What is a Tropical Rainforest?

Tropical Rainforests are the earths oldest Ecosystems. They are around the equator, between the Tropics of Cancer and the Tropics of Capricorn. they are found in many different areas including Asia, Australia, South America and Central America. Tropical Rainforests have existed on earth     for hundreds of millions of years.

The structure of the Tropical Rainforest

The tropical Rainforest is made up of four set layers, these are the Emergent, Upper Canopy, Understory and Forest Floor.


The Emergent
The Emergent is the highest layer of the Rainforest. These trees are spaced wide apart and are 100-240ft tall. They have umbrella-shaped canopies that grow above the forest. The trees have straight, smooth trunks with few branches. The branches then have small, pointed leaves because they are exposed to drying wind. The trees in this layer have a shallow root system although have buttresses to support their size, which spread to a distance of 30ft.


The Upper Canopy
The Upper Canopy comes next after the Emergent. The trees are 60-130ft tall. This allows light to be easily reached at the top of this layer, but reduces light below. Most of the Rainforest animals live in this layer because there is lots of food available. The leaves have 'drip tips', that allow the rain to run off. This keeps them dry and prevents mold and mildew, from forming in the humid enviroment. 


The Understory
The Understory comes next and is also knows and the Lower Canopy. The trees are 60ft tall. The layer is made up of Upper Canopy trunks, shrubs, plants and small trees. There is little air movement and because of this, the humidity is constantly high. Also this layer is in constant shade. 


Shrub Layer/ Forest Floor
The shrub layer and forest floor are very dark and usually completely shaded. As a result of this, very few bushes or herbs can grow there. Less than 1% of light that strikes the top of the Rainforest, reaches the forest floor. The top soil is very thin and poor quality. Also lots of litter falls to the ground, where it is quickly broken down by decomposers like termites and Fungi. The heat and Humidity, also help to break down the litter. This organic matter is then quickly absorbed by shallow tree roots.


The reason the trees grow in this way, is because when the Rainforests were first starting to grow, it became apparent that they grow best in the damp and heat. As a result of this, they 
structure was formed because all the plants are reaching for the sunlight. That is the reason, the plants at the bottom are very small whereas the plants at the top are very tall. 

The structure of the Tropical Rainforest

Plants and Animals Adaptations to the Tropical Rainforest

The plants need sunlight for photosynthesis (the way they make their own food). This is because the plant traps the sun's energy in the chlorophyll, in the leaves. This is then used to turn carbon dioxide and water into glucose. The glucose gives the plants energy to grow. The sunlight is a huge part of photosynthesis, which keeps the plants live. To be able to reach the sun, and to survive in the Tropical Rainforest, plants have many adaptations:


Lianas
Lianas are thick, twisted vines which loop around tree trunks to reach the sunlight. Also they hang from tree's to reach it as well. This helps, because it speeds up the process of getting to the sunlight, as it is constantly moving from tree to tree while they are growing. As a result they achieve more sunlight and grow better. 

Lianas hanging on to the trees.

Epiphytes
Epiphytes, which are also known as air plants, are small plants which grow on tree branches, rather than in the soil. They have special roots which are different to in the soil, to help them grow on the trees. The reasons may be, in the soil it is very dark and there is no sunlight, therefore they don't grow as well. The soil is very acidic and lacks nutrients therefore it doesn't grow as much also. Therefore on the tree, they are growing a great deal better than in the soil. 

Many Epiphytes on a tree branch.

Drip Tips
Tropical Rainforests receive 160 to 400 inches of rainfall per year and the rain can be very heavy. To adapt to this, most leaves of trees have pointed tips and are very slippery. This is to help the rain glide off the leaves so they don't cause damage. Also, this keeps them dry which prevents mold or mildew from forming, in the humid enviroment. This helps them to survive in the Rainforests.

A leaf with drip tip.

Buttress Roots

The trees in the Rainforest weigh hundreds of tonnes and are some of the tallest living structures on earth but they have roots in very thin soil. Whenever it rains, which is very often, the soil is washed away leaving even thinner soil. To anchor the tree and prevent it falling over, they have huge buttresses roots that spread to a distance of 30ft. They come in various shapes and sizes but all have the same purpose, which is to stabilize the tree. 

