The removal of invasive species as part of the restoration process can allow natives organisms to rebound. An ecosystem that incurs damages from invasive species is coastal sand dunes, which are dynamic systems. Some coastal sand dunes on the west coast of the United States have been invaded by Ammophila arenaria. The invasive grass, A. arenaria, is thought to alter and stabilize foredune morphology and reduce populations of native species. The objectives of my research are to examine the effects that manual and mechanical A. arenaria removal techniques have on coastal sand dune morphology and vegetative cover over time. The California State Parks Redwood District manages three coastal sand dune ecosystems where A. arenaria removal efforts have been conducted: Little River State Beach, Gold Bluffs Beach in Prairie Creek Redwoods State Park, and Tolowa Dunes State Park. I surveyed the vegetative cover at each of the three locations in each treatment method, manual and mechanical, and in untreated control plots during the summer and early fall of 2017. In order to measure dune morphology at restored and unrestored sites, I used an Unmanned Aerial Vehicle (UAV) that was flown over the mechanical removal and control areas. I then created a Digital Elevation Model (DEM) from photos taken during the UAV flights using Structure from Motion software. Overall, both mechanical and manual treatments lowered A. arenaria cover. Mechanical removal lowered the foredune elevation compared to control areas and changed the dune morphology in treatment areas into hummocks at Little River. Although mechanical removal was effective at lowering A. arenaria cover, it also lowered native plant diversity compared to manual removal, but was higher than control diversity. With endemic species of concern on coastal sand dunes, manual removal of A. arenaria will afford greater native plant diversity and cover compared to mechanical removal
