Soil degradation
Big idea: Soil degradation is one of the biggest threats to food security. We lose billions of tonnes of topsoil every year — faster than it can be replaced.
Types of soil degradation
- Erosion — topsoil blown or washed away (wind/water erosion)
- Salinization — salt accumulates, toxic to plants (from irrigation in dry areas)
- Compaction — heavy machinery crushes pore spaces, reduces aeration
- Nutrient depletion — continuous cropping without replenishment
- Contamination — pollution from chemicals, heavy metals, waste
- Desertification — productive land becomes desert
Human causes of degradation
- Deforestation — removes root systems that hold soil, increases erosion
- Overgrazing — animals remove vegetation, compact soil
- Intensive agriculture — monocultures deplete specific nutrients
- Irrigation — can cause salinization and waterlogging
- Urbanization — soil sealed under concrete, lost permanently
ESSAY TOPIC (9 marks): "Discuss human impacts on soil." Structure: (1) types of degradation, (2) human causes, (3) environmental impacts, (4) management strategies, (5) balanced conclusion on whether degradation can be reversed.