Rainforest

The Daintree Rainforest in Queensland, Australia.

A rainforest, is a large, dense forest in a hot, humid region (tropical or subtropical).

Rainforests have an abundance of diverse plant and animal life, much of which is still uncatalogued by the scientific community. There are literally millions of species in the rainforest.

Rainforests once covered about 14% of the Earth but have been reduced in size now to only about 6% of the Earth's surface. Even though half the rainforests of the world are gone, they still hold more than half of all plant and animal species on Earth.

The largest tropical rainforests exist in the Amazon basin (the Amazon Rainforest), in Nicaragua (Los Guatuzos, Bosawás and Indio-Maiz), the southern Yucatan peninsula-El Peten-Belize contiguous area of Central America (including the Calakmul Biosphere Reserve), in much of equatorial Africa from Cameroon to the Democratic Republic of Congo, in much of southeastern Asia from Myanmar to Indonesia and Papua New Guinea, eastern Queensland, Australia and in some parts of the United States. Outside of the tropics, temperate rainforests can be found in British Columbia, southeastern Alaska, western Oregon and Washington, the western Caucasus (Ajaria region of Georgia), parts of the western Balkans, New Zealand, Tasmania, and parts of eastern Australia.

While the Amazon Rainforest is largest in size the Atlantica Rainforest near Rio de Janeiro which has been reduced in size by over 90% it still holds more biodiversity than the Amazon.

While it's commonly believed that rainforests provide much of the oxygen for the planet, and are the "lungs of the world", most rainforests do not in fact provide oxygen for the rest of the world. Through the decomposition of dead plant matter, rainforests consume as much oxygen as they produce, except in certain conditions (primarily swamp forests) where the dead plant matter does not decay, but is preserved underground instead (ultimately to form new coal deposits over enough time). Still, rainforests act as major consumers of atmospheric carbon and may play a large role in cooling air that passes through them. As such, many scientists feel that the rainforests are of vital importance within the global climate system.

Characteristics

Rainforests are characterized by high rainfall, with definitions setting minimum normal annual rainfall between 2 meters (about six 1/2 feet ) The soil can be poor because high rainfall tends to leach out soluble nutrients.

Rainforests are home to two-thirds of all the living animal and plant species on the planet. It has been estimated that many hundreds of millions of new species of plants, insects, and microorganisms are still undiscovered and as yet unnamed by science. Tropical rainforests are called the "jewel of the earth", the "Earth's lungs", and the "world's largest pharmacy" because of the large amount of natural medicines discovered there.

Despite the growth of flora in a rainforest, the actual quality of the soil is quite poor. Rapid bacterial decay prevents the accumulation of humus.

The undergrowth in a rainforest is restricted in many areas by the lack of sunlight at ground level. This makes it possible for people and other animals to walk through the forest. If the leaf canopy is destroyed or thinned for any reason, the ground beneath is soon colonised by a dense tangled growth of vines, shrubs and small trees called jungle.

Temperate rainforests

Temperate rain forest in the Mount Hood Wilderness, Oregon, United States. This area, on the west side of the mountain, receives over 2.5 meters of rain per year.

Olympic Peninsula. Temperate rain forests often grow right up to the shoreline.

Temperate rain forests are coniferous or broadleaf forests that occur in the mid-latitudes in areas of high rainfall. Most of these occur in Oceanic-Moist Climates (Northwestern North America (Northwestern California to Southeastern Alaska), Northwest Europe (British Isles and Norway), Southern Chile, Southeastern Australia (Tasmania/Victoria), the West Coast of New Zealand's South Island and some occur in Subtropical-Moist Climates (The Colchian temperate rain forests of the Eastern Black Sea region, New Zealand's North Island, South Africa's Garden Route, southern/western Japan, and the mountain temperate coniferous rain forests of Taiwan's Central Mountain Ranges).

Temperate rain forests are distinguished from other temperate forests by a few factors:

• Rainfall: high rainfall (minimum 2,000-3,000 mm/year, depending on latitude), usually from moisture-laden winds off the ocean.
• Proximity to the ocean: temperate rain forests depend on the proximity to the ocean to moderate seasonal variations in temperature, creating milder winters and cooler summers than continental-climate areas. Many temperate rain forests have summer fogs that keep the forests cool and moist in the hottest months.
• Coastal mountains: temperate rain forests occur where mountains ranges are close to the coast; coastal mountains increase rainfall on the ocean-facing slopes.

Temperate rain forests may be predominantly coniferous (with deciduous trees in understory), broadleaf evergreen, or mixed forests with deciduous species, and occur in Temperate broadleaf and mixed forests and Temperate coniferous forests ecoregions.

