Blue Carbon:
The Role of Coastal Ecosystems in
Climate Change Mitigation and Adaptation

Hari Srinivas
Policy Analysis Series E-198. July 2023.

Blue Carbon refers to the carbon stored in the world's ocean and coastal ecosystems, such as mangroves, tidal marshes and seagrasses. Coastal ecosystems play a vital role in mitigating the impact of greenhouse gases on the atmosphere, by sequestrating and storing significant amounts of carbon. The international community has recognized the significance of Blue Carbon in climate change mitigation and adaptation, and research is ongoing to understand the carbon accumulation processes in these ecosystems. Coastal ecosystems provide numerous benefits to local communities and the global environment, including storm protection, food security, water quality regulation, and recreation. Protecting and restoring these ecosystems is crucial for combating climate change and providing healthy coastal environments for people.

Blue Carbon, Coastal Ecosystems, Climate Change Mitigation, Adaptation, Sequestration, Mangroves, Tidal Marshes, Seagrasses, Carbon Sink, Carbon Cycle, Coastal Habitats, Greenhouse Gases, Storm Protection, Food Security, Water Quality, Recreation, Climate Change, Carbon Accumulation.
Blue carbon can be defined as carbon captured by the world's ocean and coastal ecosystems. Interconnected communities of living organisms and their physical environment, functioning harmoniously through various ecological processes.. Oceans and coasts provide a natural way of reducing the impact of greenhouse gases on our atmosphere, through sequestrationRemoval of carbon from the carbon cycle of this carbon. The term "Blue Carbon" was first coined in the 2000s to describe the disproportionately large and positive contribution of coastal ecosystems to global carbon sequestration. The role of blue carbon in climate change mitigation and adaptation has gained international prominence, particularly in the processes of the UNFCCCUnited Nations Framework COnvention on Climate Change.

Understanding how climate change affects carbon accumulation in coastal areas (also called blue carbon ecosystems) and during their restoration is a high priority for science research, so as to provide information for local environmental decision making.

Importance of Coastal Ecosystems

Why are coastal ecosystems important in the process of generating blue carbon and other services? There are a number of benefits and services and coastal ecosystems provide to local communities and the global environment:

  • Protection from storms surges
  • Protection from sea level rise,
  • Prevention of shoreline erosion,
  • Filtering land-based sources of pollution
  • Regulation and improvement of coastal water quality,
  • Provision of (nursery)habitat for fisheries
  • Securing food security for coastal communities.
  • Mitigation of climate change impacts
  • Recreational opportunities such as ecotourism
  • Financial opportunities to community conducting restoration

Blue carbon ecosystems - typically mangroves, tidal and salt marshes, and seagrasses [See Appendix]- are highly productive coastal ecosystems that are particularly important for their capacity to store carbon within the plants that grow there and in the sediments below. The UN's Intergovernmental Oceanographic Commission and concluded that such ecosystems are considered a key component of nature-based solutions to combat climate change.

Types of coastal ecosystems

Research has shown that, though not universal, coastal ecosystems remove far more carbon per area than terrestrial forests. It has been estimated that a given area of mangrove forest, for example, can store up to 10 times as much carbon as the same area of land-based forest.

The Earth's warming climate is reducing snow and ice. The warming of the polar seas causes the sea surface to freeze less in winter and glaciers to retreat, generating more open, ice-free water. Less sea ice provides a longer growing season for marine plants called microalgae (phytoplankton) and removes more carbon, in the form of carbon dioxide, from the atmosphere. The growth of microalgae provides more food for animals that eat the algae and store this carbon through growth of their bodies. The carbon stored by marine life is called blue carbon.

When marine animals die some of the blue carbon is buried in the seabed, and that carbon is removed from the carbon cycle. This trapping of carbon in the seabed or in other places is called sequestration. The amount of polar blue carbon increases with climate warming. This is known as negative feedback on climate change. Any negative feedback on climate change is important to help combat global warming.

Source: Barnes D (2020) What Is Blue Carbon and Why Is It Important?. Frontiers. 8:154. doi: 10.3389/frym.2019.00154

What is Blue Carbon? Blue carbon is the carbon stored in coastal and marine ecosystems. such as mangroves, tidal marshes and seagrasses - which sequester and store large quantities of blue carbon in both the plants and the sediment below. For example, over 95% of the carbon in seagrass meadows is stored in the soils.
Sea grasses, mangroves, tidal/salt marshes and wetlands along coastal areas capture and hold carbon, acting as a carbon "sink". These coastal systems, though much smaller in size than the planet's forests, sequester this carbon at a much faster rate, and can continue to do so for millions of years.

Most of the carbon taken up by these ecosystems is stored below ground in the ground and other sediment layers. The carbon found in coastal soil is often thousands of years old - despite covering less than one percent of the ocean, they are able to store over 50% of the seabed carbon reserves.

The bigger picture of blue carbon is one of coastal habitat conservation. When these systems are damaged, an enormous amount of carbon is emitted back into the atmosphere, where it can then contribute to climate change.

Coastal ecosystems tend to be damaged due to a number of reasons such as land clearing and coastal developments, severe weather events, climate change impacts or land-based sources of pollution Protecting and restoring coastal habitats is a key approach to combacting the negative impacts of climate change. When the carbon in coastal systems is protected, it results in healthy coastal environments that provide many other benefits to people, such as recreational opportunities, storm protection, and nursery habitat for commercial and recreational fisheries.

83% of the global carbon cycle is circulated through the ocean.

Coastal habitats cover less than 2% of the total ocean area.

Coastal habitats account for approximately half of the total carbon sequestered in ocean sediments.

