URBAN EXPANSION AND CHANGES IN NORMALIZED DIFFERENCE VEGETATION INDEX OF BENIN CITY

Abstract

The study examined the trends in urban expansion and changes in vegetation of Benin City between 1991 to 2006 and 2021. The study employed remote sensing and geographic information systems for the spatial analysis. The result of the analyzed data showed a spatio-temporal urban expansion in the built-up area. The built-up area of Benin City increased spatially by  116.67km² between 1991 and 2006 and by 203.67km² between 2006 and 2021. For the 30years period (1991-2021), Benin City witnessed areal expansion of 633.54km². This indicates a remarkable vegetation loss of about 29km² in lieu of urban expansion. The trend of depletion in vegetation was followed up by massive urbanization that led to expansion of the built- up area of 34.4587km² within the periods. Also, findings revealed that there was a corollary between urban expansion and decrease in vegetation. The computed NDVI showed a significant reduction in vegetation of the study area. The NDVI of 1991 was 0.63 (approx.63%), by 2006 it decreased to 0.53 (approx.53%) and by 2021 it has reduced to 0.47 (approx.47%). This was substantiated with the use of one-way Analysis of Variance (ANOVA) in validating the result. The test statistics showed a significant difference in the mean of NDVI for the three consecutive periods (P<0.005). The mean NDVI for the three periods showed, 0.64 in 1992, 0.53 in 2006 and 0.47 in 2022. This implies that, as the city expands, it encroached into vegetated areas progressively. Hence, urban expansion lends credence to decrease in urban vegetation which results in several ecological challenges. In view of this, the study recommends adaptation measures such as afforestation, legislation on deforestation, green revolution, creation of shelter belts, parks and reserves and effective planning that is geared toward creating a conducive environment.