Study Notes on Climate Change and Soil Degradation

Climate Change and Human Impact on Soil

  • Human Activities Affecting Climate

    • Significant effects from local human activities on climate.
    • Deforestation as a main factor impacting climate.
    • Vegetation plays a role in soil preservation and contributes to atmospheric water vapor.
    • Deforestation can lead to increased aridity in local areas.

  • Soil Degradation

    • Definition of soil degradation: decline in soil quality, primarily soil fertility.
    • Fertility refers to soil's ability to support life, including plants and microorganisms.
    • Soil degradation occurs due to both natural processes and unsustainable human practices.

  • Types of Soil Degradation

    • Erosion: removal of soil by wind and water.

    • Types of erosion discussed:

      • Wind erosion: dramatic removal of soil by wind, especially in agricultural fields (example: Ontario).
      • Water erosion: excess precipitation leading to flooding and soil removal.

    • Biological Degradation: loss of organic components, leading to reduced soil fertility.

    • The O horizon (organic layer) and A horizon (topsoil) can be depleted naturally or through intensive agriculture.

    • Slash and burn practices can temporarily enhance fertility but ultimately degrade soil and contribute to erosion.

    • Prolonged degradation takes decades for soil recovery.

    • Physical Degradation: compaction of soil.

    • Compaction reduces air and water voids essential for plant roots, resulting from heavy machinery use or overgrazing by cattle.

    • Overgrazing compacts soil, affecting fertility.

    • Chemical Degradation: caused by chemical spills, pesticides, herbicides.

    • Chemical amendments lead to loss of soil biodiversity and disrupt the ecosystem of microorganisms essential for soil health.

  • Case Study: The Dust Bowl (1930s USA)

    • Region involved: Great Plains, especially parts of Kansas, Oklahoma, Colorado, and Texas.
    • Environmental background: prior to the 1930s, the region experienced wetter conditions; agriculture expanded intensely.
    • In the 1930s, climatic changes led to lower precipitation, causing crop failures and intensifying dust storms.
    • Intensive agriculture practices caused removal of millions of tons of fertile soil by wind erosion, leading to severe ecological consequences.
    • Historical images depict the stark effects of wind erosion due to agricultural practices.

  • Recovery and Soil Conservation Strategies

    • Introduction of contour crop rotation, center pivot irrigation, and windbreaks.
    • Contour crop rotation involves planting crops in contour lines to prevent soil erosion.
    • Center pivot irrigation efficiently targets crops, reducing evaporation.
    • Windbreaks help protect soil from wind damage, preserving soil health.
    • Crop rotation encourages soil nutrients replenishment, decreasing reliance on synthetic fertilizers.

  • Desertification in the Sahel

    • Definition of desertification: once arable land becoming non-arable or unproductive.
    • Distinction: desertification is not merely the encroachment of sand dunes.
    • History of the Sahel shows climatic changes from wetter to drier conditions impacting agricultural practices and leading to desertification.
    • Key causes:
    • Overgrazing: loss of vegetation reduces moisture availability.
    • Inefficient irrigation practices increase evaporation and salt accumulation.
    • Slash and burn agriculture reduces biodiversity and fertility, exacerbating drought.

  • Initiatives for Soil Recovery

    • Removal of intensive agricultural practices to allow natural regeneration.
    • Improving irrigation methods (e.g., drip irrigation) to minimize evaporation.
    • The Great Green Wall of Africa initiative aims to restore degraded land across different African countries through integrated approaches, utilizing local flora to combat desertification.