Measuring the Success of a Coastal Sand Dune Restoration on Tybee Island: Plant Growth, Sand Accretion, and Implications for Management

Coastal communities are developing rapidly in the face of increased risks of sea level rise and hurricanes stemming from anthropogenic climate change. In the US, erosion is projected to cost $530 million/year in property loss, but beaches and dune systems can minimize these losses. Dunes are vital to coastal protection, particularly when they are colonized by native plant species that stabilize sand with their root systems and accumulate sand by trapping particles with their stems and leaves. Dune construction can be used as a nature-based solution to climate change, but more studies are needed to fully understand the best practices that should be associated with vegetating constructed dunes. To gain more insight into dune restoration, I conducted a 15 month study on Tybee Island, GA, the site of new dune construction. I examined the effects of planting density on plant survival and growth and on sand accretion, and I compared accretion rates to those on pre-existing dunes on Tybee and unvegetated sites on the constructed dune. Overall survival of newly installed plants on the constructed dune was 96.9%, and these plants on average doubled in percent cover and height and increased in stem density by 10 stems. At the completion of the study, percent cover and average height of plants on the constructed dune were the same as those on the reference dune, but growth of newly installed plants decreased with increased density of planting. Accretion was highest in the reference dune, followed by the planted sites, and accretion was nearly 0 cm in the bare sites. Planting density was the best predictor of sand accumulation, with accumulation increasing with higher planting densities. However, at 5 plants/m2, this increase starts to level off, the same density beyond which plant growth drops. While specific restoration strategies must be viewed through the lens of management goals, these findings are consistent with the literature and have proven to work well on Tybee Island. The results of this study provide a framework both to future restoration projects on Tybee and to those taking place in other coastal communities