Unveiling the drivers of riparian vegetation change in Mediterranean river systems via remote sensing

Riparian ecosystems in Mediterranean landscapes are critical for biodiversity conservation and ecosystem services. This study investigates riparian vegetation change dynamics in a Mediterranean ecosystem in southern Italy, focusing on the potential relationship with environmental and anthropogenic factors contributing to the observed dynamics over the study period. We used 25-year of Landsat imagery to assess riparian vegetation cover and surface water changes, analyzing temporal trends of Normalized Difference Vegetation Index (NDVI) and Modified Normalized Difference Water Index (MNDWI), respectively. Statistical trend analysis revealed for the 96% of the changing areas a significant increase in riparian vegetation cover classified between “light” to “moderate improvements” in terms of trend’s magnitude. The greening process is particularly pronounced in areas with gentler slopes and higher Strahler stream orders. Conversely, we found a decrease in the surface area covered by water over the observed period. We used Structural Equation Model (SEM) to identify the relationship between water availability (surface water, precipitation, soil moisture) and riparian vegetation change trends. Reduction in surface water appears as the primary factor influencing vegetation change. Although the contribution to vegetation dynamics of topography, environmental conditions, land use and reduced anthropogenic pressure e.g. decline in traditional agriculture and land abandonment remain negligible outside the core of conceptualized model, their role in creating favourable conditions for riparian vegetation expansion cannot be overlooked. An understanding of these patterns and interactions is important for the development of effective adaptive management strategies to sustain both ecosystem functions and conservation efforts in riparian areas.