The research, led by Henry Sawyerr and Olaniyi Afolabi Opasola of Kwara State University together with Edet Otto of Ajayi Crowther University, addresses a conspicuous gap in sustainability science. While ecological footprint accounting has been applied extensively at national and regional scales over the past two decades, city-level analyses remain rare, particularly in developing countries where environmental performance has often been overlooked. Without such localised data, urban policymakers lack the evidence needed to design interventions tailored to the specific consumption patterns and land constraints of their cities. The Kano study offers a replicable framework for data-scarce contexts across Africa, where rapid urbanisation is colliding with limited bio-productive land.

Methodologically, the team adopted a bottom-up approach, contrasting with the top-down national accounts that dominate the footprint literature. Between February and April 2024, the researchers administered a structured household survey to 487 households in Kano Municipal Local Government Area, one of eight local government areas that make up the metropolis. The questionnaire, adapted from earlier footprint studies, covered six consumption components: food, energy, transportation, waste, water, and goods and services. Households reported typical weekly and monthly consumption patterns, which were annualised using established conversion factors and cross-validated against official price and expenditure data from the Nigerian Bureau of Statistics. The instrument achieved a Cronbach’s alpha of 0.76, indicating acceptable internal consistency.

Estimating the city’s biocapacity required a fundamentally different data stream: the physical extent of its productive land. The researchers turned to remote sensing, downloading Landsat satellite imagery from the United States Geological Survey’s Earth Explorer portal and classifying land cover using a maximum likelihood supervised classification technique. The imagery, captured by the Operational Land Imager and Thermal Infrared Sensor, allowed the team to divide the metropolis into four land cover categories: water bodies, vegetation, built-up land, and fallow land. These spatially explicit areas were then multiplied by national yield factors and equivalence factors drawn from the Global Footprint Network to compute the biocapacity in global hectares. The integration of remote-sensing-derived biocapacity with disaggregated household consumption data represents a methodological advance for footprint studies in the African context.

The sectoral breakdown of Kano’s footprint delivered the study’s most surprising result. Food consumption accounted for 48 percent of the total ecological footprint, dwarfing the contributions of built-up land at 21.4 percent and energy at 10.9 percent. This challenges the common assumption that transport and energy dominate urban environmental impacts. The food figure appears to be driven largely by dietary composition: meat accounted for 40.5 percent of the food categories consumed, and animal-based diets carry disproportionately high land and carbon requirements. The finding aligns with a growing body of international evidence, including analyses showing that food represents the largest share of the European ecological footprint at around 30 percent, and studies of Chinese, Mediterranean, Portuguese, and Indonesian cities that similarly identify food as the leading footprint component.

The prominence of built-up land in the footprint reflects the sheer pace of Kano’s physical expansion. Between 1991 and 2020, built-up areas in the metropolis grew by approximately 152.55 square kilometres, and projections suggest this could reach 364.88 square kilometres by 2050. The city’s population, recorded at 2,828,861 in the 2006 census, is now estimated at around 4,648,400, and this densification has been accompanied by significant vegetation loss and declining ecological services. With Nigeria’s urban population projected to rise from 53.9 percent to roughly 79.9 percent of the national total by 2050, the pressure on bio-productive land around cities like Kano is set to intensify dramatically.

Energy, by contrast, contributed a comparatively modest 10.9 percent of the footprint, a result the researchers attribute in part to Nigeria’s recent economic turbulence. The removal of fuel subsidies and the subsequent surge in energy prices reduced household demand during the reference year, with data showing a 32 percent average daily decrease in fuel consumption in the post-subsidy period. Nevertheless, the energy picture remains concerning: petrol generators accounted for 52.1 percent of the energy footprint share, a consequence of Nigeria’s chronic power outages and unreliable grid supply. The study notes that the recent adoption of liquefied petroleum gas under the National Gas Expansion Programme, which aims to convert 60 million households by 2030, signals a transition toward cleaner cooking fuels, but fossil-fuel-based sources still overshadow the roughly one-third share of cleaner energy in household use.

To classify Kano’s overall environmental performance, the team calculated an Ecological Footprint Index, which expresses the percentage difference between biocapacity and footprint. The index came out at minus 3.0, placing the metropolis at the most unsustainable level on the four-point classification scale. The researchers emphasise that Kano’s deficit, while numerically small compared with high-income cities, is qualitatively different: wealthy urban centres overshoot because their footprints are enormous, whereas Kano’s deficit stems from critically low biocapacity. Similar deficits have been documented in rapidly urbanising cities from Metro Vancouver to Islamabad, Alexandria, and João Monlevade in Brazil, suggesting that ecological overshoot is a defining feature of contemporary urban growth rather than an anomaly of any particular region or income level.

The policy implications are concrete. The authors recommend supporting urban agriculture initiatives to localise food production, pointing to the example of Ghent in Belgium, where the Thursday Veggie Day campaign successfully reduced food-related footprints and could be adapted to promote plant-based diets in Kano. On land use, they call for compact urban development, green zoning, and enforcement of planning laws to conserve remaining bio-productive land. On energy, they propose subsidising solar power and domestic cooking gas, citing South Africa’s solar geyser subsidy scheme as a model for incentivising low-footprint household energy transitions. The study acknowledges its limitations, including reliance on self-reported consumption data vulnerable to recall bias, a cross-sectional design that captures only a single year, and the exclusion of industrial and institutional consumption, which means the true footprint of the metropolis is likely higher than the household-based estimate suggests. Even so, the researchers argue that the findings provide an essential baseline. Future work, they suggest, should employ longitudinal designs and scenario-based modelling to simulate how interventions such as renewable energy adoption and dietary shifts might alter the city’s footprint trajectory over time, helping Nigerian cities align with the Sustainable Development Goals and the Paris Climate Agreement.

Subject of Research: Ecological footprint and biocapacity assessment of Kano metropolis, Nigeria, for urban sustainability

Article Title: Geospatial analysis of ecological footprint for urban sustainability: evidence from Nigeria

Article References: Sawyerr, H., Opasola, O. A., & Otto, E. (2025). Geospatial analysis of ecological footprint for urban sustainability: evidence from Nigeria. BMC Environmental Science, 2(1), Article 18. https://doi.org/10.1186/s44329-025-00033-7

Image Credits: AI Generated

DOI: 10.1186/s44329-025-00033-7

Keywords: ecological footprint, biocapacity, urban sustainability, Kano, Nigeria, remote sensing, land use change, food consumption, energy footprint, urbanisation, GIS, sustainable cities