Spatial Configuration and Extent Explains the Urban Heat Mitigation Potential due to Green Spaces: Analysis over Addis Ababa, Ethiopia

Berhanu Keno Terfa,Dev Niyogi,Nengcheng Chen,Xiang Zhang

doi:10.3390/rs12182876

Abstract

Urban green space (UGS) is considered a mitigative intervention for urban heat. While increasing the UGS coverage is expected to reduce the urban heat, studies on the effects of UGS configuration have produced inconsistent results. To investigate this inconsistency further, this study conducted a multi-spatial and multi-temporal resolution analysis in the Addis Ababa city metropolitan area for assessing the relationship between UGS patterns and land surface temperature (LST). Landsat images were used to generate land cover and LST maps. Regression models were developed to investigate whether controlling for the proportion of the green area (PGS), fragmentation, shape, complexity, and proximity distance can affect surface temperature. Results indicated that the UGS patches with aggregated, regular and simple shapes and connectivity throughout the urban landscape were more effective in decreasing the LST as compared to the fragmented and complicated spatial patterns. This finding highlighted that in addition to increasing the amount of UGS, optimizing the spatial structure of UGS, could be an effective and useful action to mitigate the urban heat island (UHI) impacts. Changing the spatial size had a significant influence on the interconnection between LST and UGS patterns as well. It also noted that the spatial arrangement of UGS was more sensitive to spatial scales than that of its composition. The relationship between the spatial configuration of UGS and LST could be changed when applying different statistical methods. This result underlined the importance of controlling the effects of the share of green spaces when calculating the impacts of the spatial configuration of UGS on LST. Furthermore, the study highlighted that applying different statistical approaches, spatial scale, and coverage of UGS can help determine the effectiveness of the association between LST and UGS patterns. These outcomes provided new insights regarding the inconsistent findings from earlier studies, which might be a result of the different approaches considered. Indeed, these findings are expected to be of help more broadly for city planning and urban heat mitigation.

Highlights

Over half the global population dwells in cities [1]
This study conducted multi-temporal, multiple statistical assessments, and varied scales to examine the connection between land surface temperature (LST) and green space patterns in Addis Ababa metropolitan area and further investigate the reasons for the inconsistency in prior studies
(1) The Urban green space (UGS) patches with aggregated, regular and simple shape and connectivity across the urban landscape are more effective in decreasing the LST than that of fragmented and complicated shape patterns

Summary

Introduction

Over half the global population dwells in cities [1]. Urbanization is typically associated with providing better socio-economic conditions. Urbanization has been associated with environmental and ecological stresses [2,3,4]. One of the widely recorded and evident impacts associated with urbanization is the increased temperature over the cities relative to the adjacent rural areas, or the urban heat island (UHI) [5,6]. Relative to the rural regions, urban areas have distinct morphology, geometry, and infrastructure that contributes to the UHI. How to understand and mitigate these adverse impacts has become a key study topic in urban ecology, geography, and climatology [15,16,17,18]

Results

Discussion

Conclusion