Key Idea: Topic 12.2 is about how we produce food, why some people still go hungry, and how disease spreads through places. It pulls together three ideas: 12.2.1 — food systems & production: the chain from field to plate (production → processing → distribution → consumption), the energy inputs and outputs of farming, energy efficiency (output ÷ input), and how new methods diffuse (the Green Revolution, vertical farming). 12.2.2 — food security & famine: food security = reliable access for all to enough safe food; famine is its extreme failure. Causes are physical, economic, political and social — and they combine. 12.2.3 — the spread of disease: how disease diffuses through space — expansion (ripples from a source) or relocation (carried by people) — and the physical/human factors and barriers that speed it up or stop it. This is Option F content, examined on Paper 1 (SL answers 2 options, HL 3 — same questions). Each option = a short data-response + structured question, then a [10] extended-answer essay (Examine / Evaluate / Discuss).
🌾 12.2.1 — Food systems & food production
A food system runs from production → processing → distribution → consumption, with inputs (energy, water, labour, seeds, fertiliser) and outputs (food, waste, emissions) at every stage. The headline skill is energy efficiency — the output ÷ input ratio — and how production changes over time as farms mechanize and new methods diffuse.
Energy input vs output of farm products (GJ/hectare/year, illustrative)
| Farm product | Energy input | Energy output | Output ÷ input (efficiency) |
|---|---|---|---|
| Cassava (low-input root crop) | 5 | 60 | 12.0 — very efficient |
| Rice (irrigated) | 15 | 75 | 5.0 |
| Wheat (mechanized) | 20 | 70 | 3.5 |
| Greenhouse lettuce | 30 | 12 | 0.4 — lowest output |
| Beef (intensive) | 40 | 8 | 0.2 — least efficient |
Key terms — food production
- Food system — production → processing → distribution → consumption, with inputs and outputs at each stage.
- Inputs / outputs — inputs = energy, water, labour, seeds, fertiliser; outputs = food (yield) plus waste and emissions.
- Energy efficiency — the output ÷ input ratio: how much food energy you get for the energy you put in.
- Intensive vs extensive — intensive = high inputs per hectare for high yield; extensive = low inputs over a large area.
- Diffusion — how a new method, seed or technology spreads (the Green Revolution in India spread unevenly).
- Vertical/indoor farming — stacking crops indoors under LED light; land-efficient but high energy demand and costly.
Tip: An intensive system uses many inputs per hectare but is often not energy-efficient — intensive beef returns only 0.2 units per unit in, while low-input cassava returns 12. To find the most efficient product, read the output ÷ input column, not the raw output. To find the lowest output, read the output column — beef (8 GJ), not the smallest input.
🍚 12.2.2 — Food security & famine
Food security exists when all people, at all times, have reliable access to enough safe, nutritious food. It rests on three pillars — availability (enough food), access (people can afford and reach it) and stability (a reliable supply). Famine is the extreme failure of all three at once. Causes are rarely single: physical, economic, political and social factors combine — a drought becomes a famine only when poverty and conflict block the response.
Factors that cause food insecurity and famine
| Type of factor | Examples | How it causes a shortage |
|---|---|---|
| Physical / environmental | Drought, flood, soil degradation, pests, climate change | Cuts the food actually grown or available in an area |
| Economic | Poverty, low incomes, rising food prices, poor transport/storage | People cannot afford or reach food even when it exists |
| Political | Conflict, civil war, corruption, weak government, sanctions | Disrupts farming, blocks aid and supply routes, mismanages reserves |
| Social | Disease (HIV/AIDS, malaria), rapid population growth, inequality | Removes labour from farms and raises the number of mouths to feed |
Key terms — food security
- Food security — reliable access for everyone, at all times, to enough safe, nutritious food.
- Food insecurity — unreliable or insufficient access to food (chronic or sudden).
- Famine — an extreme, widespread food shortage causing mass hunger, malnutrition and excess deaths.
- Three pillars — availability (enough food), access (afford and reach it) and stability (reliable over time).
- The Sahel — an African belt (Niger, Chad, Mali) where recurrent drought, poverty and conflict turn shortages into famine.
- The Green Revolution — high-yield crops, irrigation and fertiliser (India, from the 1960s) that helped end recurrent famine in Punjab.
