Optimizing the Valuation and Implementation Path of the Gross Ecosystem Product: A Case Study of Tonglu County, Hangzhou City

: Ecosystem products and services are fundamental to human survival and development. The gross ecosystem product can be defined as the total value of products and services provided by ecosystems for human wellbeing and sustainable socioeconomic development. This includes the value of production system products, ecosystem regulation services, and ecosystem cultural services. The valuation of gross ecosystem product offers crucial technical support for constructing mechanisms by which to realize them, and it holds significant importance in promoting the comprehensive green transformation of economic and social development. In this study, we introduce the definition and accounting methods of the gross ecosystem product and explore the application of the gross ecosystem product and ecosystem asset accounting in ecological benefit assessment, using Tonglu County in Hangzhou City, Zhejiang Province, as an example. Finally, we provide recommendations by which to strengthen gross ecosystem product accounting and explore mechanisms for realizing ecological values based on this foundation. The results indicate that in 2021, the total gross ecosystem product value of Tonglu County reached CNY 55.129 billion, equivalent to 1.33 times the gross domestic product of that year. Among the various services, regulatory services contributed the most to the total ecological products, with climate regulation being the largest contributor at CNY 27.199 billion, accounting for 49.34%. Tonglu County boasts abundant natural resources, which hold significant value. By conducting an audit of the total ecological products, we can precisely determine the value of the ecosystem. This aids relevant departments in estimating the value of ecological products in Tonglu County’s ecosystem. Such information can support the formulation of ecological protection and sustainable development policies in Tonglu County, while also serving as a reference for estimating the total ecological products and enhancing the ecological value in other counties.


Introduction
Ecosystem components and their ecological processes not only create and sustain the Earth's life support system, forming the necessary conditions for human survival and development, but also provide essential resources for human life, such as food, medicine, timber, and raw materials for industrial and agricultural production.The functions of ecosystem products and services are the foundation of human survival and development [1,2].However, in the process of economic and social development, activities such as resource exploitation, large-scale engineering construction, and environmental pollution have led to the degradation of ecosystem services and the destruction of ecosystems, exacerbating a series of environmental issues.This has become a major threat to the sustainable development of the economy and society, as well as to the living conditions of humanity.Since the 1990s, scientists have recognized the supporting role of ecosystems in human survival and development.They have discovered that the focus on the material products provided by natural ecosystems has led to insufficient appreciation of the value of ecosystem regulation services (such as water conservation, biodiversity protection, flood control, environmental purification, and climate regulation).This lack of recognition has hindered the transformation of these services into economic benefits, becoming a primary cause of environmental degradation [3].Consequently, global efforts have been made to conduct research on ecosystem services, evaluating the contributions of various ecosystems to human wellbeing.
Among these valuation studies, the most representative are those of Prof. Gretchen Daily [4] and Prof. Robert Costanza [5], who proposed in 1997 to quantify the services provided by ecosystems to human beings in terms of ecosystem service values.In 2001, the United Nations launched the Millennium Ecosystem Assessment (MA) [6] program, aiming to integrate ecological conservation goals into economic and social decision-making by evaluating ecosystem services on a global scale.In 2007, the European Union proposed the Economics of Ecosystems and Biodiversity Program (TEEB) [7]; in 2010, the World Bank proposed the Wealth Accounts and Valuation of Ecosystems Program (WAVES); and in 2014, the United Nations Statistics Division (UNSD) released a series of results such as Experimental Ecosystem Accounting (EEA) [8], which is based on the System of Environmental-Economic Accounting (SEEA) [9].Researchers have conducted numerous investigations with respect to ecological value accounting in terms of methodology and policy application.Among them, EEA involves valuing ecosystem services by dividing them into three categories: product provisioning, regulating services, and cultural services; this method has been widely applied.In China, Ouyang Zhiyun [1] also proposed the concept of the gross ecosystem product (GEP) on this basis.He observed that the GEP is the aggregated value of final ecosystem goods and services supplied annually to people in a given region, such as a country, a province, or a county.This was endorsed by the United Nations and has since been gradually refined to form harmonized standards and definitions.It was also employed in the accounting of provincial GEP in Guizhou Province in 2010, which set off a research boom in this field in China.The accounting of GEP originates from the concept of gross domestic product (GDP) and addresses the fact that GDP cannot fully reflect the contribution of nature to economic activities and human welfare; it has also become an important reference indicator for evaluating the performance of ecological civilization construction.A wide range of scholars have successively conducted GEP accounting studies on different ecosystems, such as forests [10], wetlands [11], grasslands [12], farmlands [13], and other ecosystems, and on different administrative scales, such as municipal [14], provincial [15], and watersheds [16].However, despite the fact that current studies on GEP are enriching, there are still some shortcomings.For example, many studies focus on GEP accounting for a single period of time or for a longer interval of years.In this way, the impacts of ecological policies and decisions on the accounting results are easily overlooked in relation to the results of the accounting, leading to the possibility of specificity in the results of the accounting.This means that the accounting results cannot comprehensively and objectively reflect the ecological potential of the study area.In addition, current GEP accounting mainly considers large-scale regions and individual ecosystems such as forests and grasslands, and there is a lack of smaller-scale GEP accounting studies for districts, counties, or specific regions.Hence, in this study, we focus on Tonglu County, accounting for its gross ecosystem product in 2021.This value serves as a key indicator supporting the assessment system for resource consumption, environmental damage, and ecological efficiency.We propose optimization suggestions for the realization pathway of ecological product value, aiming to establish it as the guiding force for the ecological performance in the construction of ecological civilization in Hangzhou.
Additionally, we seek to offer a reference for the accounting and realization pathway of ecological product values in other counties across China.

