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Rainforest: the story on HearLore | HearLore
Rainforest
In 1917, naturalist William Beebe declared that another continent of life remained to be discovered, not upon the Earth, but one to two hundred feet above it, extending over thousands of square miles. This statement captured the essence of the rainforest canopy, a dense, continuous layer of foliage that forms the roof of the forest and houses the majority of the world's largest trees. These trees, known as emergents, reach heights of 45 to 55 meters, with some species growing as tall as 70 to 80 meters to withstand the hot temperatures and strong winds that occur above the canopy. The canopy is home to 50 percent of all plant species and a quarter of all insect species, creating a complex ecosystem that scientists have only recently begun to explore with practical methods like firing ropes into trees using crossbows or using balloons and airships to float above the highest branches. This science of accessing the tropical forest canopy using aerial platforms is called dendronautics, and it remains in its infancy despite the critical importance of understanding this hidden world.
The Soil Paradox
Despite the lush vegetation that characterizes rainforests, the soil quality is often quite poor, creating a paradox where life thrives on a foundation of scarcity. Rapid bacterial decay prevents the accumulation of humus, and the concentration of iron and aluminium oxides by the laterization process gives the oxisols a bright red colour, sometimes producing mineral deposits such as bauxite. Most trees have roots near the surface because there are insufficient nutrients below the surface, and most of the trees' minerals come from the top layer of decomposing leaves and animals. The soil is highly acidic, and the type of clay particles present in tropical rainforest soil has a poor ability to trap nutrients and stop them from washing away. Even if humans artificially add nutrients to the soil, the nutrients mostly wash away and are not absorbed by the plants, as the high volume of rain in tropical rainforests washes nutrients out of the soil more quickly than in other climates. When rainforest trees are cleared, rain can accumulate on the exposed soil surfaces, creating run-off, and beginning a process of soil erosion that eventually leads to the formation of streams and rivers and the possibility of flooding.
The Hidden Layers
Beneath the canopy lies the understory, a dimly lit world where only about 5 percent of the sunlight shining on the rainforest canopy reaches the ground. This layer is home to a number of birds, snakes, and lizards, as well as predators such as jaguars, boa constrictors, and leopards. The leaves are much larger at this level, and insect life is abundant, but the forest floor, the bottom-most layer, receives only 2 percent of the sunlight. Away from riverbanks, swamps, and clearings, the forest floor is relatively clear of vegetation because of the low sunlight penetration. 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, creating a cycle of life and death that is essential to the rainforest's survival. The understory can be called a shrub layer, although the shrub layer may also be considered a separate layer, and it is home to many seedlings that will grow to the canopy level.
What is the height of emergent trees in the rainforest?
Emergent trees in the rainforest reach heights of 45 to 55 meters, with some species growing as tall as 70 to 80 meters to withstand the hot temperatures and strong winds that occur above the canopy.
Why is the soil quality in the rainforest poor despite lush vegetation?
The soil quality in the rainforest is poor because rapid bacterial decay prevents the accumulation of humus, and the concentration of iron and aluminium oxides by the laterization process gives the oxisols a bright red colour. Most trees have roots near the surface because there are insufficient nutrients below the surface, and the high volume of rain washes nutrients out of the soil more quickly than in other climates.
How much sunlight reaches the forest floor of the rainforest?
The forest floor of the rainforest receives only 2 percent of the sunlight, which makes it relatively clear of vegetation away from riverbanks, swamps, and clearings. This layer contains decaying plant and animal matter that disappears quickly because the warm, humid conditions promote rapid decay.
How many uncontacted tribes were confirmed in Brazil on the 18th of January 2007?
On the 18th of January 2007, FUNAI reported that it had confirmed the presence of 67 different uncontacted tribes in Brazil, up from 40 in 2005. This addition allowed Brazil to overtake the island of New Guinea as the country having the largest number of uncontacted tribes.
What percentage of all biotic species are indigenous to the rainforests?
Estimates vary from 40 percent to 75 percent of all biotic species being indigenous to the rainforests, and there may be many millions of species of plants, insects, and microorganisms still undiscovered in tropical rainforests. Tropical rainforests have been called the world's largest pharmacy because over one quarter of natural medicines have been discovered there.
