COS 91-4 - The natural capital of seagrass beds in the Caribbean: Evaluating their ecosystem services and blue carbon trade potential

Abstract: Seagrass beds provide tremendous services to society, including the storage of carbon, with important implications for climate change mitigation. Prioritizing conservation of this valuable natural capital is of global significance, and including seagrass beds in global carbon markets through projects that minimize loss, increase area, or restore degraded areas represents a mechanism towards this end. We used newly available Caribbean seagrass distribution data, carbon storage data from the literature, and iterative sampling models to scale carbon in seagrass biomass and sediment across the Caribbean region. We calculated an economic value for the total ecosystem services provided by this seagrass and for the carbon stored in these seagrass beds. We estimated the 88,170 km² of seagrass in the Caribbean stores 1,336.3 (360.5-2335.0, minimum and maximum estimates, respectively) Tg carbon. These results showed that seagrass beds in the Caribbean could account for up to half of global seagrass area and a third of the estimated carbon stored in all seagrass beds on Earth, with uncertainty stemming from the lack of accurate global seagrass distribution data. The value of Caribbean seagrass ecosystems in terms of total ecosystem services and carbon alone was estimated to be $255 billion yr^-1 and $88.3 billion, respectively, highlighting their potential monetary importance for the region. In The Bahamas, the country with the largest area of seagrass in the Caribbean, we estimated the value of ecosystem services provided by seagrass beds to be $156 billion yr^-1 and the value of carbon alone in seagrass to be $54.0 billion. Despite being conservative estimates of ecosystem service evaluations, these numbers still represent more than 15 and 5 times the country’s 2020 gross domestic product ($9.91 billion), respectively. This study shows that Caribbean seagrass beds are globally substantial reservoirs of carbon, and our estimates can be immediately used by governments and managers to motivate seagrass conservation efforts. Our findings highlight the importance of integrating seagrass beds into global carbon markets to promote urgently needed conservation of these highly threatened and globally important ecosystems.