تحلیل ارزش‌گذاری خدمات اکوسیستم در فرایند رشد شتابان شهری مطالعه موردی: کلان‌شهر تهران

ABSTRACT
The rapid physical growth of Tehran metropolis over the past decades has made extensive changes in land use and had significant consequences on the value of urban ecosystem services. This study employs descriptive-analytical method to analyze the physical growth of Tehran and evaluate its impacts on the value of ecosystem services. The data used include images of Multispectral Scanner System (MSS), Landsat thematic mapper (TM) and Operational Land Imager (OLI) sensors in 1972, 1986, 2005, and 2024, which were classified in ENVI software after radiometric and atmospheric correction. The reference control points acquired from Google Earth were utilized to validate the classification results, and the error matrix and kappa index were calculated, which indicated the classification's high accuracy. Then, using the Castanza valuation model, the value of ecosystem services was calculated at each time period based on global coefficients (dollar per hectare per year). The results demonstrate that the physical growth of the city has increased from 14559 hectares in 1972 to more than 68645 hectares in 2024; This amount of physical growth has led to a substantial reduction in agricultural uses, pastures, and orchards, a total of $ 266 million of the net worth of ecosystem services. The largest decline was related to support, regulatory, and supplier services such as soil conservation, biodiversity, food production, and climate regulation. In contrast, the restricted increase in urban green infrastructure has not been able to compensate lost natural performance. These findings indicate that Tehran is on the path of instability due to the loss of natural capital and ecological functions.
Extended Abstract
Introduction
Urbanization is one of the most imperative transformational trends of the 21st century, which, beyond rural-urban migration, fundamentally has changed lifestyle, economic structures, and land use patterns. This phenomenon not only upsurges the concentration of population, but also with the physical expansion of cities, affects natural systems and changes the ecological structure of the land. The gradual destruction of urban ecosystem services is a key consequence of urbanization. Ecosystem services, as tangible or intangible benefits of ecological functions, shape the backbone of urban sustainability and health. These services include food supply, temperature regulation, runoff reduction, air refining, carbon storage, biodiversity support, and the cultural and psychological values of natural spaces. Numerous studies have warned that urban development, regardless of these services, has consequences such as heat islands, increased floods, reduced air quality, and decline in the mental health of residents.
Urban ecosystem services can be evaluated in four dimensions: economic, regulatory-environmental, socio-cultural, and urban resilience. Ignoring these dimensions, particularly in developing countries, has led to spatial instability; Therefore, the integration of multiple values of ecosystem services is an inevitable necessity in urban planning. In Iran, despite the rapid growth of urbanization, the concept of urban ecosystem services has not been seriously considered in spatial policies and urban plans. The development of cities is mainly based on physical and functional indicators, and the lack of ecological analysis and valuation of ecosystem services is absolutely obvious. During the last half century, the metropolis of Tehran has witnessed widespread physical growth and severe land use changes, which has been accompanied by the removal of large parts of agricultural land, gardens, and natural open spaces. Tehran’s urban area, as the epicenter of political, economic, industrial, and demographics of Iran, has suffered rapid and extensive changes in its spatial, physical, and environmental structure in recent decades. This city, which has over 16 million population and makes up about 20% of Iran’s population, has become one of the most complex metropolitan areas in the Middle East following the campaigns of urban modernization, land reform, rising oil revenues, rapid growth of industry and infrastructure. The region's share of Iran's GDP is over 25% and the value of its industrial production is close to 23%, which indicates a very high concentration of economic, administrative, and service activities. Nevertheless, unruly physical growth, the sporadic expansion of formal and informal settlements, drastic changes in land use, and the destruction of natural resources have had serious environmental consequences. The hysterical development of the city, regardless of available natural capacity, is not only a threat to environmental sustainability, but also reduces vital services such as urban temperature regulation, runoff control, and the quality of life. Accordingly, the purpose is to analyze the impacts of physical growth in Tehran on the value of urban ecosystem services and provide solutions to reform this trend in order to bolster sustainability and ecological rehabilitation.
 
