Exposure of marine turtle nesting grounds to coastal modifications: Implications for management

Coastal areas are used by both marine turtles and humans which may result in marine turtle nesting grounds being exposed to human activities like coastal modifications. Several studies have investigated the effects of specific types of coastal modifications on marine turtles and their habitat. However, limited information exists on cumulative exposure of nesting grounds to coastal modifications. This study examines the spatial and temporal exposure of 203 marine turtle nesting grounds in Florida to coastal modifications. For this, we used coastal permits issued from 1985 through 2016 as a proxy for coastal modifications. To test the suitability of the permit database as a proxy for coastal modification, 34 marine turtle nesting beaches in the Florida Panhandle were ground-truthed to determine the presence of coastal modifications and their correlation with issued permits. The modification types analyzed were 1) construction landward of dune, 2) construction in dune, 3) construction on beach, 4) construction in water, 5) beach armoring, 6) other shoreline stabilization, 7) beach sand placement, 8) beach cleaning 9) dune vegetation planting, 10) sand fencing, 11) special events, and 12) stormwater outfall. The most common permit type was construction landward of the dune (65.72%), followed by construction within the dune (16.43%). The cumulative number of permits for the state of Florida increased over time (between 1985 and 2016) from less than one thousand permits issued per year to over four thousand permits issued per year. 93.5% of the nesting beaches examined throughout the state were exposed to cumulative coastal modifications. Of the high-density nesting beaches, twenty-six had high exposure to coastal modifications, whereas fifteen had low exposure to coastal modifications. Our study highlights the need for conservation strategies to consider the cumulative impacts of coastal modifications to marine turtle nesting grounds.