Region of Earth surrounding the Equator
The
tropics
are the regions of
Earth
surrounding the
Equator
. They are defined in
latitude
by the
Tropic of Cancer
in the
Northern Hemisphere
at 23°26′10.0″ (or 23.43611°) N and the
Tropic of Capricorn
in
the
Southern Hemisphere
at 23°26′10.0″ (or 23.43611°) S. The tropics are also referred to as the
tropical zone
and the
torrid zone
(see
geographical zone
).
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 are not 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
and the
polar regions
on either side of the equatorial zone.
The tropics constitute 39.8% of Earth's surface area
[1]
and contain 36% of Earth's
landmass
.
[2]
As of 2014
[update]
, the region was home also to 40% of the world's
population
, and this figure was then projected to reach 50% by 2050. Because of
global warming
, the weather conditions of the tropics are expanding with areas in the
subtropics
,
[3]
having more extreme weather events such as heatwaves and more intense storms.
[4]
[3]
These changes in weather conditions may make certain parts of the tropics uninhabitable.
[5]
Etymology
[
edit
]
The word "tropic" comes via
Latin
from
Ancient Greek
τροπ?
(
trop?
), meaning "to turn" or "change direction".
[6]
Astronomical definition
[
edit
]
The tropics are defined as the region between the
Tropic of Cancer
in the
Northern Hemisphere
at 23°26′10.0″ (or 23.43611°) N and the
Tropic of Capricorn
in the
Southern Hemisphere
at 23°26′10.0″ (or 23.43611°) S;
[8]
these latitudes correspond to the
axial tilt of the Earth
.
The Tropic of Cancer is the Northernmost latitude from which the
Sun
can ever be seen
directly overhead
, and the Tropic of Capricorn is the Southernmost.
[8]
This means that the tropical zone includes everywhere on Earth which is a
subsolar point
at least once during the
solar year
. Thus the maximum latitudes of the tropics have equal distances 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 the tropics are a geographic convention, and their variance from the true latitudes is very small.
Seasons and climate
[
edit
]
Many tropical areas have both a dry and a wet season. The
wet season
, rainy season or green season is the time of year, ranging from one or more months when most of the average annual
rainfall
in a region falls.
[9]
Areas with wet seasons are disseminated across portions of the tropics and
subtropics
, some even in
temperate
regions.
[10]
Under the
Koppen climate classification
, for
tropical climates
, a wet-season month is defined as one or more months where average precipitation is 60 mm (2.4 in) or more.
[11]
Some areas with pronounced rainy seasons see a break in rainfall during mid-season when the
intertropical convergence zone
or
monsoon trough
moves poleward of their location during the middle of the warm season;
[12]
Typical vegetation in these areas ranges from moist
seasonal tropical forests
to
savannahs
.
When the wet season occurs during the warm season, or
summer
,
precipitation
falls mainly during the late afternoon and early evening hours. The wet season is a time when
air quality
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
nutrients are washed away and erosion increases. The incidence of
malaria
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
Koppen climate classification
, much of the area within the geographical tropics is classed not as "tropical" but as "dry" (
arid
or
semi-arid
), including the
Sahara Desert
, the
Atacama Desert
and
Australian Outback
. Also, there are
alpine tundra
and snow-capped peaks, including
Mauna Kea
,
Mount Kilimanjaro
,
Puncak Jaya
and the
Andes
as far south as the northernmost parts of
Chile
and
Peru
.
Climate change
[
edit
]
The climate is changing in the tropics, as it is in the rest of the world.
[13]
The effects of steadily rising concentrations of
greenhouse gases
on the climate may be less obvious to tropical residents, however, because they are overlain by considerable natural variability. Much of this variability is driven by the
El Nino-Southern Oscillation (ENSO)
. The Tropics has warmed by 0.7-0.8°C over the last century?only slightly less than the global average?but a strong
El Nino
made 1998 the warmest year in most areas, with no significant warming since. Climate models predict a further 1-2°C warming by 2050 and 1-4°C by 2100.
Ecosystems
[
edit
]
Tropical plants
and animals are those species native to the tropics. Tropical ecosystems may consist of
tropical rainforests
,
seasonal tropical forests
,
dry (often deciduous) forests
, spiny forests,
deserts
,
savannahs
,
grasslands
and other habitat types. There are often wide areas of
biodiversity
, and species
endemism
present, particularly in rainforests and seasonal forests. Some examples of important biodiversity and high-endemism ecosystems are
El Yunque National Forest
in
Puerto Rico
,
Costa Rican
and
Nicaraguan
rainforests,
Amazon Rainforest
territories of several
South American
countries,
Madagascar dry deciduous forests
, the
Waterberg Biosphere
of
South Africa
, and eastern
Madagascar
rainforests. Often the soils of tropical forests are low in
nutrient
content, making them quite vulnerable to
slash-and-burn
deforestation
techniques, which are sometimes an element of
shifting cultivation
agricultural systems.
