Eco-system

The climate of the rain forest is hot, wet and sticky. It is very humid. It rains every day, so regularly that you could set your watch to it. The rain comes down suddenly and stops just as suddenly. It is convectional rainfall. (The sun heats the land, which heats the air next to the land, causing it to expand and rise. When it gets to a certain height, it condenses to dew point and forms clouds. Then it rains. Storms are common with convectional rainfall.)

The plants in the rain forest have had to adapt to the unusual weather conditions in the forest. There are many different ways they have done this:

• Trees can grow tall, up to 40m through into the emergent layer, so they can get sunlight.
• Leaves have down curving tips so that rain drips off.
• The rain forest is deciduous, but it appears evergreen because the trees all lose their leaves at different times.
• The trees are straight and only have branches at the top. They are supported by buttress roots.
• Rivers flood for a few months every year so the plants are adapted so that they can handle the extra water and do not drown.
• Undergrowth springs up wherever light can reach the forest floor.
• Fallen leaves and plant matter rot swiftly to provide nutrients for the rest of the plants.
• Lianas climb up trees to reach the light.

Millions of plants and animals co-exist in the rain forest, such as Leaf-cutter ants, shown in the picture. There are species which are as yet undiscovered by humans. Everything depends on all of the others. For example, here is one cycle:

1. Dead organic material rots.

2. Nutrients help trees grow.

Another example is the weather. The rain provides water for all of the biotic community. The cycle of dependence is called an ecosystem.

Amazonian Indians

The Indians live by a process called "shifting cultivation". This means that they live in one area and farm it, moving on when the land is no longer viable to farm. This does not harm the forest as it recovers. They are forced to move on because the soil has few nutrients and growing the crops removes what little there is, meaning that it will no longer grow enough food and the farmers have to move on. The rapid growth and rotting cycle of rainforest plants makes the situation worse. The Indians build huge houses from wood and foliage. They cut down trees to extend the clearing and feed their fires. The ash provides nutrients for the soil. Then the women plant the crops (manioc, yams, beans and pumpkins). They do not just farm, they also fish and hunt. After 4 to 5 harvests, it is time to move on again.

However, the increasing use of the Amazon by big business has cut down the size of land available for them to farm. Therefore, the Indians have to return to a previously used piece of land before it is fully recovered (which takes about 50 years). Indians are also in danger from western diseases, which they have no immunity against.

Farming

Huge areas of rain forest are burned every week to create agricultural land and animal pastures. The loss of the trees has an enormous effect on the environment. For photosynthesis, trees take in carbon dioxide, which is harmful to humans in large quanities so when there are fewer trees, there is more carbon dioxide. It is also devastating for animals who lose their habitats.
Much of the smoke escapes into the atmosphere where it adds to the "blanket" over the earth, stopping the heat from the sun escaping the earth and thereby adding to global warming. The environmental problems here and in other rain forest regions has led to a "Save the Rainforest" movement.

A large farming industry is cattle farming. This industry creates a large amount money from exporting the produce. To create spacious pastures for their animals, the ranch owners "slash and burn" large areas of rain forest. Once the trees have been burned, the land is ready for use. However, if they move on, it will take a long time for the forest to grow back and when it does, it will be thick secondary jungle.

Although the hamburger business is very profitable for cattle farmers in this area, it is the main cause of the environmental problems mentioned above i.e. increased carbon dioxide levels and loss of habitat for many different species of animals. The Amazonian rain forest is a major area for the intake of carbon dioxide. Removal of many more of the trees would be catastrophic for the entire planet. A hamburger is cheap, quick food which is a enjoyed all over the world. However, is it worth it if it means running the risk of an irreversible change to the world's climate?

Mining

Brazil is full of valuable minerals and it is a very important industry. People search for gold, diamonds, bauxite (aluminium ore), magnese, iron, tin, copper and lead. The Brazilian Gold Rush began in 1980 when gold was discovered in Serra Palada. Some poor people have moved away from their homes to the mines in search of work and money. The job is very dangerous, with up to 20,000 workers in each "hole". Most of the mines' profits go to the owners so the wages are very low. Larger operators are forcing the smaller ones out of business.

All this activity results in seemingly inevitable environmental damage. Up to 9,000 tons of mercury, which is used in the mining process, has been washed into the region's rivers. Huge quantities of sediment has also been washed into the rivers, which already contain many other unsavoury things as a direct result of the miners' presence. The rivers are polluted with oil, rubbish and human sewage. All around the vicinity of the mines, vegetation, animals and settlements have been destroyed. On the other hand, the larger companies are beginning to take steps to protect the environment, such as landscaping and replanting.

Trans-Amazonian Highway

This is a vast road stretching for 5,300km across the Amazon region. It stretches from Recife in the east to the Peruvian Andes in the west. Construction began in the early part of the 1970's, but it has since been completed. It is the main east to west route and is crossed by north to south roads. Several of these, including the Trans-Amazonian Highway, are made from gravel! A few, however, are paved and some are still being built. There is one railway and another is proposed. All of this is part of an ambitious Amazon development plan from the Brazilian government. As well as improving transport links, they are also upgrading communications and power, thus improving the local infrastructure.

The disadvantages about this work are the environmental hazards. There are machines belching smoke into the air. Many trees have been cut down for road construction, causing loss of habitat. At least one previously unknown, rain forest tribe has been discovered every year of the project. Their land is gone but they had no say in the matter. Although it is bad for the environment, it is very good for logging, ranching and mining industries as it makes transport of workers and materials much easier and cheaper.

H.E.P.

If people want to develop the rain forest, they must have power. The best way of providing this is hydro-electric power, or H.E.P. There are huge rivers in the Amazon region, which will obviously create a lot of power. There are many extremely controversial plans about this. Unfortunately, this also means irreversible environmental damage. Land is flooded. Not many jobs are created because it is expensive to employ workers to operate the facilities. 70,000 people had to leave their homes to allow the building of just one dam. Farmers received no advice about farming on the new, irrigated land. On the other hand, the dams provide irrigation and therefore increased yield from these same farms, which means more money for the poor farmers.

Before a dam is built primary rain forest is abundant. There is an Indian village and farming land is used for "shifting cultivation" (see above). The river is used for washing, drinking and fishing.

Afterwards there is deforestation, agricultural land is flooded, river flow is controlled, the village has disappeared under water, there is a new road and, of course, there is the huge reservoir and the concrete dam itself.

The biggest H.E.P. project in the Amazon is the Tocantins River Basin Hydro Electric Project which plans to convert the Tocantins River into a series of lakes and hydro-electric dams, stretching for 1,200 miles. There will be 8 large dams and 19 smaller dams.

The Brazilian government has a plan which should be completed by 2,010. They hope for a total of 31 dams in the Amazon.

Related h2g2 Links

" About the Amazon." .