location =
, country =
, country1 =
, ...
, the
Atacama Desert
The Atacama Desert ( es, Desierto de Atacama) is a desert plateau in South America covering a 1,600 km (990 mi) strip of land on the Pacific coast, west of the Andes Mountains. The Atacama Desert is the driest nonpolar desert in th ...
and
Australian Outback
The Outback is a remote, vast, sparsely populated area of Australia. The Outback is more remote than the bush. While often envisaged as being arid, the Outback regions extend from the northern to southern Australian coastlines and encompass a n ...
. Also, there are
alpine tundra and snow-capped peaks, including
Mauna Kea,
Mount Kilimanjaro,
Puncak Jaya
Puncak Jaya (; literally "Glorious Peak") or Carstensz Pyramid, Mount Jayawijaya or Mount Carstensz () on the island of New Guinea, with an elevation of , is the highest mountain peak of an island on Earth. The mountain is located in the Sudi ...
and the
Andes
The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
as far south as the northernmost parts of
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
and
Perú.
Ecosystems
Tropical plants and animals are those species native to the tropics. Tropical ecosystems may consist of
tropical rainforest
Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equa ...
s,
seasonal tropical forests,
dry (often deciduous) forests, spiny forests,
deserts
A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...
,
savannahs,
grasslands and other habitat types. There are often wide areas of
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
, and species
endemism
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...
present, particularly in rainforests and seasonal forests. Some examples of important biodiversity and high endemism ecosystems are
El Yunque National Forest
El Yunque National Forest ( es, Bosque Nacional El Yunque), formerly known as the Caribbean National Forest (or ''Bosque Nacional del Caribe''), is a forest located in northeastern Puerto Rico. It is the only tropical rainforest in the United Sta ...
in
Puerto Rico
Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and unincorporated ...
,
Costa Rican and
Nicaragua
Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the countr ...
n rainforests,
Amazon Rainforest territories of several
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...
n countries,
Madagascar dry deciduous forests
The Madagascar dry deciduous forests represent a tropical dry forest ecoregion situated in the western and northern part of Madagascar. The area has high numbers of endemic plant and animal species but has suffered large-scale clearance for agric ...
, the
Waterberg Biosphere
The Waterberg ( nso, Thaba Meetse) is a mountainous massif of approximately in north Limpopo Province, South Africa.
The average height of the mountain range is 600 m with a few peaks rising up to 2000 m above sea level. Vaalwater town is l ...
of
South Africa
South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
, and eastern
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
rainforests. Often the soils of tropical forests are low in
nutrient content, making them quite vulnerable to
slash-and-burn
Slash-and-burn agriculture is a farming method that involves the cutting and burning of plants in a forest or woodland to create a field called a swidden. The method begins by cutting down the trees and woody plants in an area. The downed veget ...
deforestation
Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated ...
techniques, which are sometimes an element of
shifting cultivation
Shifting cultivation is an agricultural system in which plots of land are cultivated temporarily, then abandoned while post-disturbance fallow vegetation is allowed to freely grow while the cultivator moves on to another plot. The period of cu ...
agricultural systems.
In
biogeography, the tropics are divided into
Paleotropics The Paleotropical Kingdom (Paleotropis) is a floristic kingdom comprising tropical areas of Africa, Asia and Oceania (excluding Australia and New Zealand), as proposed by Ronald Good and Armen Takhtajan. Part of its flora, inherited from the anc ...
(Africa, Asia and Australia) and
Neotropics
The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone.
Definition
In bioge ...
(Caribbean, Central America, and South America). Together, they are sometimes referred to as the
Pantropic. The system of
biogeographic realm
A biogeographic realm or ecozone is the broadest biogeographic division of Earth's land surface, based on distributional patterns of terrestrial organisms. They are subdivided into bioregions, which are further subdivided into ecoregions.
De ...
s differs somewhat; the
Neotropical realm
The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone.
Definition
In biogeo ...
includes both the Neotropics and temperate South America, and the Paleotropics correspond to the
Afrotropical,
Indomalayan
The Indomalayan realm is one of the eight biogeographic realms. It extends across most of South and Southeast Asia and into the southern parts of East Asia.
Also called the Oriental realm by biogeographers, Indomalaya spreads all over the Indi ...
,
Oceanian, and tropical
Australasian realm
The Australasian realm is a biogeographic realm that is coincident with, but not (by some definitions) the same as, the geographical region of Australasia. The realm includes Australia, the island of New Guinea (comprising Papua New Guinea and th ...
s.
Flora
Flora are plants found in a specific region at a specific time. In Latin it means a "flower".
![Tropical wet forests](https://upload.wikimedia.org/wikipedia/commons/d/d4/Tropical_wet_forests.svg)
Some well-known plants that are exclusively found or originate from the tropics or are often associated with the tropics include:
*
Stone fruits such as
mangos
A mango is an edible stone fruit produced by the tropical tree ''Mangifera indica''. It is believed to have originated in the region between northwestern Myanmar, Bangladesh, and northeastern India. ''M. indica'' has been cultivated in South ...
,
peaches
The peach (''Prunus persica'') is a deciduous tree first domesticated and cultivated in Zhejiang province of Eastern China. It bears edible juicy fruits with various characteristics, most called peaches and others (the glossy-skinned, non-fu ...
