5.3 Soil degradation and conservation

Significant Ideas:

  • Fertile soils require significant time to develop through the process of succession.
  • Human activities may reduce soil fertility and increase soil erosion.
  • Soil conservation strategies exist and may be used to preserve soil fertility and reduce soil erosion.

Knowledge and understanding:

  1. Soil ecosystems change through succession. Fertile soil contains a community of organisms that work to maintain functioning nutrient cycles and that are resistant to soil erosion.
  2. Human activities that can reduce soil fertility include deforestation, intensive grazing, urbanization and certain agricultural practices (such as irrigation and monoculture).
  3. Commercial, industrialized food production systems generally tend to reduce soil fertility more than small-scale subsistence farming methods.
  4. Reduced soil fertility may result in soil erosion, toxification, salination and desertification.
  5. Soil conservation measures include soil conditioners (such as organic materials and lime), wind reduction techniques (wind breaks, shelter belts), cultivation techniques (terracing, contour ploughing, strip cultivation) and avoiding the use of marginal lands.

Applications and skills:

  • Explain the relationship between soil ecosystem succession and soil fertility.
  • Discuss the influences of human activities on soil fertility and soil erosion.
  • Evaluate the soil management strategies of a given commercial farming system and of a given subsistence farming system.

International-mindedness:

  • Variant use of soil systems can lead to different degradation and conservation.

Theory of knowledge:

  • Our understanding of soil conservation has progressed in recent years—what constitutes progress in different areas of knowledge?
  • Fertile soil can be considered as a non-renewable resource because once depleted, it can take significant time to restore the fertility—how does our perception of time influence our understanding of change?

Connections:

  • Communities and ecosystems (2.2)
  • Investigating ecosystems (2.5)
  • Introduction to soil systems (5.1)
  • Terrestrial food production systems and food choices (5.2)
  • Biomes, zonation and succession (2.4)
  • Climate change—causes and impacts (7.2)
  • Resource use in society (8.2)