This document summarizes a study that used local ecological knowledge to explore the impacts of expanding eucalyptus tree cover on water security in the Ethiopian highlands. Farmers reported decreases in water availability, increases in sedimentation, and conflicts over water resources due to reduced tree cover and uncontrolled eucalyptus expansion. While eucalyptus provided economic benefits by leaving the area, the water-related costs were borne locally through impacts on downstream communities. The study highlights trade-offs between provisioning and regulating ecosystem services associated with land use and tree cover changes.