Blue carbon

Topic: Biodiversity and its Conservation · NCERT: Beyond NCERT

Meaning

Blue carbon is the carbon that coastal and marine ecosystems take from the air and store. The main ones are mangroves, seagrass meadows and salt marshes. These ecosystems bury carbon in their soils much faster per hectare than land forests do, and the carbon can stay there for centuries. This makes them important tools against climate change. Mangroves also protect coasts from cyclones.

Explanation

How blue carbon is stored (cause → process → result)

• Step 1: plants take in carbon.
• Mangroves, seagrass and salt-marsh plants absorb carbon dioxide from the air and water by photosynthesis.

• They use it to build leaves, stems and roots.

• Step 2: the soil is waterlogged.

• Sea water or tidal water covers the soil all the time or twice a day.

• Waterlogged soil has very little oxygen.

• Step 3: dead matter rots very slowly.

• Microbes need oxygen to break down dead roots and leaves.

• With little oxygen, rotting almost stops.

• Result: the carbon stays buried.

• Dead plant matter builds up layer by layer in the soil.
• The carbon stays locked away for centuries.
• Per hectare, these ecosystems bury carbon far faster than land forests.

The three main blue carbon ecosystems

Ecosystem	What it is	Link to other concepts
Mangroves	Salt-tolerant forest in river deltas and estuaries (where a river meets the sea) on tropical coasts	Sundarbans, Bhitarkanika
Seagrass meadows	Underwater flowering plants that grow like grass on shallow sea floors	Food for the dugong ("sea cow")
Salt marshes	Low coastal land with grasses, flooded by tides	A type of coastal wetland

• The soil, not the tree or plant above it, holds most of the stored carbon. This is where blue carbon differs from a land forest.

Conditions it needs

• Calm, shallow coastal water, such as deltas, estuaries, lagoons and sheltered bays.
• Waterlogged soil with little oxygen, so dead matter does not rot quickly.
• Silt coming in steadily. Mangrove roots trap silt, and new silt keeps burying the older carbon.
• A tropical coast for mangroves, because they grow only in warm coastal waters.

Extra benefits

• Coastal protection: mangrove roots break storm waves and slow cyclone surges (a cyclone surge is a sudden rise of sea water pushed onto land by a storm).
• Fish nursery: young fish and prawns grow among mangrove roots.
• Stops erosion: roots trap silt and hold the shoreline in place.
• Habitat: seagrass beds feed the dugong, a Schedule I animal.

Where it occurs

India's mangroves (ISFR 2023)

• Total area: 4,991.68 sq km, or 0.15% of India's land area [2].
• Up 363.68 sq km (7.86%) from 2013 to 2023 [2].
• West Bengal (Sundarbans) has the largest share: 2,119.16 sq km, or 42.45% of India's mangroves. It gained 22.16 sq km since ISFR 2013 [3].

Key blue carbon sites in India

Site	State	Type / note
Sundarbans	West Bengal	Delta of the Ganga, Brahmaputra and Meghna rivers at the head of the Bay of Bengal. India shares it with Bangladesh. Sundarban Wetland (2019) is India's largest Ramsar site at 4,23,000 ha [1]
Bhitarkanika Mangroves	Odisha	Ramsar site (2002; 65,000 ha) [1], next to the Gahirmatha turtle beach
Pichavaram Mangrove	Tamil Nadu	Ramsar site (2022) [1]
Point Calimere	Tamil Nadu	Coastal Ramsar site (2002) [1]
Thane Creek	Maharashtra	Coastal Ramsar site (2022) [1]
Aghanashini Estuary	Karnataka	Estuary Ramsar site (2023) [1]
Seagrass beds	Gulf of Mannar, Palk Bay (Tamil Nadu), Gulf of Kachchh (Gujarat), Andaman and Nicobar waters	Dugong habitat. India's first Dugong Conservation Reserve was set up in Palk Bay in 2022

Programmes

• MISHTI (Mangrove Initiative for Shoreline Habitats & Tangible Incomes), 2023: plans to plant and grow mangroves on about 540 sq km of India's coast. It runs in all coastal States and UTs [4].
• Mangrove Alliance for Climate (MAC): launched at COP27 (Sharm el-Sheikh, Egypt, 2022) and led by the UAE and Indonesia. India is a member.

Don't confuse with

• Green carbon: carbon stored by land forests and vegetation, mostly in trees above ground. Blue carbon is stored by coastal and marine ecosystems, mostly in waterlogged soil, and it is buried faster per hectare.
• Black carbon: soot from burning fuel and biomass. It is an air pollutant that warms the climate. It is not a carbon store.
• Blue economy: using ocean resources for growth, such as fishing, shipping and ports. Blue carbon refers only to the carbon stored by coastal ecosystems.
• Coral reefs: reefs are marine ecosystems but they are not in the main blue carbon list. That list is mangroves, seagrass meadows and salt marshes. Reefs are threatened by heat stress and bleaching (corals push out their zooxanthellae algae and turn white).

Prelims Hooks

• The three main blue carbon ecosystems are mangroves, seagrass meadows and salt marshes. Most of the carbon is stored in their waterlogged, low-oxygen soil, not in the plants above ground.
• ISFR 2023: India's mangroves cover 4,991.68 sq km (0.15% of India's area). They grew 7.86% between 2013 and 2023 [2].
• West Bengal (Sundarbans) has the largest share of India's mangroves: 42.45% (2,119.16 sq km) [3]. The Sundarbans is the delta of the Ganga–Brahmaputra–Meghna and is shared with Bangladesh.
• MISHTI (2023) aims to cover about 540 sq km with mangroves in all coastal States and UTs [4].
• The Mangrove Alliance for Climate was launched at COP27, Egypt (2022) and led by the UAE and Indonesia. India is a member.
• Seagrass–dugong link: the dugong eats only seagrass. When seagrass beds are lost, both a blue carbon store and dugong habitat are lost. India's first Dugong Conservation Reserve is in Palk Bay, Tamil Nadu (2022).

Mains Points

• Blue carbon as a climate tool (GS-III):
• Mangroves, seagrass and salt marshes store carbon in their soils for centuries, and they bury it faster per hectare than land forests.
• The same ecosystems are a natural defence against cyclones, as in the Sundarbans and Bhitarkanika, so they help with both slowing climate change and adapting to it.

• India's mangroves grew 7.86% between 2013 and 2023 [2]. MISHTI targets about 540 sq km [4], and India has joined the Mangrove Alliance for Climate.

• Threats and gaps:

• Farming, cities and coastal building take over wetland land. Silt and invasive weeds also damage wetlands.
• When seagrass beds are lost, stored carbon is lost and dugongs lose their only food.

• Coastal and marine wetlands have fewer Ramsar sites than inland bird sanctuaries. Designating a site does not protect it unless there is also a management plan.

• Way forward:

• Protect habitats through the Wetlands (Conservation and Management) Rules 2017 and State Wetland Authorities.
• Protect more coastal Ramsar sites and conservation reserves, such as the Palk Bay dugong reserve.
• Link blue carbon protection to the CBD's Kunming-Montreal target of protecting 30% of land and sea by 2030 ("30x30").

Related concepts

• Wetland
• Ramsar Convention
• Ramsar sites of India
• Montreux Record
• Coral bleaching
• Great Barrier Reef
• Dugong
• Olive ridley turtle

Read more

• Wetlands, coasts and seas: Ramsar sites, mangroves, reefs and marine species