Tropical rainforests are very wet places, receiving heavy rainfall either seasonally or throughout the year. They are close to the equator and get lots of sunlight and warmth. Temperatures are uniformly high - between 20 and 35°C. They usually receive more than 200 cm rainfall per year.
What is a Tropical forest?
A tropical rain forest has more kinds of trees than any other area in the world. Scientists have counted about 100 to 300 species in one 2 1/2-acre (1-hectare) area in South America. Seventy percent of the plants in the rainforest are trees
For biologists, tropical rainforests are some of the richest, most exciting areas on earth! They are home to gigantic trees, colourful birds, millions of brightly hued insects, and a variety of fascinating mammals. There are 3 main regions of tropical rainforest: in Central and South America, in West and Central Africa, and in Southeast Asia. The Amazon Basin forest is the largest, covering 6 million sq km.
Although rainforests are such important centres of biodiversity, they cover only about 6% of the Earth's land surface, less than half the area they covered not so very long ago.
All tropical rain forests resemble one another in some ways. Many of the trees have straight trunks that don't branch out for 100 feet or more. There is no sense in growing branches below the canopy where there is little light. The majority of the trees have smooth, thin bark because there is no need to protect the them from water loss and freezing temperatures. It also makes it difficult for epiphytes and plant parasites to get a hold on the trunks. The bark of different species is so similar that it is difficult to identify a tree by its bark. Many trees can only be identified by their flowers.
Animal life in tropical rainforsts
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.
The ecosystem of the rainforest
When early explorers first discovered the rainforests of Africa, Southeast Asia and South America, they They were amazed by the dense growth, trees with giant buttresses, vines and epiphytes . The tropical vegetation grew so dense that it was difficult to cut one's way through it. It was thought at the time that the soil of a rainforest must be very fertile, filled with nutrients, enabling it to support the immense trees and other vegetation they found.
Today we know that the soil of the tropical rainforests is shallow, very poor in nutrients and almost without soluble minerals. Thousands of years of heavy rains have washed away the nutrients in the soil obtained from weathered rocks. The rainforest has a very short nutrient cycle. Nutrients generally stay in an ecosystem by being recycled and in a rainforest are mainly found in the living plants and the layers of decomposing leaf litter. Various species of decomposers like insects, bacteria, and fungi make quick work of turning dead plant and animal matter into nutrients. Plants take up these nutrients the moment they are released.
A study in the Amazon rainforest found that 99% of nutrients are held in root mats. When a rainforest is burned or cut down the nutrients are removed from the ecosystem. The soil can only be used for a very short time before it becomes completely depleted of all nutrients.
Amazon river basin rainforest contains a wider variety of plant and animal life than any other biome in the world. The second largest population of plant and animal life can be found in scattered locations and islands of Southeast Asia. The lowest variety can be found in Africa. There may be 40 to 100 different species in 2.5 acres ( 1 hectare) of a tropical rain forest.
Rainforsts -- An endangered habitat
Rainforests are perhaps the most endangered habitat on earth. Each year, some 140,000 sq km of rainforests are destroyed. Rainforests are being felled for timber by logging companies and cleared by people for farming. The most endangered rainforests are those in West Africa, where human populations are doubling every 20 years, and in Central America and South-East Asia.
Although large areas of rainforest remain in Central Africa and South America, they, too, are disappearing at an alarming rate. Time is short if we are to save the remaining rainforests for future genrations.
For example, although tropical forests may look as though they are lush, they are actually highly susceptible to destruction. This is because the soils in which they grow are lacking in nutrients. It may take Centuries to re-grow a forest that was cut down by humans or destroyed by fire, and many of the world's severely threatened animals and plants live in these forests. If the current rate of forest loss continues, huge quantities of plant and animal species will disappear.
- In Peninsular Malaysia, more tree species are found in 125 acres of Tropical Forest than in the entire North America.
- In Peru a single bush may contain more ant species than in the British Isles.
- A study has shown that there are possibly over 30 million species of insects *dwelling in the canopies of tropical forests.
- 63,000 square miles of Rainforests are being destroyed each year.
- Rainforests higher than 3,000 feet above sea level are called cloud forests.
- Already over half of the world's tropical forests have been lost.
- Madagascar is the home to a rainforest where 60 percent of it's 12,000 different plant species are unique to that island.
- When you visit a pharmacist, one in every four purchases will have come from a tropical forest.
- Medicine produced in tropical forests bring in commercially 30 billion dollars a year.
- Large areas of South and Central America are cleared and burned for cattle ranching. This is so that farmers can provide cheap beef to consumers in the West.
- Every year approximately four billion tons of carbon accumulates in the air each year, about 30% of this comes directly from the continued burning of the rainforests.
- More than anything else, rainforest is destroyed by peasant farmers. However, the responsibility for this lies largely with the governments who fail to promote land reform and sustainable agricultural practices as an alternative to forest clearance.
- Greater than a quarter of our rainforest is in Brazil.