Lesson Notes By Weeks and Term v5 - Grade 12

Lesson Video

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Performance objectives

• Explain the impact of human population growth.
• Describe food security and its threats in South Africa.
• Explain how sustainable agriculture can improve food security.
• Understand the concept of bioaccumulation.
• Apply knowledge to answer exam-style questions.

Lesson summary

Human impact on the environment is a critical topic, particularly in South Africa, where the interplay between socio-economic development and environmental sustainability is constantly challenged. Our country's rich biodiversity faces immense pressure from population growth, industrial activities, and unsustainable resource utilization. Understanding these impacts is essential, not only for academic success in Life Sciences but also for informed citizenship and participation in creating a sustainable future for all South Africans.

Lesson notes

2. 1. Human Population Growth and its Impact The exponential growth of the human population is a primary driver of environmental degradation. More people require more resources – land, water, food, energy, and minerals. In South Africa, this is particularly evident in: Increased demand for land: Leads to deforestation for agriculture and housing, resulting in habitat loss and biodiversity decline. For example, the conversion of grasslands in Mpumalanga for maize production has significantly impacted the local ecosystem.

Water scarcity: South Africa is a water-stressed country. Increased demand for water for agriculture, industry, and domestic use strains our water resources, leading to water shortages and pollution. The frequent droughts experienced in the Western Cape underscore this challenge.

Pollution: Increased industrial activity and urbanization contribute to air and water pollution, affecting human health and ecosystems. The Vaal River pollution crisis exemplifies this issue.

Waste generation: More people generate more waste, which, if not managed properly, pollutes the environment and poses health risks. Causes of Population Growth in South Africa: Improved Healthcare: Increased access to healthcare services has led to lower mortality rates, contributing to population growth.

Lack of Access to Family Planning: In some communities, there is limited access to family planning services and information, leading to higher birth rates.

Socio-cultural Factors: Cultural norms and beliefs can influence family size preferences.

Poverty: In some instances, families view children as a source of labour or economic support, leading to larger families.

Example: Consider a rural community in KwaZulu-Natal. Improved access to healthcare through mobile clinics has lowered infant mortality rates. Simultaneously, limited access to family planning information results in families having more children. This increases the pressure on local resources like firewood, grazing land, and water sources, leading to deforestation and soil erosion. 2.

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

Threats to Food Security in South Africa: Unsustainable Agriculture: Practices like monoculture farming (growing the same crop repeatedly), excessive use of fertilizers and pesticides, and improper irrigation deplete soil nutrients, pollute water sources, and reduce biodiversity.

Deforestation: Clearing forests for agriculture or other purposes destroys habitats, reduces carbon sequestration, and increases soil erosion, impacting agricultural productivity.

Pollution: Air, water, and soil pollution contaminates crops and livestock, making them unsafe for consumption and reducing yields. Mining operations in certain areas release heavy metals into the soil, rendering it unusable for agriculture.

Climate Change: Changing rainfall patterns, increased temperatures, and extreme weather events like droughts and floods disrupt agricultural production, leading to crop failures and livestock losses.

Alien Invasive Plants: These plants compete with indigenous vegetation for resources, reducing biodiversity and impacting agricultural productivity. For example, wattle trees consume large amounts of water, reducing water availability for agriculture.

Soil Erosion: Loss of topsoil reduces soil fertility and water retention capacity, hindering agricultural production. Poor farming practices, deforestation, and overgrazing contribute to soil erosion.

Example: A maize farmer in the Free State practices monoculture farming, using large quantities of chemical fertilizers and pesticides. Over time, the soil becomes depleted of nutrients, and the pesticides contaminate nearby water sources. The yield decreases, and the farmer struggles to maintain food security. 2.

3. Sustainable Agricultural Practices Sustainable agriculture aims to produce food while minimizing environmental impacts and ensuring long-term productivity.

Key practices include: Crop Rotation: Alternating different crops in a field helps to improve soil fertility, reduce pest and disease infestations, and break weed cycles. For example, rotating maize with legumes (like beans or peas) can replenish nitrogen in the soil.

Conservation Tillage: Reducing or eliminating tillage (plowing) helps to conserve soil moisture, reduce soil erosion, and improve soil structure.

Integrated Pest Management (IPM): Using a combination of biological, cultural, and chemical methods to control pests, minimizing the use of harmful pesticides.

Water Conservation: Employing irrigation techniques like drip irrigation and water harvesting to conserve water resources.

Organic Farming: Avoiding the use of synthetic fertilizers and pesticides, relying instead on natural methods like composting and biological control.