1. What are some types of natural vegetation?2. How are forests useful to humans?3. What happens if we overuse forests?

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By the end of the lesson,

You should be able to:– List and elaborate three uses of forests.

Looks manageable? Let's start!

Functions/Uses of the forest

6.Habitat for life

7. Provides timber, fuel, medicine, food, chemicals

8. Recreation

9. Research and education

1. Maintains water supply

2. Replenishes oxygen, removes carbon dioxide

3. Maintains nutrients in the soil

4. Prevent floods

5. Protect coasts

a) maintains the quantity of water supply

b) maintains the quality of water supply

1. Maintaining water supplya) maintains the quantity

of water supply throughtranspiration

1. Forests release large amounts of water vapour into the atmosphere through transpiration.

2. Water vapour condenses into tiny droplets of water in the atmosphere and form clouds.

3. The clouds precipitate as rain when they have too much water to hold.

4. The rain that falls replenishes the water in rivers and reservoirs.

1. Maintaining water supplyb) maintains the quality of water supply through

i) filtering it

Soil traps and filters impurities in rainwater and in waste water (such as dead animals, rubbish, human waste) that seeps underground before it flows into rivers and reservoirs.

→ This water is thus relatively clean

1. Maintaining water supplyb) maintains the quality

of water supply by i) filtering it

Biodegradable waste that has been trapped is decomposed by bacteria present in the forests.

E.g. Mangrove roots filter river water of its waste materials before it flows into the sea. The waste is broken down into nutrients for the mangroves.

1. Maintaining water supplyb) maintains the quality of water supply throughii) intercepting foliage

1. The foliage of the forest intercepts and weakens the impact of raindrops hitting the ground.

2. Forest soil thus remains porous enough to let water seep underground.

3. This water is stored as groundwater, which flows to and replenishes nearby rivers and reservoirs.

+ Interception slows down surface runoff so less soil particles are washed into the river, making the water cleaner.

Textbook p. 182

Rainwater seeping into the soil

is filtered by the soil.

Foliage interception slows down surface runoff.

Less soil particles get washed into the river

Water that finally gets to the river is cleaner.

How does the water quality in forested areas compare with urban areas, like....

Singapore, Rio de Janeiro, London,

Shanghai, Johannesburg, Cairo?

Textbook p. 182

Concrete surfaces means that rainfall runs over the ground quickly

+collects impurities along the way

2. Replenishes O2, removes CO2

Forests: 'Green Lungs of the Earth'

During photosynthesis,

the greenhouse gas CO2 is absorbed, preventing global temperatures from rising.

O2 is released, renewing oxygen supply for all life.

3. Maintains nutrients in the soil

2. Decomposers cause dead matter to rot.

3. Calcium, nitrates and phosphates are released from dead matter into the soil

4. Plants absorb these nutrients in the soil.

1. Dead plant and animal matter accumulate on the forest floor.

4. Prevents floods

Forest roots hold the soil firmly together. This:

a) keeps the soil porous as a store for rainwater flowing over the ground

b) prevents soil from being eroded and deposited in riverbeds, reducing their capacity to contain water.

5. Protects coasts

Mangroves form the first line of defense against wave attack and coastal hazards.

E.g. Sri Lanka, 2004 Boxing Day tsunami -

Only 2 deaths in a village with densely growing mangroves; up to 6000 deaths in a nearby village with no mangroves (BBC News)

6. Habitat for life

Matschie's tree-kangaroo, Papua New Guinea's tropical rainforests

American pika, temperate coniferous forests

Tigers, tropical rainforests and monsoon forests

Forests are habitats for flora (plants) and fauna (animals), providing

Food

Shelter from heat or cold

Protection from predators

(Unfortunately, some are endangered, e.g. Matschie's tree-kangaroo and all species of tigers)

7. Provides valuable resources

Valuable resources include timber for furniture and buildings.

Teak, meranti, rattan (tropical rainforest); mahogany, pine, spruce (temperate coniferous forests)

United Nations' Food and Agriculture Organization (FAO) estimate that every year, the global timber industry earns over S$332 billion!

7. Provides valuable resources

Valuable resources include medicine.

Quinine, treatment for malaria, from Cinchona trees (tropical rainforest)

Tannin from mangrove Rhizophora and redwood trees (coniferous forests) to make anti-diarrhea pills

7. Provides valuable resources

Valuable resources include chemicals.

Pine and fir resin as wood varnish

Tannin from mangrove Rhizophora and redwoods to treat leather and make orange food dyes

8. Recreation

Forests can be used for ecotourism.

Tourists who want to experience nature without harming it.

These forests are sometimes national parks and wildlife reserves.

More of this when we study deforestation in Kalimantan.

Yosemite National Park, CaliforniaUSA

Sungei Buloh Wetland Reserve, Singapore

Functions/Uses of the forest

6.Habitat for life

7. Provides timber, fuel, medicine, food, chemicals

8. Recreation

9. Research and education

1. Maintains water supply

2. Replenishes oxygen, removes carbon dioxide

3. Maintains nutrients in the soil

4. Prevent floods

5. Protect coasts

What's next?

We will study the final section for this topic:

What happens when humans interact with the forest?

We'll study deforestation (the destruction of tropical rainforests) in Kalimantan, Indonesia. Read textbook pp. 196-201.