Effects of Urban Vegetation in Mitigating Land Surface Temperature (LST) in Kaduna Metropolis, Nigeria

Abstract

Urban vegetation plays a vital role in mitigating higher temperature through shade, evapotranspiration and high albedo. Replacement of vegetation with urban land uses results in the increase in Land Surface Temperature (LST). This study analyses the effects of urban vegetation in mitigating LST in Kaduna metropolis, Nigeria. Landsat 8 data was used to classify the area into built-up area, vegetation, bare land and water bodies using random forest supervised classification. Information on the vegetation density was obtained using Normalized Difference Vegetation Index (NDVI), while single channel algorithm was used for the retrieval of LST. The effect of vegetation on LST was quantified using correlation analysis. The results showed that built-up area was the largest land cover, occupying 157.99km2 (46.53%), followed by vegetation with 143.34km2 (42.22%). Bare land had 34.26km2 (10.09%), while water bodies occupied 3.95km2 (1.16%). The vegetation density that mitigates LST indicated by NDVI showed higher values (0.38-0.69) in the suburb with higher vegetation density, which resulted in low LST range (22o-26oC). Lower NDVI values (0.05-0.38) were recorded in the bare land and built-up area with sparse vegetation. This resulted in moderate (28o-30oC) and high (30o-34oC) LST respectively. Lowest NDVI (-0.26 – 0.05) and LST (22oC – 26oC) were recorded in the water bodies. There was negative correlation (-0.55) between NDVI and LST, indicating the effect of vegetation in mitigating LST. Proper urban planning is necessary by planting more trees in the metropolis as part of LST mitigation strategies.