Terrestrial ecosystems store almost three times as much carbon as is in the atmosphere. Tropical and boreal forests represent the largest stores. The maintenance of existing carbon reservoirs is among the highest priorities in striving for climate change mitigation.
Terrestrial ecosystems store about 2100 Gt C in living organisms, litter and soil organic matter, which is almost three times that currently present in the atmosphere. Different ecosystem types store different amounts of carbon depending on their species compositions, soil types, climate and other features. This map shows today’s best available map of the terrestrial distribution of carbon. It combines a globally consistent dataset of carbon stored in live biomass (Ruesch and Gibbs 2008) with a dataset on soil carbon to 1 m depth (IGBP-DIS 2000, this is likely to underestimate carbon stored in peat soils). It shows that the largest amounts of carbon are stored in the tropics, mostly as biomass, and in high latitude ecosystems where the stocks are largely located in permanently frozen layers of soil (permafrost) and in peat.
Dividing the world into seven biomes, we estimate that tropical and subtropical forests store the largest amount of carbon, almost 550 Gt. The boreal forest biome then follows with carbon stocks of approximately 384 Gt. While deserts and dry shrublands have very little aboveground biomass, they are significant soil carbon reservoirs and cover very large areas, so that their overall contribution to carbon storage is notable. Conversely, the tundra biome covers the smallest area, but has the highest density of carbon storage.