Humans intervene in tropical rainforests in order to bring real or imagined benefits to themselves or the local population.
Case study: human intervention in the Amazon
Short-term benefits of clearing rainforest areas
A village in a cleared area of rainforest
- Land for agriculture, houses and roads.
- Jobs for local workers in road building, logging, agriculture, mining and construction.
- The generation of income (often in valuable foreign currency) for the LEDCwhen wood, minerals, and other resources are sold.
- Scientific investigation into rainforest plants may provide new food sources and medicines.
These benefits, however, come at a cost. Clearing rainforest threatens the survival of many plant and animal species and can lead to serious environmental degradation. Widespread deforestationdamages the whole biosphere (the balance of living and non-living things) with serious long-term consequences.
The case study of human intervention in the Amazon looks at some of the issues around rainforest development.
Positive impacts of human intervention
- Improved transportation – new roads and airports. Better transportation means easier access to raw materials like minerals and timber. Rainforest resources can be transported away and sold.
- Infrastructure, hospitals and education can be improved from the money gained from selling natural resources.
- Profits from selling resources can be used to improve a country’s infrastructure. For example, profits from the sale of rainforest resources can be used to build schools and hospitals.
- Raw materials, eg tropical hardwoods such as ebony and mahogany, can be sold for a good price abroad.
- Mineral deposits in the Amazon include bauxite (the main constituent of aluminium), iron ore, manganese, gold, silver and diamonds. Minerals can be sold for high profits.
- Large-scale farming brings money into the country and provides food and jobs for the country’s growing population.
- Small-scale farming provides food for rainforest communities and the landless poor of Brazil.
Problems of human intervention
Commercial logging activity
- New roads divide up parts of the rainforest and can cut off connections between different biotic and abioticsystems. For example, a road can stop monkeys such as the golden lion tamarin from travelling to gather food and, in turn, distribute seeds to re-sow plants in the forest.
- Land clearance for farming, transportation and mining can lead to deforestation. Hardwood trees take many years to grow so can be difficult to replace.
- Fertile soils that make farming possible are quickly washed away when the forest is cleared. If soil ends up in rivers, this can lead to flooding.
- Loss of animal habitat occurs when trees are cut down. Hence, deforestation can result in endangering animals and plant life, or even causing them to become extinct.
- Profits from large-scale farming and selling resources often go back to MEDCsor large companies and don’t benefit the rainforest communities.
A burning section of the Amazon in Para State, Brazil
Shifting cultivation is a traditional, sustainablemethod of agriculture that has been practised by indigenous tribes for centuries. It occurs in areas of the Amazon rainforest, Central and West Africa and Indonesia. Along with other aspects of their culture and traditional way of life, it is under threat from large-scale clearance of the forests.
How shifting cultivation works
- A small area of land is cleared and the vegetation burned, providing a source of nutrients from the ash.
- For a few years the soil remains sufficiently fertile for the tribe to grow crops.
- When the soil’s fertility is exhausted, the tribe moves on and clears another small area of forest.
- The original area is regenerated, as it receives nutrients and seeds from surrounding vegetation.
- As no lasting damage occurs, this method of agriculture is sustainable.
- It is sometimes called ‘slash and burn’ agriculture.
Sustainable management of the forest
Brazil needs to exploit the Amazon’s resources to develop, so leaving it untouched is not an option.
Uncontrolled and unchecked exploitation can cause irreversible damage such as loss of biodiversity, soil erosion, flooding and climate change. So, sustainable use of the forest is essential. Sustainable development will meet the needs of Brazil’s population without compromising the needs of future generations.
Possible strategies include:
- Agro-forestry – growing trees and crops at the same time. This lets farmers take advantage of shelter from the canopy of trees. It prevents soil erosion, and the crops benefit from the nutrients from the dead organic matter.
- Selective logging – trees are only felled when they reach a particular height. This allows young trees a guaranteed life span – the forest will regain full maturity after around 30 – 50 years.
- Education – ensuring that those involved in exploitation and management of the forest understand the consequences behind their actions.
- Afforestation – the opposite of deforestation. If trees are cut down, they are replaced to maintain the canopy.
- Forest reserves – areas protected from exploitation.
- Monitoring – use of satellite technology and photography to check that any activities taking place are legal and follow guidelines for sustainability.