Loss of Biodiversity (Grade 11 NSC Matric Life Sciences): Revision Notes

Loss of Biodiversity

Introduction

Biodiversity describes the incredible variety of all living things found on our planet Earth. When we talk about the loss of biodiversity, we're referring to the most serious and damaging impact that humans are having on our natural environment.

Understanding why biodiversity matters is crucial for protecting our planet's future. Healthy ecosystems with rich biodiversity provide us with essential services that we often take for granted.

Why biodiversity is essential for life on earth

Biodiversity plays a vital role in maintaining the natural systems that support all life. Here's why we need to protect it:

• Clean air and water: Diverse ecosystems help philtre pollutants and maintain water quality
• Climate regulation: Different species work together to keep our climate stable
• Healthy soils: Various organisms create and maintain fertile soil for growing food
• Pollination services: Many plants rely on animals to reproduce and spread their seeds
• Food and fuel resources: Nature provides us with countless materials we depend on daily
• Natural pest management: Predators help control harmful insects without chemicals
• Medicine and healthcare: Many of our medicines come from plants and microorganisms
• Recreation and tourism: Natural areas provide spaces for enjoyment and economic benefits

Key terminology

Understanding these important terms will help you master this topic:

Term	Definition
Extinction	When a species has completely died out and no longer exists
Maintain	To provide for or enable life to keep stable and continuing
Diversity	A wide range of different things
Biodiversity	The variety of all living organisms on Earth
Biome	Large community of plants and animals living in a region with specific climate conditions
Predators	Organisms that hunt and feed on other organisms (called prey)
Habitat	The place where organisms live, including all living and non-living environmental factors
Urbanisation	The increasing development and growth of towns and cities
Migration	Long-distance movement of organisms, often happening seasonally
Sustainable	Managing resources in a way that doesn't use them up completely
Invasion	When organisms rapidly spread and take over an area

Major factors that reduce biodiversity

Several human activities are causing serious damage to biodiversity around the world. These factors often work together, making the problem even worse for wildlife and ecosystems.

Habitat destruction

Habitat destruction happens when natural environments are damaged or completely removed. This is the biggest single threat to biodiversity globally. Let's examine the main causes:

Farming methods and overgrazing

Poor farming practices can seriously damage ecosystems. When farmers keep too many animals in one area for too long, several problems occur:

• Soil becomes polluted from excessive animal waste and urine
• Soil erosion strips away the fertile top layer
• Native plants disappear, allowing alien species to move in
• The variety of plant life decreases, leading to land becoming desert-like
• Overall ecosystem health declines dramatically

Monoculture farming creates additional problems. When farmers grow the same single crop year after year:

• Indigenous plant species are lost from the area
• Specific insect pests multiply rapidly because they have unlimited food
• Heavy use of pesticides and fertilisers pollutes the environment
• Nearby water sources become contaminated and nutrient-rich (eutrophication)

Golf estate developments

Luxury golf developments are becoming increasingly common in South Africa, but they cause significant environmental damage:

Golf estates are often built in areas that naturally have high biodiversity. The construction process involves:

• Building high-density housing that removes indigenous plants and trees
• Clearing land affects dependent animal and bird populations
• Creating the same pollution problems as urban developments
• Installing private gardens that encourage alien invasive species
• Maintaining golf courses requires massive amounts of water, pesticides, and fertilisers

Mining operations

Both surface mining and underground mining cause severe habitat destruction:

Surface mining (also called open-cast mining) has particularly devastating effects:

• Takes up enormous amounts of land space
• Generates significant noise and dust pollution
• Destroys plant and animal habitats when vegetation and topsoil are removed
• Produces dangerous waste including gas emissions, solid waste, and liquid pollution
• Results in acid mine drainage that poisons underground water and river systems
• Heavy mining trucks compact soil and destroy remaining vegetation
• Exposes topsoil to erosion and further land degradation

Urbanisation and city growth

As human populations grow, cities expand rapidly, requiring more land for development.

This urban sprawl negatively affects biodiversity by:

• Increasing all types of pollution (air, land, water, noise, and light pollution)
• Creating physical barriers that prevent animal migration and breeding
• Causing rainwater runoff that leads to flooding problems
• Allowing poisons to build up in the environment (bioaccumulation)
• Encouraging the growth of alien plant species

The expansion of informal settlements and high-density housing permanently changes the landscape, requiring large open areas to be redeveloped for biodiversity to recover.

Deforestation

Deforestation means the large-scale removal of indigenous trees and forests. Although forests cover less than 1% of South Africa's total land area, they account for a significant portion of our biodiversity.

