Community Level Systems: The Carbon Cycle

The Carbon Cycle

Carbon Sources and Sinks

The carbon cycle is a biogeochemical cycle and centres around carbon, a key element for life, in its multiple forms.
Carbon is a crucial component of vital organic molecules like proteins, lipids, nucleic acids, and carbohydrates.
Carbon sinks are reservoirs where carbon can be stored. Oceans, forests, and the atmosphere are major carbon sinks.
Carbon sources are places from which carbon is released into the atmosphere during processes like respiration, combustion, and decay.

Photosynthesis and Carbon Dioxide

In the process of photosynthesis, green plants, algae, and some bacteria convert carbon dioxide from the air into glucose, storing carbon in their tissues.
This process transforms solar energy into chemical energy in the form of glucose. The by-product of this process is oxygen.
Photosynthesis helps maintain the balance of carbon dioxide in the atmosphere.
The chemical equation for photosynthesis is: 6CO₂ + 6H₂O –> C₆H₁₂O₆ + 6O₂

Respiration, Combustion and Decay

During respiration, animals and plants convert glucose back into carbon dioxide and water, releasing energy in the process. This carbon dioxide is expelled into the atmosphere.
Through combustion, carbon stored in plants as glucose (or fossil fuels) is released as carbon dioxide when burnt.
When plants, animals, and microorganisms die, decomposers break down their bodies during decay, releasing the carbon back into the atmosphere as carbon dioxide.
These processes ensure the constant cycling of carbon through the environment.

Human Impact on the Carbon Cycle

Fossil fuels are carbon-rich energy sources formed over millions of years from the remains of ancient plants and animals. Their combustion releases previously stored carbon as carbon dioxide.
Excessive burning of fossil fuels and large-scale deforestation by humans are introducing more carbon dioxide into the atmosphere than can be absorbed through photosynthesis, causing a rise in levels of atmospheric carbon dioxide.
This surge in carbon dioxide is contributing to an increase in the Earth’s global temperature via the greenhouse effect, leading to climate change.
Measures are being taken to decrease human impact on the carbon cycle through renewable energy sources and sustainable practices.