The Carbon Cycle

• The carbon cycle is a nutrient cycle essential for life on Earth, where carbon, a key building block of all organisms, is recycled and reused.
• Carbon is present in the atmosphere primarily as carbon dioxide (CO2), and also finds itself in bodies of water and living organisms.
• Through photosynthesis, green plants and algae absorb carbon dioxide and water to create glucose (their food) and oxygen. This process is powered by sunlight.
• Animals, then, indirectly intake this carbon when they consume these plants or other animals that have done so. It becomes part of their biological makeup through complex processes such as protein synthesis.
• Respiration, the process by which most organisms generate energy, involves using glucose and oxygen to produce carbon dioxide, water, and energy. This carbon dioxide returns to the atmosphere or water.
• Upon death, if organisms are buried over time, their carbon can be stored in the Earth’s crust as fossil fuels or sedimentary rock layers, essentially locking it away for potentially millions of years.
• These locked-away sources of carbon can, however, be released back into the atmosphere or oceans through combustion (burning) of fossil fuels or through natural processes like volcanic activity.
• Marine critters like shellfish use carbon to construct shells. When these creatures die, their shells sink to the ocean floor, eventually creating sedimentary rocks like limestone. Over geologic timescales, these rocks can be thrust back to the surface, weathered away by rain, and re-release the carbon back to the atmosphere.
• Finally, an often overlooked part of the carbon cycle is the decomposition process. When plants and animals die, their remains are broken down by decomposers (like bacteria and fungi), releasing carbon back into the environment.
• Understanding the carbon cycle is critical when considering impacts on the environment like climate change. For instance, burning fossil fuels releases significant amounts of carbon dioxide, which contributes to the greenhouse effect and global warming.
• Similarly, deforestation not only removes trees, which absorb carbon dioxide for photosynthesis, but also can result in the soil releasing more carbon dioxide if the tree roots are removed or if the soil is disturbed.