Transcript Rainforest
Rainforests Rainforests have been called the womb of life because they are home to 50-90% of the species on Earth. It’s vegetation helps clean the earth’s atmosphere and regulate the climate. Several hundred million people live in or depend on rainforests. Many of the world’s important food crops and domestic animals have been developed from rainforest species. Tropical rainforests are the result of the unique climatic conditions found between the Tropics of Cancer and Capricorn. Constant heat and humidity allow trees and plants to grow year round. Columns of hot air rise and condense out as rain, resulting in annual rainfall of 80 to 400 inches: temperatures average over 80 degrees Fahrenheit. Structure of the Rainforest Emergent trees Above the upper canopy, tower a few emergent trees, sometimes as tall as 130 feet. In all the forest, they alone enjoy unobstructed access to the sun and sky. The Canopy The vast carpet of green comprises the canopy that hovers over the forest below. It absorbs as much as 90% of the sunlight falling on the forest, darkening the lower regions. Here 65-100 feet up live butterflies and mammals. Temperatures here reach 96 F but the humidity is only 60%, compared to 90% down below. The Understory In the undeveloped forest undisturbed rainforest is clear of vegetation close to the ground because so little light filters down through the canopy, sometimes only 1 to 2 per cent. Temperatures are cooler, averaging about 82 F with humidity at about 90%. By most estimates, the world’s forests are disappearing at an alarming rate. Logging, fires, and land-clearing for agriculture and grazing account for most of the loss. More than 80 percent of the Earth’s natural forests already have been destroyed. Among the obvious consequences of deforestation is the loss of living space. Seventy percent of the Earth’s land animals and plants reside in forests. It has been estimated that at least 40 species are perishing every day. This is a rate hundreds of times faster than at any period in recent geological time. Rainforests are also a vital source of medicines. Today, less than 1% of the world's tropical forest plants have been tested for pharmaceutical properties, yet at least 25% of all modern drugs came originally from rainforests. 70% of all plants known to have anti-tumor properties come from tropical rainforests. Any one of these could lead to breakthroughs in the treatment of cancer. The potential of this living pharmaceutical factory remains almost completely untapped. The potential and fragility of the rainforests as an invaluable source of medicine is illustrated in the following account from the World Rainforest Report no.26: "Starting with twigs from a Malaysian gum tree, researchers in 1991 isolated a compound that blocked the spread of the AIDS virus in human cells. The team sent biologists racing back to Malaysia for more samples from the tree. But when they got to the swamp, the tree was gone, it had been cut down. And no tree found since has produced the same compound. " But the harm doesn’t stop there. Rain forests help generate rainfall in drought-prone countries elsewhere. Deforestation may have catastrophic global effects as well. Trees are natural consumers of carbon dioxide— one of the greenhouse gases whose buildup in the atmosphere contributes to global warming. No one knows just how the rest of the global ecosystem depends on rainforests, but we may find out in the next 30 to 50 years. That is how long it is estimated that it will take for tropical forests to disappear altogether if current trends continue. The Amazon The Amazon is the world's largest tropical rainforest, spanning Brazil, Colombia, Ecuador, Peru, Bolivia, and Venezuela . Within the 2.5 million square miles of the Amazon Basin resides a wealth of life richer than anyplace else on earth, including 500 mammals, 175 different lizards, 300 other reptile species, tree climbers of every kind, and a third of the world's birds. Millions of species still remain undiscovered. The basin also has huge reserves of bauxite, nickel, copper, tin and timber. Trees and vegetation in the basin help to balance carbon dioxide and oxygen. The basin holds 20% of the earth’s fresh water, more than the next six largest rivers combined. The flow of the Amazon is so powerful that it dilutes the saltwater more than one hundred miles beyond the coastline. Most of the people living in South America today have both European and indigenous ancestors. Until recently, however, few of them lived in the Amazon. They preferred to live in established cities along the coasts and in the Andes mountains. But in the past few decades, more and more mestizos have moved to the Amazon. They were having trouble finding work in their hometowns and saw opportunity in the Amazon. Many went looking for agricultural land. Others took jobs in oil fields or other industries. Settlement in the Ecuadorian Amazon 1960 to 1990 About a third of Ecuador lies within the Amazon. Since the 1950s, Ecuadorians (mostly mestizos) from the Andean highlands and the western coastal plain have been migrating to the Amazon. The population of the Ecuadorian Amazon has increased from about 60,000 people in the 1950s to 350,000 people now. By clearing forest to build homes, plant crops, and extract petroleum, these people have had a dramatic impact on the rainforest. The deforestation of the Amazon basin may have long reaching effects. When the trees are removed, we reduce the amount of carbon dioxide taken from the air. Some scientists predict that the buildup of carbon dioxide will cause global warming. If the temperature of the earth rises, polar ice will melt, raising the level of the ocean. Plants and animals are also in danger of extinction and medical advances may be delayed or negated as a result of deforestation. What is lost as the rain forests disappear is more than biodiversity and a stable environment. The rain forests also hold secrets of nature that might improve and extend the quality of people’s lives. Endangered Species of South America http://www.eduweb.com/amazon.html http://www.rainforestinfo.org.au/ http://passporttoknowledge.com/rainforest/main.html http://www.nationalgeographic.com/eye/deforestation/deforestat ion.html http://www.junglephotos.com/ http://www.mrdowling.com/712-amazon.html Rainforest Quiz! 1. Where are rainforests found around the world? 2. What is the world’s largest tropical rainforest? 3. What country’s population in the rainforest increase from 60,000 to 350,000? 4. Name two causes of deforestation. 5. Name two effects of deforestation. BONUS: Name the three layers of the rainforest. 1. What are Costa Rica’s major exports, and what do they mean to its economy? 2. What is ecotourism, and why is it important to Costa Rica? 3. What is the real condition of the tropical rainforests in Costa Rica and throughout the world? 4. What is being done to preserve rain forest ecosystems? 5. Can people and natural ecosystems coexist? Explain.