Modeling the cooling effect of urban green infrastructures with an ecosystem services approach ( case study: Tehran metropolis)

Abstract

ABSTRACT:BACKGROUND AND OBJECTIVES: The heating of inner cities is an immense global phenomenon, and urban green spaces are crucial in mitigating this predicament. This study evaluates the cooling effects of urban green infrastructures in a dry region, specifically the Middle East by analyzing Tehran, a metropolis severely impacted by urban heating. We use advanced methodologies to estimate regulating ecosystem services.METHODS: This research employed a multi-stage methodology utilizing satellite data and in-situ measurements. Land use/land cover maps of Tehran were generated using Landsat imagery from Thematic Mapper (2002), Enhanced Thematic Mapper Plus (2012), and Operational Land Imager (2022), processed with geometric and radiometric corrections in ENVI 5.3. A supervised classification via the Super Vector Machine algorithm identified four land use categories: built-up areas, barren lands, green spaces, and water bodies. The cooling effects of these land uses, analyzed using the InVEST ecosystem service software, were assessed over the 2002-2022 period, incorporating variables such as evapotranspiration, temperature, and shading effects.FINDINGS: The results showed a decline in green spaces from 13.1% in 2002 to 11.9% in 2012 and 11.8% in 2022, with a projected further decline to 11.7% by 2032. The reduction rate was significant in the first decade, with a loss of 717 hectares, compared to 14 hectares in the second decade. An additional reduction of 66 hectares is predicted over the next decade. The Urban Heat Mitigation Index was highest in the green District 22 with values of 0.91, 0.79, and 0.66, respectively, and lowest in District 10 with values of 0.22, 0.21, and 0.19. Projections for 2032 suggest that District 22 will maintain the highest cooling capacity at 0.65, while District 10 will remain the lowest at 0.19.CONCLUSION: This study highlights the critical relationship between urban development and green infrastructure. It particularly underscores the importance of preserving green infrastructure as a means to mitigate urban heat, with a focus on its influence on Tehran's microclimate and overall environmental quality. The findings indicate a worrying decline in green spaces, posing significant challenges for urban environmental management. This persistent loss of natural areas undermines ecological stability and urban resilience, especially in terms of heat mitigation and quality of life. Additionally, the uneven distribution of green spaces exacerbates vulnerability in specific Districts, emphasizing the pressing need for sustainable urban planning in Tehran. This study assessed past and future changes to provide valuable insights for urban decision-makers and managers.