Unmanned Aerial Systems as tools for green turtle population assessment in coastal marine protected areas in Uruguay.
The green turtle is a highly migratory endangered species that performs annual migrations to and from foraging areas. Along their wide distribution range, thousands of stranded turtles impacted by direct threats have been reported yearly in the Southwestern Atlantic Ocean (SWAO), indicating strong anthropogenic pressures. Critical areas for sea turtle conservation and management have been identified in SWAO between Brazil and Argentina, including the whole marine and estuarine coast of Uruguay. Furthermore, this region is a crucial foraging ground for migrating juvenile green turtles which feed mainly on seaweed from rocky promontories. The seaweeds are a fundamental component of these rocky marine ecosystems, providing food and shelter to many animal species, and are key and ecosystem engineer species. In the last decades, several efforts have been made to protect sea turtles and reduce the threats from direct take, bycatch, and other activities. However, little attention has been given to evaluate habitat degradation (coastal development, climatic changes, etc.) at feeding grounds in SWAO.
The implementation of novel tools such as Unmanned Aerial Systems (UASs, also known as drones), is becoming more accessible, with improved operational controls and better capabilities to hold several types of sensors and high-resolution cameras, and their utility in ecological studies has increased. However, their implementation has been neglected for these types of habitats and species in the SWAO, due in part to the limited sampling protocols available. For this reason, the aim of this project is to develop and consolidate a holistic approach to the analysis and conservation of the green turtle and its coastal habitats. Efforts will be directed to the investigation of an endangered species with the application of new technologies, the reinforcement of regional conservation and management networks, and integration of these components with community capacity-building. Since juvenile green turtles have high fidelity to feeding grounds in the SWAO, this project will use UAS to analyze the ecological role of the green turtle in these coastal habitats and to evaluate how their distribution patterns are affected by climate-related habitat variability.
For this project I will use an UAS to conduct aerial surveys to estimate green turtle density in two Coastal and Marine Protected Areas (CAMPs) during different seasons of the year and to evaluate possible changes in seaweed cover associated with invasive species, sand deposition, among other stressors.
For green turtles, the UAS surveys will collect video of the area covered following specific flight patterns previously developed during 2019/2020, when I tested the methodology in a pilot study in the Rio de La Plata estuary, Argentina (Project Nº GCP/ARG/025/GFF).
For the habitat coverage, we will fly the UAS in a mapping pattern which will result in an orthomosaic of the area. I aim to conduct four aerial surveys per month for green turtle density and two aerial surveys per month for habitat mapping during a one-year period in both CMPAs. I will conduct the aerial surveys as well as analyze the data collected. Furthermore, I will analyze the turtle video data and create a habitat orthomosaic using ArcMap 10.6x, and further analyze the turtle density, seaweed cover and sand deposition variation over time using appropriate statistical and spatial models including Structure from Motion and others.
Finally, I will combine both data sources and conduct a green turtle habitat suitability analysis and relate the changes in rocky promontory community composition to seasonal density and distribution of green turtles.