Carbon Cycle

The carbon cycle is one of the biogeochemical cycles. Plants absorb CO₂ from the atmosphere during photosynthesis, also called primary production, and release CO₂ back in to the atmosphere during respiration. Another major exchange of CO₂ occurs between the oceans and the atmosphere. The dissolved CO₂ in the oceans is used by marine biota in photosynthesis.

Two other important processes are fossil fuel burning and changing land use. In fossil fuel burning, coal, oil, natural gas, and gasoline are consumed by industry, power plants, and automobiles. Notice that the arrow goes only one way: from industry to the atmosphere. Changing land use is a broad term which encompasses a host of essentially human activities. They include agriculture, deforestation, and reforestation.