Study Area
Tonglu County, situated under the jurisdiction of Hangzhou City in Zhejiang Province, is positioned in the western part of the province.The topography features low hills, marked by the confluence of the Fenshui River and Fuchun River, and is surrounded by mountains on all sides.The central region comprises narrow valley plains, with interspersed hills scattered throughout the landscape.Geographically, Tonglu County falls between latitude 29 • 35 ′ and 30 • 05 ′ and east longitude 119 • 10 ′ and 119 • 58 ′ (Figure 1).The entire territorial expanse measures approximately 77 km in length from east to west and is around 55 km wide from north to south, encompassing a total area of 1825 square kilometers.The region experiences a subtropical monsoon climate characterized by four distinct seasons, abundant sunshine, and copious precipitation.The average annual temperature is recorded at 17.2 • C, and the average annual precipitation is 1588.7 mm.As of 2022, Tonglu County administratively comprised 4 streets, 6 towns, and 4 townships.This includes 181 administrative villages, 4 economic associations, and 37 communities.The household population is reported to be 419,200.
logical efficiency.We propose optimization suggestions for the realization pathway of ecological product value, aiming to establish it as the guiding force for the ecological performance in the construction of ecological civilization in Hangzhou.Additionally, we seek to offer a reference for the accounting and realization pathway of ecological product values in other counties across China.

Study Area
Tonglu County, situated under the jurisdiction of Hangzhou City in Zhejiang Province, is positioned in the western part of the province.The topography features low hills, marked by the confluence of the Fenshui River and Fuchun River, and is surrounded by mountains on all sides.The central region comprises narrow valley plains, with interspersed hills scattered throughout the landscape.Geographically, Tonglu County falls between latitude 29°35′ and 30°05′ and east longitude 119°10′ and 119°58′ (Figure 1).The entire territorial expanse measures approximately 77 km in length from east to west and is around 55 km wide from north to south, encompassing a total area of 1825 square kilometers.The region experiences a subtropical monsoon climate characterized by four distinct seasons, abundant sunshine, and copious precipitation.The average annual temperature is recorded at 17.2 °C, and the average annual precipitation is 1588.7 mm.As of 2022, Tonglu County administratively comprised 4 streets, 6 towns, and 4 townships.This includes 181 administrative villages, 4 economic associations, and 37 communities.The household population is reported to be 419,200.General Secretary Xi Jinping, during his tenure as Secretary of the Zhejiang Provincial Party Committee, emphasized the significance of nature in his statement, "Clear waters and green mountains are as valuable as mountains of gold and silver."Over the past decade, Tonglu County has been steadfast in addressing the delicate balance between "green mountains" and "golden mountains."Through the realization of the value of ecological products, the county aims to transform its "green mountains" into "golden mountains."When carrying out GEP accounting, assessing the ecological and economic value General Secretary Xi Jinping, during his tenure as Secretary of the Zhejiang Provincial Party Committee, emphasized the significance of nature in his statement, "Clear waters and green mountains are as valuable as mountains of gold and silver".Over the past decade, Tonglu County has been steadfast in addressing the delicate balance between "green mountains" and "golden mountains".Through the realization of the value of ecological products, the county aims to transform its "green mountains" into "golden mountains".When carrying out GEP accounting, assessing the ecological and economic value of "clear waters and green mountains" and monitoring and evaluating the effectiveness of ecological protection are important initiatives.These will help with the implementation of the construction of ecological civilization in Tonglu County, exploring the mechanism of realizing the value of ecological products, and promoting the harmonious development of humans and nature.

