Climate and vegetation dynamics along altitudinal gradients in Dawuro Zone, Southwest Ethiopia: Implications for agricultural adaptation and ecosystem resilience
摘要
Climate and vegetation dynamics vary significantly along altitudinal gradients due to systematic changes in ecological conditions with increasing elevation. This study examines altitude-dependent climate and vegetation dynamics in the highland, midland, and lowland altitudinal zones of Dawuro, Southwest Ethiopia. Monthly precipitation and temperature data at a 4 km × 4 km spatial resolution were obtained from the TerraClimate dataset for the period 1990–2024. The dataset was validated against observed station data, and the results indicated strong alignment, with correlation coefficients of 0.835 (Gojeb) and 0.814 (Tercha), R2 values of 0.74 at both stations, and mean biases of 22.49 and − 20.23, respectively. Based on these results, TerraClimate data were used for subsequent analyses. Vegetation greenness, vegetation stress, rainfall variability, and drought conditions were analyzed using the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Standardized Vegetation Index (SVI), coefficient of variation (CV), and Standardized Precipitation Index (SPI). Trend analysis was conducted using the Mann–Kendall test and Sen’s slope estimator, while correlation analysis was employed to examine climate–vegetation relationships. In addition, ArcGIS and Google Earth Engine were used to assess spatial and temporal patterns across the study area. The results revealed significant warming trends in both minimum and maximum temperatures across all altitudinal zones, with the most pronounced increases observed in the lowlands. In contrast, precipitation exhibited moderate inter-annual variability without a significant long-term trend. SPI-12 results indicated predominantly normal moisture conditions, with intermittent mild drought periods in the early 1990s, 1999–2002, 2011–2012, and 2017–2019. Results of remote sensing vegetation indices (NDVI and SVI) showed an overall greening trend, particularly in the highland and lowland zones, which is associated with improved soil moisture conditions and land management practices such as watershed management and land rehabilitation efforts. However, vegetation recovery in the midland zone was comparatively weaker, likely due to increasing land-use pressure. Correlation analysis demonstrated that vegetation productivity is primarily driven by moisture availability and is negatively affected by rising temperatures. The findings further indicate that lowland ecosystems are the most vulnerable to heat and water stress. Overall, the results highlight the urgent need for altitude-specific, climate-smart adaptation strategies. Priority interventions should include improved water and soil management systems, drought early warning mechanisms, and ecological restoration efforts. Such measures are essential to enhance vegetation resilience, agricultural productivity, and environmental sustainability across Ethiopia’s diverse agroecological zones.