Photosynthesis, Fermentation, Cell Respiration
Life and the carbon cycle
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NASA PACE observations reveal a diatom bloom off the Kamchatka Peninsula. NASA Goddard Space Flight Center / Kel Elkins · Image source
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Photosynthesis
All green plants take up CO2 from the air (in aquatic plants out of the water) and water in the ground, including mineral salts and form with the help of sunlight all organic materials out of which they exist. As a direct energy storage material, glucose is formed, which is then transformed to starch.
The cellular "machines", which manage this process are the Chloroplasts. The enzyme of the Chloroplasts takes up the CO2 and binds it to a sugar molecule called: Ribulose-1,5-Bisphosphat
Ribulose-1,5-Bisphosphat-Carboxylase (RUBISCO) - this enzyme is the most frequent and most important enzyme on this planet, because it represents the start of the food chain! CO2 is exhaled by the majority of organisms, a process called cell respiration.
All aerobic organisms (animals, plants, fungi and many bacteria) oxidise organic matter to produce energy. This they accomplish with enzymes in cells, or specific cell structures (mitochondria) so slowly that the gained energy can be stored in ATP. The waste heat is used for warming up the body. The oxidisation can be...
CO2 arises, among other things, as the combustion product.
In addition to soil organisms of which the bacteria have the highest proliferation and considered in official models of the IPCC Climate Panel of the UN as a global emission source with about 50 giga tons/year of CO2 emission, the entire global respiration of insects as terrestrial organisms however is in the literature consistently and considerably underestimated. The number of individuals is estimated in the order of 1019 but seems to be more likely in the order of >1030 and thus to be regarded as the most common of the multi cellular organisms.
Just one aphid culture amounts to >1019 animals in a season! The billions of mammals including humans are comparably negligible. On corresponding entomological (the scientific study of insects) web sites one can find test results for insects of the most important types undertaken with a spirometer. Spirometry (meaning the measuring of breath), allows reproducible measurements of the CO2-emission of living organisms. Exhalation of CO2 depends among other things on the age, the nourishment, the state of health, the climate and the current activity (achievement revenue) of the test object.
The 2026 Indicators of Global Climate Change update reports that the number of days experiencing marine heatwaves more than tripled between 1991 and 2025. Marine heatwaves can stress ecosystems, but impacts vary by species, location and duration.
The biological carbon cycle moves enormous quantities of carbon between the atmosphere, plants, soils and oceans. Photosynthesis removes CO₂ from the air, while plant, animal and microbial respiration returns carbon to the atmosphere. These large natural exchanges are not the same as a net addition of carbon to the atmosphere: over a full year, much of the carbon taken up by photosynthesis is returned through respiration and decomposition.
NOAA’s carbon-cycle documentation describes terrestrial biosphere exchanges on the order of 120 petagrams of carbon per year in each direction. The net balance is much smaller and varies with climate, land use, fires and ecosystem condition. The key accounting question is therefore not simply how much CO₂ organisms emit, but whether the natural reservoirs are, overall, absorbing or releasing carbon.
The original page’s numerical speculation about insect populations and their global CO₂ emissions should not be treated as an established carbon-budget estimate. Global carbon accounting relies on measured atmospheric changes, inventories, flux observations and modelled exchanges, not extrapolations from unverified population claims.
Sources: NOAA CarbonTracker documentation · Global Carbon Budget 2025.
Plants, soils and oceans exchange large amounts of carbon with the atmosphere in both directions. The net balance—whether reservoirs absorb or release more than they take up—is the relevant quantity for explaining changes in atmospheric CO₂. The diagram is conceptual and intentionally does not assign unverified flow values.
Sources: Global Carbon Budget 2025
