Yes, plants do add carbon dioxide (CO2) to the atmosphere through a natural process called respiration. While plants are well-known for absorbing CO2 during photosynthesis, they also release it.
The Dual Role of Plants in the Carbon Cycle
Plants play a vital, dual role in the Earth's carbon cycle.
- Photosynthesis: This is the process where plants absorb carbon dioxide from the atmosphere, along with water and sunlight, to create energy (sugars) and oxygen. This process removes CO2 from the atmosphere.
- Respiration: Like all living organisms, plants need energy to live and grow, even at night or when photosynthesis isn't happening. Respiration is the process where plants break down stored sugars and, in doing so, release carbon dioxide back into the atmosphere.
Think of it like breathing for humans – we take in oxygen and release carbon dioxide. Plants do something similar with CO2 during respiration.
Respiration: A Significant Release of CO2
While photosynthesis absorbs large amounts of CO2, plant respiration is a significant source of CO2 release.
According to a study involving ANU and international collaborators, plants release more carbon dioxide into the atmosphere through respiration than expected. The study highlights that plants use photosynthesis to capture carbon dioxide and then release a substantial portion of it, releasing half of it into the atmosphere through respiration.
This finding indicates that the amount of CO2 released by plants through respiration is a crucial factor in understanding the global carbon cycle.
Balancing Capture and Release
Ultimately, the net effect of plants on atmospheric CO2 depends on the balance between the CO2 they absorb through photosynthesis and the CO2 they release through respiration.
Factors influencing this balance include:
- Light availability: Photosynthesis requires light, while respiration happens continuously.
- Temperature: Both processes are affected by temperature, but potentially to different degrees.
- Plant type and age: Different species and older parts of plants can have varying respiration rates.
- Environmental conditions: Drought, nutrient availability, and other stressors can impact both photosynthesis and respiration.
While healthy, growing plants typically absorb more CO2 over their lifetime than they release (acting as a carbon sink), the respiration process means they are constantly adding CO2 back into the atmosphere as part of their normal biological functions.
