Environmental Hazard: Desertification – JSS3 Basic Science Lesson Note (First Term)

Desertification is the process by which productive land becomes dry and turns into desert.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Define desertification.
2. Name the regions of Nigeria that are prone to desertification.
3. State the causes of desertification.
4. State the effects of desertification.
5. List methods of controlling desertification.

What is desertification?

Desertification is the spread of desert into land that people could once live on and farm.

• Desert: a very dry area with little rain, few plants and poor soil.
• Encroachment: the slow spread of the desert into nearby habitable land.
• Prone areas: the zones near and around deserts are the most at risk.
• Environmental hazard: it is a hazard because it damages land, crops, water and the lives of people.

How do human activities contribute to desertification?

Human activities remove the plant cover that protects the soil, and this starts the spread of desert.

1. People cut trees, overgraze grass or burn the bush, so the soil is left bare.
2. Strong sunlight and heat reach the bare soil.
3. Water evaporates quickly, so the soil dries out and its texture becomes loose.
4. Wind and rain carry away the loose soil.
5. The land loses its fertility and becomes desert.

Which parts of Nigeria are prone to desertification?

The parts of Nigeria prone to desertification are the Sahel and Sudan savannah zones in the far North, close to the hot Sahara desert.

What are the causes of desertification?

The causes of desertification are overgrazing, deforestation, bush burning, climate change, natural disaster, urbanisation and poor farming practice.

• Overgrazing: too many animals eat the grass cover and their hooves loosen the soil.
• Deforestation: cutting trees removes roots that hold the soil and shade that keeps it moist.
• Bush burning: fire destroys plant cover and the organisms that keep soil fertile.
• Climate change: less rainfall, higher temperatures and longer dry seasons dry out the land.
• Natural disaster: long periods of drought leave the soil dry and open to wind.
• Urbanisation: land is cleared for buildings and roads, so plant cover is lost.
• Poor farming practice: farming the same land again and again wears out the soil.

What are the effects of desertification?

The effects of desertification are the loss of farmland, water problems, movement of people and poverty.

• Difficult farming: the soil loses fertility, so crops fail and grass for livestock is scarce.
• Flooding: bare, hard soil cannot absorb water, so rain runs off and may cause floods.
• Poor water quality: streams and wells dry up or become dirty with sand and dust.
• Overpopulation of other areas: people move to places that are still green, and these become overcrowded.
• Poverty: poor harvests and loss of animals reduce food and income.

How can desertification be controlled?

Desertification is controlled by protecting and restoring the plant cover that holds the soil.

• Avoid deforestation: cut fewer trees and replace those that are cut.
• Afforestation: plant trees on bare land to hold soil and slow the wind.
• Bush fallowing and shifting cultivation: rest farmland for some years so the soil recovers.
• Public enlightenment: teach people the dangers of desertification through radio, schools and community talks.
• Mulching: cover the soil with dry grass or leaves to keep moisture and stop sand from shifting.
• Artificial bunds: build low ridges of earth or stones to trap water and reduce erosion.
• Improved drainage: channel excess water properly so it does not wash away the soil.
• Controlled grazing: keep only the number of animals the land can support.

Evaluation

1. Define desertification.
2. State four causes of desertification.
3. State three effects of desertification.
4. Mention four methods of controlling desertification.

Assignment

1. Name the two savannah zones of Nigeria that are prone to desertification and give two towns in each.
2. Name the cause of desertification that is linked to livestock and explain how it leads to desert.
3. Choose the correct statement: (A) Desertification is the burning of bush. (B) Desertification is the encroachment of desert into habitable land. (C) Desertification is the planting of new seedlings.