# Explain how changes in the distribution of biomes due to climate change could reduce the ability of terrestrial ecosystems to act as carbon sinks.

> IB DP Biology Standard Level (2023 syllabus) — D4.3 Climate change · Explain · 4 marks

## Mark scheme (4 marks)

1. Rising temperatures and altered precipitation patterns cause a poleward or upward (altitudinal) shift in biome boundaries.
2. Forest / high-biomass biomes at the trailing edge are replaced by lower-biomass biomes such as shrubland, grassland or desert, reducing overall carbon stored in vegetation.
3. Higher temperatures increase rates of decomposition / soil respiration, releasing stored organic carbon as CO₂.
4. As terrestrial ecosystems release more CO₂ than they absorb, they shift from net carbon sinks to net carbon sources, amplifying the greenhouse effect / creating a positive feedback.

## Key terms

- [biome](https://www.gradenine.co.uk/glossary/biome)
- [carbon sink](https://www.gradenine.co.uk/glossary/carbon-sink)

## 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-changes-in-the-distribution-3221d7b9) · Published by Druglandscape Ltd.