Analysis of Urban Green Spaces Based on Sentinel-2A: Case Studies from Slovakia

Abstract

Urban expansion and its ecological footprint increases globally at an unprecedented scale and consequently, the importance of urban greenery assessment grows. The diversity and quality of urban green spaces (UGS) and human well-being are tightly linked, and UGS provide a wide range of ecosystem services (e.g., urban heat mitigation, stormwater infiltration, food security, physical recreation). Analyses and inter-city comparison of UGS patterns and their functions requires not only detailed information on their relative quantity but also a closer examination of UGS in terms of quality and land use, which can be derived from the land cover composition and spatial structure. In this study, we present an approach to UGS extraction from newly available Sentinel-2A satellite imagery, provided in the frame of the European Copernicus program. We investigate and map the spatial distribution of UGS in three cities in Slovakia: Bratislava, Žilina and Trnava. Supervised maximum likelihood classification was used to identify UGS polygons. Based on their function and physiognomy, each UGS polygon was assigned to one of the fifteen classes, and each class was further described by the proportion of tree canopy and its ecosystem services. Our results document that the substantial part of UGS is covered by the class Urban greenery in family housing areas (mainly including privately-owned gardens) with the class abundance between 17.7% and 42.2% of the total UGS area. The presented case studies showed the possibilities of semi-automatic extraction of UGS classes from Sentinel-2A data that may improve the transfer of scientific knowledge to local urban environmental monitoring and management.

Urban Ecosystem Services Quantification through Remote Sensing Approach: A Systematic Review

“…Supporting services (habitats and genetic diversity) and cultural services (recreation and aesthetic contemplation) were generally obtained by interpreting urban green coverage and identifying significant localities for maintenance of local species of fauna and flora, as well as social interactions and social life, respectively [76,78,79]. The provision services were only related to fresh water and food supply which were identified through water bodies and urban agriculture in urban and peri-urban localities and mainly related to urban green coverage [9,16,33,65,67,[79][80][81][82].…”

“…LULC has the advantage of being a product that is more easily understood by readers; however, radiometric indexes calculation (such as NDVI, LAI, NDGB, and MNDWI), and methodologies directly related with interpretation of sensor's data, produces more accurate and well-defined results, strictly based on band math, irrespective of human interpretation [38,78,94]. These indexes have been used in some papers to increase the LULC accuracy from ML techniques [42,108].…”

Assessing the Ecosystem Services of Various Types of Urban Green Spaces Based on i-Tree Eco

“…Urban ecosystem services of green spaces have been identified, quantified, and assessed to inform taxpayers and support urban planning and decision-making processes [14][15][16][17][18][19][20]. However, urban ecosystem services are rarely involved in actual urban design and planning because of the lack of sufficient basic research about urban green space ecosystem services [21,22].…”

A Methodology to Monitor Urban Expansion and Green Space Change Using a Time Series of Multi-Sensor SPOT and Sentinel-2A Images

“…Additionally, the European Space Agency launched the Sentinel sensors, making it easier to obtain high-resolution satellite images [31]. Thus, many scholars use recent images provided by Sentinel satellites to monitor green space changes and urban expansion [32][33][34][35][36]. The use of SPOT imagery and these recently available data enables us to monitor urban expansion and green space change over long periods.…”