Blue Carbon: India’s Coastal Carbon Stores Explained

Blue carbon is the carbon captured from the air and stored by coastal and marine ecosystems, chiefly mangroves, seagrass meadows and salt marshes, and in India it describes the carbon locked in the Sundarbans, Bhitarkanika, Pichavaram, Gulf of Kutch, Gulf of Mannar and other tidal and shallow-sea habitats. The name comes from the blue of the ocean, in contrast with the green carbon held in land forests, and it refers above all to carbon buried in waterlogged coastal sediments.

Blue carbon matters because these ecosystems cover only a small slice of the planet and of India, yet they bury carbon at high rates and keep it for centuries. Protecting them cuts emissions, restoring them removes carbon from the air, and both also shield coasts and sustain fisheries. This article explains how blue carbon works, what India has, what the MISHTI scheme adds and where the science and accounting remain uncertain.

Key Takeaways

• Blue carbon is the carbon stored by mangroves, seagrasses and salt marshes, and most of it is held in the waterlogged sediment beneath these plants rather than in the plants themselves.
• Per hectare, coastal blue carbon ecosystems often store and bury carbon at much higher rates than most land forests, although their total area is small, so they are a valuable part of the answer rather than the whole of it.
• India has about 5,000 square kilometres of mangroves, plus seagrass meadows and salt marshes that are less well mapped, so the national blue carbon stock is still being measured.
• Destroying a blue carbon habitat can turn it from a carbon store into a source of emissions, which makes protecting existing mangroves, seagrass and marshes as important as planting new ones.
• The MISHTI scheme, launched in 2023, aims to plant mangroves over about 540 square kilometres, and other programmes are restoring seagrass and coastal wetlands.
• Carbon credits, permanence, measurement and sea-level rise remain open questions, and scientists disagree on how large blue carbon can become in India’s climate strategy.

What is blue carbon?

Blue carbon is the organic carbon stored in the plants and, above all, the sediments of coastal and marine ecosystems such as mangroves, seagrass meadows and tidal salt marshes. It is a subset of the wider carbon cycle, defined by where the carbon is kept and for how long.

The term was popularised by a 2009 report of the United Nations Environment Programme, which drew attention to the fact that vegetated coasts bury large amounts of carbon. Scientists mainly count three ecosystems: mangrove forests, seagrass meadows and tidal marshes. Some researchers also include tidal flats, kelp forests, algae and other marine systems, but the evidence for permanent storage is strongest for the first three.

In India, blue carbon is closely tied to the coastline’s major habitats. The Sundarbans and other mangroves are the best studied. Seagrass meadows grow in shallow, sandy waters of the Gulf of Mannar, Palk Bay, Chilika Lake and the Lakshadweep and Andaman and Nicobar islands, while salt marshes and tidal wetlands occur along parts of the Gujarat coast, the Sundarbans and the Mumbai creeks.

How do coastal ecosystems store carbon?

Coastal ecosystems store carbon by absorbing carbon dioxide through photosynthesis and then burying the dead plant matter in wet, oxygen-poor mud where it decomposes very slowly. This burial, not the living plant, is the heart of blue carbon.

The process has several steps that reinforce one another:

• Capture: mangroves, seagrasses and marsh plants grow quickly and take in carbon dioxide.
• Trapping: roots, blades and stems slow the water and trap particles, including carbon-rich material carried from rivers and the sea.
• Burial: dead roots, leaves and trapped material sink into waterlogged sediment with very little oxygen.
• Slow decay: without oxygen, microbes break down organic matter slowly, so carbon stays locked in the mud for centuries to millennia.
• Vertical growth: as the sea rises slowly, the sediment layer builds upward, adding more storage space, provided the supply of silt is adequate.

On land, forests keep much of their carbon in standing wood, which can be lost to fire, felling or decay. In coastal wetlands, by contrast, a large share of the carbon, often well over half and sometimes much more, is in the soil below the plants. In deep mangrove sediments, the carbon store can run to several hundred tonnes of carbon per hectare, and in some of the richest Indo-Pacific stands it can be higher still.

