What is a natural source of atmospheric carbon dioxide?

What is a natural source of atmospheric carbon dioxide?

• A. Volcanic eruptions
• B. Photosynthesis
• C. Decomposition of organic matter
• D. Respiration of animals

Answer: (C)

Decomposition of organic matter is a natural source of atmospheric CO2 because as microbes break down dead plant and animal material, they release carbon dioxide during respiration, returning carbon to the air. This process happens continuously in soils, litter, and water, making it a widespread and ongoing contributor to atmospheric CO2. Photosynthesis removes CO2 from the atmosphere, so it isn’t a source. Volcanic eruptions do release CO2, but they are episodic and contribute less to the overall annual CO2 flux than the steady output from decomposition and related respiration.

Decomposition of organic matter is a natural source of atmospheric CO2 because as microbes break down dead plant and animal material, they release carbon dioxide during respiration, returning carbon to the air. This process happens continuously in soils, litter, and water, making it a widespread and ongoing contributor to atmospheric CO2. Photosynthesis removes CO2 from the atmosphere, so it isn’t a source. Volcanic eruptions do release CO2, but they are episodic and contribute less to the overall annual CO2 flux than the steady output from decomposition and related respiration.