Coastal areas like mangroves, tidal marshes, and seagrass meadows hold a lot of carbon. This carbon has built up over time, thanks to plants and natural events. These areas capture and store more carbon per unit area than forests on land. This carbon is often called ‘blue carbon.’
These plant-covered ecosystems pull carbon dioxide (CO2) out of the air. This makes them good at storing away carbon. Because of this, climate experts are starting to see how they can help slow down climate change.
Coastal blue carbon ecosystems provide many benefits, but they are in danger. Each year, the world between 340,000 and 980,000 hectares of these ecosystems. Globally, up to 67% of mangroves, and at least 35% of tidal marshes and 29% of seagrass meadows have been lost.
If we continue at this rate, in the next 100 years, we could lose an additional 30-40% of tidal marshes and seagrasses, as well as almost all unprotected mangroves. When these ecosystems are damaged or lost, they can release a lot of the greenhouse gas, carbon dioxide.
What Are Blue Carbon Ecosystems?
Mangroves
- Mangroves are tropical forests located between land and sea. They get flooded by tides regularly. They’re among the tropics’ most carbon-rich forests.
- They sequester carbon at a rate of 6 to 8 Mg CO₂e/ha per year. This rate is 2 to 4 times higher than in mature tropical forests globally.
- Mangroves provide annual ecosystem services worth at least US $1.6 billion. These services include:
- Supporting fisheries by offering vital spawning grounds for commercial fish species.
- Filtering pollutants from coastal waters, contributing to good marine water quality.
- Shielding coastal communities and development from storms, floods, and erosion.
- Over the past 50 years, the world has lost 30-50% of the world’s mangroves. The loss continues at a 2% rate annually.
- Main reasons for mangrove destruction are deforestation for building aquaculture ponds and other unsustainable coastal developments.
- Experts believe that emissions from mangrove degradation can account for up to 10% of global deforestation emissions. This is despite mangroves making up only 0.7% of tropical forest area.
Tidal Marshes
- Most of the carbon in these ecosystems is in the soil, which can be meters deep.
- Tidal marshes sequester carbon at a rate of 6 to 8 Mg CO2e/ha (Mg of CO2 equivalent per hectare) annually.
- This rate is two to four times higher than mature tropical forests.
- Tidal marshes filter pollutants from land runoff, which helps preserve water quality in coastal areas.
- These marshes are crucial habitats for various stages of marine species’ life cycles, contributing to healthy fisheries and coastal marine ecosystems.
- Tidal marshes serve a vital role in protecting coastal communities by absorbing the energy of storms and floods, acting as a natural buffer and mitigating erosion. Their ability to act as a safeguard against environmental threats makes them invaluable to our coastal ecosystems.
- Tidal and freshwater marshes are experiencing a concerning decline, with a loss rate of 1-2% per year.
- Coastal development, agriculture, and rising sea levels pose significant risks to these ecosystems, endangering their delicate balance and long-term sustainability.
Seagrasses
- Seagrasses are underwater plants with long roots. They are found near the coast of every continent, except for Antarctica.
- These plants store carbon in their deep soil layers, which can be up to four meters deep.
- While they only make up less than 0.2% of the oceans, they store about 10% of the carbon in ocean sediment every year. This equates to 27.4Tg of carbon annually.
- In terms of carbon storage per area, seagrasses can hold double the amount that land forests can.
- The total amount of organic carbon stored in all seagrass ecosystems could be as much as 19.9 billion metric tons.
- Seagrasses also clean the water by filtering sediment and other nutrients. They help build and secure sediment, which protects coasts from erosion, storms, and flooding.
- These plants provide important habitats for various marine species, including fish, sea turtles, and manatees.
- However, seagrass ecosystems are under threat, with a global loss rate of about 1.5% per year that is increasing. So far, we’ve lost about 29% of these ecosystems.
- The main threats to seagrasses are poor water quality due to harmful land activities like deforestation and dredging.
Do Blue Carbon Ecosystems release substantial amounts of CO2 per unit area when converted or degraded, in comparison to other ecosystems?
- Coastal ecosystem degradation leads to large amounts of blue carbon being released as CO2.
- The annual emission due to this degradation is estimated to be 0.15-1.02 billion tons of CO2.
- Despite covering only 2-6% of total tropical forest area, mangroves, tidal marshes, and seagrass meadows account for 3-19% of global deforestation carbon emissions.
- Earlier estimations significantly underestimated greenhouse gas impacts as they didn’t account for the released carbon.
- Recent studies reveal that annual emissions from these three blue carbon ecosystems (0.45 Pg CO2 yr−1) are equal to the UK’s annual fossil fuel CO2 emissions, which is the world’s 9th highest emitter.
Where Are Coastal Blue Carbon Ecosystems Found?
- Coastal blue carbon ecosystems are located on every continent’s coastlines, excluding Antarctica.
- Mangroves, which grow in the intertidal zone of tropical and subtropical shores, are most abundant in Indonesia, Australia, Mexico, Brazil, Nigeria, Malaysia, Myanmar, Papua New Guinea, Cuba, India, Bangladesh, and Mozambique.
- Tidal marshes, present from the sub-arctic to the tropics, are most extensive in temperate zones — primarily in Europe, North America, Australia, and higher latitudes of South America and Africa.
- Seagrass meadows, underwater-flowering plant communities, exist in coastal waters worldwide, except Antarctica, with up to 13 species co-occurring in tropical areas.
- Although many countries are working on mapping and quantifying these systems, comprehensive regional and global maps of coastal blue carbon hot spots are still lacking.
Blue Carbon And Climate Change Mitigation
Existing Mechanisms
- A plethora of mechanisms already exist that promote climate change mitigation by preserving and restoring natural systems.
- These mechanisms can be modified and applied to blue carbon ecosystems in coastal regions.
Policy Considerations
- Significant international bodies, such as the United Nations Framework Convention on Climate Change (UNFCCC), are starting to factor blue carbon into their ecosystem discussions.
- Reduction of Emissions from Deforestation and Forest Degradation (REDD+) and National Appropriate Mitigation Actions (NAMAs) are emerging as ways for developing nations to tap into international carbon mitigation funding and enact national policies.
Local Scale Initiatives
- Clean Development Mechanisms (CDMs) are being crafted to finance local climate mitigation responses, potentially including coastal ecosystem preservation.
- Voluntary carbon markets could provide additional financial resources for coastal ecosystem conservation and restoration efforts.
Study Materials For UPSC: Discover More Environment Notes
- Invasive Alien Species
- Net Zero Emissions
- Understanding The Effects of Climate Change On The Ocean
- Nature Conservation And Indegenous People