Rapid Urban Expansion and Ecosystem Degradation along an Unsustainable Trajectory: Spatiotemporal Analysis of Land Use/Land Cover Change in the Western Area Peninsula, Sierra Leone

Abstract

Rapid, unplanned urbanisation in Sub-Saharan Africa is fundamentally restructuring land systems, with acute consequences for ecosystem integrity, climate resilience, and biodiversity conservation. This study investigates land use/land cover change dynamics in the Western Area Peninsula of Sierra Leone, a globally significant coastal biodiversity hotspot, over 2014–2024, using multi-temporal Landsat 8 OLI/TIRS imagery and a Support Vector Machine classification framework. Seven LULC classes were mapped at biennial intervals to quantify the magnitude, rate, and ecological trajectory of land transformation, providing the first continuous, high-frequency temporal baseline for this critically understudied coastal system. Results reveal a 154.0% expansion of built-up land (139.00 to 353.03 km²; +214.03 km² net), occurring at direct cost to ecologically sensitive landscapes: forest cover contracted by 59.0% (131.61 to 54.02 km²), mangrove ecosystems by 54.4% (104.67 to 47.77 km²), and combined agricultural and shrubland areas by over 70%. Classification reliability was consistently high across all biennial epochs (overall accuracy: 94.07–100%; Kappa: 0.89–1.00). Comparative trajectory analysis shows that urbanisation rates in the Western Area Peninsula substantially exceed those of Accra (\~4.2% yr⁻¹) and Lagos (\~3.2% yr⁻¹), signalling an unsustainable land transformation pathway inconsistent with Sierra Leone's Nationally Determined Contributions under the Paris Agreement and its Sustainable Development Goal obligations. The study estimates a cumulative forest carbon loss of 0.62–1.16 Mt CO₂-equivalent and projects that, at current rates, forest cover will fall below the SDG 15 monitoring threshold of 10% national land area within this decade. These findings deliver critical geospatial evidence to underpin integrated land-use planning, targeted ecosystem conservation, and climate-resilient urban governance.