Why do blue carbon ecosystems matter for climate?

Blue carbon ecosystems matter for climate because they combine rapid, long-lasting carbon burial with strong protection against coastal hazards, giving climate benefits both through mitigation and adaptation. They also have a particularly high storage density compared with most land ecosystems.

Studies commonly report that mangroves, seagrasses and marshes bury carbon per unit area at rates several times higher than mature land forests, which is the reasoning behind the claim that they lock carbon away faster. However, the figures vary widely between sites and methods. The more careful way to say it is that per hectare they are exceptional, while the total area they cover is small.

The second reason is the damage side. When mangroves are cleared or seagrass beds are dredged, stored carbon in the sediment can oxidise and escape as carbon dioxide, and drained wetlands can keep emitting for years. Global assessments suggest that loss of coastal ecosystems is a meaningful but not enormous source of emissions, so protecting them is considered one of the more cost-effective climate actions available.

How much blue carbon does India have?

India’s blue carbon stock is substantial in places but not yet measured with the precision of its land forests. Mangroves, covering roughly 5,000 square kilometres, are the best documented, while seagrass and salt marsh data are patchier.

Researchers, including those at the National Centre for Sustainable Coastal Management in Chennai, have been measuring carbon in mangrove and seagrass sediments, and early results suggest large variation: deltaic mangroves with deep, fine-grained muds hold far more carbon than sparse arid-zone stands in Kutch. National totals quoted in the media therefore rest on assumptions and should be read as estimates.

It also helps to keep the scale in view. India’s blue carbon habitats cover a very small share of the national territory, and even complete protection and generous restoration would offset only a modest part of the country’s annual emissions. Their value lies in being among the cheapest, most multi-purpose natural climate solutions, not in replacing emission cuts.

What is India doing for blue carbon?

India is advancing blue carbon through mangrove restoration under the MISHTI scheme, state-level planting, seagrass restoration and coastal research, although there is not yet a dedicated national blue carbon policy at full scale. Much of the action sits within wider coastal and forestry programmes.

• MISHTI: the Mangrove Initiative for Shoreline Habitats and Tangible Incomes, launched in June 2023, targets mangrove planting along the coast and on salt pans across about 540 square kilometres over roughly five years in several states and union territories.
• State programmes: Gujarat, Odisha, West Bengal, Andhra Pradesh, Tamil Nadu and Maharashtra run mangrove protection and replanting, often with village committees.
• Seagrass restoration: pilot efforts in the Gulf of Mannar and Palk Bay in Tamil Nadu have transplanted seagrass in degraded patches, with results still being monitored.
• Coastal law: the Coastal Regulation Zone rules give mangroves the highest protection category and a protective buffer, which helps prevent loss.
• Research: institutions measure sediment carbon, map habitats using satellites and test restoration methods.

Internationally, India has voiced support for nature-based climate solutions, and its updated climate pledges recognise forests and trees as a carbon sink. How much blue carbon will be counted in the national inventory and in a domestic carbon market is a question that policymakers are still working out.

Can blue carbon earn carbon credits?

Blue carbon can in principle earn carbon credits if a project proves that it protects or restores a habitat in a way that adds measurable, lasting carbon storage beyond what would have happened anyway. Several international registries have methods for tidal wetland and seagrass projects.

In practice, the path is demanding. A credible project must show additionality, meaning the carbon benefit would not have occurred without the project, and permanence, meaning the carbon stays stored. It must measure carbon in soil as well as in plants, and it must ensure that local communities who depend on the coast share in the benefits and do not lose access to their fishing grounds.

India has been building a domestic carbon credit trading scheme, and how coastal wetlands fit into it is not yet settled. Some conservationists welcome the finance that credits could bring to mangrove protection, while others worry about selling fragile ecosystems as offsets, about double-counting and about benefits flowing to outside investors rather than local people.

