How the spatial pattern of urban form affects temperature adjustment ecosystem service using the InVEST urban cooling model in Tehran

Introduction: The increasing growth of population and as the rapid expansion of urbanization has caused extensive changes in cities morphology, climate and natural environment. The continuation of such a trend, increases the emission of greenhouse gases and leads to formation of heat islands in urban areas. In the future, urban heat island effect will be one of the main challenges to be managed in urban areas. To achieve sustainable development, it is very important to use long-term benefits of ecosystem services in city planning and designing. Ecosystem services are defined as "the cornerstone of sustainable development science" due to the focus on interaction between nature and society. Therefore, the mapping and quantification of important ecosystem services is a tool for decision-makers and country managers to manage and monitor the supply level of ecosystem services. Urban cooling capacity is one of the benefits of urban ecosystem services that help reducing urban heat island effects. The purpose of this research is to present the long-term benefits of using nature-based planning approach in reducing heat islands effect in Tehran.
Material and methods: In this research, Tehran is selected as the capital and also the most populous city of Iran, which has numerous heat islands focused on different activity centers. The cooling capacity of Tehran and its districts was evaluated using urban cooling capacity model in InVEST software, by statistical techniques such as Moran's correlation model and Gates-Ord model.
Results and discussion: Evaluating the Moran's correlation model showed the spatial pattern of temperature adjustment ecosystem services in Tehran is structured and clustered. The identification of ecosystem service hotspots using Gates-Ord model showed, Cooling in Tehran areas is influenced by two factors: altitude and vegetation cover. The presence of natural infrastructure and vegetation reduces heat island effect and also reduces urban temperature in some areas; which have large green and open spaces (including districts 4 and 22). The high density of population, building and traffic in streets (including districts 10, 11 and 12) has led to a decrease in cooling capacity of these areas, which shows the necessity of redefining urban features to control temperature. The northern areas of Tehran, including districts 1, 2 and 5, have low reference evaporation and transpiration due to their location at high altitudes and low temperatures. These districts always experience lower temperatures due to the rivers, natural waterways, large green spaces and low-rise residential structure. We can see the effect of northern regions ecosystem on neighboring regions such as district 3. The reason is low height of buildings, natural corridors between natural spots and the green spaces cohesion, which has caused the effect of temperature adjustment penetrate to adjacent areas.
Conclusion: The output of urban cooling model shows urban green and open spaces play a valuable role in reducing the heat island phenomenon. The high density of buildings and population, in other words, the high level of built-up lands in the central regions, has led to a decrease in cooling capacity of central districts. It is important to develop effective solutions to maintain ecosystem services and increase vegetation and continuous green patches to control temperature of big cities such as Tehran. At the end, Using nature-based planning approach and integration ecosystem services in city planning will significantly reduce the heat islands effects and bring long-term benefits to cities in different dimensions.