Lesson Notes By Weeks and Term v5 - Grade 12

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Performance objectives

• Describe the causes and consequences of pollution.
• Explain the effects of deforestation and alien plant invasions.
• Discuss the evidence for and impacts of climate change.
• Evaluate human impact on biodiversity.
• Analyse the effectiveness of conservation strategies.

Lesson summary

The Earth's ecosystems are under immense pressure from human activities. As future citizens of South Africa, understanding the consequences of our actions on the environment is crucial for developing sustainable practices and policies. This topic delves into the various ways human activities negatively impact our environment, focusing on issues relevant to South Africa and beyond. We will explore topics like pollution, deforestation, alien plant invasions, climate change, and strategies for mitigating these issues.

Lesson notes

2.1 Pollution Pollution refers to the contamination of the environment by harmful substances, impacting air, water, and soil.

Water Pollution: Caused by industrial discharge, agricultural runoff (containing fertilizers and pesticides), sewage, and plastic waste. In South Africa, mining activities contribute significantly through acid mine drainage, polluting rivers and groundwater.

Example: The Witwatersrand gold mines release heavy metals and acidic water, contaminating the Vaal River, a crucial water source for Gauteng.

The effects include: Eutrophication: Excessive nutrients (from fertilizers) lead to algal blooms, depleting oxygen and killing aquatic life.

Toxicity: Heavy metals and pesticides can poison aquatic organisms and accumulate in the food chain, impacting human health through consumption of contaminated fish.

Waterborne diseases: Contaminated water can transmit diseases like cholera and typhoid.

Air Pollution: Primarily caused by burning fossil fuels (coal in power plants, vehicle emissions), industrial processes, and burning of waste. In South Africa, coal-fired power plants contribute significantly to air pollution, particularly in Mpumalanga.

Effects include: Respiratory problems: Air pollutants like particulate matter (PM2.5 and PM10), sulfur dioxide (SO2), and nitrogen oxides (NOx) can cause asthma, bronchitis, and other respiratory illnesses.

Acid rain: SO2 and NOx react with water in the atmosphere to form acid rain, which damages ecosystems and infrastructure.

Smog: A mixture of air pollutants that reduces visibility and poses health risks.

Soil Pollution: Caused by industrial waste, agricultural chemicals, mining activities, and improper waste disposal.

Example: Uncontrolled dumping of industrial waste can contaminate soil with heavy metals and toxic chemicals.

Effects include: Reduced soil fertility: Pollutants can kill beneficial soil microorganisms and alter soil chemistry, reducing its ability to support plant growth.

Contamination of groundwater: Pollutants can leach into groundwater, contaminating drinking water sources.

Bioaccumulation: Pollutants can be absorbed by plants and accumulate in the food chain, posing risks to human and animal health. 2.2 Deforestation Deforestation is the clearing of forests for other land uses, such as agriculture, urbanization, and mining. In South Africa, deforestation is driven by factors like firewood collection, agriculture expansion, and urbanization.

The impacts include: Loss of biodiversity: Forests are home to a vast array of plant and animal species. Deforestation leads to habitat loss and species extinction.

Soil erosion: Trees protect the soil from erosion. Deforestation exposes the soil to wind and rain, leading to soil loss and degradation.

Climate change: Forests absorb carbon dioxide from the atmosphere. Deforestation releases stored carbon dioxide, contributing to climate change.

Disruption of water cycles: Forests play a crucial role in regulating water cycles. Deforestation can lead to reduced rainfall and increased runoff, impacting water availability. 2.3 Alien Plant Invasions Alien plant species are those that are introduced to an area outside their natural range. Some alien species become invasive, outcompeting native plants and disrupting ecosystems. In South Africa, alien plant invasions are a major threat to biodiversity and water resources.

Examples include: Black Wattle (Acacia mearnsii): Introduced for tannin production, it spreads rapidly, displacing native vegetation and reducing water availability. Eucalyptus (Eucalyptus spp.): Planted for timber, it consumes large amounts of water and reduces biodiversity.

Water Hyacinth (Eichhornia crassipes): A floating aquatic plant that forms dense mats, blocking sunlight and reducing oxygen levels in water bodies. The impacts of alien plant invasions include: Loss of biodiversity: Invasive plants outcompete native plants, leading to a decline in native plant populations and impacting animals that depend on them.

Reduced water availability: Invasive plants often consume more water than native plants, reducing water availability for other uses.

Increased fire risk: Some invasive plants are highly flammable, increasing the risk of wildfires.

Economic costs: Controlling invasive plants can be expensive. 2.4 Climate Change Climate change refers to long-term shifts in temperature and weather patterns, primarily caused by human activities that release greenhouse gases (GHGs) into the atmosphere.

Evidence for climate change includes: Rising global temperatures: Average global temperatures have increased significantly over the past century.

Melting glaciers and ice sheets: Glaciers and ice sheets are melting at an accelerated rate, contributing to sea level rise.

Sea level rise: Sea levels are rising due to thermal expansion of water and melting of glaciers and ice sheets.