A carbon sink is any reservoir, natural or otherwise, that accumulates and stores some carbon-containing chemical compound for an indefinite period and thereby lowers the concentration of carbon dioxide (CO2) from the atmosphere.

Globally, the two most important carbon sinks are vegetation and the ocean. Public awareness of the significance of CO2 sinks has grown since passage of the 1997 Kyoto Protocol, which promotes their use as a form of carbon offset. There are also different strategies used to enhance this process. Soil is an important carbon storage medium. Much of the organic carbon retained in the soil of agricultural areas has been depleted due to intensive farming. "Blue carbon" designates carbon that is fixed via the ocean ecosystems. Mangroves, salt marshes and seagrasses make up a majority of ocean plant life and store large quantities of carbon.

Many efforts are being made to enhancing natural sequestration in soils and the oceans. In addition, a range of artificial sequestration initiatives are underway such as changed building construction materials, carbon capture and storage and geological sequestration.

 

Note:   The above text is excerpted from the Wikipedia article Carbon sink, which has been released under the GNU Free Documentation License.