Key Idea: Topic 5.2 explores how humans produce food on land, the trade-offs of intensive vs extensive farming, the environmental impacts of agriculture, how diets affect sustainability, and strategies for sustainable agriculture + soil conservation.
🚜 Agriculture as a system
- Agriculture has inputs (fertilizer, water, energy, labour) and outputs (food + waste/pollution)
- Farming choices change energy flow + nutrient cycling compared to natural ecosystems
⚖️ Intensive vs extensive
Intensive: High yield per area. High inputs (fertilizer, pesticides, irrigation, tech). Often higher pollution per hectare.
Extensive: Low yield per area. Low inputs, large land area. Risk: habitat loss from land expansion + overgrazing.
Use the debate: land sparing vs land sharing (depends on goals + context).
🌍 Environmental impacts of agriculture
- Water: irrigation depletion, pesticide contamination, eutrophication from nutrient runoff
- Soil: erosion, compaction, organic matter loss, salinization
- Biodiversity: habitat destruction, monocultures, non-target pesticide impacts
- Climate: CO₂ (machinery/land use), CH₄ (livestock), N₂O (fertilizers)
🥗 Food choices + diets
- Trophic efficiency (~10% transfer) → plant-based diets usually lower footprint than meat-heavy diets
- Food miles matter, but total footprint also depends on production method + storage
✅ Sustainable agriculture + soil conservation
- Sustainable farming: maintain soil health, reduce pollution, conserve water, protect biodiversity, remain economically viable
- Practices: IPM, precision agriculture, agroforestry, organic/regenerative methods
- Soil conservation: contour ploughing, terracing, cover crops, windbreaks, no-till, crop rotation, composting
✅ Exam Checklist
- Compare intensive vs extensive with 2 pros/cons each
- Explain eutrophication as a cause-effect chain
- Explain why diets differ + sustainability implications
- Name 4 soil conservation methods + how each works