Carbon Cycle

The continuous movement of carbon between the atmosphere, the ocean, living organisms and rock and soil reservoirs, primarily as carbon dioxide, methane and organic compounds. Photosynthetic organisms draw carbon dioxide out of the atmosphere and fix it into sugars; respiration, decomposition and combustion return it; the ocean absorbs and releases carbon dioxide at its surface and stores far more in dissolved form in the deep water; and, over millions of years, some carbon is buried and locked into rock and, eventually, fossil fuels. Forests hold a large share of the land's actively cycling carbon in living wood: a single mature giant sequoia, among the most massive living trees on Earth, can store carbon equivalent to many ordinary trees combined, which is why old-growth forest loss and forest fire both register as measurable disturbances to the global carbon budget rather than only a local one.