Agricultural activities are essential for food production, but some farming practices can affect the ecological system when they are not properly controlled. Practices such as bush burning, overgrazing, deforestation, excessive use of fertilizers and pesticides can disturb the natural balance between soil, water, plants and animals. These activities may lead to soil degradation, pollution, erosion, loss of biodiversity and destruction of natural habitats. Understanding the effects of agricultural activities on ecological system helps farmers choose practices that protect the environment while maintaining agricultural production.
Learning Objectives
At the end of this lesson, students should be able to:
- Explain what agricultural activities are and give examples.
- Describe what the ecological system means.
- State positive effects of agricultural activities on the ecological system.
- Explain negative effects of agricultural activities on land, water, air and living organisms.
- Explain how agricultural activities affect soil fertility and biodiversity.
- Suggest sustainable agricultural practices that protect the ecological system.
Effects of Agricultural Activities on the Ecological System
1. Bush Burning
Bush burning is the setting of fire to vegetation in order to clear land for farming or other purposes. Although farmers may use fire as a quick method of clearing land, uncontrolled or repeated bush burning can damage the ecological system.
Effects of Bush Burning on the Ecological System
- Destroys organic matter and humus in the soil.
- Kills beneficial soil microorganisms.
- Pollutes the air with smoke and gases such as carbon monoxide.
- Exposes the soil to erosion and leaching.
- Reduces the water-holding capacity of the soil.
- Destroys natural habitats of plants and animals.
- Disrupts food chains and affects the balance of organisms in the area.
- The heat from fire can destroy seeds and young plants, making natural vegetation recovery difficult.
- Some mineral nutrients may temporarily become available in the ash, but repeated burning can eventually reduce soil fertility.
2. Overgrazing
Overgrazing occurs when too many animals feed on a piece of land for a long period, removing vegetation faster than it can naturally regenerate. Continuous grazing without allowing pasture to recover can seriously affect the soil and vegetation.
Effects of Overgrazing on the Ecological System
- Removes much of the protective vegetation cover.
- Exposes the soil to wind and water erosion.
- Causes soil compaction due to continuous trampling by animal hooves.
- Damages soil structure.
- Reduces the ability of plants to regenerate.
- Reduces the quality and growth of pasture.
- Encourages the formation of bare land.
- May contribute to desertification in areas where vegetation is continually destroyed.
3. Fertilizer Application
Fertilizers are substances added to the soil to supply nutrients needed for plant growth. When the correct type and amount are applied, fertilizers can improve soil fertility and increase crop yield. However, excessive or improper application can have negative effects on the ecological system.
Effects of Fertilizer Application on the Ecological System
- Moderate application can improve soil fertility and crop yield.
- Appropriate fertilizer use can support plant growth and soil biological activity.
- Excessive use of some fertilizers can increase soil acidity.
- Continuous excessive application may affect soil organisms and soil quality.
- Fertilizer nutrients can be washed from farmland into rivers, streams and ponds.
- Excess nutrients in water can cause eutrophication, leading to excessive growth of algae and aquatic plants.
- Eutrophication can reduce the amount of oxygen available in water and harm aquatic organisms such as fish.
4. Application of Pesticides and Herbicides
Pesticides are chemicals used to control harmful pests, while herbicides are used to control unwanted plants or weeds. They can help farmers protect crops, but careless or excessive use can affect other organisms and pollute the environment.
Effects of Pesticides and Herbicides on the Ecological System
- Can cause pollution of soil, water and air.
- May kill useful organisms that are not the intended targets, such as bees and some soil organisms.
- Can leave chemical residues in the soil and water.
- Chemicals washed into rivers, streams and ponds may harm aquatic organisms.
- Excessive use may affect crop growth and soil organisms.
- Some chemicals can enter food chains and affect animals that feed on contaminated organisms.
- Improper use can create health risks for humans and animals.
5. Tillage
Tillage is the breaking, turning or loosening of soil before planting. It can help prepare the soil for planting and improve aeration, but continuous and intensive tillage can damage the ecological condition of farmland.
Effects of Continuous Tillage on the Ecological System
- Loosens the soil and improves aeration.
- Exposes some soil organisms to direct sunlight and drying.
- Can encourage the loss of nutrients through leaching.
- Leaves the soil more exposed to wind and water erosion.
- Continuous intensive tillage can reduce soil fertility.
- Can disturb soil structure.
- May reduce the population and activities of some soil organisms.
- Changes the natural ecological conditions of the farmland.
6. Deforestation
Deforestation is the continuous removal of trees and other forest vegetation without adequate replacement. Forests provide habitats for animals, protect the soil and play an important role in the water cycle. Removing large areas of vegetation can therefore have serious environmental effects.
Effects of Deforestation on the Ecological System
- Encourages soil erosion and can increase the risk of flooding.
- Reduces the amount of organic matter returned to the soil.
- Reduces vegetation cover that helps protect the soil.
- Destroys habitats of wildlife.
- Disrupts the water cycle and can affect local rainfall patterns.
- Reduces the protection provided by forests around watersheds.
- Can reduce soil biological activity.
- Encourages nutrient loss through erosion and leaching.
- May contribute to desertification in dry areas when vegetation is continuously removed.
7. Bush Clearing or Clean Clearing
Bush clearing is the removal of vegetation from a piece of land before cultivation. Clean clearing involves removing most or all vegetation, including grasses, shrubs and other plants. Although it makes land easier to cultivate, complete removal of vegetation can leave the soil poorly protected.
Effects of Bush Clearing on the Ecological System
- Removes vegetation that protects the soil.
- Exposes rich topsoil to erosion.
- Exposes the soil to direct sunlight.
- Increases evaporation of water from the soil.
- Can increase soil temperature.
- Reduces the amount of organic matter returned to the soil.
- May reduce the population of some soil organisms.
- Increases the risk of erosion and leaching.
- Removes habitats and sources of food for some organisms.
- Makes the land more vulnerable to environmental degradation when the soil is left bare.
Importance of Protecting the Ecological System
The ecological system supports agricultural production by providing fertile soil, water, organisms, vegetation and other natural resources. When agricultural activities are poorly managed, these resources can be damaged and the productivity of farmland may decline.
Farmers can reduce these harmful effects by using sustainable agricultural practices such as crop rotation, afforestation, controlled grazing, proper fertilizer application, integrated pest management, organic farming and minimum or reduced tillage. These practices help to protect the soil, water, plants and animals while keeping farmland productive for future generations.
Evaluation Questions on effects of agricultural activities on ecological system
- Define bush burning and list four effects of bush burning on the ecological system.
- What is overgrazing, and how does it affect soil structure?
- List five effects of deforestation on the ecological system.
- Explain how pesticides can affect aquatic life.
- State four ways farmers can protect the ecological system from harmful agricultural activities.