Buttress roots

Food Web

This is a food web for a Tropical Rainforest. In this food web, the Predators are the Fox and the Owl, which are always carnivores and only eat meat. This is because they are not eaten by anything, but eat the Mouse, Frog, Snake and Squirrel. They all come next as the Primary consumers, which are generally carnivores or omnivores. Omnivores eat both meat and vegetation. Primary consumers are eaten by the Predators and eat the Secondary consumers. In this food web, they are the Cricket and Rabbit. These are always herbivores and only eat vegetation. After, comes the decomposers. Decomposers are things like Fungi and Bacteria which help put nutrients back into the soil. They do this by eating dead animals and plants and then descreeting it into feces. This then puts nutrients back into the soil which helps the plants to grow.

Tribes in the Tropical Rainforest

There are around 50 million tribal people living in the worlds Rainforests, who depend on them for food and shelter to survive. As we destroy the forest, we are killing many people too. There are 3 main tribes which are well known, these are the Pygmy tribe, the Huli tribe and the Yanomami tribe. 


The Pygmy Tribe
The Pygmies are a Tropical Rainforest tribe that live in equatorial Rainforest regions. They are one tribe which are split into different smaller groups. These groups are the Bambuti, the Batwa, the Bayaka and the Bagyeli. The 'Ba' which each group starts with, stands for 'people'. They live scattered over  a huge area in central and western Africa, the Democratic Republic of Congo, Congo, Cameroon, Gabon, Central African Republic, Rwanda, Burundi and Uganda. The different groups speak different languages, mostly related to non-Pygmy people close by. Although there are a few words which they all share, which gives the impression they may have shared a language in the past e.g. Jengi, which means forest spirit.  

The Pygmy people know the forest, its plants and its animals extremely well. They live by hunting animals like Pigs, Monkeys and Antelopes. Also they live by fishing and gathering honey, wild yams, berries and other plants. For the tribe, the forest provides what they need to survive. Pygmy groups have close ties with neighboring farming villagers and work for them or exchange forest produce for crops and other goods.

The Pygmy tribe

The Huli Tribe
The Huli tribe has a population of 65,000 people and is one of the most famous tribes in Papua New Guinea. The tribe (known as wig-men) set their home a small distance away from Tari City, which is situated in central highland of Papua New Guinea. 
Huli's are mostly cultivated, but approximately 1 tenth live a traditional life. Although this is true, for main events, the men come back to their indigenous customs. For these occasions, the city of Tari is filled with aborigines, dressed in Huli clothing of short skirts and traditional wigs decorated with feathers. They are also famous for painting their faces (usually red and yellow) and making wigs out of their own hair. The wigs are also decorated with feathers from Paradise birds and feathers from colorful Parrots. The back side of the Huli's throat is ornamented with various decorations, the most striking being a beak of a Hornbil. 

A member of the Huli tribe with the painted face and wearing a wig.

The Huli Tribe

The men and women live separate from each other, living in group houses. In the Huli society there is no government of any kind. Power and importance can be gained by any man. If he proves his worth, others will tend to follow his lead. 
To live, they hunt Yams, Manioc, on ocassion meat from village raised Pigs and wild Cassowary or other forest game such as tree Kangaroos. They also use the Rainforest to make the rounded grass huts they live in.




The Yanomami Tribe
The Yanomami tribe are one of the largest, relatively isolated, tribes in South America. They live in the Rainforests and Mountains of Northern Brazil and Southern Venezuela and have a population of 32,000 people. The Yanomami territory in Brazil, is twice the size of Switzerland. In Venezuela, the Yanomami live in the 8.2 million hectare Alco Orinoco - Casiquiare Biosphere Reserve. Together, these form the largest forested indigenous territory, in the world.
The Yanomami live in large, circular houses called Yanos or Shabonos. Some can hold up to 400 people. The central area is used for activities and each family has a hearth where food is prepared and cooked during the day.

The Yanomami tribe.

They believe strongly in equality among people. Each community is independent from other and they do not recognise 'chiefs'.  Decisions are made after long debates, after everyone has had their say. 
They use about 500 different plants for food, medicine, house building and other things. They provide for themselves by hunting, gathering, fishing and growing crops. Men hunt for game like Peccary, Tapir, Dear and Monkey and regularly use curare (a plant extract) to poison their prey. Hunting counts as 10% of their food but is considered the most prestigious of skills and meat is valued by everyone. Woman grow crops on their gardens which counts for 80% of the food. They also collect nuts, shellfish and insect larvae. Also they harvest 15 different types of wild honey. Men and women fish and Timbo (or fish poison) is used in communal fishing trips. They pound up bundles of vines, which are floated on the water. The poison stuns the fish, so they rise to the surface and are scooped up into baskets. 