When woodlands and forested areas are destroyed for timber, agriculture, fuel, and other human activities, it leads to:

• Destruction of habitats for insects (especially important pollinators like bees) and amphibians such as frogs
• Loss of larger dependent species that rely on these smaller animals
• Disappearance of many medicinal and food plant species
• Reduced ecosystem services that forests provide

Loss of wetlands and grasslands

Wetlands are among the most biodiverse habitats on Earth, supporting rich communities of plants and animals:

When wetlands are polluted or removed for development, we lose:

• Biodiversity of soils and vegetation, including valuable medicinal plants
• Natural capacity for freshwater purification and storage
• Erosion control and flood prevention services
• Habitats for fish and other aquatic animals
• Tourism, recreation, and wildlife conservation opportunities

Grasslands function as natural grazing areas that support incredible biodiversity of wild animals and bird species:

If grassland habitats are removed, eroded, or polluted, we lose:

• Several endangered and threatened species that survive on grass seeds, worms, and insects
• Many useful and medicinal plant species
• Ecotourism opportunities like hiking trails
• Natural flood control and water filtering capabilities of grasslands

Poaching

Poaching refers to the illegal hunting or collecting of species for food or profit. The relentless removal of any species creates a ripple effect that harms all other species depending on them for survival, resulting in biodiversity loss.

In South Africa, several iconic animals are heavily poached, often for just small body parts:

Abalone

Abalone are marine snails considered a delicacy in Asia with high market value. However, abalone face serious conservation challenges:

• They take 7 years to mature before they can reproduce
• Overharvesting has caused declining populations
• Illegal poaching and trading seriously affects marine biodiversity

Rhino

Rhinos are killed illegally for their horns, which are made of keratin (the same substance found in human hair, nails, and claws).

Unfortunately, many people believe rhino horn has healing and other special properties. This has created a serious conservation crisis:

Elephants

Elephants face poaching pressure for their ivory tusks, used in ornaments and jewellery, particularly for Asian markets.

Elephants play a crucial role in ecosystem health, which makes their decline through poaching particularly damaging to biodiversity. They help maintain grasslands and create water access for other animals during dry seasons.

Bushmeat

Traditional African hunters historically depended on wild animals for food. However, modern hunting practices have become unsustainable:

• Upgraded automatic weapons allow hunters to kill more animals
• New roads into wild areas enable large-scale commercial hunting
• Protected species like gorillas and chimpanzees are now endangered
• Animals are being killed faster than natural populations can replace them

Alien plant invasions

Alien plants are non-native species that outcompete indigenous vegetation. They spread rapidly and become the dominant plants in an area, leading to significant biodiversity loss.

Strategies to reduce biodiversity loss

Fortunately, there are effective ways to reduce biodiversity loss through proper management of alien species and sustainable environmental practices.

Control of alien plant invasions

Alien plants can be removed using three main approaches:

Mechanical control

• Removing plants by hand or using machines to cut them down
• This method works well but is expensive and requires significant time investment

Chemical control

• Spraying or injecting plants with herbicides to kill them
• Also expensive and potentially risky as chemicals can pollute land and water
• May harm many other plant and animal species unintentionally

Biological control

This involves introducing natural enemies of alien species as control agents:

• Examples include wasps that create galls on Port Jackson willows, or fungi that prevent black wattle from reproducing
• This is often the most affordable option available
• However, it can be risky if the natural enemies multiply uncontrollably and begin attacking indigenous species

Sustainable use of the environment

Sustainable use means managing and using natural resources so that future generations will still be able to use those same resources.

Supporting traditional knowledge

• Traditional healers can be encouraged to grow medicinal plants rather than harvesting from the wild
• Rural unemployed people, especially women, can learn to harvest wild plants responsibly

This approach helps preserve traditional knowledge while protecting plant populations from over-exploitation.

Community-based conservation

Local communities can develop sustainable harvesting practices that protect biodiversity while providing economic benefits. For example, traditional leaders often established rules preventing damage to plants during bark collection for medicinal purposes.

Case studies: valuable indigenous plants under threat

Several indigenous South African plants have significant economic value but face serious conservation challenges due to increasing demand.

Devil's claw

Devil's claw produces hooked-shaped fruit that grows in arid sandy regions of southern Africa. It's exported internationally as a treatment for back pain, fever, and arthritis.

Conservation concerns include:

• Current demand for wild Devil's claw is unsustainable because the plant needs four years to mature before harvesting
• It's listed as a protected plant and may not be harvested from the wild without proper permits and training
• Commercial cultivation on large scales is now being developed to protect wild populations

African potato

African potato is a grassland plant with long narrow leaves and yellow star-shaped flowers. It's used for treating TB, HIV, diabetes, arthritis, cancers, and urinary tract infections.

Conservation challenges:

• Harvesting the underground parts has led to massive reductions in wild plant populations and habitat destruction
• As the plant's popularity and fame increase, government regulation of sustainable management and harvesting becomes essential
• Some indigenous plant nurseries are beginning to grow and trade African potato plants

Hoodia

Hoodia is a spiny succulent plant that has been used for generations by Khoisan people as an appetite suppressant and thirst quencher in desert regions. It's now marketed worldwide as a weight-loss product.

Despite being a protected plant that cannot be legally harvested from the wild:

• Thousands of tonnes have been illegally harvested and exported
• This threatens both the sustainable harvesting rights of the Khoisan people and the long-term survival of the species