Some countries donate blue carbon

Climate change mitigation and adaptation, including through nature-based measures, are urgently needed. Now mapping and valuation of global vegetated coastal and marine blue carbon ecosystems shows how interlinked countries are when dealing with climate change.

Towards the end of the eighteenth century, Adam Smith’s famous The Wealth of Nations highlighted the role of the different aspects comprising a country’s wealth, including its natural resources or natural capital. Today, the ‘inclusive wealth’ concept, encompassing the different forms of capital which constitute the wealth of a country (natural, manufactured, human and social capital), expands this idea⁶. Blue carbon ecosystems are valuable natural capital assets. One way to value their worth is using the social cost of carbon (SCC), which is estimated through complex models that include physical and economic variables. The SCC values the ‘marginal’ damaging effects of an additional ton of CO₂ emissions in the atmosphere, or the benefit of a removed ton of CO₂ emissions, for society⁷. Greenhouse gas emissions to the atmosphere are a global problem; therefore, the SCC is a global estimate. Based on the assumption that climate change effects are felt differently in different countries, in 2018, Ricke et al.⁸ elaborated a new model to calculate these damages at the national level through the country-specific SCC (CSCC). To value blue carbon assets, the extent of each ecosystem, and how much carbon it sequesters and stores, have to be known. The areal extent is multiplied by the carbon burial rate of the blue carbon ecosystems in a specific geographical region — the precise species of mangroves, saltmarshes and seagrasses also plays a role in terms of carbon sequestration and storage rate — and by the chosen SCC. Uncertainty surrounding these factors is high because of the current lack of data on the precise extent of worldwide vegetated coastal and marine ecosystems, as well as their carbon sequestration and storage rates, and because of the uncertainty surrounding some of the chosen physical and economic variables used in the models estimating the SCC⁹.