Assessing Vegetation Responses to Dam-Induced Hydrological Change: A 40-Year Landsat Time-Series Analysis in the Downstream Serrahis River Watershed, Cyprus

This study presents a methodological framework to assess the impact of dam construction on vegetation dynamics, using the Klirou–Malounta–Akaki Dam in Cyprus as a case study. Unlike many dams that incorporate controlled flood pulses, this structure lacks a designed flood regime, raising the question of whether observed changes in riparian vegetation are primarily driven by localized microclimatic or geomorphological factors rather than direct hydrological alterations. A temporal analysis covering 20 years before and after dam construction (1984–2024) was implemented to distinguish baseline vegetation conditions from post-construction shifts. The analysis focused on an upstream area within the Serrahis River watershed. Enhanced Vegetation Index (EVI) time series, derived from Landsat 5, 7, and 8 and processed via Google Earth Engine and R, were harmonized using a Random Forest cross-sensor calibration approach. Pixel-wise trend analysis at 30 m resolution revealed cluster areas of vegetation increase, suggesting localized greening effects. However, ground-truthing surveys revealed that such increases were often associated with the spread of non-native Eucalyptus spp., a drought-tolerant species adapted to stable or intermittent surface flows. While the EVI trends may imply ecosystem recovery, they also indicate a shift in species composition, potentially favouring resilient non-native taxa at the expense of native species reliant on seasonal flooding. These findings underscore the importance of interpreting vegetation indices in ecological context. Although stabilized hydrology may enhance water storage, it can simultaneously drive biodiversity loss, highlighting the need for balanced water management strategies in water scarce Mediterranean environments.