Spatiotemporal assessment of vegetation and soil moisture dynamics for evaluating ecosystem resilience in Oromia, Ethiopia

Assessing the spatial and temporal dynamics of vegetation and soil moisture is essential for understanding ecosystem resilience under climate variability. Oromia, Ethiopia’s largest and most ecologically diverse region, faces recurrent droughts and land degradation that threaten livelihoods and natural resources. This study investigates vegetation dynamics, soil moisture variability, and drought-induced resilience patterns from 2001 to 2023 using integrated remote sensing datasets. Multi-temporal MODIS NDVI (2001–2023) and SMAP soil moisture (2015–2023) data were processed on the Google Earth Engine (GEE) platform. Annual composites were generated, zonal statistics were extracted for each administrative zone, and temporal trends were analyzed using linear regression and coefficients of variation (CV). The Vegetation Condition Index (VCI) was derived from NDVI to classify drought intensity, which was inversely interpreted as ecosystem resilience. Correlation analysis was used to quantify the relationship between NDVI and soil moisture, and final outputs were visualized as GeoTIFF layers for spatial interpretation. Results revealed distinct ecological gradients across Oromia. The western highlands (Ilubabor, Jimma, Kelem Wollega, and West Wollega) exhibited high NDVI, strong soil moisture retention, and high resilience (VCI > 60), reflecting stable vegetation and favorable rainfall. Conversely, the eastern and southern lowlands (Borena, East Shewa, East and West Hararghe) displayed low vegetation productivity, declining soil moisture, and very low resilience (VCI < 40), indicating recurring drought stress. NDVI and soil moisture both peaked between 2018 and 2020 but declined significantly afterward. Correlation analysis showed a strong positive association (R2 = 0.65, p < 0.01) between vegetation greenness and soil moisture, underscoring their ecological interdependence. The VCI-based resilience framework effectively captured spatial drought–resilience gradients across Oromia, offering a robust basis for regional adaptation planning. Policy measures should prioritize restoration and water conservation in low-resilience zones, invest in sustainable land management in moderately resilient areas, and protect high-resilience ecosystems as climate buffers. While the approach demonstrates strong potential for large-scale drought monitoring, the absence of ground validation and socioeconomic indicators limits full ecological interpretation. Future work should integrate ground-based observations and climate projections to enhance drought-resilience modeling accuracy.