Assessing the CO2 capture potential of seagrass restoration projects

The long-term carbon sequestration expected for seagrass restoration programs was examined by developing a model that combined models of patch growth, patch survival in seagrass planting projects, and estimates of seagrass CO2 sequestration per unit area for the five seagrass species commonly used in restoration programs. The model was initiated with planting units of 1 m2, and assumed a time lag of two years for these planting units to start sequestering carbon. The model results indicated that the cumulative C sequestered increased rapidly over time and with planting density to reach an asymptote at a planting density of 100 units per ha (or 6 m spacing between units). At this planting density, the modeled cumulative C sequestered ranges from 177 to over 1337 tons CO2 ha-1 after 50 years. The value corresponding to this carbon sequestration suggests that the costs of seagrass restoration programs may be fully recovered by the total CO2 captured in societies with a carbon tax in place, providing additional ecosystem services derived from the role of seagrasses in providing ecosystem services, such as enhanced biodiversity. Seagrass restoration programs are economically viable strategies to mitigate climate change, particularly in subtropical and tropical island states where land-based options have a limited scope.