Are vulnerable neighbourhoods left behind? Urban cooling disparities from greenspace inequality in Antananarivo, Madagascar

Abstract

The escalation of urbanisation contributes significantly to urban heat in both affluent and impoverished neighbourhoods. Community thermal vulnerability is often characterised by socio-demographic composition, with little consideration as places where people are unequally exposed to greenspace and how they associate with cooling disparities. Combining land surface temperature, this Antananarivo case study employed greenspace exposure Gini coefficient to map the locations of vulnerable neighbourhoods and evaluate how their cooling effect differ from others. Results show that nearly 25 % neighbourhoods were unequal where values of exposure to greenspace is disproportionately higher in some of grid cells than others, raising vulnerability to urban heat. These vulnerable neighbourhoods exhibited an average 0.01 °C greater cooling effect compared to the rest of more equal neighbourhoods. Specifically, main cooling role for vulnerable neighbourhoods is agricultural land with a 1 % coverage increase leading to a 0.02–0.03 °C temperature reduction in the day. Comparatively, the cooling effect for equal neighbourhoods relies on non-agricultural greenspace with 1 % coverage increase resulting in a 0.01–0.02 °C temperature reduction at night. Meanwhile, cooling models from 2017 and 2022 identified greenspace thresholds of 62% and 78% existing in equal neighbourhoods, which estimated to reduce average 0.78 °C, 1.24 °C nighttime temperature to bring equal neighbourhoods who were experiencing the high temperature to a more comfortable range regardless of any other factors. However, there was no thresholds detected in vulnerable neighbourhoods. Cooling disparities between vulnerable and equal neighbourhoods is influenced by factors of urbanisation, topology conditions, vegetation canopy, land cover, and day-to-night land surface temperature variations. These cooling disparities also depicted the trajectory of how neighbourhoods evolve from being equal to becoming vulnerable. Our findings emphasise the contributions of equitable greenspace distributions to urban heat mitigation and adaptation, implicating cooling strategies for marginalised communities in Antananarivo and other urban centres across Africa and beyond.