Developing a composite index for urban ecosystem services (Hyrcanian forests-Gorgan)

Area of Science:

• Environmental science
• Urban ecology
• Ecosystem services assessment

Background:

• The Anthropocene is characterized by irreversible human impacts, including land use change and urban growth, which degrade ecosystem services (ESs).
• Gorgan has experienced significant environmental transformations, necessitating an understanding of their effects on ecosystem functions.
• Previous studies have not utilized hexagonal units for integrated ES assessment over extended periods.

Purpose of the Study:

• To investigate the spatiotemporal dynamics of urban ecosystem services (ESs) in Gorgan over 35 years.
• To develop and apply a composite total ecosystem services (TES) index to quantify and evaluate ES supply.
• To identify key drivers of ES changes and their consequences for urban environmental quality.

Main Methods:

• An integrated approach combining physical and ecological data was employed.
• A hexagonal unit system was utilized for the first time in this type of ES study.
• Six key ESs (water yield, flood control, net primary production, soil retention, carbon sequestration, air pollution removal) were modeled, quantified, and aggregated into a TES index.

Main Results:

• The total ecosystem services (TES) index in Gorgan decreased substantially, from 0.427 in 1985 to 0.192 in 2020.
• Hyrcanian forests provided the highest TES, while urbanized areas exhibited the lowest ES values.
• Declining ESs correlated with reduced air quality, increased flood risk, soil erosion, and ecological imbalances.

Conclusions:

• The composite TES index effectively quantifies overall ecosystem function and highlights critical environmental degradation.
• Urban expansion and land use change in Gorgan have led to a significant decline in vital ecosystem services.
• Addressing the ES shortage is crucial to mitigate environmental crises and promote sustainable urban development.