The carbon cycle refers to the fixation of atmospheric carbon dioxide (CO2 ) through photosynthesis and the simultaneous or subsequent release of carbon dioxide through respiration. Through this process, carbon is cycled continuously through three main global reservoirs: the oceans, the atmosphere, and the terrestrial biosphere (including vegetation and soils). Over time, human activities have altered the amount of carbon that flows through and is stored in the various reservoirs.
To stop rising concentrations of CO2 in the atmosphere, countries are actively seeking ways to increase carbon storage capacity on land. The large amount of land area covered by grasslands as well as the relatively unexplored potential for grassland soils to store carbon has increased interest in the carbon cycles of these ecosystems.
The following summarizes key findings of the PAGE study regarding carbon storage in grassland ecosystems, as well as the quality and availability of data.
PAGE measures and indicators
Data sources and comments
Potential carbon stored in grasslands and other terrestrial ecosystems Estimates for storage in above-and below-ground live vegetation Above- and below-ground vegetation carbon storage estimates (Olson et al. 1983) as modified by USGS/EDC (1999). Estimates for storage in soil Soil carbon storage estimates based on the International Soil Reference and Information Centre (ISRIC) and World Inventory of Soil Emission Potentials (WISE) global data set of derived soil properties developed by Batjes (1996) and Batjes and Bridges (1994); FAO digital soil map of the world (FAO 1995).
Trends and modifications in storage capacity Various studies reporting on loss of organic carbon or on a reduction in carbon storage potential based on current practices.