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IGCSE · Cambridge (CIE) · 0654

Explain effects of deforestation

Deforestation can reduce biodiversity, cause extinction, remove soil protection, increase flooding and raise atmospheric carbon dioxide.

Habitat destruction · Cambridge IGCSE 0654 · B19.1

Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.

Before you begin

  • Know that organisms interact with other organisms and their environment.

Work on paper. Try each question before revealing help, and explain why your method works.

Quick readiness check

Which outcome is directly linked to reduced root support after deforestation?

What you will learn

  • Explain five undesirable effects of deforestation
  • Link each effect to a plausible environmental process

Connect tree removal to habitat and soil

Removing forest reduces living space and resources, so fewer species may remain and some may become extinct. Roots help hold soil in place; after trees are removed, exposed soil can be eroded or washed away.

With less interception by leaves and less uptake by roots, more rainwater can reach the ground and flow over it quickly. This can increase flooding. The exact risk depends on local rainfall, slope, soil and land management.

Connect forest carbon with atmospheric carbon dioxide

Trees remove carbon dioxide from the air during photosynthesis and store carbon in biomass. When forests are cleared, less carbon dioxide is removed from the atmosphere; burning or decay of cleared vegetation can release stored carbon. These changes can increase atmospheric carbon dioxide.

Explain the named outcomes separately: loss of habitat reduces biodiversity and can cause extinction; loss of root cover increases soil loss; altered water movement can increase flooding; changed carbon uptake and release can increase atmospheric carbon dioxide.

Sources for this lesson

Pause and explain

How can deforestation increase atmospheric carbon dioxide?

Put the idea to work

Worked example

After a forest is cleared, heavy rain washes soil into a river and nearby areas flood more often. Explain both observations.

Show the worked solution
  1. Link soil loss to reduced root support.
  2. Link flooding to faster surface runoff after tree cover is removed.

Answer Removing trees reduces root support for soil, so rain can erode and carry it away. Reduced interception and water uptake can increase rapid runoff, raising flood risk.

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From guided practice to a new situation

Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.

1 · Guided

Explain how deforestation can reduce biodiversity and lead to extinction.

Give me a hint

Start with habitat removal and connect it to species survival.

Compare my reasoning
  1. Forest organisms lose some of their habitat and resources.
  2. Some species may no longer survive in the changed area.

Deforestation removes or changes habitat and resources. The number of species may fall, and species unable to survive the change may become extinct.

Look for these in your work

  • Habitat change identified
  • Biodiversity and extinction distinguished
2 · Independent

Explain the connection between deforestation and flooding.

Give me a hint

Think about interception, uptake and surface flow.

Compare my reasoning
  1. Fewer leaves intercept rain and fewer roots take up water.
  2. More water may flow rapidly over the ground.

With fewer trees, less rain is intercepted and less water is taken up. More rapid surface runoff can increase flood risk, depending on local conditions.

Look for these in your work

  • Water pathway stated
  • Flood risk qualified
3 · Transfer

Give the five undesirable effects of deforestation required by the syllabus.

Give me a hint

Recall biodiversity, extinction, soil, flooding and atmospheric carbon dioxide.

Compare my reasoning
  1. Reduced biodiversity and extinction.
  2. Soil loss, flooding and increased atmospheric carbon dioxide.

Deforestation can reduce biodiversity, cause extinction, increase soil loss, increase flooding and increase carbon dioxide in the atmosphere.

Look for these in your work

  • All five effects named
  • No extra outcomes substituted

Common mistakes

  • Listing effects without explaining how they arise
  • Saying all cleared forest is immediately burned
  • Treating local flood risk as identical in every location
Recall without your notes

What can you explain now?

Which outcome is directly linked to reduced root support after deforestation?

Compare with the explanation

Greater soil loss through erosion

Roots help hold soil in place.

After trying it yourself, choose your next review. This is your self-assessment.

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Make it stick

Name and explain the five undesirable effects of deforestation in the syllabus.

If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.

Keep learning Sciences — Co-ordinated (Double)

Course scope and assessment

This 2028–2029 pathway maps all 152 detailed subject-content sections in the published 0654 syllabus to original teaching and staged practice. It adapts teaching from the related single-science pathways and excludes clear 0610-only topics such as classification systems, human excretion, tropic responses, food supply, population dynamics, detailed pollution and biotechnology. Some explanations may include wider single-science context. A 0654-specific objective-by-objective review, Core/Supplement audit, human subject-teacher review, supervised laboratory experience and cumulative assessment remain in progress. Written practice is self-checked and does not predict an official grade. The 2025–2027 syllabus has not been reconciled here; choose the 2028–2029 syllabus only.

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