,
plums
A plum is a fruit of some species in ''Prunus'' subg. ''Prunus'.'' Dried plums are called prunes.
History
Plums may have been one of the first fruits domesticated by humans. Three of the most abundantly cultivated species are not found i ...
,
avocado
The avocado (''Persea americana'') is a medium-sized, evergreen tree in the laurel family ( Lauraceae). It is native to the Americas and was first domesticated by Mesoamerican tribes more than 5,000 years ago. Then as now it was prized for ...
, etc.
*
Citrus fruits
''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is nativ ...
such as
oranges
An orange is a fruit of various citrus species in the family Rutaceae (see list of plants known as orange); it primarily refers to ''Citrus'' × ''sinensis'', which is also called sweet orange, to distinguish it from the related ''Citrus × ...
,
lemons
The lemon (''Citrus limon'') is a species of small evergreen trees in the flowering plant family Rutaceae, native to Asia, primarily Northeast India (Assam), Northern Myanmar or China.
The tree's ellipsoidal yellow fruit is used for culina ...
,
mandarins, etc.
*
Banana trees
A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", distingu ...
*
Bird of paradise flower![Pitaya cross section ed2](https://upload.wikimedia.org/wikipedia/commons/4/43/Pitaya_cross_section_ed2.jpg)
*
Palm trees
Palm most commonly refers to:
* Palm of the hand, the central region of the front of the hand
* Palm plants, of family Arecaceae
**List of Arecaceae genera
* Several other plants known as "palm"
Palm or Palms may also refer to:
Music
* Palm ( ...
![Kew Gardens giant water lily](https://upload.wikimedia.org/wikipedia/commons/2/2e/Kew_Gardens_giant_water_lily.JPG)
**
Coconut trees
*
Ferns
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except th ...
*
Orchids
Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant.
Along with the Asteraceae, they are one of the two largest families of flowering ...
*
Papaya trees
*
Dragon fruit
A pitaya () or pitahaya () is the fruit of several different cactus species indigenous to the Americas. Pitaya usually refers to fruit of the genus ''Stenocereus'', while pitahaya or dragon fruit refers to fruit of the genus ''Selenicereus'' ...
*
Bamboo
Bamboos are a diverse group of evergreen perennial flowering plants making up the subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family. The origin of the word "bamboo" is uncertain, ...
*
Jackfruit
The jackfruit (''Artocarpus heterophyllus''), also known as jack tree, is a species of tree in the fig, mulberry, and breadfruit family ( Moraceae). Its origin is in the region between the Western Ghats of southern India, all of Bangladesh, ...
*
Giant Water Lily
*
Rubber Tree
''Hevea brasiliensis'', the Pará rubber tree, ''sharinga'' tree, seringueira, or most commonly, rubber tree or rubber plant, is a flowering plant belonging to the spurge family Euphorbiaceae originally native to the Amazon basin, but is now ...
*
Cacao
*
Coffee
Coffee is a drink prepared from roasted coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content. It is the most popular hot drink in the world.
Seeds of ...
Tropicality
''Tropicality'' refers to the image of the tropics that people from outside the tropics have of the region, ranging from critical to verging on fetishism. The idea of tropicality gained renewed interest in geographical discourse when French geographer
Pierre Gourou published ''Les Pays Tropicaux'' (''The Tropical World'' in English), in the late 1940s.
![Juruá River in Brazil](https://upload.wikimedia.org/wikipedia/commons/f/fd/Juru%C3%A1_River_in_Brazil.jpg)
Tropicality encompassed two major images. One, is that the tropics represent a '
Garden of Eden', a heaven on Earth, a land of rich
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
or a tropical paradise.
[Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 7. Journal of Tropical Geography] The alternative is that the tropics consist of wild, unconquerable nature. The latter view was often discussed in old Western literature more so than the first.
Evidence suggests over time that the view of the tropics as such in popular literature has been supplanted by more well-rounded and sophisticated interpretations.
Western scholars tried to theorise why tropical areas were relatively more inhospitable to human civilisations than colder regions of the Northern Hemisphere. A popular explanation focused on the differences in climate. Tropical jungles and rainforests have much more humid and hotter weather than colder and drier temperaments of the Northern Hemisphere, giving to a more diverse biosphere. This theme led some scholars to suggest that humid hot climates correlate to human populations lacking control over nature e.g. 'the wild Amazonian rainforests'.
[Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 13. Journal of Tropical Geography]
See also
*
Hardiness zone
*
Subtropics
*
Tropical ecology
Tropical ecology is the study of the relationships between the biotic and abiotic components of the tropics, or the area of the Earth that lies between the Tropic of Cancer and the Tropic of Capricorn (23.4378° N and 23.4378° S, respectively). Th ...
*
Tropical marine climate
A tropical marine climate is a tropical climate that is primarily influenced by the ocean. It is usually experienced by islands and coastal areas 10° to 20° north and south of the equator. There are two main seasons in a tropical marine climate: ...
*
Tropical year
A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky of a celestial body of the Solar System such as the Earth, completing a full cycle of seasons; for example, the time f ...
References
External links
{{Authority control
Seasons