OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What are some consequences of deforestation?

1. Reduced biodiversity and increased oxygen levels

2. Flash floods and soil erosion

3. Increased rainfall and river silting

4. Growth of new forests and habitats

The correct answer is: Flash floods and soil erosion

Deforestation has significant consequences, and one of the primary effects is flash floods and soil erosion. When forests are cleared, the trees that normally absorb large amounts of rainfall and stabilise the soil are removed. This can lead to an increase in surface runoff, as there are fewer plants to absorb and slow down the rainwater. The sudden influx of water can overwhelm rivers, leading to flash floods. Additionally, without the root systems of trees to hold the soil in place, the soil can easily be washed away, resulting in soil erosion. This erosion can degrade the land, making it less fertile and affecting both wildlife habitats and agricultural productivity. The other options suggest outcomes that are not typically associated with deforestation. For example, rather than increasing oxygen levels, deforestation actually decreases the ability of forests to produce oxygen, as trees play a crucial role in photosynthesis. Increased rainfall would not be a direct consequence of deforestation; instead, it may disrupt local rainfall patterns. Finally, while new forests can grow in certain circumstances, deforestation usually refers to the removal of existing forests, not the expansion of new habitats.