Natural Vegetation

Pure Geography SA2 Overall Revision Notes

Chapter 3: The Earth’s Natural Vegetation

Comparison of Forests



Uses of Forests

Function/Use Explanation

Maintaining the water supply (quantity and quality)

1. Quality: The forest will support the natural processes that filter water by reducing the amount of surface runoff, making it remain clear and free from substances that is harmful to organisms, making it suitable for drinking and supporting life.

2. Quantity: The forest will ensure that there is a continuous flow of water through the water cycle.

Replenishing oxygen and removing carbon dioxide

1. Forests are also known as the “Green lungs of the Earth”. 2. This is because during photosynthesis, trees take in carbon dioxide and give out oxygen. 3. As Carbon Dioxide is a greenhouse gas, reducing the amounts of carbon dioxide will help prevent global

temperatures from rising, regulating the temperature of the Earth

Maintaining nutrients in the soil

1. Decomposing vegetation on the forest floor release nutrients back into the soil and hold the particles together to prevent the soil to run off.

2. Therefore, forests maintain quality of the soil by preventing nutrients from being removed by soil erosion.

Preventing floods

1. Absence of roots may lead to soil erosion. 2. Soil erosion will cause the river bed to be shallower and reduce its ability to contain water. 3. Therefore, the likelihood of flooding increases when forests are cleared.

Protecting coasts

1. Mangrove protects coastal areas from storms and strong waves 2. Example: During the 2004 Indian Ocean Tsunami, mangrove forests prevented some of the coastal

villages in South-eastern India from being destroyed.

Natural treatment of waste water

1. Mangrove forest can process waste materials carried by water from streams and rivers. Soil in mangrove forests contains bacteria that can break down biodegradable materials into nutrients.

2. Their roots help trap waste materials and filter the water before entering the sea. 3. However, there is a limit to the amount of sewage that can be absorbed; therefore people should not

just dump all their rubbish there. Habitat for Flora and Fauna

1. Forests are home to more than 50% of all species in the world, including tigers and rare species of orchids found in tropical rainforests in Malaysia and Grizzly bears in coniferous forests of North America.

2. Forests are also home to approximately 60 million people living in the tropical rainforests of South America, SEA and Africa. Examples include Hunter Gatherers (Korubu tribe in Amazon) and Shifting Cultivators in Indonesia.

A source of useful materials

1. Forests provide timber worth more than $200 billion per year. 2. Hardwood can be used for furniture making, ship building and manufacturing musical instruments.

Examples include mahogany and teak found in tropical rainforests. 3. Softwood can be used for housing, construction, furniture and flooring. Examples include pine, fir and

spruce. 4. Forests also provide Medicines. Example: Quinine, a drug for treating Malaria is extracted from the

Cinchona tree from the Brazilian rainforest. 5. Forests provide fuelwood and charcoal as well. Over 2 billion people worldwide still rely on fuelwood as

their main source of energy. 6. Example of usage of charcoal: Mangrove trees like Rhizophora are cut down in Malaysia’s Matang

Forest to produce charcoal.

Recreation 1. Forests can be used for camping, fishing, sight-seeing and hiking. They are popular among urban people as they can provide solace from stressful daily routines.

2. The introduction of ecotourism allows urban dwellers to appreciate the beauty of forests and engage in activities which do not harm the environment. Examples include Taman Negara in Malaysia.

Research and Education

1. Scientists study forest plants to develop new medicines and varieties of crops. 2. They also study the interactions between forest animals and their environment with the plants to

understand how changes in the weather affect the animals and plants in the forest ecosystem which helps people to adapt in the process as well.



Causes of Large – Scale Deforestation

Cause Explanation Example

Population Increase 1. Due to high birth rate in countries 2. This puts pressure on forested land which is deforested for housing,

agriculture, transport and industrial infrastructure.

Brazil is one of the most populous country in the world with a population of 194 million people in 2005.

Settlements 1. Settlements are houses and farms people live and own. It can be a rural or urban settlement.

2. Government is trying to resettle people from densely populated cities into less densely populated parts of the country.

3. Each relocated family is given a piece of land and offered subsidies to convert the cleared land into farmland.

Rapid Urbanisation 1. Urbanisation is the physical growth of rural land into urban areas (villages converted to cities)

2. Forested land is cleared for new housing estates, hospitals, schools, etc.

Land Transport Systems

1. Fragmentation: Habitat is separated into many different parts. The 5100km long Transamazonian Highway cutting the Amazon Forest

Agriculture 1. Contributes about 10% of country’s income 2. Employs about 25% of population 3. 3 main types: Shifting cultivation, subsistence/commercial farming 4. Shifting cultivation: tribal farmers cut down small sections of the forest

and burn the trees. A small scale – not a heavy threat 5. Subsistence cultivation: Self-sufficient farming where farmers grow

enough food to find their family and themselves. Collective practice is damaging.

