BIOLOGY · Stage 9 · Chapter 12: The Carbon Cycle and Climate Change
Biology 12.2 People and the carbon cycle — Fossil Fuels and Deforestation — Alhussan International Academy - Biology (Stages 7-9) Revision Notes & Topical Questions
5 min read 6 parts Lesson 2 of 6
Lesson summary
12.2 People and the carbon cycle — Fossil Fuels and Deforestation — Alhussan International Academy — Biology (Stages 7–9) notes: Explain how burning fossil fuels and deforestation add carbon dioxide to the atmosphere and strengthen the greenhouse effect.Greenhouse gases — carbon …
- Effect of more carbon dioxide
- Before the industrial revolution
- Carbon sinks
- Electricity
- Less removal
- Other effects
Section 1 of 6The greenhouse effect
1Greenhouse gases2 points
- carbon dioxide and other gases trap energy from the Sun, like the glass in a greenhouse.
- They trap enough to keep the Earth's surface warm, but not so much that it overheats.
2Effect of more carbon dioxide2 points
- more energy is trapped and temperatures at the surface rise.
- Many ecosystems are finely balanced, so a change in temperature may decide whether a type of organism lives or dies.
Section 2 of 6The balance of the carbon cycle
- Before the industrial revolution
- carbon dioxide in the atmosphere was fairly stable because photosynthesis and dissolving in the oceans balanced respiration, decay and combustion.
- Now
- human activity adds carbon dioxide faster than natural processes can remove it, so the concentration is rising.
- Carbon sinks = places such as forests, coral reefs and oceans that naturally absorb and store carbon.
- Some human activities add carbon dioxide and others interfere with carbon sinks.
Section 3 of 6Burning fossil fuels
- Formation
- coal, oil and natural gas formed over millions of years from the remains of plants and microscopic organisms that were buried and compressed.
- They are stores of carbon taken from the air long ago and are non-renewable.
- Burning
- hydrocarbon + oxygen → carbon dioxide + water, which releases the carbon in a short time.
- Transport
- cars, lorries, boats and planes burn fuels made from oil and release about 6.7 gigatonnes (Gt) of carbon dioxide each year.
- One gigatonne is one thousand million tonnes.
- Electricity
- generation by burning coal, oil or gas adds around 33 Gt each year.
- Total
- about 36.2 billion tonnes of carbon dioxide were produced worldwide in 2017.
Section 4 of 6Deforestation
- Deforestation = clearing forests for farmland, timber, cattle grazing, roads and housing.
- Less removal
- trees take in carbon dioxide in photosynthesis, so fewer trees mean less is removed from the air.
- Globally, forests absorb 33% less carbon dioxide than they did 30 years ago.
- Release
- when cleared trees are burned or left to rot, the stored carbon is released by combustion and by decomposers respiring.
- Soil carbon can also be lost.
- Other effects
- forests help keep water in the soil, so their loss can cause soil erosion and floods.
Section 5 of 6Who produces most
- Emissions by region in 2017
- Asia produced 53% of global emissions, North America 18%, Europe 17%, Africa 3.7%, South America 3.2% and Oceania 1.3%.
- International aviation and shipping added 3.2%.
- Historical emissions 1751-2017
- Europe produced 33%, Asia 29%, North America 29%, Africa 3%, South America 3% and Oceania 1.2%.
- Why patterns change
- the use of science and technology changes in different countries.
- Wealth
- as people get richer they use more transport and more electricity for clean water, lighting, refrigeration, heating and air conditioning.
Section 6 of 6Other human effects and solutions
| Activity | Effect on carbon cycle | Possible solution |
|---|---|---|
| Burning fossil fuels | Adds carbon dioxide | Use renewable energy; save energy |
| Deforestation | Removes a carbon dioxide sink; releases stored carbon | Protect forests; replant trees |
| Farming livestock | Adds methane | Change diet; improve feed |
- Planting
- reforestation and afforestation increase carbon dioxide uptake.
- Carbon capture
- it traps carbon dioxide from power stations and stores it underground.
- Agreements
- international agreements try to limit emissions but must balance climate goals with the energy needs of poorer countries.
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