Tropical Rain ForestThe tropical rain forest is a forest of tall trees in a region of year-round warmth. An average of 50 to 260 inches (125 to 660 cm.) of rain falls yearly.
Rain forests belong to the tropical wet climate group. The temperature in a rain forest rarely gets higher than 93 °F (34 °C) or drops below 68 °F (20 °C); average humidity is between 77 and 88%; rainfall is often more than 100 inches a year. There is usually a brief season of less rain. In monsoonal areas, there is a real dry season. Almost all rain forests lie near the equator.
Rainforests now cover less than 6% of Earth's land surface. Scientists estimate that more than half of all 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. 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.
About 1/4 of all the medicines we use come from rainforest 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.
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.
Despite these differences, each of the three largest rainforests--the American, the African, and the Asian--has a different group of animal and plant species. Each rain forest has many species of monkeys, all of which differ from the species of the other two rain forests. In addition, different areas of the same rain forest may have different species. Many kinds of trees that grow in the mountains of the Amazon rain forest do not grow in the lowlands of that same forest.
The tropical rain forest can be found in three major geographical areas around the world.
Tropical Rainforest Layers
Tropical rainforests have four layers:
Emergent Layer
These giant trees thrust above the dense canopy layer and have huge mushroom-shaped crowns. These trees enjoy the greatest amount of sunlight but also must endure high temperatures, low humidity, and strong winds.
Canopy Layer
The broad, irregular crowns of these trees form a tight, continuous canopy 60 to 90 feet above the ground. The branches are often densely covered with other plants (epiphytes) and tied together with vines (lianas). The canopy is home to 90% of the organisms found in the rain forest; many seeking the brighter light in the treetops.
Understory
Receiving only 2-15% of the sunlight that falls on the canopy, the understory is a dark place. It is relatively open and contains young trees and leafy herbaceous plants that tolerate low light. Many popular house plants come from this layer. Only along rivers and roadways and in treefall and cut areas is sunlight sufficient to allow growth to become thick and impenetrable.
Forest Floor
The forest floor receives less than 2% of the sunlight and consequently, little grows here except plants adapted to very low light. On the floor is a thin layer of fallen leaves, seeds, fruits, and branches that very quickly decomposes. Only a thin layer of decaying organic matter is found, unlike in temperate deciduous forest.
Did you know that enough rainforests are being destroyed every minute to fill 50 football fields? We need to preserve these valuable resources because they are the lungs of our planet, and can possibly hold cures for many of our most deadly diseases. The tropical rainforests are a critical link in the ecological chains of our our earth's biosphere.
Despite covering only 2% of our planet's surface, over half of the earth's animal, insect species, and flora live there. Within a four mile square area of a tropical rainforest, you would find:
- Over 750 species of trees
- 1500 different kinds of flowering plants
- 125 species of mammals
- 400 species of birds
- 100 reptiles
- 60 amphibians
- countless insects
- 150 species of butterflies
**Only 1% of these species has ever been studied**
Important Facts- Amazon rainforests produce about 40% of the world's oxygen
- One in four pharmaceuticals comes from a plant in the tropical rainforests
- 1400 rainforest plants are believed to offer cures for cancer
- 40% of tropical rainforests have already been lost in Latin America and Southeast Asia
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