Soil erosion

• Soil formation and soil erosion are in dynamic equilibrium
• Soil formation:

  Rocks -> regolith -> Soil

  Organic matter -> humus -> Soil

  Soil = regolith + humus + air + water + biota
• Vegetation

  • Vegetation increases interception which reduces the kinetic energy of the raindrops, reducing rainsplash.
  • Vegetation root binds the soil, keeping it together and reducing erosion.
  • It acts as a windbreak that reduces wind blow
  • It adds dead organic matter to the soil, increasing soil formation
  • Vegetation means leaf litter which reduces rainsplash and adds humus to the soil
• High infiltration rates

  • High infiltration rates decreases surface run-off because water does not build up on the surface
• Soil organic matter

  • Soil organic matter takes in water which decreases surface run-off. It also holds soil together.
• Environmental impacts:

  • Loss of nutrients - washed or blown away means decreased fertility and decreased crop growth
  • Desertification - Global climate change means low rainfall, soil erodes to the point where it can't hold water - no plants can grow
  • Air pollution - atmospheric particulates cause diming, decreasing photosynthesis and causing respiratory issues
  • Turbidity increases - murky + dark water decreases photosynthesis and increases water treatment required. Sediment builds up = flooding
  • Flooding - rivers overflow and banks are eroded
  • Landslides - subsidence and collapsing of soil
• Human impacts on soil erosion:

  • vegetation removal - deforestation
  • Overgrazing - too many/much livestock
  • Ploughing - breaks up peds
  • Reducing soil biota - via pesticides
  • Soil compaction - livestock and machinery
  • Cultivating steep slopes
• Human impacts on soil erosion

  Vegetation removal:

  e.g deforestation for building materials, farmland or mineral mines

  • Decreased interception
  • soil exposed to increased rainsplash.
  • decreased infiltration = increased runoff.
  • decreased wind barriers = increased wind blow
  • Decreased root binding the soil = increased erosion
  • Decreased leaf litter = decreased soil formation
• Human impacts on soil erosion

  Overgrazing:

  e.g too many/much livestock

  • eating at a rate that doesn't allow vegetation to recover
  • This leads to decreased vegetation
  • decreased interception = increased rainsplash
  • decreased root binding = increased erosion
  • decreased windbreaks = increased wind blow
  • decreased leaf litter = decreased soil formation
• Human impacts on soil erosion

  Ploughing:

  Breaking up peds

  • Soil is less dense so it is easily carried away by wind blow and surface run-off
• Human impacts on soil erosion

  Reducing soil biota:

  Pesticides kill biota

  • Decreased decomposition = decreased soil formation
  • Decreased earthworms = decreased aeration of soil = decreased infiltration = increased surface run-off
• Human impacts on soil erosion

  Soil compaction:

  Due to heavy machinery and livestock around a waterhole

  • Decreased gaps in the soil = decreased infiltration = increased surface run-off
• Human impacts on soil erosion

  Cultivation steep slopes:

  • Gravity increases surface run-off
  • Increased ploughing/compaction/overgrazing/ or decreased vegetation = increased wind blow