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
Patrick Moseray *
Institute of Geography and Development Studies, School of Environmental Sciences, Njala University, Njala Campus, Sierra Leone.
Peter Makieu
School of Electronic and Information Engineering, Suzhou University of Science and Technology, Jiangsu Province, China.
Lamin R. Mansaray
Institute of Geography and Development Studies, School of Environmental Sciences, Njala University, Njala Campus, Sierra Leone.
*Author to whom correspondence should be addressed.
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.
Keywords: Land use/land cover, remote sensing, urban expansion, ecosystem degradation, support vector machine, coastal biodiversity, SDG 15, Sierra Leone, West Africa