Tropical Rain Forest
Tropical rain forests are found in three major geographical areas around the world.
- Central America – Amazon River basin
- Africa – Zaire basin, eastern Madgascar
- Asia-Pacific – West coast of India, Assam, Southeast Asia, New Guinea and Queensland, Australia
Once tropical rain forests blanketed the Earth like a wide green belt around the equator. Just a few thousand years ago rain forests covered 14 percent of the Earth’s land surface. In the present, different authorities have guessed rainforests’ coverage to be between two and six percent of Earth's land surface. Even then, scientists estimate that more than half of the world's plant and animal species live in tropical rain forests. Tropical rainforests produce 40% of Earth's oxygen.
A tropical rain forest has more kinds of trees than any other area in the world. Seventy percent of the plants in the rain forest are trees. Upto 300 species have been counted in one 2 1/2-acre (1-hectare) area in a rainforest. According to a report by the United States’ National Academy of Sciences, a 4-square-mile (1,000 hectare) patch of rain forest contains up to 1,500 species of flowering plants, as many as 750 species of trees, 125 species of mammals, 400 species of birds, 150 species of butterflies, 100 species of reptiles, and 60 species of amphibians.
About one-fourth of all the medicines we use come from rain forest plants. Curare comes from a tropical vine, and is used as an anesthetic and to relax muscles during surgery. Quinine, from the cinchona tree, is used to treat malaria. A person with lymphocytic leukemia has a 99% chance that the disease will go into remission because of the rosy periwinkle. More than 1,400 varieties of tropical plants are thought to be potential cures for cancer.
There are four very distinct layers of trees in a tropical rain forest. These layers have been identified as the emergent, upper canopy, understorey, and forest floor.
- Emergent trees are spaced wide apart, and are 100 to 240 feet tall with umbrella-shaped canopies that grow above the forest.
- The upper canopy of 60 to 130 foot trees allows light to be easily available at the top of this layer, but greatly reduced any light below it. Most of the rainforest's animals live in the upper canopy. There is so much food available at this level that some animals never go down to the forest floor.
- The understory, or lower canopy, consists of 60 foot trees. This layer is made up of the trunks of canopy trees, shrubs, plants and small trees. There is little air movement. As a result the humidity is constantly high. This level is in constant shade.
- The forest floor is usually completely shaded, except where a canopy tree has fallen and created an opening. Most areas of the forest floor receive so little light that few bushes or herbs can grow there. Less than 1 % of the light that strikes the top of the forest penetrates to the forest floor. The top soil is very thin and of poor quality.
Rainforest plants have made many adaptations to their environment. With over 80 inches of rain per year, plants have made adaptations that help them shed water off their leaves quickly so the branches don't get weighed down and break.
Many species of animal life can be found in the rain forest. Common characteristics found among mammals and birds (and reptiles and amphibians, too) include adaptations to a life in the trees, such as the prehensile tails of New World monkeys. Other characteristics are bright colors and sharp patterns, loud vocalizations, and diets heavy on fruits. Insects make up the largest single group of animals that live in tropical forests. They include brightly colored butterflies, mosquitoes, camouflaged stick insects, and huge colonies of ants.
Humans already have destroyed half of the world’s rainforest in the last two to three hundred years. Rain forests are being eliminated for timber, minerals, agriculture, and human settlement. Other motives, such as the desire to conquer nature or to control unoccupied territory, also are factors in deforestation.
Destruction of rainforests affects human life on the entire globe. These effects are the results of extinction of many species, the loss of resources and the decrease in carbon sinks. Loss of rainforests reduce biodiversity and threatens the stability of the climate globally.
Conserving and regenerating rainforests has proved to be a difficult prospect. Inspite of efforts like creating conservation zones, the destruction of rainforests is increasing. It is essential to incorporate social and economic concerns in the solutions for conserving rainforests. A majority of areas with the world's rainforests also have the world's poorest populations, and they depend on these forests for their survival. It is necessary for policies to succeed that the well-being of these populations is not ignored.
The latest trend is to concentrate on improving the utilisation of lands already cleared, and to rehabilitate and restore the damaged rainforests.