Carbon Cycle

Important notes on the carbon cycle

• Carbon is an essential element for the life of animals, plants and people and for the balance of the earth’s climate;
• The carbon cycle involves several sinks including rocks and marine sediments, vegetation, oceans and the atmosphere;
• Human activities, through increasing carbon emissions, alter the cycle of this element, causing climate change.

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The carbon cycle is one of the fundamental biogeochemical cycles for life on earth and consists of a complex system of delicate balances and interactions between the biosphere, atmosphere, oceans and soil.
The carbon cycle comprises several stages including photosynthesis, respiration, decomposition and deposition of organic carbon. During photosynthesis, plants capture carbon in the atmosphere by converting sunlight into chemical energy. Plants use carbon to grow, and bind carbon molecules to their organic molecules. Over time, plants release some of the carbon into the atmosphere through respiration. When plants die or are consumed by animals, carbon can be transferred to the soil through decomposition and the process of humus formation. In the soil, carbon can be stored for long periods. Soil degradation and deforestation are examples of processes that release large amounts of carbon into the atmosphere.
The oceans also play a crucial role in the carbon cycle. They absorb large quantities of atmospheric carbon through the dissolution process. This carbon can be utilised by marine algae during photosynthesis, creating a ‘biological pump’ that transfers carbon to the ocean depths when the algae die and sink.
The largest stores of carbon are carbonate minerals in rocks and dissolved carbon in the ocean. The former include fossil fuels, the burning of which then results in the immediate and massive release of quantities of carbon that had taken thousands of years to store. This causes an imbalance in the carbon cycle and disrupts the delicate balance of the earth’s climate.