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Spatio-Temporal Pattern of Urban Vegetation in the Central Business Area of the Wa Municipality of Ghana

2022; RELX Group (Netherlands); Linguagem: Inglês

10.2139/ssrn.4003282

1556-5068

Raymond Aabeyir, Kenneth Peprah, Kwame Oppong Hackman,

Urban Heat Island Mitigation

Increasing physical infrastructure development influences the spatial distribution of vegetation and temperature in many cities around the globe. However, in emerging cities such Wa Municipality in Ghana and elsewhere, research attention has focused on urban expansion or urban sprawl and the impacts thereof on the peri-urban vegetation. Considering importance of vegetation in regulating temperature, reducing windstorm, carbon sequestration and creating beauty, this paper concentrate on the threat posed by urban retrofitting activities on vegetation in open spaces in the Central Business District (CBD). Tree density was assessed by griding the CBD into 232 plots of 1ha or less. A sample of 157 plots was selected to enumerate and estimate tree density in the area. Normalised Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) maps were prepared from 2014, 2017 and 2020 Landsat 8 satellite images. Point NDVI and LST values were extracted for 600 random points and used to analyse the spatial distribution using Moran I global and local tests, performed two-sample t-test and Pearson correlation statistical test. The results revealed that the average tree density in the Wa CBD was 3 trees ha-1, which was classified as very low. The spatial distribution of the NDVI values showed low, high and insignicant clusters The NDVI values were within the range of 0.019 – 0.219. The clusters of high values were found around state institutional structures, where large open spaces existed while clusters of low values were found around the market, transport stations and densely populated areas where open spaces were very few. The surface temperatures trend revealed increasing minimum and maximum surface temperatures. The minimum LST were 320C, 330C and 360C in 2014, 2017 and 2020 respectively and the maximum temperatures were 360C, 370C and 400C for 2014, 2017 and 2020 respectively. It is concluded that NDVI values in the CBD are low, signifying the presence of isolated trees and patches of vegetation. Low and relatively high NDVI values cluster, revealing areas without vegetation or area with patches of vegetation, respectively. And, as greenness reduces LST increases. The Wa Municipal Assembly should convert open spaces that are bare into green vegetation parks within the CBD and liaise with the Regional Office of the Forestry Commission to plant trees in the CBD.