Developing a Composite index for Urban Ecosystem Services (Hyrcanian Forests‐Gorgan)

ABSTRACT

The current era has been termed the “Anthropocene”, resulting in the irreversible impact of human activities. Land use change (LCU) and urban growth are examples of these disturbances leading to the reduction of many ecosystem services (ESs). The subject of this study, Gorgan, has undergone significant changes that significantly impacted the area. Studying these changes and understanding their effects on the ecosystem is essential. An integrated method was used to investigate the process of changing the urban ESs over 35 years, taking into account the physical and ecological characteristics of the area. This marks the first time such a study has been conducted in the hexagon unit. Then, the composite Total Ecosystem Services (TES) index was calculated from the modelled and quantified combination of six ESs, including Water yield, Flood volume, Net Primary Production, Soil retention, Carbon sequestration, and Air pollution removal. Afterward, the ESs were mapped and evaluated across time and space. The TES is proposed as an appropriate measure for quantifying ESs supply and can indicate the overall function of ESs. According to the findings, the TES value declined from 0.427 in 1985 to 0.247 in 2005 and reached 0.192 in 2020. Moreover, the Hyrcanian forests were the main source of the highest TES in Gorgan city, while urban areas had the lowest levels. The shortage of ESs in the study area has resulted in various crises. These include reduced air quality, heightened flood risk, soil erosion, and ecological imbalances in urban regions.