Built-up expansion and urban land use trade-offs in peri-urban Cotonou (Benin), West Africa: A scenario-based remote sensing approach

Abstract

• Built-up areas grew by 12 % from 2002 to 2023, while vegetation declined by 11.8 %. • Urban growth followed a diffusion pattern with scattered new development patches. • Abomey-Calavi and Sèmè-Podji had steady medium-speed urban expansion. • Vegetation may decline by 15.1 % under a rapid growth scenario by 2050. • Scenario-based modeling supports sustainable planning in peri-urban Benin. In sub-Saharan Africa, understanding how urban land use and land cover (LULC) are changing is key to assessing the vulnerability of peri-urban ecosystems and improving spatial planning strategies. This study analyzes the dynamics of built-up expansion and associated land use trade-offs in the municipalities surrounding Cotonou, Benin, from 2002 to 2023, and simulates urban spatial growth trajectories to 2050 under three contrasting development scenarios. Multispectral Landsat imagery was classified using the Random Forest algorithm, and scenario-based projections were generated through the Land Change Modeler (LCM) in TerrSet. Classification accuracies were high (Kappa > 0.98), ensuring the reliability of results. Over the two-decade period, built-up/bare soil areas expanded by 12 %, while vegetation and others areas declined by 11.8 %, reflecting a moderate diffusion pattern and medium-speed urban spatial growth. Scenario projections indicate continued land conversion under the Rapid Economic Growth and Current Trend scenarios, primarily at the expense of vegetated areas. In contrast, the Green-city scenario highlights the potential for reversing land degradation through reforestation and spatial containment. These findings reveal critical trade-offs between development and environmental conservation, and demonstrate the value of scenario-based remote sensing approaches for guiding sustainable urban planning in rapidly transforming urban fringes of coastal West Africa.