Lesson Notes By Weeks and Term v5 - Grade 12

Lesson Video

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Performance objectives

• Explain the causes and consequences of food insecurity in SA.
• Discuss threats to biodiversity and conservation strategies.
• Describe the causes and effects of climate change.
• Analyse challenges and solutions for waste management.
• Evaluate the impact of human population growth.

Lesson summary

The human impact on the environment is a critical area of study in Life Sciences, particularly in Grade 12, because our actions have profound and lasting consequences for the planet and all its inhabitants. In South Africa, these impacts are particularly felt due to our diverse ecosystems, reliance on natural resources, and historical socio-economic disparities that exacerbate environmental challenges. Understanding these impacts is not just about learning facts; it's about equipping you with the knowledge and skills to become responsible and informed citizens who can contribute to a sustainable future for our country and the world.

Lesson notes

2.1 Food Security Food security exists when all people, at all times, have physical, social, and economic access to sufficient, safe, and nutritious food to meet their dietary needs and food preferences for an active and healthy life.

Causes of food insecurity: Unsustainable agricultural practices: Monoculture farming depletes soil nutrients, leading to reduced yields and increased reliance on fertilizers. Overgrazing leads to soil erosion and desertification.

Climate Change: Changes in rainfall patterns, increased temperatures, and extreme weather events like droughts and floods disrupt crop production and livestock farming.

Poverty and Inequality: Lack of access to land, credit, and markets limits the ability of small-scale farmers to produce sufficient food. High food prices make it unaffordable for poor households to access nutritious food.

Land Degradation: Soil erosion, deforestation, and pollution reduce the productivity of agricultural land.

Water Scarcity: Limited access to water for irrigation restricts crop production.

Pests and Diseases: Crop losses due to pests and diseases reduce food availability.

Consequences of food insecurity: Malnutrition: Undernutrition, micronutrient deficiencies, and stunting, especially in children.

Health Problems: Increased susceptibility to infections and chronic diseases.

Economic Losses: Reduced productivity and increased healthcare costs.

Social Unrest: Food shortages can lead to social unrest and conflict. South African

Examples: The recurring droughts in the Western Cape have severely impacted agricultural production and water availability. High rates of poverty and inequality in rural areas limit access to food for many households. The legacy of apartheid has resulted in unequal access to land and resources, contributing to food insecurity among previously disadvantaged communities. 2.2 Loss of Biodiversity Biodiversity refers to the variety of life on Earth at all its levels, from genes to ecosystems, and can encompass the evolutionary, ecological, and cultural processes that sustain life.

Threats to Biodiversity: Habitat Destruction: Deforestation, urbanization, and agricultural expansion destroy natural habitats, leading to loss of species.

Poaching: Illegal hunting of animals for meat, trophies, or medicinal purposes threatens endangered species.

Alien Invasive Species: Introduction of non-native species that outcompete native species and disrupt ecosystems.

Example: The Hakea plant in the Western Cape outcompetes native Fynbos.

Unsustainable Use of Natural Resources: Overfishing, overgrazing, and excessive logging deplete natural resources and damage ecosystems.

Pollution: Air, water, and soil pollution contaminates habitats and harms wildlife.

Climate Change: Changes in temperature, rainfall, and sea levels alter habitats and threaten species survival.

Conservation Strategies: Establishing protected areas: National parks, nature reserves, and marine protected areas provide safe havens for wildlife.

Controlling alien invasive species: Implementing measures to prevent the introduction and spread of invasive species. Promoting sustainable agriculture and forestry: Encouraging practices that minimize environmental impact. Combating poaching and illegal wildlife trade: Strengthening law enforcement and raising awareness about the importance of wildlife conservation.

Restoring degraded ecosystems: Reforestation, wetland restoration, and soil conservation efforts. 2.3 Climate Change Climate change refers to long-term shifts in temperatures and weather patterns. These shifts may be natural, but since the 1800s, human activities have been the main driver of climate change, primarily due to burning fossil fuels (like coal, oil and gas), which produces heat-trapping gases.

Causes of Climate Change: Greenhouse Effect: The greenhouse effect is a natural process that warms the Earth's surface. When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back into space and the rest is absorbed and re-radiated by greenhouse gases. Greenhouse gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases. These gases trap heat in the atmosphere, keeping the Earth warm enough to sustain life.

However, human activities, such as burning fossil fuels and deforestation, have increased the concentration of greenhouse gases in the atmosphere, enhancing the greenhouse effect and causing global warming.

Global Warming: The increase in Earth's average surface temperature due to the enhanced greenhouse effect.

Ozone Depletion: The thinning of the ozone layer in the stratosphere, which protects the Earth from harmful ultraviolet (UV) radiation. Ozone depletion is caused by human-made chemicals, such as chlorofluorocarbons (CFCs), which were formerly used in refrigerants, aerosols, and solvents. While technically separate from global warming, the effects are intertwined and contribute to overall climate destabilization.