Integrating Earth Observation techniques into the reporting activities: an overview and some suggestions for the aquatic habitats

For aquatic environments, conventional monitoring approaches are extremely time-consuming and costly, reducing our capability to detect changes in plant community and habitat quality over time. Additionally, compared to terrestrial ecosystems, the aquatic ones are exceptionally dynamic systems, and therefore need regular monitoring as well as spatial-wise retrospective assessments to capture their successional patterns. Furthermore, aquatic ecosystems are often remote, hardy accessible or even inaccessible from the ground. In this context, the use of the Earth Observation (EO) data acquired - from remote platforms (airborne or spaceborne) - and techniques may offer a viable and cost-effective alternative to field-based monitoring of some habitat features. This is of particular interest in light of periodic monitoring activities imposed by the EU Habitats Directive (HD) to evaluate the quality of the compositional and structural attributes of habitats, as well as of their functions. Within this framework, an efficient and quantitative assessment of habitat conditions could greatly benefit from the development and implementation of new monitoring approaches based on the use of EO techniques, which should take into account the technical limitations of remote sensing data. Based on a preliminary review of the EO literature focused on the monitoring of aquatic habitats, we reconsidered a series of remote sensing-based case studies carried out in some of the most relevant Italian aquatic ecosystems (Mantua, Garda, and Iseo lakes among others) trying to decline them into the context of the reporting activities of HD. We focused on aquatic habitats under different aspects, investigating the community types (Villa et al., 2015), morphological traits (Villa et al., 2017), and dynamics (Villa et al., 2018; Ghirardi et al., 2019) of macrophytes, or evaluating the phytoplankton-macrophyte coexistence (Bolpagni et al., 2014).