Afforestation as Carbon Dioxide Removal

Afforestation is the deliberate establishment of forest on land that has not recently been forested. It becomes carbon dioxide removal when growing vegetation takes CO2 from the atmosphere and stores more carbon than would have been stored without the intervention, after accounting for associated emissions.

How carbon is removed and stored

Trees absorb atmospheric CO2 through photosynthesis and convert it into organic matter. Carbon accumulates in above-ground and below-ground biomass, dead wood, litter and soil organic carbon as roots and plant residues enter the soil.

• The climate benefit is the net removal after subtracting carbon released through respiration, decomposition, site preparation, planting, management and harvesting.
• Removal continues while the forest's carbon stocks are increasing; mature ecosystems may retain large stocks even when annual net uptake slows.

Conditions for credible carbon removal

The removal must be additional, meaning that it would not have occurred under the baseline land use. Its value also depends on permanence, because fire, drought, pests, logging or land conversion can return stored carbon to the atmosphere.

• Monitoring must cover changes across relevant carbon pools rather than counting only standing tree trunks.
• Accounting should address leakage, where displaced agriculture or wood extraction causes emissions elsewhere.
• Carbon accumulation is finite because forest carbon stocks eventually approach saturation under prevailing ecological conditions.

Ecological benefits and limitations

Well-designed afforestation using native, diverse species can support biodiversity, soil conservation, water regulation and local livelihoods alongside carbon storage. Poorly located plantations may compete for land and water, or damage naturally open ecosystems.

• Afforestation should not replace natural grasslands, savannas or wetlands merely to increase tree cover.
• Species choice, climate, soil, previous land use and forest management determine the rate and durability of carbon storage.
• Afforestation complements, but cannot substitute for, rapid reductions in greenhouse-gas emissions.