Assessing Urban Forest Structure and Carbon Sequestration in Kano Metropolis, Kano State Nigeria

Abstract

Urban forests are critical carbon sinks and microclimate regulators, but their structure and sequestration potential remain underexplored in semi-arid African cities. This study quantified the structural characteristics, aboveground biomass (AGB), and carbon stock of urban forests in Kano Metropolis, Nigeria. Field inventory was conducted across institutional grounds, residential areas, parks, and roadside plantings. The following data were collected on all the sample trees such as the species identity, diameter at breast height (DBH), and total height. Biomass was estimated non-destructively using Pantropical allometric equation and converted to carbon using a 0.5 factor. Structural parameters such as DBH distribution, basal area, and density were also computed. Results revealed dominance of Azadirachta indica and Mangifera indica, which together comprised more than 60% of individuals. While most trees were small-sized (DBH < 30 cm), a few large trees (>60 cm DBH) accounted for more than half of total biomass. Total AGB was estimated at 7,858.17 tons, equivalent to 3,929.08 tons of carbon stock. Institutional grounds and parks stored the highest biomass per unit area. These findings demonstrated the ecological value of urban forests in carbon storage but also highlight structural vulnerabilities due to species dominance. Sustainable management should prioritize species diversification, protection of large-diameter individuals, and integration of AGB estimates into urban climate action plans.