Urban Expansion and Landscape Structure Changes in Kpalimé City (Togo) Between 1985 and 2024: GIS Approach, Landscape Metrics and CA-Markov Modeling

ABSTRACT: African cities are undergoing significant changes with multiple social, economic, and environmental consequences. This study aims to assess the spatio-temporal changes in land cover in the city of Kpalimé (Togo) between 1985 and 2024, in order to analyze urban expansion, its landscape impacts, and its future prospects. The approach is based on the use of Landsat satellite data (TM, ETM+, OLI/TIRS) from 1985, 2000, 2015, and 2024, downloaded from the Google Earth Engine platform, and on the use of remote sensing indices (NDVI, NDBI, BU), combined with supervised classification (MLC) using ArcGIS 10.4. Four land cover classes were distinguished: Agglomerations, Crops/fallows, bare soil, and forest lands. Eight (8) landscape ecology indicators were calculated, including dominance (pland), aggregation (ai, clumpy), fragmentation and connectivity (np, cohesion), plot morphology (Frac_mn), and diversity (shdi, sidi). The accuracy of the classifications was deemed satisfactory (84.6% to 94%), with Kappa coefficients ranging from 0.79 to 0.92, ensuring the reliability of the results. The analyzes highlight a significant increase in agglomerations, which rose from 429.07 ha (5.13%) in 1985 to 1,624.26 ha (44.11%) in 2024, representing a gain of 1,195.19 ha. This growth was concentrated primarily between 2000 and 2015 (779.84 ha), a period characterized by intense land pressure and uncontrolled urbanization. After a prolonged decline, crops/fallows have recently rebounded (528.28 ha between 2015 and 2024), while forestlands, initially expanding, have experienced a significant decrease (-1106.6 ha between 2015 and 2024) due to human pressures and increasing urbanization. Landscape indicators confirm increased fragmentation of the urban fabric at the turn of the millennium, followed by a process of consolidation and densification, characteristic of evolving urban dynamics. Predictive modeling, carried out using Markov chains (MOLUSCE plugin for QGIS 3.40), projects an expansion of built-up areas to 2119.02 ha (57.58%) by 2050, confirming the trend of accelerated urbanization at the expense of natural and agricultural areas. These results highlight a crucial issue for the urban and environmental planning of Kpalimé. They emphasize the urgent need to develop integrated territorial policies capable of guiding urban growth while preserving the ecological functions and agricultural resources essential to the sustainability and resilience of the city.