Data Sources and Pre-Processing
In order to better calculate the total ecosystem value of Tonglu County in 2021, we collected and integrated multiple data sources, including statistical data, price reference data, and geospatial data.Statistical data, covering agriculture, forestry, animal husbandry, and fishery output, as well as reservoir and pond capacity, were sourced from various government bulletins of Tonglu County.Price reference data, encompassing water price, electricity price, reservoir construction cost, etc., were gathered through thorough market research and literature reviews.Geospatial data play a pivotal role in this study, with Tonglu County's land cover data, featuring a spatial resolution of 30 m, obtained from the Third National Land Survey database.NDVI and NPP, which are crucial indicators, were derived from MODIS data products of the National Aeronautics and Space Administration (https: //ladsweb.modaps.eosdis.nasa.gov/,accessed on 17 May 2023), with spatial resolutions of 1 km and 500 m, respectively.Digital elevation data were acquired from the Geospatial Data Cloud Platform (http://www.digitalelevationdata.com)and accessed on 7 May 2023, with a spatial resolution of 30 m, through the Geospatial Data Cloud Platform (gscloud.cn/,accessed on 10 May 2023).Adhering to accounting guidelines, all the aforementioned data were uniformly projected onto the CGCS2000_GK_Zone_40 coordinate system in ArcGIS 10.8, and raster data were standardized to a 30 m resolution.
According to the investigation and analysis, combined with the characteristics of the ecosystem of Tonglu County, based on the three land types, the spatial resolution was 30 m, and the land areas of Tonglu County were divided into five types of ecosystems: forest ecosystem, wetland ecosystem, farmland ecosystem, urban ecosystem, grassland ecosystem, and other land areas (Figure 2).As can be seen from Table 1, among the major ecosystems in Tonglu County, the forest ecosystem has the largest area of 1395 km 2 , accounting for 76%, followed by the farmland ecosystem with 224 km 2 , accounting for 12% (Table 1).

Technological Route
The value accounting framework of ecological products in this study is shown in Figure 3.The gross ecosystem product of Tonglu County was calculated from two perspectives: functional quantity and value quantity.First of all, we determined the geographical scope of accounting, clarified the ecosystem distribution, and compiled a list of ecological products.Then, we collected ecological environment, hydrological, and meteorological monitoring data, as well as statistical data pertaining to functional departments, and preliminarily calculated the functional quantity of various ecosystem material products and services.Next, the price of ecological products and services was determined according to the pricing table of the total ecosystem production of Zhejiang Province and the consumer price index of Zhejiang Province, and the values of various ecosystem material products and services were calculated.Finally, based on the functional quantity and pricing of various ecological products and services in Tonglu County, the total ecosystem product value was calculated.The specific accounting methods in this study primarily adhere to two government-published standard documents: "Ecosystem Assessment Gross Ecosystem Product (GEP) Accounting Technical Specification" [17] and "Gross Ecosystem Product (GEP) Accounting Technical Specification for Terrestrial Ecosystems-Local Standard of Zhejiang Province" [18].

Ecosystem Product Supply
Material products refer to the products that humans obtain from the ecosystem and can be traded in the market to meet the material needs of human life, production, and development, including agricultural, forestry, animal husbandry, fishery, and other products, as well as ecological energy.The accounting data with respect to the direct use of supply products in such product categories were obtained from the agriculture, forestry, animal husbandry, and fishery section of the Statistical Yearbook of Tonglu County 2022 [19], and the renewable energy data in respect of the conversion and utilization of supply products: photoelectric and hydropower data were taken from the "14th Five-Year Plan"

Ecosystem Product Supply
Material products refer to the products that humans obtain from the ecosystem and can be traded in the market to meet the material needs of human life, production, and development, including agricultural, forestry, animal husbandry, fishery, and other products, as well as ecological energy.The accounting data with respect to the direct use of supply products in such product categories were obtained from the agriculture, forestry, animal husbandry, and fishery section of the Statistical Yearbook of Tonglu County 2022 [19], and the renewable energy data in respect of the conversion and utilization of supply products: photoelectric and hydropower data were taken from the "14th Five-Year Plan" of Tonglu County Power Grid Development [20].Since the ecosystem material products can be traded in the market and there are corresponding market prices, we used the market value method to calculate the value of the ecosystem material products and services [21].The calculation followed Formula (1): where EMPV is the value of ecosystem material products (yuan/a); E i is the production of ecosystem products of category i (determined according to the unit of measurement of the product, e.g., kg/a), and P i is the price of ecosystem products of category i (determined according to the unit of measurement of the product, e.g., yuan/kg).
It is estimated that in 2021, the value of ecosystem products provided by Tonglu County was CNY 3.93 billion, of which the value of agricultural products was CNY 2.67 billion, the value of forestry products was CNY 471 million, the value of animal husbandry products was CNY 428 million, and the value of fishery products was CNY 213 million.Among the renewable energy sources, the total amount of hydropower was 175 million kWh, the total amount of photoelectric was 99 million kWh, and the total value of the two was CNY 148 million (Table 2).

