7.3 Biodiversity and the effect of human interaction on ecosystems

7.3.1 Biodiversity

FSL: GCSE Biology Revision "Biodiversity"

- Biodiversity is defined as the variety of all the different species of organisms on earth, or within an ecosystem.
- Different species may depend on each other for survival. This can be in multiple ways:

Food
Habitat (e.g. shelter, nesting sites)
Physical environment (e.g. temperature, water availability. most common with trees (e.g. roots))

- Good biodiversity is where there are multiple organisms that can fulfill the requirements of other organisms.
- This ensures the stability of ecosystems by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment.
- The future of the human species on Earth relies on us maintaining a good level of biodiversity.
- We rely on other organisms for many different things, including:

Food: Crops, fruits, meat, pollinators, etc.
Habitat: Forests, grasslands, deserts
Physical environment: Water, air, soil, temperature

- Many human activities are reducing biodiversity and only recently have measures been taken to try to stop this reduction.

7.3.2 Waste Management

FSL: GCSE Biology Revision "Waste Management"

- Rapid growth in human population and the resulting increase in demand for food and resources has led to a significant increase in waste.
- Unless waste and chemicals are managed properly, they can end up in landfills, oceans, rivers, and the atmosphere.
- This is collectively pollution.
- Pollution can occur:

In water (sewage, fertiliser, toxic chemicals, oil spills)
In air (smoke, acidic gases)
On land (landfill, toxic chemicals)

- Waste management is the process of reducing, reusing, and recycling waste.
- It is important to manage waste properly to reduce the amount of waste that ends up polluting the environment.

Pollution location	Pollution type	How it occurs	Effects
In water	Sewage	Untreated waste from homes and industries enters water bodies.	Causes waterborne diseases, depletes oxygen levels, and harms aquatic life.
In water	Fertiliser	Runoff from agricultural fields enters rivers and lakes.	Causes algal blooms, leading to oxygen depletion and aquatic life death.
In water	Toxic chemicals	Industrial waste and pesticides contaminate water sources.	Harms aquatic life, accumulates in the food chain, and affects human health.
In water	Oil spills	Accidental spills from ships, pipelines, or offshore drilling.	Coats marine animals, destroys habitats, and contaminates food sources.
In air	Smoke	Burning of fossil fuels, wildfires, and industrial emissions.	Causes respiratory issues, contributes to climate change, and reduces air quality.
In air	Acidic gases	Emissions from factories and vehicles release sulfur dioxide and nitrogen oxides.	Leads to acid rain, which damages ecosystems, buildings, and water sources.
On land	Landfill	Disposal of non-biodegradable waste and household trash in designated areas.	Causes soil contamination, releases methane, and attracts pests.
On land	Toxic chemicals	Improper disposal of industrial and electronic waste.	Pollutes soil, harms wildlife, and can enter the food chain.

7.3.3 Land Use

FSL: GCSE Biology Revision "Land Use"

- Humans reduce the amount of land available for other animals and plants by building, quarrying, farming and dumping waste.
- This reduces biodiversity because it reduces the amount of habitat available and interrupts food chains and webs, so there is less prey for animals.
- Examples of land use include:

Agriculture: Farming, grazing, and crops.
Forestry: Logging, cutting down trees, and wood.
Urbanisation: Buildings, roads, and other infrastructure.
Mining: Extracting minerals from the earth.
Industry: Manufacturing, mining, and construction.

Peat Bogs

- Peat bogs are destroyed mainly due to:

Peat Extraction – Peat is removed for use as fuel or as a component of compost in gardening.
Agriculture – Some peatlands are drained to create farmland.
Development – Peatlands are destroyed to make space for roads, buildings, or infrastructure.
Climate Change – Warmer temperatures and changes in rainfall can dry out peat bogs, making them more vulnerable.

- Effects of Peat Bog Destruction:

Increased Carbon Dioxide (CO₂) Emissions: Peat stores large amounts of carbon. When peat is burned or decomposes after being drained, CO₂ is released, contributing to global warming.
Loss of Biodiversity: Peat bogs are habitats for rare plants, insects, and birds. Their destruction leads to a decline in species that depend on them.
Flooding Risk: Peatlands act like sponges, absorbing rainwater. Their destruction increases the risk of flooding in nearby areas.
Soil Erosion: Once peatlands dry out, the soil becomes loose and easily washed away, reducing fertile land.

