Lesson Notes By Weeks and Term v5 - Grade 12

Lesson Video

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Performance objectives

• Describe human impacts on biodiversity with South African examples.
• Explain the causes and consequences of water pollution, especially eutrophication.
• Analyse the impact of climate change on South African ecosystems.
• Evaluate strategies for managing human impact on the environment.
• Discuss the importance of sustainable resource management.

Lesson summary

This week, we delve into the critical relationship between humans and their environment. Our focus is on understanding how human activities impact the environment and, conversely, how the environment influences human responses and well-being. This is particularly relevant in South Africa, where we face unique environmental challenges such as water scarcity, biodiversity loss, and the impacts of climate change, all of which directly affect our communities and economy. Understanding these interactions is crucial for developing sustainable practices and ensuring a healthy future for all South Africans.

Lesson notes

2. 1. Impact of Human Activities on Biodiversity Biodiversity, the variety of life on Earth, is crucial for ecosystem stability and human well-being. Human activities significantly threaten biodiversity through: Habitat Destruction: Conversion of natural habitats (forests, grasslands, wetlands) for agriculture, urban development, and mining is a major driver of biodiversity loss. In South Africa, the expansion of sugarcane farming in KwaZulu-Natal and the clearing of fynbos for agriculture and housing developments are prime examples. This leads to the loss of species-specific habitats, isolating populations and increasing the risk of extinction.

Example: The endangered Riverine Rabbit, endemic to the Karoo region, faces severe habitat loss due to agricultural expansion.

Alien Invasive Species: Introduction of non-native species that outcompete indigenous species for resources, disrupt ecosystems, and can even cause extinction. In South Africa, the Water Hyacinth (Eichhornia crassipes) is a notorious example. It rapidly proliferates in rivers and dams, blocking sunlight, reducing oxygen levels, and displacing native aquatic plants and animals. Another example is the Black Wattle (Acacia mearnsii), which invades grasslands and fynbos, altering soil composition and reducing water availability for indigenous species. Control measures, like biocontrol agents and manual removal, are often costly and time-consuming.

Overexploitation of Resources: Unsustainable harvesting of natural resources, such as overfishing, poaching of wildlife, and excessive logging, can deplete populations and even drive species to extinction. Poaching of rhinos for their horns and abalone for the illegal market are serious threats to biodiversity in South Africa. Overfishing of certain fish species along the coastline has led to population declines and disrupts the marine food web.

Example: Consider the impact of illegal rhino poaching. Rhinos are keystone species, playing a crucial role in shaping their environment through grazing. Their decline can lead to changes in vegetation structure, affecting other species that depend on that habitat. The economic impact is also significant, as it damages the tourism industry, which relies on wildlife viewing. 2.

2. Water Pollution in South Africa Water pollution is a major concern in South Africa, impacting both human health and ecosystems.

Common sources of pollution include: Agricultural Runoff: Fertilizers and pesticides used in agriculture can wash into rivers and dams, causing eutrophication and contamination. Eutrophication is the excessive enrichment of water bodies with nutrients, leading to algal blooms.

Industrial Effluents: Discharge of untreated or poorly treated wastewater from industries (mining, manufacturing) can introduce harmful chemicals, heavy metals, and pathogens into water sources.

Sewage and Sanitation: Inadequate sewage treatment facilities and improper sanitation practices, particularly in informal settlements, can lead to the contamination of water sources with sewage, bacteria, and viruses.

Mining Activities: Acid mine drainage (AMD) is a severe environmental problem in South Africa's mining regions. It is formed when sulfide minerals are exposed to air and water, producing sulfuric acid and releasing heavy metals into the water.

Eutrophication: The process of eutrophication unfolds as follows: Nutrient Enrichment: Excessive nutrients (nitrates and phosphates) from agricultural runoff or sewage enter the water body.

Algal Bloom: These nutrients stimulate rapid growth of algae, forming a dense algal bloom on the water's surface.

Sunlight Blockage: The algal bloom blocks sunlight from reaching submerged plants, inhibiting their photosynthesis.

Oxygen Depletion: When the algae die, bacteria decompose them, consuming large amounts of oxygen in the process.

Hypoxia/Anoxia: Oxygen levels in the water drop to dangerously low levels (hypoxia) or become completely depleted (anoxia), killing fish and other aquatic organisms.

Ecosystem Disruption: The entire aquatic ecosystem is disrupted, leading to loss of biodiversity and potential health risks for humans who consume contaminated water.

Example: The Hartbeespoort Dam in South Africa has suffered from severe eutrophication for decades, resulting in frequent algal blooms that impact water quality, tourism, and recreational activities. 2.

3. Impact of Climate Change on South African Ecosystems and Human Communities Climate change, driven by increased greenhouse gas emissions, is having profound effects on South Africa: Altered Rainfall Patterns: Changes in rainfall patterns lead to more frequent and intense droughts in some regions and increased flooding in others. This impacts agriculture, water availability, and food security.

Rising Temperatures: Rising temperatures increase evaporation rates, exacerbating water scarcity. They also affect crop yields and the distribution of plant and animal species.