Urban green spaces as nature-based solutions for carbon storage and human thermal comfort: evidence from Jimma City, Ethiopia

Abstract

Urban green spaces provide critical ecosystem services, including carbon storage and thermal regulation, yet their condition remains poorly quantified in many rapidly urbanizing African cities. This study assessed the potential of urban green spaces as nature-based solutions for carbon sequestration and human thermal comfort in Jimma City, Ethiopia, using a locally calibrated Urban Green Space Condition Index (UGSCI) derived from Landsat 8 imagery and geospatial techniques. Key findings reveal that only 18% of the study area exhibits good green space conditions, with total aboveground carbon stock estimated at 2.18 million Mg C and a mean carbon density of 208.7 Mg C/ha. Dense vegetation stored substantially more carbon per unit area than built-up areas. A strong negative relationship between UGSCI and thermal discomfort (R 2 = 0.61) confirms that improving green space condition significantly enhances urban cooling. The UGSCI framework offers a replicable, low-cost methodology for monitoring urban environmental quality, readily transferable to other rapidly urbanizing cities in the Global South. By establishing a carbon stock baseline for Jimma City and identifying priority areas for green space investment and highlighting environmental justice implications, this study provides evidence-based guidance for sustainable urban planning and climate adaptation, directly supporting progress toward Sustainable Development Goals 11 (Sustainable Cities) and 13 (Climate Action).