What carbon sequestration is
Carbon sequestration is the process by which carbon dioxide (CO2) is removed from the atmosphere and stored -- in plants, soils, oceans, or geological formations -- for decades, centuries, or longer. It is not a single mechanism but a family of linked processes, all of which depend on the health of natural systems.1
Natural ecosystems are the dominant engine of sequestration. Together, land and ocean systems currently absorb close to half of all human-generated CO2 emissions each year.2 Without that buffer, atmospheric concentrations would be rising considerably faster than they already are.
Types of carbon sequestration
Sequestration operates across very different environments, on different timescales, and at different scales of carbon density.
Terrestrial sequestration happens wherever plants grow and soils accumulate organic matter. Forests, grasslands, and peatlands are the principal stores. Old-growth forests carry the largest above-ground carbon stocks; peatlands -- which cover only 3% of the land surface -- hold roughly twice the carbon of all the world's forests combined.3 Carbon enters through photosynthesis and is retained in roots, woody biomass, leaf litter, and soil organic matter.
Blue carbon sequestration is the term for carbon stored by coastal and marine ecosystems: mangroves, salt marshes, and seagrass meadows. Though small in area, these systems are among the most carbon-dense on Earth -- storing two to five times more carbon per hectare than tropical forests, primarily in waterlogged sediments where decomposition is extremely slow.4 See our guide to blue carbon for more detail.
Geological sequestration involves injecting captured CO2 into deep rock formations, where it mineralizes over time. It is the only sequestration method that operates independently of living systems, but it requires significant infrastructure and energy to function.
Technological approaches -- direct air capture (DAC), bioenergy with carbon capture and storage (BECCS), and enhanced rock weathering -- are at various stages of development. They are promising supplements but currently operate at tiny scale relative to natural systems, and they remain expensive and energy-intensive.5
Carbon sequestration and rewilding
Rewilding is one of the most scalable ways to rebuild carbon sequestration capacity, because it works with natural processes rather than trying to engineer around them. Restoring forests, reconnecting wetlands, and reintroducing ecosystem engineers such as beavers -- whose dams slow water flow and rebuild carbon-rich floodplain soils -- all increase net carbon storage across landscapes.6
Nature-based carbon sequestration and biodiversity recovery are not competing priorities. The ecosystems that store the most carbon -- old-growth forests, peatlands, coastal wetlands -- also support the greatest concentration of species. Protecting and restoring them delivers both goals simultaneously.
Natural succession also plays a role. When land is allowed to regenerate without intervention, plant communities self-organize into progressively more carbon-dense structures over time. Early-successional grasslands and scrub give way to woodland and ultimately to closed-canopy forest, with soil carbon accumulating throughout the transition.
Threats to carbon sinks
The scale of natural carbon sequestration makes it vulnerable to disruption. Deforestation, wetland drainage, soil degradation, ocean acidification, and climate-driven events like wildfire and drought all reduce the capacity of ecosystems to absorb CO2. More dangerously, a degraded ecosystem can flip from carbon sink to carbon source -- releasing centuries of stored carbon in a relatively short period.7
Peatland drainage for agriculture is a clear example. Intact peatlands sequester carbon at a slow but steady rate over thousands of years. Drain them, and that stored carbon oxidizes rapidly -- in some regions contributing more to annual emissions than entire sectors of the energy economy.
Carbon sequestration in climate policy
Natural carbon sequestration sits at the center of most credible national and international climate strategies. It features in Nationally Determined Contributions under the Paris Agreement, in the Convention on Biological Diversity's 30x30 conservation targets, and in voluntary carbon markets where blue carbon and forest carbon credits are among the most traded instruments.8
The alignment between climate policy and biodiversity conservation is increasingly explicit. The Kunming-Montreal Global Biodiversity Framework, agreed in 2022, set targets for protecting 30% of land and ocean by 2030 -- a commitment that is as much a carbon policy as a nature policy.
Frequently asked questions
See which parts of your life contribute most, and what it would take to offset them through nature-based sequestration.
- Friedlingstein, P. et al. (2023). Global Carbon Budget 2023. Earth System Science Data. doi:10.5194/essd-15-5301-2023
- IPCC (2021). Climate Change 2021: The Physical Science Basis. Chapter 5: Global Carbon and Other Biogeochemical Cycles and Feedbacks. Cambridge University Press.
- Parish, F. et al. (2008). Assessment on Peatlands, Biodiversity and Climate Change. Global Environment Centre / Wetlands International.
- Donato, D.C. et al. (2011). Mangroves among the most carbon-rich forests in the tropics. Nature Geoscience, 4, 293-297. doi:10.1038/ngeo1123
- Fasihi, M. et al. (2019). Techno-economic assessment of CO2 direct air capture plants. Joule, 3(5), 1113-1134.
- Sandom, C.J. et al. (2019). Rewilding in the English uplands: policy and practice. Journal of Applied Ecology, 56(2), 266-273.
- Griscom, B.W. et al. (2017). Natural climate solutions. PNAS, 114(44), 11645-11650. doi:10.1073/pnas.1710465114
- UNFCCC (2022). National Determined Contributions Registry. United Nations Framework Convention on Climate Change.