Changes in Ecosystem Service Values in Response to the Planting of Eucalyptus and Acacia Species in the Gilgel Abay Watershed, Northwest Ethiopia

Plantation of Eucalyptus and Acacia species emerges as a promising alternative in the tropics in a scenario of high demand for provisional and regulating ecosystem services. The research aimed to characterize the spatiotemporal dynamics of ecosystem service values in response to planting practices of Eucalyptus and Acacia species in the Gilgel Abay watershed, Northwest Ethiopia. The threshold values of NDVI were employed to classify land-use/covers using cloud-free satellite imagery data in 1984, 1998, 2013, and 2021. The benefit transfer method of modified value coefficient was used to estimate ecosystem service values (ESVs) of the study watershed. Total ESV decreased from 1984 to 1998 due to the expansion of cultivated land at the expense of natural forests, shrubs, and grasslands. As food production increased, performance levels of climate regulation, erosion control, and nutrient cycle declined. In contrast, the service values of erosion control, climate regulation, and nutrient cycles were the major contributors to the overall increase in ESV from 1998 to 2021. This was caused by expanding Acacia and Eucalyptus species plantation at the expense of cultivated land in the watershed. The research revealed a trade-off relationship between provisional and other ecosystem services, such as regulating and supporting ecosystem service values in response to land-use system transformation. As a result, it is suggested that synergistic interactions between regulating, provisional, and supporting ecosystem service values be developed by merging plantation and cultivated land. Maintaining the right proportions of degraded plantations, protected natural forests, farmlands, and wetland ecosystems can be the most effective way to provide optimal multiple ecosystem services.