What are the limits and debates around blue carbon?

The main limits of blue carbon are its small area, difficulty of measurement, vulnerability to sea-level rise and the risk that planting is mistaken for restoration. Scientists agree on the potential but disagree on its scale and on how it should be counted.

• Measurement: soil carbon varies enormously from site to site, so regional averages can mislead, and high-quality sediment surveys are costly.
• Methane and other gases: wetlands can emit methane and nitrous oxide, particularly in low-salinity or nutrient-polluted waters, which can reduce the net climate benefit.
• Coastal squeeze: where roads, embankments and settlements block inland migration, rising seas can drown mangroves and marshes instead of letting them move.
• Planting versus restoring: mass planting on the wrong mudflat often fails, and fixing tidal flow is usually more effective than planting seedlings.
• Total contribution: because the area is limited, blue carbon cannot substitute for cutting fossil fuel use.
• Equity: restoration can restrict fishing or grazing unless local people are involved from the start.

There is also a timing point. Newly planted mangroves take years to accumulate meaningful carbon, whereas intact old forests already hold large stocks, so the most reliable gain is usually to avoid losing the existing ones.

How does blue carbon differ from green carbon?

Blue carbon differs from green carbon mainly in where the carbon is stored: blue carbon sits largely in waterlogged coastal sediment, while green carbon sits largely in the wood and soil of land forests. The processes are similar, but the storage conditions and the permanence differ.

Green carbon in land forests is stored in trees and soil, and it is exposed to fire, drought and logging. Blue carbon is better protected from fire and decays slowly in wet mud, but it is exposed to sea-level rise, storms and coastal development. Both are forms of natural climate solution, and India’s forests, discussed as a carbon sink in its national climate pledge, and its coastal wetlands complement each other.

Bottom Line

Blue carbon turns India’s muddy, salty, often overlooked coasts into climate assets. Mangroves, seagrasses and salt marshes hold a lot of carbon for their size and protect shorelines at the same time. The sensible policy is to protect what exists, restore tidal flow, plant carefully and measure honestly, while treating blue carbon as a valuable supplement to, not a substitute for, deep emission cuts.

Frequently Asked Questions

What is blue carbon?

Blue carbon is the carbon captured and stored by coastal and marine ecosystems, mainly mangroves, seagrass meadows and salt marshes. Most of it is buried in the waterlogged sediment beneath these plants, where it decays very slowly and can stay locked away for centuries.

Which ecosystems count as blue carbon in India?

In India, the main blue carbon ecosystems are mangroves such as the Sundarbans and Bhitarkanika, seagrass meadows in the Gulf of Mannar, Palk Bay, Chilika and the islands, and salt marshes and tidal flats along parts of the Gujarat coast and deltas. Mangroves are the best mapped.

Why does blue carbon store more carbon than forests on land?

Per hectare, blue carbon ecosystems often store and bury more carbon than land forests because dead plant matter sinks into oxygen-poor mud and decays slowly, and the sediment keeps building upward. Their total area is small, so overall they hold less carbon than India’s land forests as a whole.

What is the MISHTI scheme?

MISHTI, the Mangrove Initiative for Shoreline Habitats and Tangible Incomes, is an Indian government scheme launched in 2023 to plant and restore mangroves along the coast and on salt pans. It targets about 540 square kilometres in coastal states and union territories over roughly five years.

Can blue carbon projects earn carbon credits in India?

Blue carbon projects can in principle earn carbon credits if they prove measurable, additional and lasting carbon storage, and international registries have methods for them. How coastal wetlands will fit into India’s domestic carbon market is still being worked out, and critics raise concerns about permanence and local rights.

What happens to blue carbon when mangroves are destroyed?

When mangroves, seagrass beds or marshes are cleared, drained or dredged, the carbon stored in their sediment can oxidise and escape as carbon dioxide, turning a store into a source of emissions. This is why protecting existing coastal habitats is considered as important as planting new ones.

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