Regulating Service Value
Ecosystems play a crucial role in enhancing human survival and improving the living environment, exerting significant influence on both economic and environmental sustainability [22], such as regulating climate, conserving water, maintaining soil, regulating flood water, degrading pollutants, fixing carbon dioxide, and providing oxygen.In this paper, the market value method [23], shadow engineering method [10], and alternative cost method [24] (Table 3) are used to calculate the value of various regulatory services in the ecosystem.The calculation is based on Formula (2): where ERV is the value of ecosystem regulation services; V wr is the value of water conservation (CNY/a); V sr is the value of ecosystem soil conservation (CNY/a); V f m is the value of ecosystem flood storage (CNY/a); V C f is the value of ecosystem carbon sequestration (CNY/a); V op is the value of ecosystem oxygen release (CNY/a); V a is the value of ecosystem atmospheric cleanup (CNY/a); V w is the value of ecosystem water cleanup (CNY/a); and V tt is the value of ecosystem climate regulation (CNY/a).When using the market value method, alternative cost method, and other value accounting methods, and using the current price to determine the reference price of each kind of ecological product, performing a multi-year comparison can determine the base year constant price.Some of the prices, such as water price, desilting project cost per unit reservoir capacity, project cost per unit reservoir capacity, and electricity price, were selected from the recommended price in the Technical Specification for the Accounting of Gross Ecosystem Product Terrestrial Ecosystem-Local Standard of Zhejiang Province [18] (Table 4).
It is estimated that in 2021, the value of ecosystem products provided by Tonglu County was CNY 41.78 billion (Table 4), including CNY 1.796 billion for water conservation, CNY 1.164 billion for soil conservation, and CNY 9.436 billion for flood regulation and storage.The value of four services, i.e., water purification, air purification, carbon fixation, and oxygen release, was less, totaling CNY 222 million.The value of climate regulation was the highest, at CNY 27.199 billion.

Water Conservation
Ecosystems throughout the forest canopy layer, dead wood layer, and soil layer intercept and store precipitation, effectively storing soil moisture and replenishing groundwater.The amount of water conservation can be calculated using the water balance method to determine the amount of water conservation; this refers to the ecosystem interception of precipitation and culinary storage runoff [25].The provision of water resources and their economic value can be calculated using the shadow engineering method; that is, a simulation of the construction of the storage and ecosystems that are equivalent to the amount of water conservancy facilities can be used to determine the cost of the water conservancy facilities and the conservancy value of water.These indicators can be used to determine the price of the reservoir capacity and the cost of the project [17].The calculation is set out in Formula (3): where V wr is the water conservation value (CNY/a), Q wr is the total water conservation volume in the accounting area (m 3 /a), and C is the water price (CNY/m 3 ).Q wr is calculated through the water balance equation.The water balance equation refers to the conservation of the mass of water in an ecosystem over a certain space and time, i.e., ecosystem water conservation is the difference between precipitation inputs and stormwater runoff and the ecosystem's own water consumption, accounted for in Equation (4): where Q wr is the amount of water retention (m 3 /a), P i is the amount of flow-producing rainfall (mm/a), R i is the amount of surface runoff (mm/a), and ET i is the amount of evapotranspiration (mm/a).A i is the area of ecosystems of type i (m 2 ), i is the type of ecosystem, and n is the total number of ecosystem types.
According to the estimation, in 2021, Tonglu County's ecosystem water conservation volume was 1.796 billion m 3 , the water price was CNY 1.00/m 3 , and the value of water conservation was CNY 1.796 billion.

Soil Conservation
The soil conservation function represents the ability of ecosystems (e.g., forests, grasslands, etc.) to protect the soil, abate the erosive power of rainfall, increase the erosion resistance of the soil, reduce soil erosion, and maintain the soil through the various layers of the forest canopy, litter, and the root system [26].The value of soil conservation mainly includes the value of reducing surface source pollution and reducing sediment deposition.Because of the lack of corresponding data to support the measurement of surface source pollution, the value of the soil conservation function is obtained through the alternative cost method and is evaluated from the viewpoint of reducing sedimentation [17].It is calculated according to Formula (5): where V sr is the ecosystem soil conservation value (CNY/a); Q sr is the amount of soil conservation (t/a); C is the cost of a desilting project per unit of reservoir (CNY/m 3 ); ρ is the soil capacity weight (t/m 3 ); and λ is the coefficient of sediment siltation.Soil retention Q sr is calculated primarily based on the revised universal soil erosion equation (RUSLE) [27], i.e., Equation ( 6): where Q sr is the amount of soil retention (t/a); P is the rainfall erosivity factor, which is expressed as the multi-year average annual rainfall erosivity index; K is the soil erodibility factor, which is usually expressed as the amount of soil loss caused by the unit rainfall erosivity on a standard sample; L is the slope length factor; S is the slope gradient factor; C is the vegetation cover and management factor; and P is the factor of the soil and water conservation measures.After accounting, Tonglu County's soil retention totals 238 million tons.The average soil capacity is 1.18 t/m 3 [25], the sediment siltation coefficient is 0.24 (the national soil erosion loss of sediment comprises 24% siltation in reservoirs, rivers, and lakes [28]), the cost of reservoir dredging is 26.27CNY/m 3 [18], and we estimate the value of the soil retention function as CNY 1.164 billion.

