High-resolution, low-altitude aerial photography in physical geography

Abstract

Intertidal landscapes are highly complex and dynamic habitats that exhibit variability over a range of spatial and temporal scales. The spatial arrangement of structure-forming biogenic features such as seagrasses and bivalves influences ecosystem function and the provision of important ecosystem services, though quantification and monitoring of intertidal landscape structure has been hindered by challenges collecting spatial data in the coastal zone. In this study, an intertidal landscape mosaic of eelgrass ( Zostera marina) and blue mussels ( Mytilus edulis) was observed using low-altitude aerial photography from a balloon-mounted digital camera platform. Imagery representing seagrass-bivalve landscape structure was classified and analysed using multiple metrics of landscape composition and configuration at the patch scale and the landscape scale. Patch-scale imagery was compared to a previously collected dataset in order to track temporal changes in seagrass patch metrics over a 26-month period. Seagrass and bivalve patches exhibited distinct spatial patterning at different spatial scales. At the patch scale, the change in seagrass metrics was consistent with patch border expansion at the expense of patch density and integrity. These methods demonstrate a novel approach for collecting high-resolution spatial data that could also be valuable to physical geographers dealing with similar fine-scale landscapes. The application of spatial metrics at multiple spatial scales quantified elements of the configuration and composition of a seagrass-bivalve habitat mosaic and allowed for the tracking of patch metrics through time to depict landscape change. Continued development of landscape metrics within intertidal habitats will increase understanding of the ecological function of these areas with benefits to management and monitoring of ecosystem health.