Land Use/Land Cover Change and Spatial Environmental Risk in Southwest Nigeria's Border Towns: A 35-Year Landsat-Based Analysis (1990–2025)

Border towns are intensely transformed and sparsely documented sites due to cross-border trade, the increase of migration into the region, and lax land use administration policies. This study quantifies changes in landuse/land cover (LULC) across three border towns in Southwest Nigeria-Saki (Oyo state), Idiroko (Ogun state), and Seme (Lagos state)-based on an analysis of a time- series of five Landsat satellite imageries taken in 1990, 2000, 2010, 2020, and 2025. Land use/land cover was digitized by extracting information from the imagery on ArcGIS pro using three LULC classes namely water bodies, vegetation/ forest/agricultural land and settlement/built up area/bare surface. Data was aggregated for the three borders towns from 1990 to 2025 at decade interval to ascertain land use/cover change on both overall land use/cover type with reference to overall percentage coverage in time frame and at decade's decadal change rate in terms of overall percentages. In Saki, vegetation/forest/agriculture decreased from 92.37 percent to 73.07percent and settlement/built up/bare was increased from 7.56percent to 26.89 percent which indicates increase in rate in 256percent during 35 years of study and accelerated sharply during the last five years. In Seme, there were decreases in vegetation/forest/agriculture from 46.89 percent to 39.93 percent and water body increased from 16.52 percent to 13.15 percent while in settlement/built up/bare increase from 36.59 percent to 46.92 percent but the rate decreased with time since built up saturation point was being reached. In Idiroko all the landuse/land cover classes changed only in minor extent in all five-time frames with vegetation increasing from 71.07 percent to 71.00 percent while settlement/built up/bare increased from 27.51percent to 27.71 percent respectively. The differing rates of land-use change suggest that land use/ cover change in border towns vary individually. Unregulated fuel wood extraction by informal cross-border trading in Saki leads to high rate of conversion, while the relatively slow rate in Idiroko could be either as a result of stringent policies on land use administration or the border town's being less saturated. The implication is that spatial and environmental risks in border towns need to be assessed specifically at an individual level with temporal analysis and integration of the socio-spatial risk mapping into national and sub national land use policy administration is recommended.