Flood Control
Flood control represents the ability of natural ecosystems to mitigate the threat and damage caused by flood peaks during the flood season by absorbing large quantities of precipitation and transit water, storing flood peak water, and reducing and lagging flood peaks, relying on their special hydrophysical properties [18].The flood storage value is calculated according to Equation ( 7): where V f m is the ecosystem flood storage value (CNY/a); C f m is the ecosystem flood storage volume (m 3 /a); and C we is the engineering cost and maintenance cost per unit of reservoir capacity (CNY/m 3 ).C f m is calculated according to Equation (8): where C f m is the flood storage volume (m 3 /a); C vc is the vegetation flood storage volume (m 3 /a); C rc is the reservoir pond flood storage volume (m 3 /a); C lc is the lake flood storage volume (m 3 /a); and C mc is the marsh flood storage volume (m 3 /a).C vc , i.e., the vegetation flood storage, is calculated according to Formula (9): where C vc is the vegetation flood storage volume (m 3 /a); P h is the heavy rainfall production rainfall (mm); R f i is the surface runoff volume generated by the ith ecosystem (mm); S iv is the area of the ith natural vegetation ecosystem (km 2 ); and i is the natural vegetation ecosystem type.C rc , the flood storage capacity of the reservoir and pond, is calculated using the actual flood storage capacity of the reservoir and pond wetland.This is calculated by assuming 35% of its total storage capacity [29] and using Equation ( 10): where C rc is the reservoir flood control capacity (m 3 /a); C t is the total reservoir capacity (m 3 ).Note: There are no lakes and swamps in the territory of Tonglu County, so C lc and C mc were not calculated.
According to the calculation, in 2021, the total reservoir capacity of Tonglu County was 9.38 m 3 , the flood storage volume of the reservoir and pond was 328 million m 3 , and with comprehensive use of the above parameters, the total flood storage volume of Tonglu County was calculated as 364 million m 3 .Using the shadow engineering method, the cost of the reservoir unit capacity was calculated as 25.89 CNY/m 3 , and the value of flood storage was calculated to be CNY 9.424 billion.

Water Purification
The water purification function refers to the function of wetland ecosystems in lakes, rivers, marshes, and other waters to adsorb, degrade, and transform water pollutants and purify the water environment.The generation of substantial waste from human activities has a significant environmental impact, highlighting the need for researchers to study waste management services for the sake of sustainable development [30].For data reasons, we only considered the value of Tonglu County ecosystems in purifying ammonia nitrogen and COD.According to the literature [16], Tonglu County pollutant emissions did not exceed the environmental function of surface water standard limits, so the use of pollutant emission accounting and the use of the alternative cost method allow us to determine the accounting ecosystem water quality purification value [18] according to Formula (11): where V w is the value of ecosystem water quality purification (CNY/a); Q wpi is the purification amount of water pollutants of category i (t/a); C i is the unit cost of treatment of water pollutants of category i (CNY/t); i is the pollutant class of a water body of category i in the study area; and n is the number of pollutant classes of a water body in the study area.
It is estimated that in 2021, Tonglu County discharged 0.84 tons of ammonia nitrogen and 38.64 tons of COD.After using the alternative cost method, the treatment cost of ammonia nitrogen was 8000 CNY/t and the treatment cost of COD was 9572.92CNY/t.Combined with the above parameters, the value of the water purification function was calculated to be CNY 320,000.

Air Purification
The air purification function refers to the ability of ecosystems to absorb, filter, block, and decompose atmospheric pollutants (e.g., sulfur dioxide, nitrogen oxides, particulate matter, etc.), purify air pollutants, and improve the atmospheric environment.In this study, we only considered the value of Tonglu County ecosystems for absorbing SO 2 and NO x .According to the literature [18], it is known that Tonglu County pollutant emissions do not exceed the quality standards of the ambient air functional area, so the use of pollutant emissions to account for the physical volume and the use of the alternative cost method (industrial management of air pollutant costs) can account for the value of ecosystem air purification [18], as per Equation ( 12): where V a is the value of ecosystem atmospheric purification (CNY/a); Q api is the purification amount of the ith type of atmospheric pollutant (t/a), i is the atmospheric pollutant category; C i is the cost of treatment of atmospheric pollutants of the ith category (CNY/t); n is the number of pollutant categories of the water body in the study area.
It is estimated that in 2021, Tonglu County emitted 150.03 tons of SO 2 and 1277.92tons of NO x .By applying the alternative cost method, the treatment cost of SO 2 was estimated at 2000 CNY/t and the treatment cost of NO x was estimated at 2518.25 CNY/t.Combined with the above parameters, the value of the air purification function was calculated to be CNY 3.52 million.

