The tropics are a region of Earth characterized by consistent warmth and abundant sunlight. This broad geographical zone supports a vast array of life and natural processes, distinguishing it from other planetary regions.
Geographical Boundaries
The northern boundary is the Tropic of Cancer (23.5° North latitude), and the southern boundary is the Tropic of Capricorn (23.5° South latitude). The Equator (0° latitude) runs centrally through this region, dividing it into Northern and Southern Hemispheres. These latitudes mark the furthest points where the sun’s rays are directly overhead at noon at least once a year.
The sun is directly overhead at the Tropic of Cancer around June 21st, during the Northern Hemisphere’s summer solstice. Conversely, the sun is directly overhead at the Tropic of Capricorn around December 21st, during the Southern Hemisphere’s summer solstice. This direct solar radiation defines the region’s climate. The area between these two tropics encompasses portions of continents such as Africa, South America, and Southeast Asia, along with numerous islands and vast oceanic expanses.
Characteristic Climate
The climate within the tropics is marked by consistently warm temperatures. Average monthly temperatures typically remain at or above 18°C (64°F), with little variation between months. This lack of significant temperature fluctuation means that the traditional four seasons experienced in temperate zones are absent.
Instead of seasonal temperature changes, tropical regions often experience wet and dry seasons. The timing and duration of these seasons can vary, with areas closer to the Equator often experiencing two wet and two dry seasons as the tropical rain belt passes over twice a year. High humidity is common, resulting from elevated temperatures, increased evaporation, and significant rainfall. Dense vegetation in some tropical areas further contributes to atmospheric moisture through a process called transpiration.
Rich Ecosystems
Stable warm temperatures and abundant rainfall in the tropics support a wide variety of life, leading to Earth’s most biodiverse ecosystems. This high productivity, driven by solar energy, allows for a greater number of species to thrive and specialize. The layered structure of vegetation in many tropical environments also creates numerous habitats and niches, further supporting diverse species.
Tropical rainforests exemplify this ecological richness, characterized by high annual rainfall and consistently high temperatures. These forests, found near the Equator, boast dense canopies and abundant plant growth, with some receiving over 2000mm of rainfall annually. Beyond rainforests, the tropics also host savannas, which are grasslands with scattered trees and shrubs, experiencing distinct wet and dry seasons. Tropical dry forests, where trees may shed leaves during drier periods, and coral reefs in warm ocean waters also contribute to the diverse array of tropical biomes.