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Science of sinks

The science governing the complex issue of sinks is quite simple. Any system that removes carbon dioxide from the atmosphere is a sink. The oceans and terrestrial ecosystems like vegetation and soils form two different types of natural sinks. The processes of photosynthesisrespiration and decomposition control the carbon cycle in them.

Plants remove carbon dioxide from the atmosphere via photosynthesisa process where sunlight facilitates conversion of carbon dioxide and water into glucose and oxygen. Trees rapidly absorb carbon dioxide during growth and as they reach maturitythe absorption plateaus. A mature oak can contain about 3 tonnes and a hectare of plantation forest can hold around 200 tonnes of carbon. A complimentary process of respirationwhich helps plants to derive energy by breaking these organic compoundsreleases carbon dioxide back into the atmosphere. Carbon dioxide is also returned to the atmosphere when plants decayburn or are cut. Soils get their carbon content from plants and store vast amounts of it as compared to plants and forests.

In the oceansphytoplanktons which are microscopic plantsconvert carbon dioxide into organic carbon through photosynthesis. This is stored in the deep ocean when microorganisms and other higher life forms that consume them die and settle at the bottom. Howeverthe uptake by oceanic sinks is limited by the quantity of carbon dioxide present in seawater and the slow rate of mixing of surface and deep ocean water. The transfer of carbon to deep ocean is important to keep it stored for relatively long periods.

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