Carbon Sequestration
The function of ecosystem carbon sequestration refers to the ability of natural ecosystems to absorb carbon dioxide (CO 2 ) from the atmosphere to synthesize organic matter and change the amount of carbon in plants or soil.This function is conducive to reducing the concentration of carbon dioxide in the atmosphere and slowing down the greenhouse effect.The carbon sequestration function of ecosystems is of great significance in reducing the pressure of emission reduction.The amount of fixed carbon dioxide was selected as the evaluation index of ecosystem carbon sequestration, and it was calculated using the net ecosystem productivity method, which involved converting the relevant conversion coefficients of net primary productivity (NPP) and net ecosystem productivity (NEP) [17].Then, the mass of fixed carbon dioxide in terrestrial ecosystems was measured according to Equation (13): where V C f is the value of carbon sequestered by ecosystems (CNY/a); Q CO 2 is the total amount of carbon sequestered by ecosystems (t-CO 2 /a); and C C is the carbon price (CNY/t).Terrestrial ecosystems fix carbon dioxide, and this can be calculated using the net ecosystem productivity estimation method according to Formula (14): where Q CO 2 is the amount of carbon sequestered by terrestrial ecosystems (t-CO 2 /a); M CO 2 /M C is defined above; and NEP is the net ecosystem productivity (t-C/a).NEP is calculated according to Equation (15): where NEP is the net ecosystem productivity (t-C/a); α is the conversion coefficient of NEP and NPP; and NPP is the net primary productivity (t-dry matter/a); M C 6 /M C 6 H 10 O 5 = 72/162 is the coefficient of dry matter converted to C.
It is estimated that the total amount of carbon sequestered in the ecosystem of Tonglu County in 2021 was 2.432 million tons.Using the market value method, the carbon trading price was estimated at 23.72 CNY/t, and the value of carbon sequestration was estimated to be CNY 0.58 billion.

Oxygenation
The oxygen-releasing function of ecosystems refers to the ability of plants to release oxygen during photosynthesis.This function is of great significance for maintaining the stability of oxygen in the atmosphere and improving the human environment.The oxygen release quantity was chosen as the evaluation index of the ecosystem oxygen release function [17].The market value method (i.e., the price of oxygen production) was used to account for the value of oxygen provided by the ecosystem, according to Equation ( 16): where V op is the value of ecosystem oxygen release (CNY/a); Q op is the amount of ecosystem oxygen release (t oxygen/a); C 0 is the price of industrial oxygen production (CNY/t).Q op denotes the amount of oxygen released.According to the chemical equation of photosynthesis, it is known that plants will release 1 mol of oxygen for every mol of carbon dioxide produced and absorbed [31], from which the quantity of the ecosystem release of oxygen can be measured according to Formula (17): where Q op is the amount of ecosystem oxygen release (t-O 2 /a); M O 2 /M CO 2 = 32/44 is the coefficient of conversion of CO 2 to O 2 ; and Q CO 2 is the amount of ecosystem carbon sequestration (t-C/a).It is estimated that the amount of oxygen released from the ecosystem of Tonglu County in 2021 was 1.769 million tons.Using the market value method, the price of oxygen was estimated at 1200 CNY/t, and the value of oxygen release was estimated to be CNY 2.123 billion.

Climate Regulation
The ecosystem climate regulation service refers to the ecological ability of ecosystems to absorb solar energy through the transpiration of vegetation and evaporation process of the water surface to reduce air temperature, increase air humidity, and improve the comfort level of the human environment [32].In this study, the energy consumed by the process of ecosystem evapotranspiration was chosen as the evaluation index of ecosystem climate regulation services.The alternative cost method (i.e., the power consumption needed to manually regulate temperature and humidity) was applied to account for the value of ecosystem transpiration to regulate temperature or humidity and the value of water surface evaporation to regulate temperature or humidity [18].The accounting was based on Equation ( 18): where V tt is the value of ecosystem climate regulation (CNY/a); E tt is the total energy consumed by ecosystems to regulate temperature or humidity (kWh/a); and P e is the local electricity price (CNY/kWh).E tt uses the total energy consumed via ecosystem transpiration and evaporation as the physical amount of climate regulation.The accounting proceeds according to Equations ( 19)-( 21): E we = E w × q × 10 3 /(3600) + E w × y where E tt is the total energy consumed by ecosystem transpiration and evaporation (kWh/a); E pt is the energy consumed by ecosystem vegetation transpiration (kWh/a); E we is the energy consumed by wetland ecosystem evaporation (kWh/a); EPP i is the heat consumed per unit area of an ecosystem of type i by transpiration (kj•m −2 d −1 ).A review of the literature shows that the values of heat consumption per unit area of forest, scrub, and grassland via transpiration heat absorption were 2837.27kj•m −2 d −1 , 1300.95 kj•m −2 d −1 , and 969.83 kj•m −2 d −1 , respectively [25].S i is the area of ecosystem type i (km 2 ); D is the number of days with a daily maximum temperature greater than 26 • C (we assumed 95 days); r is the air conditioning efficiency ratio, i.e., 3.0; i is the type of ecosystem (forest, scrub, grassland); E w is the evaporation volume (m 3 ); q is the latent heat of volatilization, i.e., the heat required to evaporate 1 g of water (J/g), which was taken as 2453.2J/g [25]; and y is the power consumption of the humidifier to convert 1 m 3 of water into steam (kWh), which was taken as 120 [33].
It is estimated that in 2021, the energy consumed by vegetation transpiration in Tonglu County was 34.855 billion kWh, the energy consumed by water surface evaporation was 15.514 billion kWh, and the local electricity price was 0.54 CNY/kWh [18].Using the alternative cost method, the value of the climate regulation function was calculated to be CNY 27.275 billion.

