Measuring Success

Coastal communities are developing rapidly despite the increased risks of sea level rise and hurricanes. Dunes are vital to coastal protection, particularly when they are colonized by native plant species that stabilize dunes and accumulate sand. Dune construction and subsequent plantings with native vegetation can be used as a nature-based solution to climate change, but more studies are needed to fully understand associated best practices. We conducted a 14-month study on Tybee Island, GA, USA, the site of new dune construction, to examine the effects of planting density on plant survivorship, plant growth and sand accretion. We also compared accretion rates to those on pre-existing dunes on Tybee Island and unvegetated sites on the constructed dune. Survivorship 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. After 14 months, 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 accretion, with accretion increasing with higher planting densities. While there are limitations of a two-season study, our results offer a framework for future studies of coastal restoration projects and have the potential to be transferable to other barrier islands.