6. Commercial Farming: Huge companies operate it in the form of extensive cattle ranching, accounting approx. 80% of deforestation.

Commercial Farming: Sugar cane, coffee and soy beans occupy much forest land. Between 1994-2003, cultivating area for soy beans nearly doubled to meet high demands.

Forest Fires 1. Burns up thousands of square kilometres every year. Can be caused by natural and/or human causes.

Economic Development and Debt Repayment

1. Money is required for economic development. 2. Brazil is one of the world’s largest debtors, owning about US $100 billion

to foreign banks and thus the country’s natural resources have to be exploited to pay and reduce national debt.

3. Commercial Logging: Eager to sell timber to developed countries when there is high demand.

4. Mining: Rich in minerals such as iron ore (high value), gold and fossil fuels like oil.

5. Hydro-electricity: Construction of dams create large reservoirs that can flood and destroy rainforest areas. Can generate up to 126000 MW of electricity.

Largest dam is the Itaipu Dam on the Parana River.



Consequences of Large – Scale Deforestation

Consequences Explanation

Global Warming With the reduction of trees in the rainforest, more carbon dioxide remains in the atmosphere, trapping more heat, leading to global warming.

Changes to the nutrient cycle and soil deterioration

Importance of forests in maintaining soil quality: 1. When trees die, they decompose quickly under hot and humid conditions, and thus nutrients are

returned to the soil. 2. If there are abundant trees, they can absorb nutrients from decomposed plants from the soil and thus

maintain the nutrient cycle. 3. In addition, Roots hold and protect the soil, preventing topsoil erosion. Branches help to intercept

rainfall.

Floods and Water Quality

1. No trees to intercept rainfall, surface runoff increased. 2. Topsoil washed into rivers, increasing height of river bed, increasing frequency of flooding. 3. Deposition of organic debris used to collect on the forest floor in the river increases acidity of the

river, may kill aquatic life.

Air Pollution 1. Millions of square kilometres of rainforests affected. 2. Dust and smoke particles accumulate in the air Haze 3. Haze closed airports and affected health.

Loss of biodiversity 1. Extinction of Flora and Fauna 2. Destruction and eventual extinction in the long run. 3. Chances of discovering useful drugs diminish. 4. The micro-leao-dourado from Brazil is having difficulty surviving due to the rapid rate of

deforestation.

Impact on Inhabitants of Rainforest

1. Population of native Brazilians have been greatly reduced from 1 million in 1550s to 700 000 presently.

2. Deforestation disrupts culture and traditional way of life. 3. Eventually, culture, knowledge and way of life will be lost.



Solutions of Large – Scale Deforestation

Towards Sustainable Management in Forests 1. Refers to the careful use of resources to allow people to use them in the future. 2. Ensure a balance between generating income through sale of forest resources and protecting forests. 3. Prevent excessive logging. 4. It must also involve local governments, native people and villages for it to be successful.

Solution Explanation

Selective/Controlled Logging

Replace clear cutting. Logging is allowed but is controlled.

Success Failure

1. MOF1arranged for education for timber

companies to inform them about the damage.

2. Identify commercially valuable trees, others are retained.

3. Allows forest to regenerate. 4. Young trees can grow as overcrowding was

reduced. 5. Minimise soil erosion.

1. Difficult to monitor and detect illegal logging activities: Lack of manpower and remoteness of forest areas.

2. Other plants that twine around 2 or more trees like lianas may affect other trees. Ferns and orchids that grow on the trees may be affected.

Conservation

Setting aside portions of the rainforest to be left undisturbed and protected.

Success Failure

1. Protect animal and plant species. 2. Leave them undisturbed and protected. 3. Allow natives to protect their lifestyle and

culture.

Difficult to monitor and detect illegal logging activities: Lack of manpower and remoteness of forest areas.

Afforestation and Reforestation

1. Afforestation refers to the planting of trees that were originally not forests. 2. Reforestation refers to the planting of trees in formerly forested areas cleared by logging.

3. Teak is used in the planting of trees as it grows quickly.

Success Failure

1. Teak trees which are commercially valuable are commonly planted as it grows well.

2. Takes a short time (5 years) to grow.

1. Rates at which forests are replanted are much slower at which they are cleared.

2. Incentives given to local people are not attractive.

3. Loss of original biodiversity, making it no different from plantations.

Controlling Forest Fires

1. Since forest fires are a major cause of deforestation and air pollution, forest fires should be controlled.

2. Limitations: Not very effective, plantation companies continue to burn forests as it the cheapest way to clear land. In addition, the locals are also reluctant as this was the traditional way inherited

from past generations.

Establishment of Laws and Policies

Government can limit the number of trees cut down and withdraw financial help given to clearance projects.

Success Failure

1. Logging permits are cancelled. 2. Financial support and tax incentives

withdrawn. 3. Limit number of trees cut down.

1. Weak enforcement. 2. Corruption.

1 Ministry of Forest Trees

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Natural Vegetation