Source: International Blue Carbon Initiative

Coastal ecosystems are some of the most productive on Earth. They provide us with essential ecosystem services, such as coastal protection from storms and nursery grounds for fish. We also know that they provide another integral service - sequestering and storing "blue" carbon from the atmosphere and oceans and hence are an essential piece of the solution to global climate change.

Blue Carbon Markets

Trading and Financing Blue Carbon Credits:

A blue carbon credit system would ensure a reallocation of incentives. Local communities would receive funds from coastal ecosystem restoration and re-forestation.

Local and national laws, regulations and policies to protect coastal ecosystems are very important in order to preserve and derive benefit from such areas. At the global level, the United Nations has advocated for broad-based action to manage, protect, conserve and restore marine and coastal ecosystems Good practices in this direction have focused on:

Responsible and sustainable development of communities to ensure that coastal residents and their assets are protected and adopt to climate change.

Protected zones:
Designate areas around coastal ecosystems as protected zones (such as banks of creeks, lagoons, estuaries, backwater and rivers subject to tidal fluctuations.

Access to Public:
Provide public awareness campaigns so as to highlight the criticality of the areas and in keeping them accessible for tourism, recreation and other economic activities

Water quality:
Safegaurding coastal water quality to protect the coastal environmental health and marine resources safe - by filtering pollution and waste from flowing into fragile ecosystems.


Ensure wetlands are protected and are not affected by urban development - to maintain wetland biodiversity, protect critical species, fight pollution and restore habitats.

Coral reefs:

Carry out research and conservation to help sustain coral reefs for the many ecosystem services and benefits that they provide - including marine habitats, protection from storms etc.

A global response to human-induced changes in coastal ecosystems and their conservation and management aim to reduce, reverse, and prevent such changes and address their underlying causes. Policies that focus on ecological goals of ensuring resilience, maintaining ecosystem interdependence (for example, between mangrove forests, seagrass beds, and coral reefs), preventing pollution nd protecting water quality, conserving critical species, and taking policy action at the appropriate level and involving appropriate stakeholders.

Ultimately, socio-economic aspects of local communities such as stakeholder consultation, participation, and education are also an important element to achieve healthy coastal ecosystems - including, for example, lack of information for management decision-making, population growth and poverty, limited technical and management capacity, poor governance, lack of stakeholder participation, and a lack of awareness of the effects of human activities.

  • Blue Carbon: Carbon stored by marine life.
  • Phytoplankton: Tiny plants or micro-algae that capture carbon.
  • Carbon Capture: Fixing carbon dioxide gas into storage away from Earth's atmosphere.
  • Carbon Sequestration: Removal of carbon from carbon cycling (e.g., by burial).Carbon squestration through coastal ecosystems is an important element of a "blue economy"
  • Benthos: Organisms (mainly animals) that live on the seabed.

Further reading:

Appendix: Coastal Ecosystems There are essentially four types of coastal habitat: mangroves, salt marshes, seagrass meadows, and coral reefs. Coastal ecosystems are generated by plants and other animals that can thrive in saltwater and fluctuating tides.

Coastal ecosystems refer to a diverse range of habitats and communities that are found along the coastlines of oceans, seas, and estuaries. They are generated by plants and other animals that can thrive in saltwater and fluctuating tides. These different coastal ecosystems are often interconnected and provide important ecosystem services, such as nutrient cycling, carbon storage, and shoreline protection.

Here are some of the major types of coastal ecosystems:

Coral Reefs:
Coral reefs are diverse underwater ecosystems that are home to a vast array of marine species. They are formed by colonies of tiny coral animals that secrete calcium carbonate to build intricate structures.
Estuaries are areas where freshwater from rivers and saltwater from the ocean mix, creating a unique habitat with varying salinity levels. They are home to a variety of plant and animal species, including fish, shellfish, and migratory birds.
Mangrove Forests:
Mangrove forests are found in tropical and subtropical regions and are characterized by trees and shrubs that can tolerate saltwater. They provide critical habitat for many species, including fish, birds, and reptiles, and also serve as important buffers against storms and erosion.
Rocky Shores:
Rocky shores are areas where the shoreline is composed of rocky cliffs or boulders. They are home to a variety of algae, mollusks, crustaceans, and other species that can withstand the harsh wave action and exposure to air during low tide.
Salt Marshes:
Salt marshes are found along the coastlines of temperate and subtropical regions. They are dominated by salt-tolerant grasses and other plants and provide important habitat for many species of birds, fish, and invertebrates.
Sandy Beaches:
Sandy beaches are areas where the shoreline is composed of sand. They provide important habitat for many species, including shorebirds, crabs, and beach grasses, and also serve as important recreational areas for humans.
Seagrass Meadows:
Seagrass meadows are found in shallow coastal waters and are dominated by various species of seagrasses. They provide important habitat for many species, including fish, invertebrates, and sea turtles.
Wetlands are ecosystems that are characterized by the presence of water, either permanently or temporarily, and support a unique and diverse range of plant and animal species. They include areas such as swamps, marshes, bogs, and fens, and are often located in transition zones between land and water. Wetlands provide important ecosystem services such as water filtration, flood control, and carbon storage.

Coastal ecosystems are incredibly valuable not only for their ecological significance, but also for the social and economic benefits they provide. These benefits include recreation, fisheries, and tourism, among others. However, coastal ecosystems are also under threat from human activities, such as coastal development, pollution, and overfishing.

It is essential that we protect and conserve these ecosystems to ensure their continued existence and the services they provide for current and future generations. Understanding the different types of coastal ecosystems and their unique characteristics is a critical first step in this conservation effort.

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