The increase of atmospheric carbon is one of the main factors of climate change. The IPCC has made a clear synthesis: the emissions produced by human activities are responsible for climate change and to limit them, it is necessary to reduce the net carbon emissions in the atmosphere. For this we have precious allies: the blue carbon ecosystems.
The importance of blue carbon ecosystems
These ecosystems are named this way due to their capacity to capture carbon present in the atmosphere. They are mangroves, seagrasses and salt marshes.
Located in coastal areas, blue carbon ecosystems are composed of halophilic (salt-tolerant) plants. These plants capture atmospheric carbon (via photosynthesis) before storing it, thanks to their roots, into the subsoil.
This environment, poor in oxygen, avoids significant microbial decomposition and thus a release of the carbon captured into the atmosphere.
These particularities of blue carbon ecosystems make them very effective carbon sinks.
They are up to 40 times more efficient per unit area than tropical forests.
Although they represent only 0.2% of the surface of the oceans, they store around 50% of the organic carbon buried in the ocean. And this is just one of the many benefits brought to human societies by these ecosystems. Home to a great biodiversity, they are also real buffer zones protecting coastal areas and are known for their ability to filter water from pollutants, allowing an improvement in the quality of coastal waters.
Blue carbon ecosystems under threat
Despite their importance and help, blue carbon ecosystems are among the most threatened ecosystems in the world.
Their global loss is estimated at nearly 67% for mangroves, 35% for salt meadows and 29% for sea grass beds.
Each year, approximately 340,000 to 980,000 hectares are destroyed worldwide.
This destruction leads to the release of carbon in gas form (CO2 and methane) into the atmosphere and the ocean, contributing to the worsening of climate change.
These ecosystems are mainly threatened by human activities such as the transformation of certain coastal areas into agricultural land or their artificialization (tourist constructions for example), the dumping of pollutants in coastal areas, etc. but also by the effects of climate change.
The preservation and restoration of these ecosystems is becoming urgent, given the benefits they offer for humans, particularly in terms of coastal protection, food production and biodiversity conservation.
The public utility of preserving and restoring these ecosystems
The multiple benefits provided by these ecosystems at the local level, in addition to those of carbon sinks, make preservation and restoration actions generally beneficial for society.
Scientific projects developed to protect these ecosystems aim to assess and monitor carbon capture by natural environments and to maximize carbon sequestration in the territory, based on the coastal ecosystem.
Surfrider teams are also committed at their level by working for a better understanding of these ecosystems. In March, our team of experts went to Txingudi Bay (which brings together seagrasses and salt meadows) in Hendaye to take samples. The results will provide a better understanding of the carbon stock in this ecosystem.
We would like to thank Dr Benjamin Amann, researcher at LIENs in La Rochelle on carbon sequestration in blue carbon ecosystems, whose help has enabled us to better understand this theme.
IPCC Climate Change 2021 : The Physical Science Basis, Summary for Policymakers
Le patrimoine mondial marin de l’UNESCO: gardien des réserves mondiales de carbone bleu, UNESCO, 2020
Estimating the Potential Blue Carbon Gains From Tidal Marsh Rehabilitation: A Case Study From South Eastern Australia, Frontiers in Marine Science, 2020
Coastal Blue Carbon: Methods for Assessing Carbon Stocks and Emissions Factors in Mangroves, Tidal Salt Marshes, and Seagrass Meadows, Intergovernmental Oceanographic Commission of UNESCO, International Union for Conservation of Nature, 2014.
Variable Impacts of Climate Change on Blue Carbon , One Earth, 2020
The Future of Blue Carbon Science , Nature Communications, 2019
Blue Carbon: The Role of Healthy Oceans in Binding Carbon: A Rapid Response Assessment. Arendal, 2009
Estimating Global “Blue Carbon” Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems , 2012