Enough food can exist in a country yet people still starve. A drought is only the trigger — whether it becomes a famine depends on poverty (can people afford food?), conflict (can it be grown and delivered?) and governance (is there a reserve and a response?). Stable, well-governed states avoid famine despite the same droughts.
🦟 12.2.3 — The geography & spread of disease
The geography of disease asks how a disease spreads from place to place — its diffusion — and what speeds it up or stops it. Expansion diffusion ripples outward from a source (cholera through a crowded settlement); relocation diffusion is carried by people who move (a traveller flying with dengue). Speed and reach depend on physical, human, economic and political factors, fought by barriers (clean water, nets, vaccination, quarantine).
A typical Option F stimulus: read the key first. Each bar's total height is the region's waste; each colour is where the waste happens (one segment, not the whole bar).
🔒 Interactive diagram
Explore the labelled diagram, charts and maps for this topic in study mode.
Factors in the spread of disease — and the mechanism
| Factor | How it speeds diffusion |
|---|---|
| Physical: warm, wet climate | Standing water and heat let mosquitoes breed fast → more vectors → more malaria/dengue |
| Physical: rainfall + flooding | Floods mix sewage with drinking water → water-borne cholera/typhoid spread |
| Human: migration + air travel | Infected people relocate the disease to new areas (relocation diffusion) |
| Human: overcrowding + poor sanitation | People live close with no clean water/toilets → fast person-to-person spread |
| Economic: poverty + weak healthcare | No money for nets, drugs, clean water or clinics → the disease is not stopped |
Key terms — disease spread
- Diffusion — the way a disease spreads outward across space and through a population over time.
- Expansion diffusion — the disease stays at its source and ripples outward (cholera through a settlement).
- Relocation diffusion — infected people carry the disease to a new area (a traveller flying with dengue).
- Vector-borne disease — spread by an organism such as a mosquito (malaria, dengue).
- Water-borne disease — spread through contaminated water (cholera, typhoid).
- Barrier — anything that slows or blocks diffusion (clean water, nets, vaccination, quarantine, a dry season).
A vector-borne disease (malaria, dengue) is spread by an organism; a water-borne disease (cholera, typhoid) by contaminated water. In a [10] disease essay, choosing the wrong type for the question (e.g. cholera when it asks for vector-borne) caps you at about 4/10 — name a real disease and place of the right type in your first line.
✍️ IB-style questions
Explain two factors that could cause high levels of food insecurity in a low-income country, and how each leads to a shortage of food.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
For one named vector-borne disease, examine the relative importance of physical and human factors in its spread.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
✅ Quick self-check
Tap each card to reveal the answer.
How do you find the most energy-efficient farm product? Read the output ÷ input ratio, not the raw output. The highest ratio (cassava at 12.0) is most efficient; intensive beef has the lowest (0.2).
What are the three pillars of food security? Availability (enough food), access (people can afford and reach it) and stability (a reliable supply over time). A famine usually means several fail at once.
Why is famine rarely caused by a single factor? A drought or flood is only the trigger — it becomes a famine only when poverty and conflict block the response. Stable, well-governed states avoid famine despite the same shocks.
Expansion vs relocation diffusion? Expansion = the disease stays and ripples outward from its source (cholera through a settlement). Relocation = an infected person moves and carries it to a new area (a traveller with dengue).
What caps a [10] disease essay hardest? Choosing the wrong disease type for the question (e.g. a water-borne disease when it asks for vector-borne) — about 4/10. Always name a real disease + place of the right type.
🎯 Highest-yield exam reminders
Exam Tips
- Energy efficiency = output ÷ input — cassava high, intensive beef low. Intensive ≠ efficient, and lowest output ≠ lowest input: read the right column.
- Read a stimulus carefully: for a stacked bar, the whole bar is a total but one colour is an origin; for an outbreak curve, Estimate the peak off the axis and quote the units.
- Food security = availability + access + stability; famine = the extreme failure. Causes are physical, economic, political AND social — and they combine.
- Diffusion = expansion (ripples out) or relocation (carried by travel/migration). Barriers (clean water, nets, vaccination, quarantine) slow it.
- Match the disease type to the question — vector-borne (malaria/dengue) vs water-borne (cholera/typhoid); the wrong type caps a [10] essay at about 4.
- On every [10] essay (Examine/Evaluate/Discuss): name a real example + place, develop two+ factors, weigh them (often OVER TIME), and finish with a clear judgement.