Rapid Assessment of Ecological Integrity for LTER Wetland Sites by Using UAV Multispectral Mapping

Abstract

Long-term ecological research (LTER) sites need a periodic assessment of the state of their ecosystems and services in order to monitor trends and prevent irreversible changes. The ecological integrity (EI) framework opens the door to evaluate any ecosystem in a comparable way, by measuring indicators on ecosystem structure and processes. Such an approach also allows to gauge the sustainability of conservation management actions in the case of protected areas. Remote sensing (RS), provided by satellite, airborne, or drone-borne sensors becomes a very synoptic and valuable tool to quickly map isolated and inaccessible areas such as wetlands. However, few RS practical indicators have been proposed to relate to EI indicators for wetlands. In this work, we suggest several RS wetlands indicators to be used for EI assessment in wetlands and specially to be applied with unmanned aerial vehicles (UAVs). We also assess the applicability of multispectral images captured by UAVs over two long-term socio-ecological research (LTSER) wetland sites to provide detailed mapping of inundation levels, water turbidity and depth as well as aquatic plant cover. We followed an empirical approach to find linear relationships between UAVs spectral reflectance and the RS indicators over the Doñana LTSER platform in SW Spain. The method assessment was carried out using ground-truth data collected in transects. The resulting empirical models were implemented for Doñana marshes and can be applied for the Braila LTSER platform in Romania. The resulting maps are a very valuable input to assess habitat diversity, wetlands dynamics, and ecosystem productivity as frequently as desired by managers or scientists. Finally, we also examined the feasibility to upscale the information obtained from the collected ground-truth data to satellite images from Sentinel-2 MSI using segments from the UAV multispectral orthomosaic. We found a close multispectral relationship between Parrot Sequoia and Sentinel-2 bands which made it possible to extend ground-truth to map inundation in satellite images.

The colors of heath flowering – quantifying spatial patterns of phenology in Calluna life‐cycle phases using high‐resolution drone imagery

“…Recent developments in sensor technology mounted on unmanned aerial vehicles (UAV) open up promising potentials for detailed ecosystem investigations (Anderson and Gaston ; Díaz‐Delgado et al. ). For the first time in research history, the structure of ecological entities can be quantified from individual plants down to the leaf scale.…”

“…A distinct differentiation between leaf emergence, flowering and fruit formation at the species level is, however, essential for assessing the ecological implications of spatial phenophase variability. Recent developments in sensor technology mounted on unmanned aerial vehicles (UAV) open up promising potentials for detailed ecosystem investigations (Anderson and Gaston 2013;D ıaz-Delgado et al 2019). For the first time in research history, the structure of ecological entities can be quantified from individual plants down to the leaf scale.…”

Investigation of Sediment-Rich Glacial Meltwater Plumes Using a High-Resolution Multispectral Sensor Mounted on an Unmanned Aerial Vehicle

“…The Parrot Sequoia+ multispectral camera is mainly used in precision agriculture, and there are very few publications concerning its utilization for hydrological investigations. Previous studies referred to, among others, SSCs in different water layers in rivers [58], the precision of digital surface models (DSM) in water pools based on multispectral camera pictures [67], or assessments of the ecological integrity of wetlands through multispectral mapping [68]. Nonetheless, there are no findings confirming the applicability of using multispectral UAVs for research on polar marine areas.…”

Use of Drones in Fishery Science

“…The variety of compact, UAS-ready sensors has expanded significantly in the last 5 years, including multispectral, hyperspectral, synthetic aperture radar, thermal, LIDAR, and other types. Although multispectral information is widely used in forestry and precision agriculture to assess vegetation health (e.g., NDVI) and to aid in classification/mapping, aquatic applications are limited (Boon and Tesfamichael 2017;Díaz-Delgado et al 2018). Compact forward-looking infrared thermal cameras mounted on UAS platforms have been used for mammal and bird inventory, poaching, fire detection, disaster response, surveillance and security, temperature and effluent mapping, and much more.…”