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For clarity, this is not meant to suggest that 60% of the uptake of carbon dioxide into the atmosphere comes from human activity. It means that the atmosphere exchanges around 210 gigatonnes of carbon annually, but absorbs between 6 and 10 gigatonnes more than it loses. Of this net gain, about 60% is attributable to the burning of fossil fuels.
Through photosynthesis, plants use CO 2 from the atmosphere, water from the ground, and energy from the sun to create sugars used for growth and fuel. [22] While using these sugars as fuel releases carbon back into the atmosphere (photorespiration), growth stores carbon in the physical structures of the plant (i.e. leaves, wood, or non-woody stems). [23]
Carbon sequestration is part of the natural carbon cycle by which carbon is exchanged among the biosphere, pedosphere (soil), geosphere, hydrosphere, and atmosphere of Earth. [ citation needed ] Carbon dioxide is naturally captured from the atmosphere through biological, chemical, or physical processes, and stored in long-term reservoirs.
The LUCAS soil organic carbon data are measured surveyed points and the aggregated results [37] at regional level show important findings. Finally, a new proposed model for estimation of soil organic carbon in agricultural soils has estimated current top SOC stock of 17.63 Gt [38] in EU agricultural soils.
The largest and one of the fastest growing human impacts on the carbon cycle and biosphere is the extraction and burning of fossil fuels, which directly transfer carbon from the geosphere into the atmosphere. Carbon dioxide is also produced and released during the calcination of limestone for clinker production. [115]
Additionally, carbon is stored in fossil fuels and is released into the atmosphere through human activities such as burning fossil fuels. In the nitrogen cycle, atmospheric nitrogen gas is converted by plants into usable forms such as ammonia and nitrates through the process of nitrogen fixation.
The flow of carbon dioxide from the atmosphere to the soil is therefore regulated with the help of living organisms. When CO 2 levels rise in the atmosphere the temperature increases and plants grow. This growth brings higher consumption of CO 2 by the plants, who process it into the soil, removing it from the atmosphere.
Climate is the dominant factor in soil formation, and soils show the distinctive characteristics of the climate zones in which they form, with a feedback to climate through transfer of carbon stocked in soil horizons back to the atmosphere. [44]