Multifunctional Evaluation of Urban Green Infrastructure for Combating Climate Change: A Case of Sancaktepe District in Istanbul Metropolitan City

Urban areas worldwide are increasingly facing environmental challenges due to rapid urbanization and climate change. Phenomena such as urban heat islands (UHI), carbon emissions, and biodiversity loss significantly impact human health and urban livability. In response, Urban Green Infrastructure (UGI) has emerged as a key strategy, linking environmental sustainability with spatial planning to promote climate resilience and sustainable development. This study evaluates the multifunctional effectiveness of UGI in mitigating climate - related impacts in Sancaktepe, a rapidly urbanizing district in Istanbul that has developed informally over environmentally sensitive land. Despite these pressures, Sancaktepe demonstrates substantial UGI potential, as indicated by data from the Istanbul Green Area Management System (YAYSIS). The evaluation focuses on four main functions: UHI mitigation, biodiversity enhancement, ecological corridor potential, and carbon sequestration. Land Surface Temperature (LST) was used to assess UHI mitigation capacity, and results show that natural vegetative zones maintain significantly lower surface temperatures than plantation areas, emphasizing the cooling effect of mature green systems. Biodiversity assessment revealed that the district includes 224 plant taxa and 10 endemic species, primarily concentrated in the Ömerli Basin and Aydos Forest. These preserved regions also support six distinct habitat types and reflect the district’s high ecological value. Carbon sequestration analysis indicates that plantation efforts across Sancaktepe's settlement areas contribute approximately 2,139,610 tons of carbon storage, although natural vegetation areas exhibit greater per - area sequestration capacity. A composite Urban Green Infrastructure Performance Index (UGI - PI) was developed to spatially synthesize these indicators using three parameters: Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), and Normalized Difference Built - up Index (NDBI). Each indicator was normalized, and the resulting index was classified into five performance categories using equal interval classification. The UGI - PI map reveals significant spatial variation: northern and eastern areas (including the Ömerli and Aydos zones) score very high in terms of UGI effectiveness, while central and southern urban neighborhoods score low due to high built - up intensity, reduced vegetation cover, and elevated surface temperatures. These low - performing areas are less effective under current conditions but may benefit from targeted small - scale interventions such as tree planting, vertical greening, and pocket parks. The integration of UGI - PI enhances the research by providing a spatial decision - support tool that identifies both conservation - priority zones and vulnerable areas requiring improvement. This framework not only evaluates the current performance of UGI systems but also contributes to strategic climate adaptation planning. The findings reinforce the need to protect natural vegetative zones while implementing targeted urban greening strategies in climate - stressed districts like Sancaktepe.