- Solutions:

Using peat-free compost
Protecting and restoring peatlands
Reducing land drainage

7.3.4 Deforestation

- Large-scale deforestation in tropical areas has occurred to:

Provide land for cattle and rice fields
Grow crops for biofuels

Consequences of deforestation include:

Loss of biodiversity
Climate change (more carbon dioxide in the atmosphere)
Soil erosion (trees help stabilise soil; leaching nutrients from the soil)
Water pollution
Loss of habitat for wildlife
Increased risk of natural disasters
Flooding (loose topsoil falls into rivers)

7.3.5 Global Warming

FSL: GCSE Biology Revision "Global Warming"

- Levels of carbon dioxide and methane in the atmosphere are increasing, and contribute to ‘global warming’.

Gas	Production
Carbon dioxide	Produced by burning fossil fuels, deforestation, and agriculture.
Methane	Produced by decomposing organic matter, such as agricultural waste, livestock, and landfills.
Nitrous oxide	Produced by exhausts from vehicles, power plants, and industrial processes.
CFCs	CFCs were used as refrigerants in the past, and despite being phased out in the largest international agreement ever (this is a whole rabbit hole) CFCs are still being released into the atmosphere from old refrigerating systems.

How Global Warming Works

The greenhouse effect is the process by which heat is trapped in the Earth's atmosphere, keeping the planet warm enough to support life. It is a natural phenomenon, but human activities have intensified it, leading to global warming.

Sunlight Reaches Earth – The Sun emits shortwave radiation (mainly visible light and ultraviolet rays), which passes through the Earth's atmosphere.
Earth Absorbs and Re-emits Heat – The Earth's surface absorbs this energy and warms up. It then emits infrared radiation (heat) back into the atmosphere.
Greenhouse Gases Trap Heat – Greenhouse gases in the atmosphere preventing it from escaping into space.
Earth Stays Warm – This trapped heat keeps the planet at an average temperature of around 15°C, which is essential for life.

Consequences of Global Warming

- Rising sea levels
- More extreme weather events
- Loss of biodiversity (food chains and habitats are disrupted)
- Increased risk of natural disasters
- Increase in species migration (animals seek cooler climates; this leads to an increase in pests in colder regions)

7.3.6 Maintaining biodiversity

FSL: GCSE Biology Revision "Maintaining Biodiversity"

- Humans have both positive and negative impacts on biodiversity.
- Here are some specific negative impacts:

Impact	Description	Reason for Importance
Deforestation in the Amazon for cattle farming	Large areas of rainforest are cleared to create grazing land for beef production.	Destroys habitats, reduces biodiversity, and contributes to climate change via CO₂ release.
Plastic pollution in oceans harming marine life	Marine animals ingest or become entangled in plastic waste.	Leads to injury or death, disrupting marine food chains and ecosystems.
Coral bleaching due to rising sea temperatures	Warmer oceans cause corals to expel algae, turning white and often dying.	Coral reefs support high biodiversity; their loss affects entire marine ecosystems.
Urban expansion destroying hedgerows in the UK	New housing developments remove hedgerows that provide food and shelter for wildlife.	Hedges are key habitats for birds, insects, and small mammals.

- And here are some positive impacts:

Positive Action	Description	Impact on Biodiversity
Breeding programmes for endangered species	Animals at risk of extinction are bred in controlled environments like zoos or wildlife parks.	Increases population numbers and helps preserve genetic diversity.
Protection and regeneration of rare habitats	Conservation of habitats such as wetlands, heathlands, and ancient woodlands.	Helps species that rely on these habitats survive and reproduce.
Reintroduction of field margins and hedgerows in monoculture farms	Planting vegetation around fields where only one crop is grown (monoculture).	Provides shelter and food for pollinators, birds, and other wildlife.
Government action to reduce deforestation and CO₂ emissions	Policies and laws that limit tree removal and promote cleaner energy sources.	Protects forests and helps slow down climate change, benefiting ecosystems globally.
Recycling of resources to reduce landfill waste	Processing used materials to make new products, avoiding excessive landfill use.	Reduces habitat destruction and pollution caused by extracting and disposing of raw materials.