Distribution of Tropical rainforest
Requirements and distribution of tropical rain forest around the world.
There are several conditions required for a tropical rain forest to grow. Primarily, there needs to be light, warmth, and moisture. The tropics receive a lot of sunlight. This is due to their location on the larger, bulging equatorial region of the globe. Here, there is little variation in the amount of sunlight during the day throughout the year. The time of the sun setting and rising does not vary much more than about an hour of the same time every day. This constant sunlight results in a high temperature. Further, the temperature does not vary much during the year. On the constantly shaded rain forest floor, the temperature will vary even less. Visitors are often shocked by how much it rains. Of course, this is the rain forest, and it is by implication an essential requirement. And not only does it rain a lot, it needs to rain all the time; that is, the rainfall generally needs to be evenly distributed throughout the year. Finally, if you are travelling through the tropical rain forest you will notice another condition. Its result is copious sweating, even when standing still. The rain forest has very high humidity, a combination of the two factors of heat and water. For many people, it is this high humidity that makes the tropical rain forest so uncomfortable.
In addition, there are certain ‘limiting’ conditions that cannot occur if tropical rain forest is to develop. The temperature must not drop so low as to allow frost to appear (Winter and Atherton 1987). ‘Moisture stress’ cannot occur for prolonged periods; if a dry season lasts for a period of a few months every year, then rain forest will not survive and a monsoon forest will develop (Whitmore 1999). In even drier situations, an open woodland or savanna will grow.
Of course, there are other secondary conditions may determine whether a tropical rain forest will develop. One of these is soil type. If the soil is deeper and more fertile, rain forest may able to develop in areas with less rain or lower temperatures that would normally limit its growth. In fact, this is the situation in large parts of the eastern and southern Amazon rain forest of South America. Following on from this, contrary to many popular beliefs, rain forest does not limit itself to poor soils. Rather, it can grow in wet and warm conditions despite poor soils. Some of the most diverse and luxuriant rain forests in the world grow on rich soils, such as the rain forests on the volcanic soils in areas of Costa Rica, Indonesia and the Atherton Tablelands in Australia.
Tropical rain forests should thus develop in areas where these conditions are met around the world. These rain forests are, by definition, within the tropics, the region bordered by the tropic of cancer in the Northern Hemisphere and the tropic of Capricorn in the south.