Effect of Forest on the Environment – JSS2 Agricultural Science Lesson Note (Third Term)

The effect of forests on the environment is the way forests clean the air, bring rain, protect the soil and supply useful materials.

Behavioural objectives

1. List the productive uses of forest resources.
2. Explain how forests purify the air and help in cloud and rain formation.
3. Describe how forests control erosion, prevent leaching and improve soil fertility.
4. Define deforestation and poaching.
5. State the effects of deforestation on the environment.
6. State ways of conserving forests.

What is a forest?

A forest is a large area of land thickly covered with trees and other plants, where many animals live.

• Plants: tall trees, shrubs, climbers and mushrooms grow together.
• Animals: wildlife such as antelopes, monkeys, birds and snakes lives in the forest.
• Examples of forest trees: Iroko, Mahogany, Obeche, Teak and Gmelina.

What are the uses of forest resources?

Forest resources are valued under four headings: productive, protective, aesthetic and economic uses.

Productive uses

• Timber: wood from Iroko, Mahogany, Obeche and Teak is used in construction and furniture, and for canoes, coffins and carvings.
• Pulp: trees such as Gmelina are processed into pulp, a raw material for paper and newsprint.
• Food: forests give edible fruits, nuts, vegetables and mushrooms.
• Meat: forest animals (wildlife) add to the protein needs of Nigerians.
• Medicines: roots, stems, leaves and bark of trees such as Neem, Eucalyptus and Cinchona cure sicknesses.
• Beddings: silk cotton from the silk cotton tree is used for pillows and mattresses.
• Domestic and industrial raw materials: forest plants give rope, fibres, dyes, resins, gum, rubber and tannins.
• Leather: animal skin is used for bags and drums.
• Fuel: charcoal and dead wood are used for cooking and heating.

Other uses

• Protective uses: forests protect the air, soil and water (explained in the next section).
• Aesthetic uses: forests give beauty, shade and places for recreation and tourism.
• Economic uses: forests give jobs and income through timber, food and other products, and they add to the economy of the country.

How does the forest affect the environment?

Forests affect the environment by purifying air, forming rain, breaking wind, controlling erosion and protecting the soil.

Purification of air

1. All living things breathe in oxygen and give out carbon dioxide during respiration.
2. Forest trees take in carbon dioxide for photosynthesis.
3. They release oxygen into the air.
4. This oxygen is needed for the respiration of living things.

Cloud and rain formation

1. Trees lose water vapour to the air through transpiration.
2. This makes the air very humid and helps clouds to form.
3. Forests also stop moisture-laden winds and make them rise.
4. The rising winds cool down and rain follows.

Other effects of forests

• Windbreak: trees reduce the force of strong wind on farmlands and bare soil, which checks erosion and desert encroachment.
• Erosion control: the thick cover of trees and shrubs reduces the impact of raindrops on the soil.
• Soil binding: roots and trunks hold the soil together so that it is not washed away.
• Improvement of soil fertility: fallen leaves decay to form humus, which makes the soil more fertile.
• Soil water conservation: the leaf canopy shades the soil from direct sunshine, so less soil water evaporates.

How do forests prevent leaching?

Leaching is the washing down of soil nutrients beyond the reach of plant roots.

1. Long tap roots of forest trees absorb nutrients that would be lost by leaching.
2. Leaves and branches fall to the ground and decay.
3. The decayed matter releases the minerals back to the surface soil.
4. Shallow-rooted plants then use these minerals.
5. The organic matter also binds the soil and improves its structure, so leaching is reduced.

How do human activities affect the forest?

Deforestation, bush burning, indiscriminate farming and poaching damage forests and reduce wildlife.

What is deforestation?

Deforestation is the continuous removal of forest trees, by bush burning or indiscriminate felling, without replacing them.

Effects of deforestation:

1. It destroys the microclimate and warms up the forest environment.
2. It reduces the supply of forest raw materials, for example timber for industries.
3. It reduces the wildlife population.
4. It may lead to desert encroachment, as sand particles are more likely to drop in areas without trees.
5. It encourages soil erosion and loss of organic matter, so the soil loses fertility.

How is wildlife depleted?

Wildlife depletion is the steady fall in the number of forest animals.

• Bush burning: fire kills animals and destroys their food and shelter.
• Farming activities: clearing land for farms removes the habitat of animals.
• Easy hunting: with the thick forest cleared, animals are easy prey for hunters.
• Migration: some animals flee to new environments.
• Extinction: some important species are being wiped out gradually.

What is poaching?

Poaching is the illegal hunting of animals in the forest.

• Effect on population: it reduces the number of forest animals.
• Effect on species: it can cause the extinction of some important animals.

How can forests be conserved?

Forest conservation is the wise use and protection of forests so that they last for future generations.

• Afforestation: planting trees in an area where there was no forest before.
• Reforestation: replanting trees in an area where forest trees have been cut down.
• Controlled felling: cutting only mature trees and replacing them.
• Forest reserves: setting aside protected areas where felling and hunting are controlled.
• Avoiding bush burning: using other ways to clear land.
• Laws against poaching: punishing illegal hunters.

What is the difference between deforestation and afforestation?

Deforestation removes forest trees without replacing them, while afforestation plants trees where there was no forest.

Evaluation

1. List five productive uses of forest resources.
2. Explain how forests help in cloud and rain formation.
3. How do forests prevent leaching of soil nutrients?
4. What is deforestation? State three of its effects.
5. What is poaching?

Assignment

In your notebook, explain how forest trees control soil erosion and purify the air, then describe two ways in which human activities reduce the wildlife population in the forest.