Skip to content
Marlbridge
Free trial

Flashcards · IB Diploma Programme Environmental Systems and Societies · Topic 5

Land flashcards

13 cards on Topic 5, subtopics 5.1 to 5.2. Pick a subtopic or study them all.

Study mode needs JavaScript. Every card is listed below, so you can still cover the answers and test yourself.

All 13 cards

For a quick read-through or printing. Cover the right-hand side to test yourself.

5.1 Soil

What is humus?
Dark, stable organic matter formed when dead material decomposes. It holds water and nutrients.
Soil as a system: give the transfers and transformations
Transfers (material moves): infiltration, percolation, leaching, mixing by earthworms, translocation between horizons. Transformations (material changes): decomposition, humification, weathering, nitrogen fixation.
Sand versus clay soils
Sand: largest particles; drains and warms quickly, well aerated, but holds little water and few nutrients. Clay: smallest particles; holds water and nutrients but drains poorly. Loam (a mix) has the highest primary productivity.
Why is soil effectively non-renewable?
It forms very slowly, from parent material, climate, organisms, relief and time, so losses by erosion cannot be replaced on a human timescale.
What is salinization and how can it be reduced?
The build-up of salts at the surface when irrigation water evaporates in hot, dry climates with poor drainage. Reduced by drip irrigation, drainage channels and flushing salts.
How do you measure soil water content and organic matter?
Water: (fresh mass − oven-dry mass) ÷ fresh mass × 100, "of fresh mass". Organic matter (loss on ignition): (dry mass − mass after strong heating) ÷ dry mass × 100.
Match conservation methods to water and wind erosion
Water erosion: contour ploughing, terracing, cover crops, mulching, no-till. Wind erosion: windbreaks, cover crops, controlled grazing. Link each method to its mechanism: slows water, slows wind, or covers the surface.

5.2 Agriculture and food

What is food security?
All people, at all times, having access to enough safe and nutritious food.
Intensive versus extensive farming
Intensive: high inputs (labour, capital, fertiliser) per unit area. Extensive: low inputs per unit area. The terms describe inputs per area, not farm size or purpose; a farm can be subsistence and intensive.
What is the energy ratio of a farm system?
Food energy out ÷ energy in. It is high for labour-based subsistence farms and low for intensive livestock, which eats crops people could eat.
Why does a plant-based diet feed more people per hectare?
Roughly 90% of energy is lost at each trophic step (an approximation, not an exact rule), so eating crops directly feeds many more people than eating animals fed on crops. Grazing land that cannot grow crops is the main exception.
Food loss versus food waste
Food loss happens early in the supply chain (harvest, storage, transport), mostly in lower-income countries. Food waste happens late (retail, households), mostly in higher-income countries.
Which greenhouse gases come from agriculture?
Methane from cattle and rice paddies; nitrous oxide from fertilised soils; carbon dioxide from machinery and land clearance.

Revise Land further