Abstract Summary
Currently, about 50% of the global population lives in urban settings, and by 2050 it is projected that the share will grow to 70% [1]. Urban areas are increasingly exposed to the impacts of climate change like frequent occurrence of extreme events e.g. heatwaves, strong winds, flash floods [2][3]. Parallelly, cities are affected by urban heat islands [4] what makes the urban thermal conditions an urgent issue to tackle towards healthy and resilient cities. Climate change challenges mentioned are within the interest of project Connecting Nature (H2020) aimed at positioning Europe as a global leader in the innovation and implementation of nature-based solutions. The City of Poznań together with Adam Mickiewicz University, as the project partners, monitor the impact of preschool gardens on local thermal conditions. Taking the above into account and a fact that certain demographic groups, such as children, are more sensitive to the health issues associated with urban living, particularly in combination with climate change [5-7], in this study we aim to recognize: 1) the thermal conditions of preschool gardens based on the land surface temperature (LST); 2) the potential of small-scale nature-based solutions (NbS) such as preschool gardens to lower the temperature at site scale (identification of cold island effect). In the study, we used Landsat 8 satellite images (5 scenes – bands 4, 5, and surface temperature layer based on band 10) taken in summer seasons in years 2018-2020 at 09.49 GMT during clear sky weather (cloudiness 0-1%) without radiation disturbances (e.g. precipitation, fast wind). As proposed by Majkowska et al. [8] we calculated average LST values for each pixel (aLST) to generate aLST distribution map for Poznań. In addition, we mapped the NDVI to group the gardens according to vegetation cover. Data on the number of kindergartens including public and non-public institutions, their location, and information on the number of children as of October 1, 2019, were obtained from the Education Department of the Poznań City Hall. The inputs were processed by using GIS software to measure the distribution of aLST in preschool gardens as well as to generate thermal profiles for 3 case studies. The results show that mean aLST for preschools with a low vegetation index (NDVI = 0,3, N=21, see Fig. 1). The average cooling effect of selected NbSs (N=3) was estimated at 0,2 - 0,3 oC (aLST) within distance of 45 m.
