Biodiversity and Conservation

Biodiversity includes:

• The variety of species in an ecosystem
• The genetic variation within a species
• The variety of ecosystems in an area

High biodiversity is important because:

• It makes ecosystems more stable and resilient (if one species declines, others can fill its role)
• It provides food, medicines, and raw materials for humans
• It maintains ecosystem services (pollination, water purification, carbon storage)

The human population is growing rapidly, and our activities are reducing biodiversity:

Land Use Changes

• Deforestation — cutting down forests for farming, timber, and building
  • Destroys habitats, reducing species populations
  • Removes trees that absorb CO₂, contributing to climate change
  • Reduces biodiversity in tropical regions (which contain the most species)
• Urbanisation — building towns and cities on natural land
• Agriculture — monoculture farming (growing one crop) reduces plant diversity; pesticides kill insects

Pollution

Global Warming

• Caused by increased greenhouse gases (CO₂, methane, water vapour) in the atmosphere
• Sources: burning fossil fuels, deforestation, agriculture (cattle produce methane)
• Effects on biodiversity:
  • Habitat loss — ice caps melting (polar bears), coral bleaching, sea level rise flooding coastal habitats
  • Distribution changes — species migrate to cooler areas; some cannot adapt fast enough
  • Changing seasons — mismatches between species (e.g., insects emerge before the flowers they pollinate)
  • Ocean acidification — CO₂ dissolves in seawater, making it more acidic, damaging coral and shellfish

Over-exploitation

• Overfishing — taking more fish than can be naturally replaced
• Hunting — driving species towards extinction (e.g., rhinos for horns)
• Over-harvesting — collecting too many plants or resources

Introduction of Invasive Species

• Non-native species introduced to new environments can outcompete native species
• Example: Grey squirrels outcompeting red squirrels in the UK

Breeding Programmes

• Captive breeding in zoos to increase populations of endangered species
• Animals may be reintroduced to the wild
• Example: Giant panda breeding programmes

Protected Areas

• Nature reserves, national parks, and marine protected areas limit human activity
• Allow ecosystems to recover naturally

Habitat Restoration

• Replanting forests (reforestation/afforestation)
• Restoring wetlands and coral reefs
• Creating wildlife corridors to connect fragmented habitats

Legislation and International Agreements

• Laws to protect endangered species (e.g., CITES — Convention on International Trade in Endangered Species)
• Fishing quotas to prevent overfishing
• Regulations on pollution and emissions
• Paris Agreement on climate change

Seed Banks

• Storing seeds from a wide variety of plant species
• Preserves genetic diversity
• Seeds can be used to restore populations if species decline
• Example: Svalbard Global Seed Vault

Sustainable Management

• Sustainable fishing — using quotas, mesh size regulations, and closed seasons
• Sustainable forestry — replanting trees at the same rate they are cut down
• Sustainable farming — reducing pesticide use, maintaining hedgerows, crop rotation

Eutrophication is a common exam topic:

1. Fertilisers from farmland are washed into rivers and lakes by rain (runoff)
2. The excess nitrates and phosphates cause algae to grow rapidly (algal bloom)
3. The dense layer of algae blocks sunlight from reaching underwater plants
4. Underwater plants die because they cannot photosynthesise
5. Decomposing bacteria break down the dead plants (and algae that eventually die)
6. The bacteria use up oxygen for aerobic respiration
7. The water becomes deoxygenated (oxygen levels drop)
8. Fish and other aquatic organisms die due to lack of oxygen

Carbon moves between the atmosphere, organisms, and the Earth:

• Photosynthesis removes CO₂ from the atmosphere (stored in plant biomass)
• Respiration releases CO₂ back into the atmosphere (from all living organisms)
• Combustion of fossil fuels and wood releases CO₂ (stored carbon)
• Decomposition by microorganisms releases CO₂ as they respire

Human activities have upset the carbon cycle balance by:

• Burning fossil fuels — releasing carbon that was stored for millions of years
• Deforestation — fewer trees to absorb CO₂; burning/decay of trees releases CO₂
• This increases CO₂ concentration in the atmosphere → enhanced greenhouse effect → global warming

Question: Explain how the use of fertilisers on farmland can lead to the death of fish in a nearby lake. (6 marks)

Solution:

Fertilisers are washed from farmland into the lake by rain (runoff). The excess nitrates and phosphates in the water cause rapid growth of algae on the surface (algal bloom). The dense algae blocks sunlight from reaching plants below the surface. These underwater plants die because they cannot photosynthesise. Bacteria decompose the dead plants and algae. The decomposing bacteria carry out aerobic respiration, using up dissolved oxygen in the water. The oxygen levels drop so low that fish and other aquatic organisms suffocate and die. This process is called eutrophication.

• For eutrophication questions, describe the full sequence (fertiliser → algal bloom → light blocked → plants die → decomposition → oxygen depletion → fish die).
• When discussing conservation, give specific methods with explanations, not just vague "protect the environment."
• Link deforestation to two effects: habitat loss (biodiversity) AND increased CO₂ (climate change).
• Remember: greenhouse gases include CO₂, methane, and water vapour.

• Biodiversity is the variety of life in an ecosystem; it ensures stability and provides resources.
• Human activities reducing biodiversity: deforestation, pollution, global warming, over-exploitation, and invasive species.
• Eutrophication is the process by which fertiliser runoff causes oxygen depletion in water, killing aquatic life.
• Conservation methods include: protected areas, breeding programmes, seed banks, legislation, and sustainable management.
• Deforestation and burning fossil fuels increase atmospheric CO₂, driving climate change.