In
biogeography
, the tropics are divided into
Paleotropics
(Africa, Asia and Australia) and
Neotropics
(Caribbean, Central America, and South America). Together, they are sometimes referred to as the
Pantropic
. The system of
biogeographic realms
differs somewhat; the
Neotropical realm
includes both the Neotropics and temperate South America, and the Paleotropics correspond to the
Afrotropical
,
Indomalayan
,
Oceanian
, and tropical
Australasian realms
.
Flora
[
edit
]
Flora
are plants found in a specific region at a specific time. Some well-known plants that are exclusively found in, originate from, or are often associated with the tropics include:
Tropicality
[
edit
]
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.
[14]
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.
[15]
Tropicality encompassed two major images. One, is that the tropics represent a '
Garden of Eden
', a heaven on Earth, a land of rich
biodiversity
or a tropical paradise.
[16]
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.
[16]
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.
[17]
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'.
[18]
See also
[
edit
]
References
[
edit
]
- ^
"How much land is in the tropics?"
.
God Plays Dice
. 2007-12-04
. Retrieved
2017-06-26
.
- ^
"tropics"
.
National Geographic Encyclopedia
. National Geographic Society. 21 January 2011
. Retrieved
2017-06-26
.
- ^
a
b
Yang, Hu; Lohmann, Gerrit; Lu, Jian; Gowan, Evan J.; Shi, Xiaoxu; Liu, Jiping; Wang, Qiang (2020-08-27).
"Tropical Expansion Driven by Poleward Advancing Midlatitude Meridional Temperature Gradients"
.
Journal of Geophysical Research: Atmospheres
.
125
(16).
Bibcode
:
2020JGRD..12533158Y
.
doi
:
10.1029/2020JD033158
.
ISSN
2169-897X
.
S2CID
225274572
.
- ^
Zeng, Xubin; Reeves Eyre, J. E. Jack; Dixon, Ross D.; Arevalo, Jorge (2021-05-28).
"Quantifying the Occurrence of Record Hot Years Through Normalized Warming Trends"
.
Geophysical Research Letters
.
48
(10).
Bibcode
:
2021GeoRL..4891626Z
.
doi
:
10.1029/2020GL091626
.
ISSN
0094-8276
.
OSTI
1798413
.
S2CID
236399809
.
- ^
"We Have a Chance to Keep the Tropics Habitable"
.
Gizmodo
. 2021-03-08
. Retrieved
2022-11-10
.
- ^
"tropic"
.
Oxford learner's dictionaries
.
- ^
"What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle?"
.
Ask an Astronomer
. Retrieved
19 November
2022
.
- ^
a
b
"Tropical zone"
.
meteoblue
. Retrieved
19 November
2022
.
- ^
Glossary of Meteorology (2009).
Rainy season.
Archived
2009-02-15 at the
Wayback Machine
American Meteorological Society. Retrieved on 2008-12-27.
- ^
Michael Pidwirny (2008).
CHAPTER 9: Introduction to the Biosphere.
PhysicalGeography.net. Retrieved on 2008-12-27.
- ^
"Updated world Koppen-Geiger climate classification map"
(PDF)
.
- ^
J . S. 0guntoyinbo and F. 0. Akintola (1983).
Rainstorm characteristics affecting water availability for agriculture.
Archived
2009-02-05 at the
Wayback Machine
IAHS Publication Number 140. Retrieved on 2008-12-27
- ^
Intergovernmental Panel on Climate Change, ed. (2014-03-24).
Climate Change 2013 ? The Physical Science Basis
.
doi
:
10.1017/cbo9781107415324
.
ISBN
978-1-107-05799-9
.
- ^
"TROPICALITY | Meaning & Definition for UK English | Lexico.com"
.
Lexico Dictionaries | English
. Archived from
the original
on March 25, 2022
. Retrieved
2022-03-25
.
- ^
Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 6. Journal of Tropical Geography
- ^
a
b
Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 7. Journal of Tropical Geography
- ^
Menadue, Christopher B. (2017-05-30).
"Trysts Tropiques: The Torrid Jungles of Science Fiction"
(PDF)
.
ETropic: Electronic Journal of Studies in the Tropics
.
16
(1).
doi
:
10.25120/etropic.16.1.2017.3570
.
ISSN
1448-2940
.
- ^
Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 13. Journal of Tropical Geography
External links
[
edit
]
- Media related to
Tropics
at Wikimedia Commons