Spatiotemporal impact of urban expansion on carbon sequestration in Jinja city

Abstract

Uganda's rapid urbanization at 5.2% annually includes Jinja's quick growth, with 3% population increase driven by various factors. Despite concerns about encroachment, Jinja's green infrastructure remains vital for climate mitigation because it absorbs CO2, though growth hampers sequestration. This study analyzed how urban expansion affects Jinja’s carbon sequestration to support SDGs 11 and 13 using a spatial–temporal quantitative research design, GIS analysis of 2001, 2011, and 2021 remotely sensed satellite data, with the CASA model and indices like the Urban Expansion Index and urban land index. This study analyzes the relationship between urban expansion and carbon changes from 2001 to 2021 using Landsat data. The study calculated NPP, carbon stocks, sequestration, and calculated urban expansion metrics like ULI and UEI. Results show rapid development: Jinja’s buil t-up area nearly doubled, with ULI rising from 6.54% in 2001 to 9.85% in 2021, and UEI from 0.142% (2001–2011) to 0.188% (2011–2021). Jinja experienced significant outward growth from 2001 to 2011, driven by unregulated urban sprawl into high-carbon green spaces, resulting in a substantial loss of carbon stocks, consistent with the UNCCD PRAIS4 Uganda report. Northern Division (which includes Mafubira, Bugembe, and Budondo) has become the main growth area, whereas the Southern Division (the old municipality) experienced slower spatial expansion. spatial regression analysis reveals, from 2001 to 2011, the urban expansion coefficient was statistically significant and negative (–23,760; p = 0.001) Quantifying both urban expansion and carbon sequestration from past trends enhances understanding of climate dynamics and supports sustainable urban planning for future urban growth, emphasizing the development of green cities.