# Explain how the edge effect, resulting from habitat fragmentation, can reduce the biodiversity of a remaining habitat patch.

> IB DP Biology Standard Level (2023 syllabus) — A4.2 Conservation of biodiversity · Explain · 4 marks

> Habitat fragmentation occurs when large, continuous areas of natural habitat are divided into smaller, isolated patches, typically due to human activities such as agriculture or urban development. The boundary between a habitat patch and the surrounding disturbed land is known as the edge.

## Mark scheme (4 marks)

1. The edge of a habitat patch has different abiotic conditions from the interior, such as increased light penetration, higher temperatures, lower humidity, or greater wind exposure.
2. Species adapted to interior/core habitat conditions cannot survive in edge zones, so interior-specialist species are lost or their populations decline.
3. In small, fragmented patches, the edge-to-interior ratio is high, meaning a large proportion of the patch is edge habitat, reducing the effective area of suitable interior habitat.
4. Increased exposure to predators, invasive species, or human disturbance from the surrounding matrix penetrates deeper into the patch via the edge, further reducing species richness.

## Key terms

- [edge effect](https://www.gradenine.co.uk/glossary/edge-effect)
- [habitat fragmentation](https://www.gradenine.co.uk/glossary/habitat-fragmentation)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-edge-effect-resulting-bf6abcb8) · Published by Druglandscape Ltd.