What Are the Tropics?
The tropics are a region of the Earth sitting roughly in the middle of the globe. Surrounding the Equator, they are bounded by two lines of latitude–the Tropic of Cancer in the Northern Hemisphere, and the Tropic of Capricorn in the Southern Hemisphere. The tropics contain about 36% of the Earth’s landmass, and about 40% of the world’s population.
The tropics include all areas on the planet where the Sun is directly overhead at least once during the solar year. As such, the latitudes of the Tropic of Cancer and the Tropic of Capricorn are roughly equal to the angle Earth tilts on its axis (~23°).
The tropics are sometimes called the tropic or torrid zone, and they are distinct from other regions of the Earth, like the middle latitudes and the polar regions, which are found on both sides of the Equator.
What Does It Mean To Be “Tropical”?
The word “tropical” is commonly used to describe any hot, wet, lush region, regardless of where the place is actually located. But this can be a bit misleading, since the climate of the tropics doesn’t always seem that “tropical”. Keep in mind that the tropics are a broad area, circling a large portion of the globe. And there is much diversity in climates and ecosystems within this region.
Generally speaking, the tropics don’t really experience the four seasons more temperate places might get. Instead, it’s more common for tropical regions to have a wet and dry season. The amount of rain during the wet season can vary greatly from one area to another though. Parts of the Amazon Basin, for example, might get up to 9 feet of rain a year. Other places like the Sahara might get less than an inch.
Related: Why Do We Have Seasons?
Furthermore, many areas within the tropics have climates that are better described as arid or semi-arid, and not “tropical”. We mentioned the Sahara, but there’s also the Atacama Desert and the Australian Outback to name a few. And conversely, the tropics are also home to alpine tundra and snow-capped peaks, like in the Andes or on top of Mount Kilimanjaro.
Plants and Wildlife
The amount of rainfall a tropical location receives directly affects the plant and animal species that can be found there. In the arid tropics of Africa, for example, the water-storing baobab tree thrives. Meanwhile, Sri Lanka gets enough yearly rainfall to support hundreds of unique frog species.
It should come as no surprise then that tropical ecosystems are extremely diverse. They include rainforests, seasonal forests, dry forests, spiny forests, deserts, rocky mountains, and more. Rainforests and seasonal forests can feature especially high levels of biodiversity, some serving as home to exotic animals and/or rare flora.
Unfortunately, many of these ecosystems face threats from encroaching human activity. The soil in tropical forest are typically low in nutrients, making them more susceptible to slash-and-burn deforestation. This type of activity not only threatens plant and animal habitats, but can lead to larger problems, as evidenced by the 2019 Amazon rainforest wildfires.
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About the Author:
Mark Heald is the Managing Editor of Sporcle.com. He enjoys spending time with his family, traveling, and bemoaning the fact the Sonics left Seattle.
