A satellite-based green index as a proxy for vegetation cover quality in a Mediterranean region

To preserve land quality and mitigating land degradation represent an important task for regional planning and environmental management of the Mediterranean region. Since land cover dynamics directly affect the landscape characteristics, remote sensing represents an effective tool for land quality assessment at large scale. In particular, the use of satellite-based vegetation indices, like the NDVI (Normalized Difference Vegetation Index), can provide important information when evaluating Vegetation Cover Quality (VCQ) patterns in terms of vegetation productivity and status, which represents one of the most sensitive landscape component to environmental degradation. This paper proposes an approach for the large-scale assessment of VCQ by means of an NDVI-based (functional) indicator using freely available MODIS (Moderate Resolution Imaging Spectroradiometer) satellite imagery. As a case study, a complex semi-arid Mediterranean landscape (Attica, Greece) experiencing drought, land-use changes, increasing human pressure, and high vulnerability to degradation was chosen. As VCQ indicator, the NDVI-based vegetation cover classification was produced by means of unsupervised multivariate statistical techniques and compared with ancillary cartographic layers, statistical indicators, and field data related to land-use management observed in the study area. Results demonstrate that the obtained remotely sensed land characterization can be effectively considered as a proxy of the VCQ status of the examined region, especially for studies of actual land degradation. Due to the large availability over time and low cost of satellite images, the proposed approach can be applied to wider regions, e.g. covering the whole Mediterranean basin, to monitor diachronically vegetation quality and indirectly control land degradation.