Process diagram: The carbon cycle

The diagram shows how carbon moves between the atmosphere, plants, animals and the soil in the carbon cycle.

Overall, the cycle has eight stages, and carbon is constantly exchanged between the air and living things. Carbon is removed from the air by plants and ocean water, but it is returned to the air by respiration, decay and the burning of fuels.

The cycle begins when carbon dioxide is absorbed from the air by plants through photosynthesis. The carbon is then stored in the leaves, stems and roots as the plants grow. When animals eat the plants, the carbon is passed along the food chain. All living things release carbon dioxide into the air through respiration.

When plants and animals die, their remains are broken down by bacteria in a process of death and decay. Over time, buried remains turn into coal and oil, which are known as fossil fuels. When these fuels are burned, combustion returns carbon to the air. Finally, some of the atmospheric carbon dioxide is taken in by seawater through ocean absorption.