Scholarly works in Social and Environmental Forestry

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    Temperature variability and impact of vegetation cover in Ibadan metropolis, Ibadan, Nigeria
    (Faculty of Agriculture, Usmanu Danfodiyo University, Sokoto, Nigeria, 2021) Nwatu, U. J.; Alo A. A.; Agbor, C. F.
    This study evaluates the changes in Urban Green Spaces (UGS) and the impact of such changes on surface temperature in Ibadan Metropolis between 1984 and 2018 using Landsat images. Digital numbers of the imageries were converted to physical quantities, radiance, and brightness temperature, while the temperature retrieval from thermal channels of Landsat imagery was carried out and the derived surface temperature validation was done through near-surface air temperature. This was followed by the reclassification of the images using Normalized Difference Vegetation Index (NDVI) as a proxy for vegetation cover and was regressed with urban temperature to observe their nexus, which explains the ability of UGS to absorb solar radiation in the study area. The land use land cover maps of the metropolis were developed from green, red and near-infrared channels of Landsat data in Idrisi software environment using maximum likelihood classifier. Results show that the mean temperature of Ibadan metropolis increased from 33.29℃ to 35.76℃ over 34 years, and the temperature of different land cover types considered in this study revealed that built-up and bare soil areas recorded the highest temperature changes compared to other land cover types (green spaces and water body). Also, the correlation analysis between UGS and ST showed a strong negative relationship with R2 values ranging from -0.71 to -0.89. The study, therefore, concludes that the relationship is strong enough to ascertain that urban vegetation cover has the capacity to mitigate climate change effects. The increase in temperature may contribute to the variations in surface temperature, thus giving rise to the urban heat island effect. The study revealed the efficiency of geospatial techniques in data capturing for reliable information on sustainable management of urban green spaces.
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    Modeling Urban Green Space Dynamics and Associated Proximate Drivers in Ibadan Metropolis, Ibadan, Nigeria
    (Forest and Forest Products Society, 2018) Alo, A.A.; Nwatu, J. U.
    However, there is dearth of information on the dynamic of UGS caused by proximate drivers (PD) in Ibadan metropolis of Oyo State, Nigeria having flooded the direct drivers. Therefore, this study was designed to assess UGS changes and the PD that contribute to the changes in the last 34 years. Landsat images of 1984 (TM), 2001 (ETM+) and 2018 (OLI), coordinates of bench mark places of Ibadan metropolis were obtained. Geometric correction and principal component analysis were carried out on the satellite images. Land cover classification was achieved using maximum likelihood classifier method. Shapefile of Ibadan metropolis was super imposed on the classified images for land use/land cover assessment and Kappa statistics was used to carry out accuracy assessment on the image classification. The change detection analysis was carried out on the classified images using geometric geoalgorithm of ArcGIS. Urban green space change (dependent variable) and Proximate Distance (distance from; UGS edges, roads, built-up area and elevation) were extracted from the Landsat images using the distance command in IDRISI with Cramer's V test of association analysis. Four land use/land cover categories were identified; urban green space, built-up, water body and bare-soil. The UGS and water body decreased from 126,344 ha (85.36%) and 233.01ha (0.16%) to 100,481.20 ha (67.88%) and 136.17ha (0.09%) respectively from 1984 to 2018. On the other hand, builtup area and bare-soil increased from 9,250.72 ha (6.25%) and 12,193 ha (8.23%) to 32,227.16 ha (21.77%) and 15,176.20 ha (10.25%) respectively from 1984 to 2018. Distance from built-up (0.59) and UGS edges (0.56) are the dominant PD of UGS dynamics. About 25,863 ha of green space at rate of 760 ha per annum is given up to built-up area and bare-soil between 1984 and 2018. Urban green space decreased with increase in built-up area. The dominant proximate drivers influencing the changes were the distance from the built-up area and urban green space edges.