Blue carbon ecosystems critical against climate change

Marine ecosystems, or blue carbon ecosystems, play important roles in supporting biodiversity and providing livelihoods. They are also critical in the fight against climate change for several reasons, according to a Mongabay-India (MI) report. In India, blue carbon ecosystems are predominantly found along the country’s vast coastline and the islands including the coastal regions of West Bengal, Gujarat, Odisha, Tamil Nadu, Kerala, Karnataka, Goa, Daman and Diu, Maharashtra, Pondicherry, and the Andaman and Nicobar Islands, the MI report adds.

According to a World Resources Institute (WRI) explainer, ‘Blue carbon’ refers to carbon that is captured from the atmosphere and stored in marine and coastal ecosystems like seagrass meadows, mangroves and tidal marshes. These ecosystems are carbon removal powerhouses, storing up to five times more carbon per area than tropical forests and absorbing it from the atmosphere about three times as quickly, too. Despite covering only around 0.5% of the seafloor, blue carbon ecosystems may account for more than 50% of all carbon buried in marine sediments.

A World Bank (WB) feature points out that oceans are the largest heat sink on the planet, absorbing 90% of the excess heat caused by climate change and 23% of human-caused CO2 emissions. Blue Carbon is critical because of the multiple benefits that it offers. First is the huge storage capacity of these ecosystems. For example, one hectare of mangroves stores five times more carbon than a similar area of forest on land. Seagrasses are another type of coastal ecosystem critical for carbon storage. Stopping seagrass destruction and degradation worldwide could save up to 650 million tons of CO2 emissions annually, roughly equivalent to the entire annual emissions of the global shipping industry.

The WB feature also says that there are many benefits that protecting and restoring these ecosystems have on making people and communities more resilient, such as reduction in flooding and erosion, storm protection, and increased job creation and food security. Another WB report had calculated that mangrove ecosystems protect more than six million people from flooding annually and prevent losses of $24 billion in productive assets. More benefits include the potential for healthy mangroves, seagrasses, and saltmarshes to generate high quality carbon credits, which, once verified and sold through transparent carbon markets, can earn additional income for local communities. Despite their multiple benefits, coastal areas storing blue carbon have been seriously eroded, with more than 50% of the world’s original salt marshes lost during the 20th century. Up to 35% of mangroves were destroyed through deforestation in the 1980s and 1990s, and an estimated 25% of total seagrass beds lost to date.

As the MI report states, marine ecosystems store around 83% of global carbon dioxide – a major greenhouse gas responsible for global warming – in the form of carbonates, organic matter, and dissolved forms. The report highlights that a study on the carbon sequestration potential of disturbed and undisturbed mangrove ecosystems in Kerala estimated that undisturbed and conserved mangroves could sequester nearly 287 tonnes of carbon per hectare annually. Salt marshes can capture up to two tonnes of carbon per hectare annually. For context, a 42-seater bus weighs an average of 9-10 tonnes, and the average weight of an armoured tank is around 65 tonnes. These ecosystems also function as a protective barrier against extreme weather events which are becoming increasingly frequent and stabilise the sediment and prevent coastal erosion. Mangroves, for instance, buffer the coastline and coastal communities from tsunamis, storm surges, and cyclones. A recent example is how the force of Cyclone Dana, which struck the Odisha coast in October 2024, was significantly impeded by the Bhitarkanika mangroves.

It is important to restore and conserve blue carbon ecosystems as a potentially highly effective, nature-based solution to climate change, says the MI report. It adds that in India, the restoration and preservation of coastal ecosystems can play a vital role in enhancing the country’s climate resilience. The Sundarbans, for example, are not only home to rich biodiversity, but also serve as an important carbon sink, as well as a coastal barrier. Protecting these ecosystems is also crucial for mitigating the effects of sea-level rise, which is a particular concern for low-lying coastal areas.