Mangrove Ecosystem: Blue Carbon, India's Distribution, and Degradation Drivers

Ecological Structure of Mangroves

Mangroves are a unique assemblage of trees, shrubs, palms, and ferns adapted to saline, waterlogged conditions. Their adaptations include salt exclusion or secretion mechanisms, prop roots and pneumatophores (specialised aerial roots for oxygen uptake in anoxic sediments), and viviparous seed germination (propagules germinate on the parent tree before dispersal). The zonation of mangrove species from sea to land varies with tidal inundation frequency. In India, dominant species include Avicennia marina (grey mangrove), Rhizophora apiculata, Bruguiera gymnorrhiza, Sonneratia species, and Heritiera fomes (Sundari tree, from which Sundarbans derives its name).

Blue Carbon: Mechanism and Significance

Blue carbon refers to the carbon sequestered by coastal and marine ecosystems. Mangroves are among the most efficient carbon sinks on the planet, sequestering carbon at rates 3-5 times greater than terrestrial forests on a per-area basis. This is because mangrove soils — called mangrove peat — accumulate organic carbon over millennia under anaerobic conditions that inhibit decomposition. The carbon is stored in three reservoirs: aboveground biomass (trunks, branches, leaves), belowground biomass (roots), and sediment organic carbon (the most significant and persistent reservoir). India's mangroves sequester nearly 4.9 million tonnes of carbon dioxide equivalent annually. The Sundarbans alone stores approximately 26.62 Tg (teragrams) of blue carbon, making it a globally significant carbon pool.

When mangroves are destroyed, this stored carbon is released rapidly into the atmosphere — often as CO2 and methane — making mangrove deforestation a significant source of greenhouse gas emissions. UNEP estimates that mangrove loss contributes 0.07-0.42 Gt CO2 equivalent per year globally. Blue carbon accounting is now being incorporated into national climate action frameworks, including Nationally Determined Contributions (NDCs) under the Paris Agreement.

India's Mangrove Distribution: State-wise Analysis

As per the India State of Forest Report (ISFR) 2023, India's total mangrove cover is 4,992 sq km. The distribution is geographically concentrated on the east coast, delta regions, and island territories. West Bengal has the highest mangrove cover (about 42%), dominated by the Sundarbans delta. Gujarat follows with approximately 23% of India's mangrove cover, concentrated in the Gulf of Kutch and Kori Creek. Andaman & Nicobar Islands account for about 12% of the cover, followed by Andhra Pradesh (8.44%), Odisha (Bhitarkanika Wildlife Sanctuary), Maharashtra (Konkan coast and Mumbai), and Tamil Nadu (Pichavaram, Muthupet lagoon). Kerala has small but ecologically significant mangroves in backwater zones.

Ecological Services of Mangroves

Mangroves provide a wide spectrum of ecosystem services. As coastal buffers, they attenuate wave energy and storm surges — studies show that a 100-metre-wide mangrove belt can reduce tsunami wave heights by up to 13-66%. They stabilise coastlines by trapping sediment, reducing erosion. As nurseries for marine life, their dense prop roots provide shelter and feeding grounds for juvenile fish, crustaceans, and molluscs, supporting fisheries livelihoods for millions of coastal communities in India. Mangroves host exceptional biodiversity: the Sundarbans supports Bengal tigers, saltwater crocodiles, Irrawaddy dolphins, and over 300 bird species. They also filter land-based pollutants before they reach coastal waters.

Important Concepts / Subtopics

Degradation Drivers

The primary drivers of mangrove degradation in India include: Aquaculture expansion (particularly shrimp farming in Andhra Pradesh, Tamil Nadu, Odisha) which involves clearing mangroves to create ponds; Coastal urbanisation, including port construction, tourism infrastructure, and industrial development; Agricultural conversion for rice and coconut cultivation; Pollution from industrial effluents, oil spills, and plastic waste; Unsustainable fuelwood collection and charcoal production by local communities; Cyclone damage — while mangroves protect coastlines, severe cyclones cause direct destruction of canopy; and Sea-level rise combined with coastal squeeze (when development prevents landward mangrove migration). The 46% reduction in soil organic blue carbon in the Indian Sundarbans due to a 31% increase in soil salinity linked to regional sea-level rise is a documented case of climate-driven degradation.

MISHTI Scheme

MISHTI (Mangrove Initiative for Shoreline Habitats and Tangible Incomes) was launched under the Union Budget 2023-24. It aims to facilitate mangrove plantation along India's coastline and on salt pan lands through convergence of MGNREGS (Mahatma Gandhi National Rural Employment Guarantee Scheme), CAMPA (Compensatory Afforestation Fund Management and Planning Authority) funds, and other relevant schemes. The initiative has a dual objective: ecological restoration of coastal ecosystems and generation of sustainable livelihoods for coastal communities. It recognises the twin roles of mangroves as carbon sinks and as protection against climate extremes.

Blue Carbon in India's Climate Policy

India's updated NDC (2022) commits to achieving 33-35% reduction in emission intensity of GDP by 2030 and creating an additional carbon sink of 2.5-3 billion tonnes of CO2 equivalent through additional forest and tree cover. Blue carbon from mangroves is now being explicitly acknowledged as a component of this carbon sink target. NITI Aayog and MoEFCC have begun exploring methodology for blue carbon accounting under REDD+ (Reducing Emissions from Deforestation and Forest Degradation) frameworks. India's Coastal Regulation Zone (CRZ) Notification 2019 also provides protection to mangroves by classifying them under CRZ-I (ecologically sensitive areas).

ISFR and Mangrove Monitoring

The Forest Survey of India (FSI) releases the India State of Forest Report (ISFR) biannually. It uses satellite remote sensing and ground-truthing to map mangrove cover. ISFR 2023 records total mangrove cover at 4,992 sq km — a net decrease of 7.43 sq km from ISFR 2021. While some states showed gains (Andhra Pradesh: +13.01 sq km; Maharashtra: +12.39 sq km), Gujarat recorded the sharpest loss (−36.39 sq km). The FSI also estimates mangrove carbon stocks and is developing methodologies aligned with IPCC guidelines for blue carbon.

Current Relevance

The Kunming-Montreal Global Biodiversity Framework (2022) includes targets to protect and restore coastal ecosystems including mangroves. India's commitment under the 30x30 target (protecting 30% of land and oceans by 2030) directly relates to mangrove conservation. The increasing frequency of cyclones in the Bay of Bengal and Arabian Sea — linked to rising sea surface temperatures — makes mangrove restoration a direct climate adaptation strategy for coastal districts. The MISHTI scheme aligns with India's G20 Presidency (2023) emphasis on sustainable development and green transition. Urban mangroves such as Mumbai's Thane Creek mangroves face mounting pressure from real estate and infrastructure projects, making CRZ enforcement a governance challenge. The GST Council's decision to exempt inputs for mangrove restoration projects under CAMPA funds from GST reflects growing policy recognition of their value.

From an exam perspective, mangroves are relevant to questions on biodiversity, climate change adaptation, coastal governance, blue economy, and tribal/fishermen community livelihoods. Questions may link the Sundarbans to the Bengal tiger habitat, cyclone resilience, and transboundary conservation with Bangladesh.