tropics

World map with the intertropical zone highlighted in red

The tropics, seated in the equatorial regions of the world, are limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately 23°26' (23.4°) N latitude, and the Tropic of Capricorn in the southern hemisphere at 23°26' (23.4°) S latitude. The tropics are also referred to as the tropical zone and the torrid zone (see geographical zone).

The tropics include all the areas on the Earth where the sun reaches a point directly overhead at least once during the solar year. In the temperate zones, north of the Tropic of Cancer and south of the Tropic of Capricorn, the sun never reaches this zenith and is never directly overhead, always passing south of it in the northern hemisphere and north of it in the southern hemisphere

Tropical seasons and climate

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A noontime scene from the Philippines on a day when the Sun is almost directly overhead.

The seasons in the tropics are dominated by the movement of the tropical rain belt (or ITCZ), which then forms from the northern to the southern tropics over the course of the year in the winter, thus causing the dry season and the wet season in turn.

Tropical sunset over the sea in Kota Kinabalu, Malaysia.

The seasons (autumn, winter, spring, and summer) are caused by the Earth's tilt. Direct rays of the sun always shine in and between the tropics. When it's the first day of winter in the Northern Hemisphere, the direct rays are over the Tropic of Capricorn, which is called the winter solstice. There are the shortest hours of daylight. When it's the first day of summer in the Northern Hemisphere, the direct rays are over the Tropic of Cancer, known as the summer solstice. These are the longest hours of daylight. When it's either the first day of spring or autumn in the Northern Hemisphere, it is known as an equinox, meaning "equal night." The direct rays are over the equator, meaning 12 hours of day and night for everyone all over the world. Equinoxes occur two days out of the whole year.

Tropical is sometimes used in a general sense for a tropical climate that is warm to hot and moist year-round, often with the sense of lush vegetation. However, there are places in the tropics that are anything but "tropical" in this sense, with even alpine tundra and snow-capped peaks, including Mauna Kea, Mt. Kilimanjaro, and the Andes as far south as the northernmost parts of Chile and Argentina. Under the Köppen climate classification, much of the area within the geographical tropics is classed not as "tropical" but as "dry (arid/semiarid)" including the Sahara Desert and Australian Outback.

Tropical ecosystems

Coconut Trees amongst the warm, tropical climate in Brazil.

Tropical plants and animals are those species native to the tropics. Tropical ecosystems may consist of rainforests, dry deciduous forests, spiny forests, desert and other habitat types. There are often significant areas of biodiversity, and species endemism present particularly in rainforests and dry deciduous forests. Some examples of important biodiversity and/or high endicism ecosystems are: Costa Rican and Nicaraguan rainforests, Brazilian and Venezuelan Amazon Rainforest territories, Madagascar dry deciduous forests, 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 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 (Central and South America). Together, they are sometimes referred to as the pantropics. The neotropic region should not be confused with the ecozone of the same name; in the Old World, this is unambiguous as the paleotropics correspond to the Afrotropical, Indomalayan, and partly the Australasian and Oceanic ecozones.

About 40 percent of the world's human population lives within the geographical tropic zone (by 2008 statistics).^[1]

See also

• Tropical year
• Tropic of Cancer
• Tropic of Capricorn
• Geographical zone
• Equator
• Tropical marine ecosystem
• Tropical disease
• Tropicalismo
• Subtropics

External links

• Tropen, Goethe-Institut (bilingual web site English/German with many informations and extracts from novels, short stories, essais, etc. written by explorers, conquerors and writers since the discovery of the so called New World)

References