What is Carbon Cycle?


The carbon cycle is Earth’s intricate process of transferring carbon among living organisms, the atmosphere, the geosphere, the hydrosphere, and the pedosphere. Carbon, essential for life on our planet due to its role in forming complex molecules like DNA and proteins, regulates Earth’s temperature as carbon dioxide (CO2) in the atmosphere. Earth, being a closed system, neither gains nor loses carbon; however, carbon continually shifts within it.

Major reservoirs of carbon include rocks, sediments, oceans, atmosphere, and living organisms. This cycle is influenced by photosynthesis, respiration, decomposition, and human activities, like burning fossil fuels, which release stored carbon into the atmosphere as greenhouse gases, impacting our climate.

What are the Key Steps of Carbon Cycle?

Here are the key stages in the carbon cycle:

  • Carbon dioxide in the atmosphere is absorbed by plants during photosynthesis.
  • Animals consume these plants, accumulating carbon in their bodies.
  • Upon death and decomposition, carbon is returned to the atmosphere.
  • Some carbon transforms into fossil fuels over time.
  • Human activities utilize these fossil fuels, releasing carbon back into the atmosphere.

What is Carbon Cycle on Land?

In the Earth’s atmosphere, carbon primarily exists as carbon dioxide (CO2). Carbon enters the atmosphere via natural processes like respiration and human activities, including the combustion of fossil fuels. During photosynthesis, plants absorb CO2 to produce carbohydrates, following this equation:

CO2 + H2O + energy → (CH2O)n + O2

Carbon compounds are transferred through the food chain, moving from producers to consumers. In living organisms, carbon is predominantly found as carbon dioxide due to respiration. Decomposers play a crucial role by decomposing deceased organisms and returning their carbon to the atmosphere, as shown in the equation:

(CH2O)n + O2 → CO2 + H2O

What is Oceanic Carbon Cycle?

The oceanic carbon cycle mirrors the terrestrial one but operates within the marine environment. Ecologically, oceans act as significant carbon reservoirs, absorbing more carbon than they release, earning them the designation of carbon sinks. Marine organisms play a crucial role in this cycle by converting carbon into calcium carbonate, a key component for constructing rigid shells similar to those found in clams and oysters.

Upon the demise of organisms possessing calcium carbonate shells, their remains decompose, leaving behind these sturdy shells. Over time, these accumulate on the ocean floor, where they undergo compaction under immense pressure, eventually forming limestone deposits.

When exposed to the atmosphere, these limestone rocks undergo weathering, releasing the stored carbon as carbon dioxide back into the atmosphere.

What is the Significance of the Carbon Cycle?

Despite its relatively low presence in the atmosphere, carbon dioxide plays a crucial role in regulating energy balance by capturing long-wave solar radiation, effectively functioning as a planetary insulating layer. Any disruption in the carbon cycle can lead to severe repercussions, including climate shifts and global warming.

Carbon is an essential building block of all living organisms on Earth, constituting key components such as proteins, lipids, and DNA. Moreover, carbon serves as the foundational element for all known life forms on our planet. Consequently, the carbon cycle, in conjunction with the nitrogen and oxygen cycles, assumes a fundamental role in sustaining life on Earth.

Recommended: What is Carbon Capture and Storage (CCS)?

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