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ENCYCLOPEDIC ENTRY
ENCYCLOPEDIC ENTRY

The Carbon Cycle

The Carbon Cycle

The carbon cycle describes how carbon transfers between different reservoirs located on Earth. This cycle is important for maintaining a stable climate and carbon balance on Earth.

Grades

5 - 8

Subjects

Biology, Conservation, Earth Science

Image

Quinault River Rainforest

Full of living entities, and the formerly living, the temperate rainforest at the Quinault River in Olympic Peninsula, Washington, and places like it are rich reservoirs of carbon.

Photograph by Sam Abell

Carbon is an essential element for all life forms on Earth. Whether these life forms take in carbon to help manufacture food or release carbon as part of respiration, the intake and output of carbon is a component of all plant and animal life.

Carbon is in a constant state of movement from place to place. It is stored in what are known as reservoirs, and it moves between these reservoirs through a variety of processes, including photosynthesis, burning fossil fuels, and simply releasing breath from the lungs. The movement of carbon from reservoir to reservoir is known as the carbon cycle.

Carbon can be stored in a variety of reservoirs, including plants and animals, which is why they are considered carbon life forms. Carbon is used by plants to build leaves and stems, which are then digested by animals and used for cellular growth. In the atmosphere, carbon is stored in the form of gases, such as carbon dioxide. It is also stored in oceans, captured by many types of marine organisms. Some organisms, such as clams or coral, use the carbon to form shells and skeletons. Most of the carbon on the planet is contained within rocks, minerals, and other sediment buried beneath the surface of the planet.

Because Earth is a closed system, the amount of carbon on the planet never changes. However, the amount of carbon in a specific reservoir can change over time as carbon moves from one reservoir to another. For example, some carbon in the atmosphere might be captured by plants to make food during photosynthesis. This carbon can then be ingested and stored in animals that eat the plants. When the animals die, they decompose, and their remains become sediment, trapping the stored carbon in layers that eventually turn into rock or minerals. Some of this sediment might form fossil fuels, such as coal, oil, or natural gas, which release carbon back into the atmosphere when the fuel is burned.

The carbon cycle is vital to life on Earth. Nature tends to keep carbon levels balanced, meaning that the amount of carbon naturally released from reservoirs is equal to the amount that is naturally absorbed by reservoirs. Maintaining this carbon balance allows the planet to remain hospitable for life. Scientists believe that humans have upset this balance by burning fossil fuels, which has added more carbon to the atmosphere than usual and led to climate change and global warming.

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Director
Tyson Brown, National Geographic Society
Author
National Geographic Society
Production Managers
Gina Borgia, National Geographic Society
Jeanna Sullivan, National Geographic Society
Program Specialists
Sarah Appleton, National Geographic Society, National Geographic Society
Margot Willis, National Geographic Society
Producer
Clint Parks
other
Last Updated

May 20, 2022

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