Lecture Notes: Clear Cutting (Topic 5.2)

Introduction

• Presenter: Mr. Smedes
• Topic: Clear cutting
  • Definition: Cutting down all trees in an area at once
  • Purpose: Harvest lumber or clear land for other uses (e.g., agriculture)
• Objective: Describe the effect of clear cutting on forests
• Essential Knowledge:
  • Economically advantageous
  • Leads to soil erosion, increased stream and soil temperatures, and flooding
  • Trees absorb pollutants and sequester CO2, reducing climate change impact

Impacts of Clear Cutting

Short-term Impacts

1. Soil Erosion

   • Without roots, topsoil is prone to erosion from wind and rain
   • Eroded soil increases turbidity in nearby water bodies
   • High turbidity affects fish (oxygen availability) and plant photosynthesis (reduced sunlight penetration)

2. Increased Soil and Water Temperatures

   • Loss of tree shade results in more sunlight absorption by soil and water
   • Direct sunlight harms soil microorganisms, dries soil, and increases erosion risk

3. Flooding and Landslides

   • Absence of root structures increases erosion risk
   • Soil compaction from machinery and reduced water holding capacity lead to runoff and flash floods

Long-term Impacts

1. Reduction of Biodiversity

   • Mature forests replaced by monoculture tree plantations
   • Low biodiversity reduces ecosystem resilience
   • Lack of dead trees affects habitat for organisms like woodpeckers and decomposers

2. Forest Ecosystem Services

   • Air Filtration: Trees intake pollutants and convert them to less harmful substances
   • CO2 Sequestration: Trees store carbon dioxide during photosynthesis, releasing oxygen
   • Biodiversity: Provides habitat, supports ecosystem resilience, and financial benefits like ecotourism

Consequences of Deforestation

• Reduces ability to filter pollutants and store CO2
• Decomposition of tree scraps releases CO2
• Slash and burn agriculture emits greenhouse gases (CO2, nitrous oxide, water vapor)
• Contributes to climate change

Suggested Practice

• Science Skill: Describe an environmental concept
• Task: Describe two ecosystem services provided by forests and explain the effect of clear cutting on each.

Conclusion

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