|MadSci Network: Earth Sciences|
You've got the right idea: plants do indeed store carbon in their fibres, but when the plant dies and the materials rot away, the carbon is released. Plants that are eaten, clearly end up quite quickly in the microorganism food-chain. After a moderate amount of time some solids remain and part of this goes into the ground to feed other mircroorganisms there while the rest becomes gasses of various kinds (CO2 and methane - CH4, etc). In the long run, all carbon is returned to the atmosphere. Some of the carbon seeping into the ground is 'locked' into carbonate rocks such as limestone stallagmites - but this is not a lot. But not all plants are vegetables or herbs - trees store carbon for a long time - but only while they are growing. When the tree dies its wood decays - but over fairly long time scales. In a jungle, there is a balance between the amount of carbon taken up by the leaves and the amount of carbon released from dead trees. In plantations trees are typically planted and cut and new trees planted so there is an export of carbon from the air to the trees and out of the plantation. Wood that is turned into books or houses or furniture stores carbon - for the lifetime of the object. By planting something green almost everywhere we could, for a while, suck up a lot of carbon, but as soon as the plants matured that would be the end of it. If in the meantime we released even more CO2, from burning oil, gas and carbon, things would not look any better when the plants reached maturity. One other possibility is to feed the oceans on minerals needed to help plankton grow. The plankton form carbonate skeletons, and these skeletons fall to the bottom of the deep oceans. Some of the skeletons are dissolved in the water before the bottom is reached and thereby enters the carbon-cycle, but the skeletons that reach the deep sea floor will be locked up there for a very long time. Because of plate tectonics all rock is recyled through the interior of the Earth sooner or later and gasses released at volcanoes reenter the atmosphere - so in the really long run (hundreds of millions of years) that is no option either. However, at the moment there is not enough knowledge about what happens to the oceans when you fertilize them to encourage increased plankton-growth, so the idea is not being tried anywhere. Some experiments with unclear outcomes have been performed. Some links: http://www.csa.com/discoveryguides/oceangard/overview.php http://www.safeclimate.net/business/images/understanding_carboncycle.jpg http://earthobservatory.nasa.gov/Library/CarbonCycle/
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