Understanding Spatial Linkages Between Terrestrial and Coastal Systems: Improving Conservation of Coastal Habitats

Coastal habitat condition is influenced by condition of landscapes draining to those habitats. Many studies show linkages between terrestrial landscapes and coastal habitats, yet few evaluate relationships over large spatial extents for the purpose of assessing condition of coastal habitats throughout large regions. To aid in addressing this need, we tested for relationships between condition of coral reefs and proximate watersheds draining to reefs. Next, we evaluated how proximity and size of watersheds affected detectability of relationships. This study was conducted around Maui, Hawaii using data from 800+ coral reef locations with 8 metrics of condition: measures of habitat complexity; crown-of-thorns starfish density; urchin density; and percent coral cover, stressed coral cover, sand, macroalgae, and crustose coralline red algae. Our results showed differential associations between coral reef metrics and different measures of watershed condition, with urban land use having strong, negative effects on multiple reef metrics. Further, the influence of multiple proximate watersheds on reefs increased with watershed size and higher intensities of human land uses. These findings illustrate complex influences of inland systems on coastal habitats. Improved understanding of what drives condition of coastal habitats will aid in efforts to conserve coral reefs from both current and future threats.