Using imagery collected by drones, scientists at the University of Exeter have created the first high resolution 3D models of Ascension Island’s turtle nesting beaches. The research, led by Miguel Varela, used a technique called photogrammetry to produce accurate digital elevation models (DEMs) of all of the main beaches used by nesting green turtles (see Varela et al. 2019). By combining DEMs with known nesting distributions and projections of sea level rise we aim to predict the potential level of habitat loss and enable forward-thinking policies that could mitigate climate change impacts on marine turtles.
DEMs have already been overlaid with the locations of > 27,000 green turtle nests recorded by the Ascension Island Marine Turtle Monitoring Programme in order to establish elevation above sea level. Flooding simulations are then applied to assess how much of the current nesting habitat would be lost under various sea level rise scenarios.
Processing of DEMs and nesting data is computationally intensive and many of the analyses are still ongoing. Nevertheless, the completion of the terrain mapping phase marks a significant step towards understanding how climate change is likely to impact Ascension’s iconic green turtles.
In future years of the Project we plan to assess how the additive effect of storm swells on top of an elevated sea level base might affect the frequency of nest flooding, as well as exploring opportunities for landward migration of nesting beaches constrained by coastal geomorphology and infrastructure. Our ultimate objective is to provide Ascension Island Government with the evidence needed to make informed decisions about coastal land use planning and habitat management around its globally important turtle nesting beaches.