Question

plants play an important role in the carbon cycle. more carbon is taken out of the atmosphere by photosynthesis than by any other process. so, areas that have lots of plants are important carbon sinks. the amazon rainforest, for example, accounts for about 25% of the co₂ absorbed on land. each year, many acres of rainforest are cut down. this clearing of the rainforest, or deforestation, affects the carbon cycle. how does deforestation affect the carbon cycle? select all that apply. as trees decompose, they release co₂ into the air. when rainforests are cleared, the amount of co₂ in air decreases. trees that were cut down no longer carry out photosynthesis.

Explanation:

1. Analyze "As trees decompose, they release CO₂ into the air": When trees are cut and decompose (e.g., due to deforestation), the stored carbon in them is released as CO₂, so this is correct.
2. Analyze "When rainforests are cleared, the amount of CO₂ in air decreases": Rainforests are carbon sinks (absorb CO₂ via photosynthesis). Clearing them means less photosynthesis to absorb CO₂, and decomposing trees release CO₂, so CO₂ in air should increase, not decrease. This is incorrect.
3. Analyze "Trees that were cut down no longer carry out photosynthesis": Photosynthesis requires a living, intact tree. Cut trees can't perform photosynthesis, so this is correct.

Answer:

• A. As trees decompose, they release CO₂ into the air.
• C. Trees that were cut down no longer carry out photosynthesis.