When are tropical rainforests in Indonesia expected to be logged out at present rates?
At present rates, tropical rainforests in Indonesia would be logged out in 10 years and Papua New Guinea in 13 to 16 years. An important reason for the increasing deforestation rate, especially in Indonesia, is the expansion of oil palm plantations to meet growing demand for cheap vegetable fats and biofuels.
Estimates vary from 40 percent to 75 percent of all biotic species being indigenous to the rainforests, and 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. The great diversity in rainforest species is in large part the result of diverse and numerous physical refuges, places in which plants are inaccessible to many herbivores, or in which animals can hide from predators. Having numerous refuges available also results in much higher total biomass than would otherwise be possible. Some species of fauna show a trend towards declining populations in rainforests, for example, reptiles that feed on amphibians and reptiles, and this trend requires close monitoring. The seasonality of rainforests affects the reproductive patterns of amphibians, and this in turn can directly affect the species of reptiles that feed on these groups, particularly species with specialized feeding, since these are less likely to use alternative resources.
The Silent Threat
Tropical and temperate rainforests have been subjected to heavy legal and illegal logging for their valuable hardwoods and agricultural clearance throughout the 20th century, and the area covered by rainforests around the world is shrinking. Biologists have estimated that large numbers of species are being driven to extinction, possibly more than 50,000 a year, and at that rate, a quarter or more of all species on Earth could be exterminated within 50 years due to the removal of habitat with destruction of the rainforests. Another factor causing the loss of rainforest is expanding urban areas, and littoral rainforest growing along coastal areas of eastern Australia is now rare due to ribbon development to accommodate the demand for seachange lifestyles. Forests are being destroyed at a rapid pace, and Brazil has declared its deforestation a national emergency, with Amazon deforestation jumping by 69 percent in 2008 compared to 2007's twelve months, according to official government data. At present rates, tropical rainforests in Indonesia would be logged out in 10 years and Papua New Guinea in 13 to 16 years, and an important reason for the increasing deforestation rate, especially in Indonesia, is the expansion of oil palm plantations to meet growing demand for cheap vegetable fats and biofuels.
The People Within
On the 18th of January 2007, FUNAI reported that it had confirmed the presence of 67 different uncontacted tribes in Brazil, up from 40 in 2005, and with this addition, Brazil has now overtaken the island of New Guinea as the country having the largest number of uncontacted tribes. The province of Irian Jaya or West Papua in the island of New Guinea is home to an estimated 44 uncontacted tribal groups, and the tribes are in danger because of the deforestation, especially in Brazil. The Central African rainforest is home of the Mbuti pygmies, one of the hunter-gatherer peoples living in equatorial rainforests characterized by their short height, below one and a half meters, or 59 inches, on average, and they were the subject of a study by Colin Turnbull, The Forest People, in 1962. There are many tribes in the rainforests of the Malaysian state of Sarawak, and some of the other tribes in Sarawak are the Kayan, Kenyah, Kejaman, Kelabit, Punan Bah, Tanjong, Sekapan, and the Lahanan, collectively referred to as Dayaks or Orangulu which means people of the interior. About half of Sarawak's 1.5 million people are Dayaks, and most Dayaks, it is believed by anthropologists, came originally from the South-East Asian mainland, and their mythologies support this.
The Climate Connection
A natural rainforest emits and absorbs vast quantities of carbon dioxide, and on a global scale, long-term fluxes are approximately in balance, so that an undisturbed rainforest would have a small net impact on atmospheric carbon dioxide levels, though they may have other climatic effects, on cloud formation, for example, by recycling water vapour. No rainforest today can be considered to be undisturbed, and human-induced deforestation plays a significant role in causing rainforests to release carbon dioxide, as do other factors, whether human-induced or natural, which result in tree death, such as burning and drought. Some climate models operating with interactive vegetation predict a large loss of Amazonian rainforest around 2050 due to drought, forest dieback, and the subsequent release of more carbon dioxide. Tropical rainforests have been called the Earth's lungs, although it is now known that rainforests contribute little net oxygen addition to the atmosphere through photosynthesis, and the broader category of tropical moist forests are located in the equatorial zone between the Tropic of Cancer and Tropic of Capricorn.