The big idea: Water, food and energy are not separate problems -- they are linked in a system called the nexus.
You cannot secure one without affecting the others:
- Growing food needs water and energy. - Producing energy needs water (cooling, hydropower) and sometimes land that could grow food. - Supplying clean water needs energy to pump, treat and move it.
So a decision in one part of the nexus has knock-on effects in the other two.
Key terms
- Nexus -- a set of connections where the three resources interact and depend on each other.
- Resource security -- having reliable, affordable access to enough water, food and energy.
- Trade-off -- gaining one resource at the cost of another (e.g. more biofuel = less food).
- Interdependence -- the resources rely on each other, so a change in one shifts the others.
How this is tested: Paper 2 asks you to Outline or Suggest a single interaction -- for example, how securing water can reduce food, or how energy choices use water. You must show the link, not just name two resources.
| Action to secure... | Effect on the other resources |
|---|---|
| Water (dams, irrigation) | Reservoirs need energy to pump; large dams can flood farmland; irrigation can cut river flow downstream. |
| Food (more farming) | Agriculture uses about 70% of the world's freshwater and needs fuel and fertiliser (energy) to grow and transport. |
| Energy (biofuels, hydro, cooling) | Biofuel crops take land and water from food; hydropower and power-plant cooling both rely on large amounts of water. |
Three interactions to remember
- Water -> food: irrigation grows crops, but over-pumping rivers and aquifers leaves less water for farms downstream.
- Energy -> water: thermal and nuclear power stations need huge volumes of water for cooling; if water is short, power output falls.
- Food -> energy: growing crops for biofuel (e.g. maize for ethanol) takes farmland and water away from food.
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Named examples (use these in essays): Top marks need named, real places. These show the nexus stretched by climate, population and choices.
Case studies
- The Nile basin -- Ethiopia's large hydropower dam stores water to make electricity, but Egypt downstream fears less river water for its farms, a clear energy-water-food clash between countries.
- California, USA -- long droughts force farmers to pump groundwater for food; pumping and moving that water uses large amounts of energy, and the aquifers are falling.
- The Aral Sea region -- decades of diverting rivers to irrigate cotton (food/cash crop) shrank the sea, ruining fisheries and the local climate.
- India's Punjab -- cheap subsidised energy lets farmers pump groundwater for food almost for free, so the water table is dropping fast.
Why the pressure is rising: A growing population and higher incomes demand more of all three resources at once, while climate change shifts rainfall and raises temperatures -- so the nexus is squeezed harder every decade.
How this is tested: The [10] 'To what extent' essay asks how far one driver (e.g. climate change, or safe water) shapes resource security and the nexus. You argue both sides with named examples and reach a judgement.
| Action to secure... | Effect on the other resources |
|---|---|
| Water (dams, irrigation) | Reservoirs need energy to pump; large dams can flood farmland; irrigation can cut river flow downstream. |
| Food (more farming) | Agriculture uses about 70% of the world's freshwater and needs fuel and fertiliser (energy) to grow and transport. |
| Energy (biofuels, hydro, cooling) | Biofuel crops take land and water from food; hydropower and power-plant cooling both rely on large amounts of water. |
IB-style question -- read the table
Using the table above: (a) outline one interaction between elements of the water-food-energy nexus [2]; (b) state which resource agriculture uses about 70% of [1].
How to answer each part
- (a) Outline one interaction. Pick one row and show the link both ways. E.g. securing energy with hydropower stores water behind a dam, which can flood farmland and cut river flow for farms downstream -- so an energy gain causes a food/water loss.
- (b) State the resource. The table says agriculture (food) uses about 70% of the world's freshwater -> the resource is water (freshwater).
Final answer
(a) one developed link, e.g. hydropower stores water but floods farmland / cuts downstream flow; (b) water (freshwater).