Progress in the remote sensing of groundwater-dependent ecosystems in semi-arid environments.

Abstract

Remote sensing of groundwater-dependent ecosystems (GDEs) has increased substantially in recent years. Of significant prominence, is the delineation and mapping of groundwater-dependent vegetation (GDV), species diversity, and water quality in these ecosystems. Groundwater-dependent ecosystems provide several ecological services such as habitat for wildlife fauna, carbon sequestration and water purification. The recent technological advancements and readily accessibility of new satellite sensors with improved sensing characteristics have resulted in numerous state-of-the-art applications for GDEs assessment and monitoring. These studies were done at varying scales, essentially in light of global climate change and variability. In this study, we review and assess the progress on the remote sensing of GDEs in semi-arid environments. We present the key trends in GDEs remote sensing that underpin many of the recent scientific research milestones and application developments. In addition, we observed a considerable shift towards the use of advanced spatial modelling techniques, using highresolution remotely sensed data to further improve the characterisation and understanding of GDEs. Thus, literature shows the successful use of freely available remotely sensed data in mapping GDEs. We conclude that the advancement in remote sensing provides unique opportunities for the assessment and monitoring of GDEs in environments currently influenced by climate change and other anthropogenic impacts. Although remarkable progress has been made, this review revealed the need for further remote sensing and geospatial analysis studies to map other GDEs aspects including water quality and species diversity. Furthermore, the mapping and characterizing of the seasonal and yearly variability and changes in GDEs is required, mainly in the face of climate change and human impacts as well as water scarcity, particularly in data-limited tropical environments.