Question

Why would deforestation cause there to be more carbon dioxide in the atmosphere?
(remember plants use carbon dioxide for photosynthesis)

Answer 1

So what information do you already know about this subject?

Answer 2

Deforestation would cause more CO2 to be in the air because plants absorb carbon dioxide through photosynthesis, with trees being the most productive at doing so. If we were to get rid of most of the world's trees, the most productive disposers of CO2 would be gone, causing an overabundance.