Resilience of a coastal ecosystem following hurricane Irma

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Coastal ecosystems like coral reefs, salt marshes and sand dunes are at the front line of climate change. On the one hand, these natural systems are increasingly called upon to shield people and properties from storms and hurricanes which are growing more intense under climate change. On the other hand, these same systems are themselves threatened by the powerful and destructive storm surges and waves that accompany the strongest storms. How fast - and how completely - coastal ecosystems can bounce back (show resilience) after a major storm, and return to shielding our shorelines, therefore becomes a pertinent question, particularly in light of the highly active and damaging Atlantic hurricane season of 2017. One such storm, hurricane Irma, brought a large storm surge to southwestern and eastern Florida, as well as to the coasts of Georgia and South Carolina, on the 10th and 11th of September. Sand dunes, an important and extensive line of coastal defence in that region and many others worldwide, suffered widespread erosion, with crucial foredunes completely wiped out in many areas. Affected dunes span urban and remote, undeveloped, areas and regions with differences in plant composition (east vs. west coast), providing a unique opportunity to investigate factors that control the ability of these ecosystems to rebound. This study will address the role of plant functional diversity (or variation in the way plants survive, grow and reproduce) in determining dune recovery. Because differences in function will allow different species to respond to the storm impacts in contrasting ways (e.g., re-growing from roots, or re-establishing from seeds) and use different parts of the beach at different times, a greater variety of plants is expected to boost recovery. This project will also address the effects of urban development in sand dune recovery, a key issue in coastal planning. And further, it will investigate a critical management issue - (how) do washed-up plants and debris affect sand dune recovery, and does their removal in cleanup efforts potentially slow recovery? To answer these questions we will do large-scale surveys spanning 24 sites, measure the diversity of plants, track the fate and growth of individual plants, and record the recovery of vegetation and dune morphology (and so coastal protection) during 3 field expeditions in 2018. To better understand the role of debris and washed up coastal plants, we will remove these from replicated patches in a field experiment, track sediment and plant community changes over the year, and use modern statistical techniques to reveal how any effects (increased nutrients, sedimentation, buffering high temperatures?) are mediated. We anticipate that these studies will: 1) illuminate the role of vegetation functional diversity in sand dune recovery; 2) reveal how vegetation recovery is affected by debris and dead plant material at a natural site, and how these processes might be lost from highly managed sites; and 3) provide a rare case study on the importance of biodiversity in providing reliable and resilient benefits to people.