EVI ‐Derived Spectral Stability of Central Chilean Sclerophyll Forests During the 2010–2025 Megadrought and a Nested 2019–2021 Hyperdrought

Abstract

Climate change is increasing the frequency, severity and persistence of droughts, particularly in Mediterranean‐type ecosystems, where seasonal water limitation strongly constrains forest canopy condition and ecosystem functioning. Satellite‐derived vegetation indices provide a valuable approach for assessing canopy‐level responses to drought over broad spatial and temporal scales. However, indices such as the Enhanced Vegetation Index (EVI) should be interpreted as indicators of canopy greenness and spectral vegetation condition rather than as direct measurements of net primary productivity or ecological recovery. Here, we assessed EVI‐derived canopy greenness, climatic associations and spectral stability of central Chilean sclerophyll forests during the 2010–2025 megadrought and a 2019–2021 nested hyperdrought disturbance phase. We analysed sclerophyll forest sectors distributed across the current latitudinal and physiographic range of this forest type in central Chile, from coastal areas to the interior depression and Andean foothills. Annual high‐greenness EVI composites were derived from Landsat imagery using the 90th percentile of valid observations, with the 2000–2009 period used as the pre‐megadrought spectral reference condition. Extreme EVI anomalies were estimated relative to this reference period. Annual precipitation anomalies and cumulative precipitation deficit were calculated from CHIRPS Daily precipitation data using a 1981–2009 hydroclimatic baseline, while warm‐season land surface temperature was derived from Landsat surface temperature products. Climate–EVI associations were evaluated using sector‐year regression models with cluster‐robust standard errors, and EVI‐derived resistance, recovery, and resilience were quantified using bounded ecological stability metrics. Annual P90 EVI showed marked spatial heterogeneity across the study sectors. Lower EVI‐derived canopy greenness was generally observed in northern and drier sectors, whereas higher values tended to occur in more southern or locally mesic sectors. Annual EVI was positively associated with precipitation anomalies and negatively associated with warm‐season land surface temperature, with the thermal association showing the stronger effect. Extreme negative EVI anomalies were concentrated during the 2019–2021 nested hyperdrought disturbance phase, especially in northern and central sectors. Stability metrics indicated moderate to high EVI‐derived resistance across most drought‐only sectors, but recovery and resilience varied among sectors during the 2022–2025 post‐hyperdrought trajectory. Overall, our results show that central Chilean sclerophyll forests exhibited spatially heterogeneous canopy‐level spectral responses to prolonged drought and nested hyperdrought conditions. These findings do not demonstrate complete ecological recovery or ecosystem resilience in a demographic or compositional sense. Rather, they provide evidence of sector‐level EVI‐derived resistance, recovery and resilience, highlighting the usefulness and limitations of satellite‐based stability metrics for assessing drought responses in Mediterranean forest ecosystems.