Methodology
This applied research adopts a descriptive-analytical approach and a combination of remote sensing techniques and spatial analysis. Landsat satellite images of MSS, TM and OLI sensors were employed for the years 1972, 1986, 2005, and 2024. The pre-processing of images including radiometric and atmospheric corrections executed in ENVI software and then with the supervised classification algorithm, seven land use categories were extracted. The basis for determining land use classes in the study area has been a set of scientific and applied factors. The selection of classes was completed according to the purpose of the research, resolution and spectral characteristics of satellite images, classification structures presented in valid domestic and international studies, as well as utilizing the specialized perspective of professors and experts in the field of remote sensing and urban planning. The accuracy assessment using the Kappa coefficient indicates values above 0.84 in all time periods, which demonstrates a high classification reliability. Ecosystem services were evaluated based on the Castanza model and global value coefficients for each user class. An integrated approach has been adopted in the process of valuing ecosystem services, based on a systematic review of credible international sources.
For this purpose, data obtained from reference studies such as De Grot, Castanza et al., as well as the results of 13 other selected studies were collected and analyzed that have directly addressed the economic evaluation of ecosystem services. In each case, the lowest and highest estimated value was extracted for each user class and each type of ecosystem service (in dollars per hectare per year). Then, by calculating the average of this price range, the normalized amount was determined as the base coefficient of the value of ecosystem services, which was founded on the calculation of the total value of services in the region. This approach, while considering the heterogeneities in valuation methods in different sources, has made it possible to have a coherent, realistic, and comparable evaluation of ecosystem services in the urban area. Sensitivity analysis was also utilized with three pessimistic, basic, and optimistic scenarios and linear regression modeling employed to investigate the relationship between the physical growth of the city and the value of ecosystem services.
 
Results and Discussion
The results indicate that Tehran, during the period of 1972 to 2024, has experienced unprecedented physical growth leading to a fundamental change in the land use structure and consequently the weakening of ecosystem services. The urban area of Tehran has increased from 14559 hectares in 1972 to 68645 hectares in 2024, which is equivalent to a net growth of 54086 hectares. In contrast, agricultural lands, orchards, and pastures have been totally reduced more than 55,000 hectares. From the ecological point of view, a fundamental change undergone in the spatial structure of the urban landscape. The share of urban land has amplified from 6.65% in 1972 to 34.31% in 2024 (increase more than 24%), which indicates the explosive growth of artificial development and the compression of man-made fabrics in the natural bed.
This profound change in the structure of the landscape has led to a net reduction of $266 million in the value of ecosystem services. In 1972, the total value of ecosystem services was about $ 804 million, most of which belonged to agricultural uses (approximately $303 million) and pastures ($266 million). Such a huge number demonstrates that in the 1970s, the natural-agricultural composition of urban and peripheral lands played a pivotal role in providing ecological services such as water regulation, food production, biodiversity preservation, and climatic balance. In the beginning of 1986, despite the relative preservation of the share of natural uses, a significant reduction detected in the value of pastures (about 10%). In 2006, the trend of devaluation of ecosystems intensified, the value of pastures diminished to about $176 million compared to 1972, and the value of agriculture reached $224 million. The obtained value of services from orchards is $67 million. The reduction, which indicates the destruction of garden lands and the replacement of them with urban development and growth, data from 2024 clearly illustrate the extensive and continuous impact of urbanization on the ecological structure of the region. The value of pastures has decreased to about $95 million and agriculture to $187 million, which indicates a decrease of 60% compared to 1972. In contrast, the value of urban green infrastructure has risen to about $141 million, possibly due to the development of parks, green belts, and new environmental policies at the urban management level.
The key point is that while green infrastructure plays a significant role in improving the quality of life of citizens, they are not a perfect alternative to natural ecosystems from an ecological and environmental perspective. Services such as material cycles, soil conservation, flood control, and carbon storage can only be provided through pasture, forest, and sustainable agriculture. In general, the value of ecosystem services from $804 million in 1972 reached $538 million, which shows a reduction of $266 million. The sensitivity analysis, to augment the validity of the results, accomplished with three scenarios of pessimistic (-25%), basic (0%), and optimistic (+25%) on global Castanza coefficients. The results exhibited the net decline regarding the value of ecosystem services in the pessimistic scenario is about $199 million and in the optimistic scenario more than $325 million. Despite the numerical differences, in all three scenarios, the trend of sharp decline is confirmed in the value of ecosystem services due to physical growth in Tehran, which indicates the validity and stability of the research results. To calculate the net reduction of service value, the sum of the decreasing values deducted from the added values.
According to the five types of land use (agriculture, gardens, pastures, green infrastructure, water resources), the first three types recorded a significant decline and the second two types had a relative increase. The total devaluation estimated $289,072,484 and the total increase was $24,677,244; Therefore, the net loss is estimated at $266/395 indicating a widespread erosion of ecosystem services in Tehran. The biggest decline, in terms of service type, occurred in the area of support and regulatory services: "Habitat" (reduction more than $45.9 million), "Genetic Resources" (more than $65 million), "Climate Regulation" (more than $9.3 million). "Waste Refining" (more than $12.2 million), "Erosion Control" (more than $2.3 million), and "Soil Formation" (more than $11 million). In the realm of supplier services, "food Production" (more than $96 million) and "water Supply" (more than $9.6 million) fell sharply, warning of the threat of food security and growing dependence on external resources.
The development of green infrastructure and water resources, although it has created a limited rise in services such as "recreation" (about $4 million), "water Regulation", and "pollination", but these increases are insignificant and unrestrained compared to the damage to habitats and food resources. They do not compensate for the ecological performance of the lost natural uses. In this regard, the rapid urbanization of Tehran through severe land reduction with ecological performance and replacement with artificial structures, has reduced viability, weakened resilience to climate change, water shortage and biological stress, and erosion of ecosystem services. A review of land use policies, purposeful development of continuous green infrastructure, and revitalization of ecosystem service functions should be at the heart of future urban planning strategies. Linear regression analysis indicates that the coefficient of determination is equal to 0.812, which means that more than 81% of the changes in the devaluation of ecosystem services are explained due to the physical expansion of the city. This finding approves the negative and strong impact of rapid and scattered urban growth on the performance of ecosystem services in Tehran.
 