The Yanomami tribe fishing

They use about 500 different plants for food, medicine, house building and other things. They provide for themselves by hunting, gathering, fishing and growing crops. 

Mining and Farming: Impact on the Tropical Rainforest

 The are many problems that the Tropical Rainforests have to face daily. Two of the main problems are mining and Farming. 

Mining
Gold, Copper, Diamonds and other important metals and gemstones are found in the Rainforests. These things are regularly extracted by miners, which cause destructive damages to the Rainforests ecosystem. Also it causes problems for people living nearby or downstream. Mining leads to direct forest loss, due to the clearing of land in the Rainforest. Indigenous people are forced to move and roads are being constructed, through previously unreachable land which as a result is opening up the Rainforest. Also it is causing water, air and land pollution as well.   

The affects after mining has taken place.

Mining today mainly revolves around gold deposits. Gold is extracted in both river channels and floodplains where rivers once were. These deposits are mined by large-scale operators and small-scale miners. These both rely on hydraulic mining techniques to blast away at river banks and clear floodplain forests. Gold is usually extracted from gravel, using a sluice box to separate heavier sediment and mercury for combining the metal. Most of the mercury is removed to be reused or burnt off. Although some may end up in rivers. 
Small-scale miners are less skilled when using the mercury. As a result of this, statistics show that they release 2.91 pounds of mercury into the waterway, for every 2.2 pounds of gold produced. Although the mercury doesn't harm the water, it causes problems when entered into a food chain. Transformed mercury compounds are toxic and bioaccumilative( absorb in organisms). As a result, top predators such as birds of prey, will have the most mercury in their system. This is because it is passed up by every animal in the food chain before it. 


Mining would have a huge impact on the local tribes in different ways. Firstly, the mercury spread to the animals may result in them dying. Therefore the indigenous people wouldn't be able to eat them. The lack of food, would result in them having less to eat, making them undernourished. If their was a great amount of animals dying, there is a risk that the human's may because of starvation.  Also, as there is a large area being destroyed to mine, this could be the tribe's housing. As a result of this if they were affected by the water or land pollution, they wouldn't have the equipment to cure it. They would lose all their belongings, which would include their hunting equipment too. This could result in them unable to hunt, therefore becoming hungry. If this lasted for a long period of time, this could be another way they die from starvation.  


Farming
Farming in the Tropical Rainforests is unable to take place because of the lack of nutrients, in the acidic soil in the forests. Nevertheless, many agricultural projects are still carried out on Rainforest land. 

Slash and burn technique taking place.

Generally, forest clearers use slash-and-burn techniques, to clear the land and on a greater scale than the technique is usually carried out on. The agriculturalists burn hundreds to thousands of hectares, rather than than the 2 to 10 acres burned usually. The slash-and-burn technique, is a method where trees and shrubs are cut down. After, the soil is burned to release nutrients locked up in vegetation, to produce a layer of nutrient rich material above the former soil. The area is then planted and for a few years there is active growth. Although after, fertilizer is required, to keep the growth going. Fertilizer could be washed into streams, affecting fish and aquatic life. Once the land has been used, it is a huge amount less productive and only a small number of cattle can survive in the area.  
When the land is appropriate for farming, usually large single crops like rice, citrus fruits, coffee, cocoa, tea and rubber are grown there. However there are a few different problems with this type of single crop growth, apart from the loss of forest. Firstly, it makes the crop highly exposed to disease and pests, as shown in Brazil and India. Also this type of planting, can become highly economically risky, because of the price changes so common in international markets. 


We believe farming in the Tropical Rainforests will have a huge affect on the tribes. This is because the area where they have set up their housing, may be at risk of being cut down and burned. Because of this, a huge amount of people would lose their homes and everything they owned. This would result in survival being hard as they wouldn't have the equipment they need to hunt for their food or the land for them to grow crops. Also in the burning stage, people may die if they get caught in the fire or are around that area because of the smoke coming off of it. If they were burned they wouldn't have the equipment needed to attempt to heal the wounds. This would result in them becoming more ill and eventually dying.