BharatNotes What is Carbon Sink?
A carbon sink is a natural or artificial reservoir that absorbs and stores more carbon than it releases into the atmosphere. The IPCC defines it as a reservoir — in soil, ocean, or vegetation — where a greenhouse gas is stored, while the UNFCCC defines a "sink" as any process, activity, or mechanism that removes a greenhouse gas, aerosol, or precursor from the atmosphere. The opposite is a carbon source, which releases more carbon than it absorbs.
A reservoir counts as a sink only if it is a net absorber: even if it emits some greenhouse gases, it must remove more than it emits. Carbon sinks are central to the global carbon cycle and are a recognised pillar of climate-change mitigation under the Paris Agreement (2015).
Major Types of Carbon Sinks
| Sink | How it stores carbon | Scale |
|---|---|---|
| Oceans | Dissolution of CO2 in seawater; uptake by phytoplankton, seagrasses, salt marshes, mangroves | Largest sink — absorbed ~30% of anthropogenic CO2 emissions during 2014-2023 (IPCC / Global Carbon Project) |
| Forests | Photosynthesis fixes CO2 in biomass and forest soil | Major terrestrial sink (LULUCF) |
| Soils | Organic carbon stored via root systems and decomposition | Significant, depends on land-management |
| Blue carbon | Coastal mangroves, seagrass, tidal marshes | High per-hectare storage |
Artificial sinks — such as Carbon Capture and Storage (CCS) and Direct Air Capture — are engineered analogues, but natural sinks remain dominant.
Significance
Carbon sinks moderate atmospheric CO2 and slow global warming. Land and ocean sinks together absorb roughly half of human CO2 emissions each year, buying time for emission cuts. They are explicitly counted in national greenhouse-gas inventories under the UNFCCC's LULUCF (Land Use, Land-Use Change and Forestry) framework, making sink enhancement a quantifiable mitigation strategy rather than a vague co-benefit.
India's Carbon Sink Status
India's updated NDC (submitted to UNFCCC, August 2022) targets an additional carbon sink of 2.5 to 3.0 billion tonnes of CO2-equivalent through additional forest and tree cover by 2030.
Per the India State of Forest Report (ISFR) 2023 (released December 2024 by the Forest Survey of India; the 18th report in the biennial series):
- Total forest and tree cover: 8,27,357 sq km — 25.17% of geographical area (forest cover 21.76%, tree cover 3.41%).
- Total carbon stock in forests: 7,285.5 million tonnes, an increase of 81.5 million tonnes over the previous assessment.
- India's forest-and-tree carbon stock equals 30.43 billion tonnes of CO2-equivalent, representing an additional sink of 2.29 billion tonnes over the 2005 base year (ISFR 2023) — putting India close to its NDC target.
Key policy vehicles include the National Mission for a Green India (GIM), launched February 2014 under the National Action Plan on Climate Change, aiming to enhance forest/tree cover on 5 million hectares and improve quality on another 5 million hectares.
UPSC Angle
Treat "carbon sink" as a hinge concept connecting the carbon cycle, the Paris Agreement, India's NDCs, and net-zero-by-2070. Memorise the 2.5-3.0 billion tonne NDC figure and the latest ISFR data, and distinguish sink (absorbs) from source (emits). Cross-link to blue carbon, REDD+, and LULUCF for Mains GS3.