Conclusion
Land use changes to meet the infrastructure requirements of the urban population, especially with inefficient planning, lead to ecosystem degradation, biodiversity reduction, and the weakening of potential ecosystem services. Tehran's physical growth over the past five decades has experienced a rapid, unruly, and lacking ecological perspective. Significant reduction of pastures (64%), agricultural land (more than 50%), and orchards are a sign of systematic destruction of natural resources and a sharp decrease in the capacity of ecosystem services. The total value lost of natural uses (agriculture, pastures, orchards) is estimated at $289 million, while the added value of green infrastructure and water storages is only $24.6 million, indicating the inability of artificial infrastructure to compensate for natural functions.
The biggest devaluation was related to regulatory and support services: soil conservation ($13.1 million), wastewater treatment ($12.2 million), biodiversity ($6.5 million), genetic resources ($65.2 million), and wildlife habitats (45.9 million dollar). Supply services, including food production ($96.6 million) and water supply ($9.6 million), reduce food security and put pressure on water resources. Even cultural services such as entertainment have declined. Linear regression analysis showed that the physical growth of the city has a negative and significant effect on the value of ecosystem services (81% explanation of variance).
The loss of these services has increased natural hazards (floods, air pollution, urban warming), declining public health and exacerbating urban instability. The inadequate expansion of green infrastructure and aquatic zones failed to compensate for the functional role of lost natural ecosystems; artificial infrastructure has never been a substitute for complicated and self-regulating processes of nature. In the realm of policy, the results are a serious alarm for the capital's viability. A fundamental revision of planning approaches, moving from physical planning to ecosystem-based planning, rehabilitating destroyed lands, stabilizing continuous green spaces, strengthening green and blue infrastructure, and introducing the economic, cultural, and social dimensions of ecosystem services is essential to decision-making processes. Tehran still has the opportunity to recreate and recover ecologically through commitment of urban management to integrate ecological knowledge with urban policy and the participation of urban society in the protection and reconstruction of natural capital.
 
Funding
There is no funding support.
 
Authors’ Contribution
This article is derived from the first author’s (Ahmad Hatami) doctoral dissertation. He carried out all stages of the research, including writing the text, data processing, analyses, and extraction of results. Dr. Hossein Mansourian (primary supervisor) contributed to developing the conceptual model, refining the problem statement and article texts, as well as the remote sensing process and map production. Dr. Hossein Hataminejad (secondary supervisor) and Dr. Ahmad Pourahmad (advisor) played roles in scientific guidance, overseeing the research process, and the final review of the article.
 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
We are grateful to all the scientific consultants of this paper.