Bokon Alexis Akakpo

University of Abomey-Calavi (UAC), Benin

Title: Impact of seasonal urban greening variability on land surface temperature: A case study from Benin (West Africa)

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Biography

Akakpo Bokon Alexis is the doctoral candidate at WASCAL, Climate Change and Human Habitat, Federal University of Technology of Minna, Nigeria. His research interests include development of agriculture, forest and biodiversity conservation and climate change and human areas sustainability. He is the Research Assistant at the Laboratory of Applied Ecology, Faculty of Agricultural Sciences (FSA) at University of Abomey-Calavi (UAC), Benin. He has five (05) papers in international peer-reviews; three (03) in national review; two (02) books and one (01) conference paper. Address: Laboratory of Applied Ecology, 01 BP 526, Cotonou Benin Republic.

Abstract

In the Republic of Benin, the seasonality of urban greening and its impact on the reduction of land surface temperature have received little attention. In order to get more precise information regarding the vegetation variation and its ability to reduce urban surface temperature, this study sought to evaluate seasonal variations of the normalized difference vegetation index (NDVI) using Landsat 7 and 8 data. Monthly NDVI series were collected using Google Earth Engine open-source while observed air temperatures were obtained at the National Meteorological Agency of Benin for the cities. A Mann-Kendall test was applied to assess the trends of NDVI and surface temperature in the two cities. The analysis of variance, followed by the Student-Newman-Keuls (SNK) test, was used to examine the significance of seasonal variation in the NDVI. Afterwards, a simple linear regression was performed to show the relationship between surface temperature and NDVI. The results of Mann-Kendall test showed no significant linear trends (P-values > 0.05), and NDVI was decreasing from 2000 to 2011 and increased up until 2020. A significant difference was shown between seasonal variations of vegetation index (NDVI) (P-Value < 0.001) in the study cities, and the months of January through March had the lowest mean NDVI values (Table). This finding can be justified by season-wise vegetation statuses in the cities. The analysis also revealed a moderate positive correlation between annual mean land surface temperature and NDVI for the dry seasons in each study city (January to March in Porto-Novo and April to June in Parakou, respectively Fig. 1 and 2). This finding implies that the state of urban vegetation in these cities during these months could not decrease the LST. This study, therefore suggests that a careful management of the cities’ urban vegetation be practiced through irrigation to ensure a long-term abatement of land surface temperature.

Keywords: vegetation index (NDVI), land surface temperature, seasonal variability, trend analysis, Benin