Edexcel iGCSE Biology-5.18B The Effects of Deforestation- Study Notes- New Syllabus

Effects of Deforestation

🌱 Introduction

Deforestation = Cutting down large areas of trees and forests.
It affects soil, water cycle, biodiversity, and atmospheric gases, causing serious ecological imbalance.

⚠️ Key Effects

1. Leaching
   Trees absorb nutrients from the soil.
   When trees are removed, rain washes away nutrients → soil becomes poor and infertile.
   Leads to reduced crop yields in surrounding areas.
2. Soil Erosion
   Tree roots hold soil together.
   Without roots, soil is easily washed away by rain or blown by wind.
   Causes land degradation, sediment in rivers, and floods.
3. Disturbance of Evapotranspiration
   Evapotranspiration = Water loss from soil + plant leaves.
   Trees help return water to atmosphere → maintain local rainfall.
   Deforestation → less water vapor → reduced rainfall → dry climate.
4. Impact on the Carbon Cycle
   Trees absorb CO₂ during photosynthesis → act as carbon sinks.
   Cutting trees → less CO₂ absorbed → more CO₂ remains in atmosphere → global warming.
   Burning wood → releases CO₂ → further adds to greenhouse gases.
5. Imbalance of Atmospheric Gases
   Less oxygen produced (fewer trees).
   More CO₂ in atmosphere → enhanced greenhouse effect.
   Contributes to climate change and global warming.
6. Other Ecological Consequences
   Loss of habitat for animals → extinction risk.
   Disruption of food chains and ecosystem stability.
   Changes in microclimate (temperature, humidity).

📊 Summary Table

💡 Quick Recap 
Deforestation → Soil + Water + Climate + Biodiversity affected
Leaching & erosion → soil loses fertility
Evapotranspiration drops → less rainfall
Carbon cycle disturbed → more CO₂ → global warming
Ecosystem imbalance → species loss & climate change
🧠 Mnemonic: “Trees Gone → Soil Fails → Rain Drops → CO₂ Rises → Life Struggles”