Cambridge IGCSE0970

Food supply

Biology 0970 Chapter Notes

What this chapter covers

Food supplyHabitat destructionPollutionConservation
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In this chapter

  1. 1Population Growth and Food Demand
  2. 2Increasing Food Production with Modern Agriculture
  3. 3The Environmental Cost of Intensive Farming
  4. 4Causes and Consequences of Famine
  5. 5The Problem of Unequal Food Distribution
  6. 6Towards Sustainable Food and Agriculture

1. Population Growth and Food Demand

The human population is growing at an exponential rate, meaning it increases more and more rapidly over time. The current population is over 8 billion and is projected to reach 9.7 billion by 2050. Every person needs food for energy, growth, and repair. Therefore, as the global population increases, the demand for food rises proportionally. This puts immense pressure on the planet's resources to produce enough food to feed everyone.

Key term

Exponential Growth: A pattern of growth that shows increasingly larger increases over time, resulting in a J-shaped curve on a graph.

Examiner insight

Examiners reward answers that clearly and directly link the concept of exponential population growth to the increased pressure on global food resources.

Common pitfall

Stating that population growth is the only cause of food shortages, while ignoring crucial factors like food waste and unequal distribution.

Fun fact

It took all of human history until 1804 for the world's population to reach 1 billion. We now add 1 billion people roughly every 12-15 years.

Worked example 13 marks

The world population was approximately 4 billion in 1975 and 8 billion in 2023. Explain why this change has led to a global challenge in food supply.

  1. 1
    1. Identify the change: The population has doubled in approximately 48 years, an example of rapid exponential growth.
  2. 2
    1. Link population to demand: Each person requires a minimum intake of food for survival and health. Doubling the population means the demand for food has also at least doubled.
  3. 3
    1. State the challenge: Producing twice as much food requires more land, water, and energy, putting a significant strain on Earth's agricultural systems and natural ecosystems. This creates a major challenge to ensure everyone has access to sufficient food.

Recap

  • The human population is growing exponentially.
  • A larger population requires a greater amount of food.
  • Increased food demand puts pressure on land, water, and energy resources.
  • Meeting future food demand is a major global challenge.

Quick check

  1. State the primary reason why food demand is increasing globally.1 mark

2. Increasing Food Production with Modern Agriculture

To meet the rising food demand, modern agriculture uses intensive farming methods to maximise yield (the amount of crop produced per unit area). Key techniques include:

  • Mechanisation: Using large machinery like tractors and combine harvesters to manage large areas of land efficiently.
  • Chemical Fertilisers: Adding substances containing key minerals like nitrates (for leaf growth), phosphates (for root growth), and potassium (for flower/fruit growth) to the soil to improve crop development.
  • Pesticides: Using chemicals to protect crops from pests. These include herbicides (kill competing weeds), insecticides (kill insects), and fungicides (kill fungal diseases).
  • Selective Breeding: Choosing parents with desirable characteristics (e.g., high yield, disease resistance) to breed together, producing improved offspring over generations.

N = Nitrogen (for healthy leaf and stem growth)

P = Phosphorus (for strong root development)

K = Potassium (for flowering, fruiting, and overall health)

Key term

Fertiliser: A chemical or natural substance added to soil to increase its fertility and provide essential nutrients for crop growth.

Examiner insight

Candidates who can name specific types of agricultural chemicals (e.g., herbicides, insecticides) and explain their specific purposes tend to score higher marks.

Common pitfall

Confusing herbicides (which kill plants) with insecticides (which kill insects).

Worked example 14 marks

Explain two ways a farmer can increase the yield of their wheat crop using modern agricultural techniques.

  1. 1
    1. Method 1: Use of fertilisers. The farmer can add NPK fertilisers to the soil.
  2. 2
    1. Explanation 1: These provide essential minerals like nitrates for growth, which may be lacking in the soil. This allows the wheat plants to grow larger and healthier, producing more grain and therefore increasing yield.
  3. 3
    1. Method 2: Use of pesticides. The farmer can spray the crop with herbicides.
  4. 4
    1. Explanation 2: Herbicides will kill weeds in the field. This reduces competition for resources like light, water, and mineral ions, meaning more of these resources are available for the wheat crop, leading to a higher yield.

