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Created by Ekaterina Gurova, EPb-131 1
What are rainforests? Rainforests are forests characterized by high rainfall, with annual rainfall between 250 and 450 centimeters. Around 40% to 75% of all biotic species are indigenous to the rainforests. It has been estimated that there may be many millions of species of plants, insects and microorganisms still undiscovered in tropical rainforests. Tropical rainforests have been called the "jewels of the Earth" and the "world's largest pharmacy", because over one quarter of natural medicines have been discovered there. Rainforests are also responsible for 28% of the world's oxygen turnover. 2
There are two types of rainforest: Tropical rainforest Temperate rainforest 3
Tropical rainforests are characterized by a warm and wet climate. Mean monthly temperatures exceed 18 °C during all months of the year. Average annual rainfall is no less than 168 cm and can exceed 1, 000 cm General distribution of tropical rainforest 4
Tropical rainforests are located in the tropics. They exist in Southeast Asia (from Myanmar to the Philippines, Malaysia, Indonesia, Papua New Guinea and northeastern Australia), Sri Lanka, sub-Saharan Africa from Cameroon to the Congo , South America, Central America, and on many of the Pacific Islands (such as Hawaii). 5
Temperate Tropical forests cover a large part of the globe, but temperate rainforests only occur in few regions around the world. Temperate rainforests are rainforests in temperate regions. They occur in o North America (in the Pacific Northwest in Alaska, British Columbia, Washington, Oregon and California) o Europe (parts of the British Isles such as the coastal areas of Ireland Scotland, southern Norway, parts of the western Balkans along the Adriatic coast, as well as in Galicia and coastal areas of the eastern Black Sea, including Georgia and coastal Turkey) o East Asia (in southern China, Highlands of Taiwan, much of Japan and Korea, and on Sakhalin Island the adjacent Russian Far East coast) o South America (southern Chile) and also in Australia and New Zealand. 6
General distribution of temperate rainforests 7
Layers of the rainforest Rainforest is typically divided into four main layers, each with different plants and animals adapted for life in that particular area: the emergent, canopy, understory and forest floor layers. emergent canopy understory forest floor 8
Emergent layer The emergent layer contains a small number of very large trees called emergents, which grow above the general canopy, reaching heights of 45– 55 m, although on occasion a few species will grow to 70– 80 m tall. They need to be able to withstand the hot temperatures and strong winds that occur above the canopy in some areas. Eagles, butterflies, bats and certain monkeys inhabit this 9 layer.
Canopy layer The canopy layer contains the majority of the largest trees, typically 30 meters to 45 meters tall. The canopy is home to 50 percent of all plant species. The fauna is similar to that found in the emergent layer, but more diverse. 10
Understory layer The understory layer lies between the canopy and the forest floor. It is home to a number of birds, snakes and lizards, as well as predators such as jaguars, boas and leopards. The leaves are much larger at this level and insect life is abundant. 11
Forest floor The forest floor, the bottom-most layer, receives only 2% of the sunlight. Only plants adapted to low light can grow in this region. It also contains decaying plant and animal matter, which disappears quickly, because the warm, humid conditions promote rapid decay. Many forms of fungi growing here help decay the animal and plant waste. 12
Flora and fauna More than half of the world's species of plants and animals are found in the rainforest. Rainforests support a very broad array of fauna, including mammals, reptiles, birds and invertebrates. Mammals may include primates, felids and other families. Reptiles include snakes, turtles, chameleons and other families. Dozens of families of invertebrates are found in rainforests. Fungi are also very common in rainforest areas as they can feed on the decomposing remains of plants 13 and animals.
Human uses Rainforests provide timber as well as animal products such as meat and hides. Rainforests also have value as tourism destinations. Many foods originally came from tropical forests, and are still mostly grown on plantations in regions that were formerly primary forest. Many plants are used as medicines. 14
Effect on global climate Rainforests play a very important role in the regulation of regional climate, as they provide up to 50% of the water cycle through transpiration, which leads to the formation of clouds over the active surface area of growth and the return of water in the form of precipitation. Rainforests also play a role in cooling the air that passes through them. Therefore rainforest is one of the most important ecosystems on the planet. Rainforests are also responsible for the cycle 15 of about 28% of the oxygen in the world.
Deforestation Tropical and temperate rainforests have been subjected to heavy logging and agricultural clearance throughout the 20 th century and the area covered by rainforests around the world is shrinking. 16