Tropical Rain Forest INTRODUCTION Tropical rain forests have more species of life than any other terrestrial environment. At least half of the species of land animals in the world live in tropical rain forests. That means they contain anywhere from 2 million to 20 million species. The area covered by rain forests is only about 6% of Earth s surface. Tropical rain forests are found near the equator, in Australia, Asia, Africa, Central and South America, the Caribbean Islands, and the Pacific Islands. Half of all tropical rain forests are found in Latin America; one third of the world s rain forests are in Brazil. Page 1 of 8
Rain forests are characterized by moisture. The humidity can cause clouds to form within the forest itself. ABIOTIC DATA Because tropical rain forests lie near the equator, the days do not get shorter in winter and longer in summer. A day has about 12 hours of sunlight throughout the year. Data from Missouri Botanical Garden The average rainfall in the rain forest is the highest for any ecoregion on Earth. The climate in tropical rain forests is constantly warm and moist. The average rainfall in most rain forests is very heavy, about 200 450 centimeters (80 180 inches) per year. Some areas, however, get as much as 1000 Page 2 of 8
centimeters (400 inches) of rain per year! Standing water and rivers are common sights in the rain forest. Rivers in the rain forest provide more than water; they are also essential for transportation of goods for the human inhabitants. One important feature of the rain-forest climate is the average temperature range. The difference between the hottest and coldest months is only about 10 C (18 F). The temperature ranges from 25 C (77 F) in the coldest months to 25 C (95 F) in the hottest months. BIOTIC DATA About 70% of rain-forest plants are trees. Tropical rain forests have a layered structure. A middle layer of trees forms a canopy, or roof, above the forest. This canopy allows little light through. Many trees have leaves with drip tips that channel water off the leaves. Thick, woody vines called lianas are found in the canopy. They can be as big around as a person. Plants called epiphytes grow on canopy trees. Epiphytes include orchids, ferns, mosses, and lichens. Epiphytes use the tree for support and get water from falling rain. Monkeys, sloths, bats, tree frogs, ants, beetles, parrots, hummingbirds, and snakes are just a few of the animals that live in the canopy. Page 3 of 8
Many orchids are epiphytes that grow on trees. Bromeliads are also epiphytes. They hold water in the center of the cup of leaves that can be home to insects and frogs. Emergents, or tall trees, poke up through the canopy. They can grown up to 30 50 meters (100 165 feet) tall. Animals such as eagles, monkeys, butterflies, insect-eating bats, and snakes live in the emergent layer. Some of these animals never travel into the layers below. Below the canopy is a layer called the understory. This part of the forest remains green all year round. Vines, small trees, ferns, and palms grow here. They don t need much direct sunlight or rainfall. Jaguars, leopards, snakes, frogs, parakeets, and many types of insects make the understory their home. Page 4 of 8
Shallow soil cannot hold up the giant rain-forest trees without the added support of buttress roots that flare out from the base. Tapirs are small, hoofed animals found in tropical rain forests. They are hunted for food. Not many plants grow on the forest floor, because not much sunlight reaches that far. Mosses, herbs, and fungi grow there. The floor is covered with wet leaves and leaf litter. This is where most of the decay occurs in the rain forest. Decay provides nutrients that return to the soil. The leaf litter may hide the largest number of rain-forest inhabitants. Many insects thrive in the leaf litter, including termites, ants, cockroaches, beetles, centipedes, millipedes, and scorpions. Earthworms and fungi use the organic litter as food. Large mammals, such as tapirs, forage for roots on the forest floor. Page 5 of 8
Fallen trees quickly begin to decompose in this warm, moist environment. Ferns, mosses, and fungi cover the forest floor. Rain-forest soil is shallow and not very fertile. Most of the nutrients that plants need to survive are contained in the trees. If the trees are cut down and taken away, the nutrients are lost to the ecoystem. It takes a long time for tropical rain forests to grow back once the trees are removed. Iguanas hide in trees over a river. When threatened, they fall into the water below and escape. Chameleons lie motionless and wait for insects to come into reach. They often change color to blend in with their surroundings. Many of the plants people keep as houseplants originated in rain forests. These include bromeliads, African violets, periwinkle, anthurium, philodendron, and Christmas cactus. Bananas, avocados, pineapples, peppers, peanuts, oranges, lemons, papaya, pepper (the spice), coconut, sugarcane, cassava, and cacao (chocolate) all grow in the rain forest. Coffee beans, cashews, and Brazil nuts are also rain-forest products. Page 6 of 8
Coffee and spices sold at an outdoor market are the same as those found in grocery stores throughout the world. Many fruits and vegetables have their origins in the rain forest. About one-fourth of all medicines come from rain-forest plants. These include curare (a tropical vine from which a surgical anesthetic is created), quinine (a treatment for malaria), and rosy periwinkle (from which a drug for lymphocytic leukemia is derived). ISSUES One hundred years ago, rain forests covered a much greater area than they do now. Today trees are cut down and burned to create new farmland. They are also cut for lumber and access to mineral resources. About 20 hectares (50 acres) of rain forest is destroyed every minute, somewhere in the world. If the destruction continues, tropical rain forests may be wiped out during the 21st century. The easiest way to clear the forest to create farmland is to cut and burn. When nutrients are depleted, the land is abandoned and a new area is cleared. Because of the poor quality of the soil, few crops can grow for more than a few years. Page 7 of 8
Eighty percent of the life-forms in tropical rain-forests have not been named or scientifically identified. Some live only in very small and remote areas and may be important sources of drugs or other medical uses. The fear is that species are disappearing with rain forests before they are discovered and scientifically described. Some species may be lost to human greed. Animals such as jaguars are hunted for their fur. Many animals are illegally captured and end up in the pet trade. Pet iguanas and parrots could be bred in captivity rather than removed from their native habitat. Ecotourism has brought many people to view and experience the rain forest. This business produces income for local inhabitants in a way that is less destructive than using the forest as farmland. Ecotourism may also create problems, however, as more people seek remote areas of the rain forest. Illegally captured parrots can end up in pet stores. A treehouse built so that tourists can experience life in the canopy. Data is available to scientists that suggests the amount of carbon dioxide in the atmosphere is increasing. This is good for plants that use it in photosynthesis to make food. But global temperatures may also be rising. This affects precipitation patterns. Precipitation has increased by about one percent over the world's continents in the last century. High latitude areas are tending to see more significant increases in rainfall, while precipitation has actually declined in many tropical areas. Page 8 of 8