Recap

  • Modern agriculture uses intensive methods to maximise food production.
  • Mechanisation allows large-scale, efficient farming.
  • Fertilisers provide essential mineral ions (N, P, K) to crops.
  • Pesticides (herbicides, insecticides) kill pests that would reduce yield.
  • Selective breeding improves the genetic qualities of crops and livestock.

Quick check

  1. What is the role of nitrates provided in fertiliser?1 mark
  2. Distinguish between an insecticide and a herbicide.2 marks

3. The Environmental Cost of Intensive Farming

While intensive farming increases food production, it can have severe negative impacts on the environment.

  • Deforestation: Large areas of forest are cleared to create space for farming crops or grazing livestock, leading to habitat loss and a reduction in biodiversity.
  • Hedgerow Removal: To create larger fields for machinery, farmers often remove hedgerows. This destroys habitats and wildlife corridors, reduces biodiversity, and can increase soil erosion.
  • Eutrophication: Fertiliser from fields can be washed into rivers and lakes. This causes a rapid growth of algae (an algal bloom). The algae block sunlight, killing plants below. When the algae and plants die, they are decomposed by bacteria, which use up large amounts of oxygen in the water. This deoxygenation kills fish and other aquatic animals.
  • Pesticide Issues: Pesticides can harm non-target species, including useful insects like bees. They can also accumulate in food chains (bioaccumulation), reaching toxic levels in top predators.

Key term

Eutrophication: The process where a body of water becomes overly enriched with nutrients, leading to excessive algal growth, subsequent oxygen depletion, and death of animal life.

Examiner insight

A clear, step-by-step explanation of eutrophication is a common high-mark question; memorising the sequence is crucial for success.

Common pitfall

Incorrectly sequencing the events of eutrophication, for example, stating that decomposers use up oxygen before the algal bloom has occurred.

Worked example 16 marks

Explain, in a series of steps, how fertiliser runoff from a farm can cause the death of organisms in a lake.

  1. 1
    1. Leaching: Rain washes excess nitrate and phosphate fertilisers from the farmland into the nearby lake.
  2. 2
    1. Algal Bloom: The high concentration of nutrients in the water causes a rapid growth and multiplication of algae on the surface.
  3. 3
    1. Light Blockage: This dense layer of algae blocks sunlight from reaching the aquatic plants living deeper in the water.
  4. 4
    1. Plant Death: The submerged plants cannot photosynthesise and die.
  5. 5
    1. Decomposition: Bacteria and other decomposers feed on the dead plants and dead algae, and their populations increase dramatically.
  6. 6
    1. Oxygen Depletion: These decomposers use up large quantities of dissolved oxygen from the water during aerobic respiration.
  7. 7
    1. Death of Animals: The oxygen level in the water becomes too low to support other aerobic organisms like fish, which then die.

Recap

  • Intensive farming can lead to deforestation and habitat loss.
  • Removing hedgerows reduces biodiversity and increases soil erosion.
  • Fertiliser runoff causes eutrophication in rivers and lakes.
  • Eutrophication involves an algal bloom, followed by decomposition and oxygen depletion.
  • Pesticides can harm wildlife and accumulate in food chains.

Quick check

  1. What is the first major event that happens when excess fertiliser enters a lake?1 mark

4. Causes and Consequences of Famine

Famine is a widespread and extreme scarcity of food in a region, leading to malnutrition, starvation, and death. It is rarely caused by a single factor, but usually a combination of several. Key causes include:

  • Natural Events: Prolonged drought prevents crops from growing, while severe flooding can destroy entire harvests and wash away fertile soil.
  • Poverty: People may be too poor to buy food, or farmers may be unable to afford seeds, fertilisers or machinery needed to grow crops.
  • Conflict: War and civil unrest disrupt farming, destroy infrastructure, and prevent aid from reaching people. Food can also be used as a weapon.
  • Unequal Distribution: As covered in the next topic, food may exist but not be in the right place or accessible to those who need it.
  • Disease: Pests and diseases can wipe out crops and livestock, drastically reducing food availability.