Cultural Services
The cultural service function of ecosystems refers to the non-material benefits that human beings obtain from ecosystems through spiritual feelings, knowledge acquisition, recreation, and aesthetic experience [34].These data are difficult to obtain, so in this study, the quantity of this variable was replaced with the leisure tourism data in the statistical yearbook.
Tonglu County ecosystem's cultural service function quantity was related to the county's farmhouse and A-level and above scenic spots, according to the data released in the Tonglu County Statistical Yearbook 2022 [18].In 2021, there were 4A-level scenic spots and 3A-level village scenic spots (i.e., 8 scenic spots and 25 scenic spots).At provincial level, there was 1 4A-level scenic spot city, 2 3A-level scenic spot towns, and 33 2A-level scenic spot villages.According to the accounting, Tonglu County's 2021 cultural service function volume was 6,399,600 people, with a cultural service value of CNY 9.420 billion.

Overall GEP Status
In 2021, the GEP of Tonglu County was about CNY 55.129 billion, which was 1.33 times the GDP of that year [18].It has an average GEP of 3013 million/km 2 , compared to the neighboring areas of Lishui City, which has an average GEP of 2904 million/km 2 [1], and Guizhou Province, which has an average GEP of 1136 million/km 2 [3].This demonstrates the good ecological background of Tonglu County.From the value volume share of the three level 1 indicators, regulating services and cultural services were the main value-contributing indicators, and the value of the product supply was lower.The value of supply products provided was about CNY 3.930 billion, accounting for 7.13% of the total output value; the value of regulation services was about CNY 41.780 billion, accounting for 75.78% of the total output value; and the value of cultural services was about CNY 9.420 billion, accounting for 17.09% of the total output value (Table 5).The value of ecosystem regulation services was about 10 times the value of ecosystem products, and the value of ecosystem cultural services was about twice the value of ecosystem products.The value of ecosystem-regulating services and cultural services was much larger than the value of product provisioning, which means that Tonglu County ecosystems have a huge value with respect to regulating services and cultural services; measuring only the value of product provisioning would seriously underestimate the contribution of Tonglu County ecosystems to human wellbeing.As far as different ecosystem services are concerned, the value of climate regulation and flood storage is higher, and the value of these two services accounts for about 66.45% of the gross ecosystem value of Tonglu County.The value of climate regulation is the largest, accounting for about 49.34% of the gross ecosystem value of Tonglu County, followed by the value of flood storage, accounting for about 17.12%, which indicates that these two services are the core services of the ecosystem of Tonglu County.Carbon sequestration and oxygen release, water conservation, and soil preservation are the next most important services, accounting for about 9.33% of the total value, which is closely related to the large area of forests and reservoirs in Tonglu County and the better ecological conservation work.The air purification and water environment purification results may be due to missing data; their output value is lower and they only account for a very small proportion (Table 5).

GEP of Different Ecosystems
Since the value of air purification and water environment purification is relatively small, and the cultural tourism data have no spatial attributes, these three items are not included in the discussion in this section.
As far as different types of ecosystems are concerned, forest ecosystems have the highest GEP of CNY 24.969 billion, accounting for 45.29% of the total value, with high values for functions such as climate regulation, oxygen release, and water containment.Wetland ecosystems have the second highest GEP, accounting for 31.19% of the total value, with the climate regulation value in first place and the flood storage value in second place (Table 6).This further confirms the importance of forest and wetland ecosystems, and the protection of forest ecosystems and wetland ecosystems should be implemented to limit development and management and prohibit indiscriminate mining, overgrazing, and other behaviors to further maintain and improve the ecosystem, so as to achieve the ecological, economic, and social sustainable development of Tonglu County.* "+": the service function is available but the volume is small and is not included in the accounting; "−": the service function is not available.