The temperate coniferous rain forests sustain the highest levels of biomass in any terrestrial ecosystem and are notable for trees of massive proportions, including Coast Redwood (Sequoia sempervirens), Coast Douglas-fir (Pseudotsuga menziesii), Sitka Spruce (Picea sitchensis), Alerce (Fitzroya cupressoides) and Kauri (Agathis australis). These forests are quite rare, occurring in small areas of Western North America, southwestern South America and northern New Zealand.

Temperate forests cover a large part of the globe, but temperate rain forests only occur in seven regions around the world; the Pacific temperate rain forests of North America, the Valdivian and Magellanic temperate rain forests of southwestern South America, the Colchian rain forests of the eastern Black Sea region (Turkey and Georgia), the New Zealand temperate rain forests, Tasmanian temperate rain forests, South Africa's Knysna-Amatole coastal forests, and pockets of rain forest in northwest Europe and southwest Japan's Taiheiyo evergreen forests. Also, there are forests similar to those in Japan in Taiwan's Montane forests of the Central Mountain Ranges along Eastern Taiwan's Pacific Coast.

Tropical rainforests

Rainforest on Fatu-Hiva, Marquesas Islands

Tropical and subtropical moist broadleaf forests, also known as tropical rain forests or tropical wet forests, are a tropical and subtropical forest biome.

Tropical and subtropical moist broadleaf forests are found in a belt around the equator and in the humid subtropics, and are characterized by warm, humid climates with high year-round rainfall. Tropical and subtropical regions with lower rainfall or distinct wet and dry seasons are home to Tropical and subtropical dry broadleaf forests and Tropical and subtropical coniferous forests. Temperate rain forests also occur in certain humid temperate coastal regions.

Tropical and subtropical moist broadleaf forests are common in several terrestrial ecozones, including parts of the Afrotropic (equatorial Africa), Indomalaya (parts of the Indian subcontinent and Southeast Asia), the Neotropic (northern South America and Central America), Australasia (eastern Indonesia, New Guinea, and northern Australia), and Oceania (the tropical islands of the Pacific Ocean). About half of the world's tropical rainforests are in the South American countries of Brazil and Peru. Rain forests 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.

• rainfall : high, year round, sometimes with seasonal variation.
• temperature : always warm
• soil : generally poor and leached.
• plants : high diversity
• animals : high diversity

Trees

Rainforest on Fatu-Hiva, Marquesas Islands

There are several common characteristics of tropical trees. Tropical species frequently possess one or more of the following attributes not commonly seen in trees of higher latitudes.

Many species have broad, woody flanges (buttresses) at the base of the trunk. Originally believed to help support the tree, now it is believed that the buttresses channel stem flow and its dissolved nutrients to the roots.

Trees are often well connected in the canopy layer especially by the growth of woody climbers or lianas, plants with epiphytic adaptations, allowing them to grow on top of existing trees in the competition for sunlight.

Other characteristics that distinguish tropical species of trees from those of temperate forests include:

Exceptionally thin bark, often only 1-2 mm thick. Usually very smooth, although sometimes armed with spines or thorns.

Cauliflory, the development of flowers (and hence fruits) directly from the trunk, rather than at the tips of branches.

Large fleshy fruits attract birds, mammals, and even fish as dispersal agents.

There are several common characteristics of tropical trees. Tropical species frequently possess one or more of the following attributes not commonly seen in trees of higher latitudes.

Many species have broad, woody flanges (buttresses) at the base of the trunk. Originally believed to help support the tree, now it is believed that the buttresses channel stem flow and its dissolved nutrients to the roots. Large leaves are common among trees of the C layer. Young individuals of trees destined for the B and A layers may also have large leaves. When they reach the canopy new leaves will be smaller. The large leaf surface helps intercept light in the sun-dappled lower strata of the forest. Drip tips facilitate drainage of precipitation off the leaf to promote transpiration. They occur in the lower layers and among the saplings of species of the emergent layer (A layer).

Trees are often well connected in the canopy layer especially by the growth of woody climbers or lianas, plants with epiphytic adaptations, allowing them to grow on top of existing trees in the competition for sunlight.

Other characteristics that are more frequent in tropical tree species than in temperate forests include:

• Exceptionally thin bark, often only 1-2 mm thick. It is usually very smooth, although sometimes covered with spines or thorns.
• Cauliflory, the development of flowers (and hence fruits) directly from the trunk, rather than at the tips of branches.
• Large fleshy fruits attract birds, mammals, and even fish as dispersal agents.

The Canopy

Away from river banks, swamps and clearings where dense undergrowth is found, the forest floor is relatively clear of vegetation, as little sunlight penetrates to ground level. The densest areas of biodiversity are found in the forest canopy, a more or less continuous cover of foliage formed by adjacent treetops.

The canopy, by some estimates, is home to 40% of all plant species, suggesting that perhaps half of all life on Earth could be found there. A quarter of all insect species are believed to exist in the rainforest canopy.