Key term

Famine: An extreme and widespread scarcity of food, caused by several factors including crop failure, population imbalance, or government policies.

Examiner insight

Examiners look for answers that discuss a range of interacting factors causing famine, not just a single cause like 'no rain'.

Common pitfall

Equating famine with a lack of food globally. Famine is a problem of access to food in a specific region, even if there are global surpluses.

Worked example 14 marks

Describe how(a) a long period of drought and(b) war can each lead to famine in a country.

  1. 1

    (a) Drought:

  2. 2
    1. A lack of rainfall means there is not enough water for crops to grow (crop failure) or for livestock to drink.
  3. 3
    1. This leads to a massive reduction in the amount of food produced locally.
  4. 4
    1. If the country cannot afford to import food, this widespread food shortage can develop into a famine.
  5. 5

    (b) War:

  6. 6
    1. Conflict forces farmers to flee their land, so crops are not planted or harvested.
  7. 7
    1. Transport links like roads and bridges may be destroyed, preventing the movement of food aid and supplies.
  8. 8
    1. Food stores may be destroyed or seized, leading to severe shortages for the civilian population and causing famine.

Recap

  • Famine is an extreme scarcity of food in a specific area.
  • Causes of famine are complex and often interconnected.
  • Natural causes include drought, flooding, and crop diseases.
  • Human causes include poverty, war, and poor governance.
  • Famine leads to severe malnutrition, starvation, and increased mortality.

Quick check

  1. List two human factors that can contribute to famine.2 marks

5. The Problem of Unequal Food Distribution

The world produces enough food to feed everyone, but it is not distributed evenly. This leads to situations where some countries have food surpluses while others face famine. Key reasons for this include:

  • Cost and Logistics: Transporting food over long distances is expensive, especially for bulky or perishable items. It may not be economically viable or practical to move surpluses to where they are needed.
  • Food Aid Issues: While essential in emergencies, long-term food aid can cause problems. Shipping cheap or free food to a region can lower the price of locally grown food, making it impossible for local farmers to compete and potentially destroying the local agricultural economy.
  • Politics and Trade: Trade barriers, political instability, and conflict can prevent food from crossing borders and reaching those in need.
  • Focus on Self-Sufficiency: Many argue that a better long-term solution is to help poorer regions become self-sufficient by providing education, farming equipment, irrigation systems (wells), and better seeds, rather than just giving them food.

Key term

Food Security: The state where all people, at all times, have physical and economic access to sufficient, safe, and nutritious food.

Examiner insight

Students who can evaluate the pros and cons of food aid versus long-term development aid demonstrate a deeper understanding and are more likely to access the top marks.

Common pitfall

Believing that shipping surplus food from rich to poor countries is a simple and effective long-term solution without any drawbacks.

Fun fact

Globally, about 14 percent of food produced is lost between harvest and retail, while an estimated 17 percent of total global food production is wasted in households, food service and retail combined.

Worked example 14 marks

Discuss the arguments for and against providing long-term food aid to a country with persistent food shortages.

  1. 1

    Argument FOR aid:

  2. 2
    1. It provides immediate relief and prevents starvation and malnutrition, saving lives in the short term.
  3. 3

    Argument AGAINST aid:

  4. 4
    1. It can make the country dependent on outside help and reduce the incentive for self-sufficiency.
  5. 5
    1. It can disrupt the local economy by driving down the price of food, which harms local farmers who cannot sell their own produce.
  6. 6

    Conclusion/Evaluation:

  7. 7
    1. Therefore, while food aid is vital for emergencies (like after a natural disaster), a more sustainable long-term solution is to provide resources like education, tools, and irrigation to help the country improve its own food production.

Recap

  • The world's food is not distributed evenly.
  • Transport costs and logistics make it difficult to move food surpluses.
  • Long-term food aid can harm local economies and create dependency.
  • A better solution is often to help people become self-sufficient in food production.
  • Food security means having reliable access to enough good quality food.

