A carbon dioxide sink is either a natural or artificial resource that captures and stores carbon dioxide. A carbon dioxide sink is beneficial to the environment because it reduces the amount of carbon dioxide, a major greenhouse gas, which may otherwise be released into the atmosphere.

The process by which a carbon dioxide sink removes carbon from the air is termed carbon sequestration. During this processes the carbon is separated and stored while leaving the oxygen. Trees and plants naturally absorb carbon dioxide for photosynthesis, sequestering the carbon and converting it into mass while releasing the oxygen back into the atmosphere.

Carbon dioxide is a natural gas that is produced by the respiration of animals, decomposition of organic matter and the burning of fossil fuels and wood. The problem that we currently face is the excessive combustion of fossil fuels which overwhelms nature’s natural recycling process. A carbon dioxide sink along with other aggressive conservation efforts helps to reduce the increasing negative impact of global warming on the environment.

Natural carbon dioxide sinks include immature forests, oceans and soil. While older mature, forests still require carbon dioxide for survival, they are not considered as much of a carbon dioxide sink as immature forests are because young vegetation needs significantly more carbon dioxide to build its mass. Artificial carbon dioxide sinks may involve sequestrating carbon dioxide from the atmosphere and storing it in rock, injecting it deep into the oceans or causing chemical reactions which change the carbon dioxide into less harmful compounds.

The Kyoto Protocol allows countries to use large enough carbon dioxide sinks as a resource in which they can deduct their actual carbon dioxide emissions from. An example of this type of carbon dioxide sink would be large forested areas and reserves. The use of agricultural land as a carbon dioxide sink is not currently permitted for this cap and trade system.