Biodiversity, Food Production and Sustainability

This final lesson in the Inheritance, Variation and Ecology module covers biodiversity, the impact of human activities on ecosystems, and how food production can be made more sustainable. These are key topics in the AQA GCSE Combined Science Trilogy specification (8464).

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What Is Biodiversity?

Biodiversity is the variety of all the different species of organisms on Earth, or within an ecosystem. High biodiversity means a wide range of different species.

Why Is Biodiversity Important?

Reason	Explanation
Ecosystem stability	More species means more food web connections, making ecosystems more resilient to change
Food security	Humans depend on diverse crops and livestock for food
Medicine	Many medicines come from plants and animals (e.g. aspirin from willow bark)
Genetic resources	Wild relatives of crops contain useful alleles for breeding resistant varieties
Ecosystem services	Pollination, water purification, soil formation all depend on biodiversity
Ethical responsibility	Many argue that all species have a right to exist

Exam Tip: AQA (8464) expects you to explain the importance of biodiversity. Always give specific examples — do not just say "biodiversity is important" without explaining why.

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Human Impacts on Biodiversity

The growing human population requires more resources, land and energy, leading to activities that reduce biodiversity:

1. Habitat Destruction

Activity	Impact
Deforestation	Loss of habitat for thousands of species; reduced CO₂ absorption
Urbanisation	Permanent loss of habitats under buildings and roads
Agricultural expansion	Natural habitats replaced by farmland
Mining	Surface habitats destroyed; waterways polluted

2. Pollution

Type	Source	Effect on Biodiversity
Water pollution	Fertiliser runoff, sewage, industrial waste	Eutrophication; death of aquatic organisms
Air pollution	Fossil fuel combustion	Acid rain damages ecosystems
Land pollution	Pesticides, herbicides, landfill	Poisons organisms; degrades soil

3. Eutrophication

Eutrophication is a frequently examined process:

1. Excess fertiliser is washed from fields into rivers and lakes
2. Algae grow rapidly on the surface (algal bloom)
3. Algae block sunlight from reaching underwater plants
4. Plants die because they cannot photosynthesise
5. Decomposing bacteria break down the dead plants
6. Bacteria use up dissolved oxygen through aerobic respiration
7. Fish and other aquatic organisms die due to lack of oxygen

graph TD
    A["Excess fertiliser<br/>enters waterway"] --> B["Algal bloom<br/>on surface"]
    B --> C["Sunlight blocked<br/>from aquatic plants"]
    C --> D["Aquatic plants<br/>die"]
    D --> E["Bacteria decompose<br/>dead material"]
    E --> F["Dissolved oxygen<br/>used up"]
    F --> G["Fish and aquatic<br/>organisms die"]
    style A fill:#c8e6c9,stroke:#2e7d32
    style B fill:#a5d6a7,stroke:#2e7d32
    style C fill:#fff9c4,stroke:#f9a825
    style D fill:#ffccbc,stroke:#d84315
    style E fill:#d7ccc8,stroke:#5d4037
    style F fill:#ef9a9a,stroke:#c62828
    style G fill:#ef5350,stroke:#c62828,color:#fff

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Deforestation and Peat Destruction

Deforestation

Deforestation — clearing forests — has major consequences:

Consequence	Explanation
Loss of biodiversity	Tropical rainforests contain the most species of any habitat
Increased CO₂	Fewer trees to absorb CO₂; burning trees releases stored carbon
Soil erosion	Roots no longer hold soil in place
Flooding	Trees no longer intercept rainfall
Loss of potential medicines	Undiscovered plant species may contain useful compounds

Peat Bogs

Peat bogs form in waterlogged, acidic conditions where decomposition is extremely slow. Dead plant material accumulates over thousands of years as peat.

Why Peat Bogs Matter	Explanation
Carbon store	Peat bogs lock away vast amounts of carbon
Biodiversity	Support unique species (e.g. sphagnum moss, sundew)
Water management	Act as natural sponges, reducing flood risk

When peat is extracted or bogs are drained:

• Stored carbon is released as CO₂ (contributing to climate change)
• Unique habitats are destroyed
• Biodiversity is lost

Exam Tip: AQA (8464) often asks about peat bogs in the context of carbon cycling and biodiversity. Make the link: peat stores carbon → destroying peat releases CO₂ → increased greenhouse effect → climate change → further biodiversity loss.

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Food Production and Efficiency

As the global population grows, more food must be produced. Farmers can increase the efficiency of food production:

Reducing Energy Loss in Food Chains

Method	How It Works
Restricting animal movement	Animals in confined spaces use less energy for movement, so more energy goes into growth (biomass)
Controlling temperature	Keeping animals warm reduces energy lost through respiration to maintain body temperature
High-energy feed	Provides more energy for growth and less is wasted

$\text{Efficiency} = \frac{\text{Energy in biomass produced}}{\text{Energy input (food)}} \times 100$Efficiency=Energy input (food)Energy in biomass produced​×100

Ethical Considerations of Factory Farming

Argument For	Argument Against
Produces cheaper food	Animals may suffer in confined conditions
Feeds large populations efficiently	Increases risk of disease spreading
Reduces land use	Routine use of antibiotics contributes to antibiotic resistance
Economic benefits for farmers	Some consider it morally wrong to restrict animals' natural behaviours

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Sustainable Food Production

Sustainability means meeting present needs without compromising the ability of future generations to meet their own needs.

Sustainable Fishing

Strategy	How It Helps
Fishing quotas	Limit catches to allow populations to recover
Minimum net mesh sizes	Allow young fish to escape and reach breeding age
Closed seasons	Ban fishing during breeding periods
Marine protected areas	No-fishing zones allow stocks to recover

Sustainable Agriculture

Strategy	How It Helps
Crop rotation	Different crops use different nutrients; prevents soil depletion
Biological control	Using natural predators instead of chemical pesticides
Organic farming	Avoids synthetic fertilisers and pesticides
Precision farming	Using technology to apply water and fertiliser only where needed
Hedgerow and habitat maintenance	Supports pollinators and natural pest control

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Maintaining Biodiversity

Strategies to maintain biodiversity include:

Strategy	Details
Breeding programmes	Captive breeding of endangered species (e.g. giant panda)
Seed banks	Storing seeds from diverse plant species (e.g. Millennium Seed Bank at Kew)
Protected areas	Nature reserves, national parks, marine protected areas
Reforestation	Planting trees to replace those that were felled
Legislation	Laws like CITES that restrict trade in endangered species
Rewilding	Allowing degraded land to return to a natural state

Exam Tip: AQA (8464) frequently asks you to "evaluate" a conservation strategy. Always discuss advantages AND disadvantages. For example: breeding programmes prevent extinction but are expensive and do not address the underlying cause (e.g. habitat loss).

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The Global Impact of Food Production