Quick check

  1. State one negative economic effect of long-term food aid on a recipient country.1 mark

6. Towards Sustainable Food and Agriculture

Sustainable food production aims to meet our current needs for food without compromising the ability of future generations to meet their needs. It involves balancing food production with environmental protection. Examples include:

  • Sustainable Fishing: To prevent overfishing and the collapse of fish stocks, methods include:
  • Fishing Quotas: Setting legal limits on the amount and type of fish that can be caught.
  • Net Regulations: Using nets with a larger mesh size allows smaller, younger fish to escape, grow, and reproduce.
  • Integrated Pest Management: Reducing reliance on chemical pesticides by using a combination of methods, such as introducing natural predators to kill pests, and growing pest-resistant crop varieties.
  • Conserving Resources: Using techniques like drip irrigation to use water more efficiently and practicing crop rotation to maintain soil fertility naturally.
  • Biotechnology: Using genetically modified (GM) crops that may be engineered to be drought-resistant, pest-resistant, or have higher nutritional value. This can increase yield while reducing the need for water or chemicals.

Key term

Sustainable: An activity that can be continued indefinitely because it meets the needs of the present without compromising the ability of future generations to meet their own needs.

Examiner insight

Answers that provide specific, explained examples of sustainable practices, like using fishing net size regulations to protect juvenile fish, are highly credited.

Common pitfall

Vaguely mentioning 'being more green' instead of providing concrete, scientific examples of sustainable agricultural or fishing practices.

Worked example 14 marks

Explain how(a) fishing quotas and(b) regulations on net mesh size help to conserve fish stocks.

  1. 1

    (a) Fishing Quotas:

  2. 2
    1. Quotas place a legal limit on the mass of a certain species of fish that can be caught. This prevents overfishing, where too many adult fish are removed from the sea.
  3. 3
    1. This ensures that enough adult fish are left in the population to reproduce and maintain the stock for future years.
  4. 4

    (b) Net Mesh Size:

  5. 5
    1. Regulations can enforce a minimum mesh size for fishing nets. A larger mesh size means that smaller, immature fish are not caught in the net and can escape.
  6. 6
    1. This allows these young fish to grow to maturity and reproduce, which helps to replenish the fish stock.

Worked example 22 marks

Outline one advantage and one disadvantage of growing genetically modified (GM) crops to increase food supply.

  1. 1
    1. Advantage: GM crops can be engineered to have increased yield, resistance to pests/diseases, or tolerance to drought. For example, pest-resistant crops reduce the need for chemical insecticides, which is better for the environment and can increase yield.
  2. 2
    1. Disadvantage: There are concerns that genes from GM crops could transfer to wild plants, creating 'superweeds'. There are also long-term concerns about their potential impact on human health and biodiversity, although these are not proven.

Recap

  • Sustainable agriculture aims to produce food without harming the environment.
  • Fishing quotas and net size regulations help to make fishing sustainable.
  • Conserving fish stocks ensures there will be fish for future generations.
  • Integrated pest management reduces the use of chemical pesticides.
  • Biotechnology and GM crops offer potential benefits and risks for food security.

Quick check

  1. Why does using a fishing net with a larger mesh size help conserve fish stocks?1 mark

End-of-chapter exercise

Test yourself on the whole chapter. Work through these before moving on.

  1. State two reasons for the increasing demand for food worldwide.2 marks
  2. Explain how the use of chemical fertilisers on a field can lead to the death of fish in a nearby river.4 marks
  3. Describe two ways in which modern technology, other than the use of fertilisers, has increased food production.4 marks
  4. Discuss the arguments for and against providing direct food aid to a country experiencing long-term food shortages.6 marks
  5. Explain how (i) flooding and (ii) human conflict can each lead to famine.4 marks
  6. Describe two methods used to make fishing more sustainable, and explain how each method works.4 marks
  7. A farmer removes the hedgerows between their fields to create one large field. State two negative environmental impacts of this action.2 marks
  8. A new species of insect that eats crop leaves has been accidentally introduced to an island. Suggest three methods, apart from widespread use of chemical insecticides, that could be used to control the pest and protect crops.3 marks
  9. Explain why 'food security' is about more than just the total amount of food produced in the world.3 marks
  10. Genetically modified (GM) crops can be designed to be resistant to herbicides. Explain how this could increase crop yield.3 marks

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