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Carbon dioxide Sinks - Plants

Though plants are very important sinks for atmospheric carbon dioxide on both land and in aquatic environments, uptake by aquatic plants is included in the discussion of oceanic carbon dioxide uptake elsewhere on the site. See Carbon dioxide Sinks - Oceans.

On land, plants themselves represent a global mass equivalent to about 1500 billion tonnes of carbon at any one time. Plants utilize carbon dioxide during photosynthesis, but also produce it during respiration. The net effect is an uptake of carbon dioxide from the atmosphere equivalent to around 60 billion tonnes of carbon each year.

Human Impact

Our primary impact on the terrestrial plant life carbon dioxide sink has been through our alterations in the vegetation types and land-use commonly occurring around the world. A switch from forested land to agricultural crops means that carbon dioxide incorporated into plant tissues is taken out of the atmosphere for a much shorter time and so the effectiveness of the plants as atmospheric carbon dioxide sinks is much reduced.

Potential for control

Much has been made of the potential for plants to increase their rate of carbon dioxide use in response to elevated atmospheric carbon dioxide concentrations, so providing a negative feedback on greenhouse gas increase and global warming. However, in depth studies of this 'carbon dioxide fertilization' effect indicate that any such response will be rather limited, with any initial increase in the plant based carbon dioxide sink disappearing within only a few years.

Certainly, it seems that relying on existing vegetation to simply sap up increasing atmospheric carbon dioxide would be ill-founded. Instead, planting of new forests and better land-management practice offer the potential for the creation of significant carbon dioxide sinks.


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