Representing just 3% of the Earth’s land surface, peatlands contain over 30% of the carbon retained in soils 4 in the form of fossilised organic matter at depth. It is estimated that this stock represents between 500 and 1000 gigatons of carbon, corresponding to 56% and 112% of the total carbon present in the Earth’s atmosphere 5 . While some soil micro-organisms emit CO2 through respiration, microalgae assimilate it, notably through photosynthesis. Any increase in temperature will stimulate this microbial photosynthesis, enhancing the CO2 capture potential of peatlands.
Regrettably, due to a lack of data, the mechanisms by which soil microalgae capture CO2 have not been incorporated into any climate projections to date. However, far from being negligible, this photosynthetic carbon fixation could mitigate the impact of climate change in the future. Further work is needed - on this and other carbon assimilation processes carried out by the micro-organisms in peat bogs - to fully quantify the potential of these ecosystems as carbon sinks and improve accuracy. Nevertheless, preserving peatlands and reducing global CO2 emissions are still the best way of mitigating worsening climate change.
1 From the Centre de recherche sur la biodiversité et l’environnement (CRBE, CNRS/UT/IRD/Toulouse INP).
2 Photosynthesis is a phenomenon taking place within chlorophyll vegetables. Thanks to sunlight, theses plants absorb CO2 from the atmosphere and release dioxygen (O2).
3 The carbon cycle regroups all transits of molecules containing carbon between soils, air and oceans on Earth.
4 In addition to oceans, Earth soils also store large amounts of carbon naturally. It is stored there in various ways (hydrocarbons, in plants through photosynthesis, limestone rocks...).
5 According to the NOAA Global Monitoring Laboratory, the atmospheric CO2 concentration in 2023 was 419,31 ppm (Trends in Atmospheric Carbon Dioxide (2025)), which is equivalent to 893 gigatons of carbon.
