The Movement of Carbon
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. It describes the movement of carbon atoms from the atmosphere, into living organisms, into the ground and oceans, and then back into the atmosphere. This continuous recycling process is fundamental to life on Earth.
Key Reservoirs and Processes
Carbon exists in various forms and is stored in major reservoirs: the atmosphere (as CO2), oceans (dissolved CO2, carbonates), land (organic matter, fossil fuels), and living organisms. Key processes driving the cycle include photosynthesis (plants absorbing CO2), respiration (organisms releasing CO2), decomposition (breakdown of organic matter), and combustion (burning fossil fuels or biomass).
An Example: Plant-Animal Exchange
A simple example involves plants and animals. During photosynthesis, plants absorb carbon dioxide from the atmosphere to create glucose, incorporating carbon into their tissues. Animals then eat plants, ingesting carbon. When animals respire, they release carbon dioxide back into the atmosphere, completing a short-term loop within the broader cycle.
Importance for Climate and Life
The carbon cycle is crucial because carbon is the fundamental building block of all organic life. It also plays a vital role in regulating Earth's climate by controlling the concentration of greenhouse gases, particularly carbon dioxide, in the atmosphere. Imbalances in the cycle, often due to human activities, can lead to significant climate changes.