Scientists have long suspected the richness of the canopy as a habitat, but have only recently developed practical methods of exploring it. As long ago as 1917, U.S. naturalist William Beebe declared that "another continent of life remains to be discovered, not upon the Earth, but one to two hundred feet above it, extending over thousands of square miles".

True exploration of this habitat only began in the 1980s, when scientists developed methods to reach the canopy, such as firing ropes into the trees using crossbows. Exploration of the canopy is still in its infancy, but other methods include the use of balloons and airships to float above the highest branches and the building of cranes and walkways planted on the forest floor.

Understory

There is a space between the canopy and the forest floor, which is known as the understorey (or understory). This is home to a number of birds, monkeys, snakes, and lizards. The leaves are much larger at this level. Insect life is also abundant.

The rainforest as a source of drugs

Tropical rain forests are called the 'world's largest pharmacy' because of the large amount of natural medicines discovered there. Nearly half of the medicines that humans use come from the rainforests.

Currently 121 prescription drugs sold worldwide come from plant derived sources including 25% of Western pharmaceuticals that are specifically derived from rainforest plants.

The National Cancer Institute has identified 3000 plants that are active against Cancer Cells. 70% of these cancer fighting plants are found in the rainforest.

Today there are over 100 pharmaceutical companies and several government agencies researching plants from the rainforest for possible cures for AIDS, Cancer, and other diseases.

Degradation of the rainforests

It is estimated that we are losing one and half acres of rainforests every second with tragic consequences to both developed and developing nations alike.

Some estimate that as much as 1/2 of the world’s plants, animals, and microorganisms may be lost if the trends of degradation to the rainforest continue unchecked in the next quarter of a century.

Tropical and temperate rainforests have been subjected to heavy logging and agricultural clearance throughout the 20th century, and the area covered by rainforests around the world is rapidly shrinking. It is estimated that the rainforest was reduced by about 58,000 km©˜ annually in the 1990s.

Biologists have estimated that large numbers of species are being driven to extinction, possibly as much as 50,000 a year (or 137 species lost per day) , due to the removal of habitat with destruction of the rainforests.

Protection and regeneration of the rainforests is a key goal of many environmental charities and organizations, including the Rain forest Alliance and the Nature Conservancy.

Rainforest Facts:

Rainforests rarely in temperature go above 93 F and below 68 F. Rainforests cover less than 6 percent of the Earth’s land surface. 70 percent of the plants in the rainforests are trees. About one fourth of all medicines in the world come from rain forests. More than 1, 400 plants in the rain forests are believed to cure cancer. Many trees grow straight for 100 feet then branch out. Over 2,500 types of vines grow in the rain forests. Tropical Rain Forests have very shallow soil with poor nutrients. Animals give nutrients and water is what keep plants alive. Over half of all animals, plants, and microorganisms live in the rainforests.

• A single pond in Brazil can sustain a greater variety of fish than is found in all of Europe's rivers.

• A 25-acre plot of rainforest in Borneo may contain more than 700 species of trees - a number equal to the total tree diversity of North America.

• A single rainforest reserve in Peru is home to more species of birds than are found in the entire United States.

• One single tree in Peru was found to harbor forty-three different species of ants - a total that approximates the entire number of ant species in the British Isles.

• The number of species of fish in the Amazon exceeds the number found in the entire Atlantic Ocean.

• At least 80% of the developed world's diet originated in the tropical rainforest. Its bountiful gifts to the world include fruits like avocados, coconuts, figs, oranges, lemons, grapefruit, bananas, guavas, pineapples, mangos and tomatoes; vegetables including corn, potatoes, rice, winter squash and yams; spices like black pepper, cayenne, chocolate, cinnamon, cloves,ginger, sugar cane, tumeric, coffee and vanilla and nuts including Brazil nuts and cashews.

• At least 3000 fruits are found in the rainforests; of these only 200 are now in use in the Western World. The Indians of the rainforest use over 2,000.

See also

• Cloud forest
• Illegal logging
• Jungle
• Tropical and subtropical moist broadleaf forests

Bibliography

• Richards, P. W. (1996). The tropical rain forest. 2nd ed. Cambridge University Press ISBN 0521421942
• Whitmore, T. C. (1998) An introduction to tropical rain forests. 2nd ed. Oxford University Press. ISBN 0198501471

External links

• Forest Conservation Portal
• Rainforest Live - Facts & Figures
• Save The Rainforest
• Tropical Rainforests
• Rainforest facts and information from The Nature Conservancy
• Rainforest Alliance
• Virtual Rainforest Trip
• CFACT.org (a free-market group that disputes some claims)
• Rainforest people - Pygmies Culture of the African rainforest people, with photos of nature and animals
• Amazon Conservation Team An organization working in partnership with indigenous people in conserving biodiversity, health, and culture in tropical America.
• Save the Amazon Rainforest
• Los Guatuzos, Nicaragua
• Indio-Maiz, Nicaragua
• British Columbia's Rainforests Essays by Elmer G. Wiens.

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