GEP of Different Administrative District
Due to the low value and lack of spatial attributes for the basic data of some items, such as the total reservoir capacity data in flood storage, and the total value of the water conservation, soil conservation, carbon sequestration variables, as well as oxygen release and climate regulation (which was estimated at CNY 32.340 billion, accounting for 58.66% of the total value of all the GEP), this section only discusses the value of water conservation, soil conservation, climate regulation, and water storage for the different administrative districts.Carbon sequestration, oxygen release, and climate regulation values are not discussed in this section.
Regarding the GDPs of different administrative regions, in terms of total amount, the total values of Fenshui Town, Fuchunjiang Town, and Baijiang Town are in the top three, accounting for 41.11% of the county, while the total values of Laoxian Street and Joshan She Township are relatively small, accounting for only 1.80% and 1.27% (Figure 4).In terms of the average amount, the average value of each unit area between the various regions is 1,648,700 CNY/km 2 , of which Tongjun Street has the highest value, at about 2,214,700 CNY/km 2 (Figure 5).This is due to the fact that Tongjun Street is mostly forested and the Fuchun River flows through its territory, so the average value of ecosystemregulating services is higher.While Chengnan Street is also located on the banks of the Fuchun River, its territory comprises mostly urban and farmland ecosystems, so the average value of ecosystem-regulating services is lower (Table 7).

Discussion of the Functional and Value Volumes of Regulating Services
Regulating services are the largest part of the three classifications of Tonglu County's GEP.The total value of ecosystem regulation services in Tonglu County in 2021 was about  Regulating services are the largest part of the three classifications of Tonglu County's GEP.The total value of ecosystem regulation services in Tonglu County in 2021 was about CNY 41.780 billion, accounting for 75.78% of the total GEP value, so it is necessary to further explore the detailed composition of its functional and value volumes and its spatial distribution characteristics.Since some accounting items lack spatial attribute data or have a small value volume, only three items (namely, water conservation, soil conservation, and carbon sequestration and oxygen release) are discussed and studied in the following sections.

Water Conservation
In 2021, the functional volume of water conservation in Tonglu County was 1.796 billion cubic meters, and the value of water conservation was about CNY 1.796 billion.The functional volume and value volume of water conservation have high, middle, and low spatial distribution characteristics on both sides (Figure 6).Combined with the ecosystem composition map of Tonglu County in Figure 2, it is obvious that most of the low-value areas are town ecosystems.From the division of administrative areas, the total water conservation values of Banshui Town, Baijiang Town, and Fengchuan Street ranked as the top three, accounting for 42.76% of the county.The average amount of water conservation per unit area between each area was 981,800 CNY/km 2 , of which the old county street value was the highest at 1,411,800 CNY/km 2 , and the Jiangnan Town value was the lowest at 551,100 CNY/km 2 (Table 8).
CNY 41.780 billion, accounting for 75.78% of the total GEP value, so it is necessary to further explore the detailed composition of its functional and value volumes and its spatial distribution characteristics.Since some accounting items lack spatial attribute data or have a small value volume, only three items (namely, water conservation, soil conservation, and carbon sequestration and oxygen release) are discussed and studied in the following sections.

Water Conservation
In 2021, the functional volume of water conservation in Tonglu County was 1.796 billion cubic meters, and the value of water conservation was about CNY 1.796 billion.The functional volume and value volume of water conservation have high, middle, and low spatial distribution characteristics on both sides (Figure 6).Combined with the ecosystem composition map of Tonglu County in Figure 2, it is obvious that most of the low-value areas are town ecosystems.From the division of administrative areas, the total water conservation values of Banshui Town, Baijiang Town, and Fengchuan Street ranked as the top three, accounting for 42.76% of the county.The average amount of water conservation per unit area between each area was 981,800 CNY/km 2 , of which the old county street value was the highest at 1,411,800 CNY/km 2 , and the Jiangnan Town value was the lowest at 551,100 CNY/km 2 (Table 8).In 2021, the functional volume of soil conservation in Tonglu County was about 238 million tons, and the value volume of soil conservation was about CNY 1.164 billion.The distribution trend of the functional volume and value volume of soil conservation increases step by step along the outward sides of the Banshui River and the Fuchun River, showing an overall trend of high in the south and low in the north.The highest parts of the value volume are in the Dachishan Forest Park, Tianzidi Scenic Spot, and other places, which are mostly surrounded by mountains (Figure 7).In terms of the division of administrative areas, in terms of the total amount, the total soil conservation value of Baijiang Township, Fengchuan Street, and Fuchunjiang Township ranked as the top three, accounting for 40.64% of the county.In terms of the average amount, the soil conservation value per unit area of each area was about 626,300 CNY/km 2 , with Zhongshan Township having the highest value at about 984,800 CNY/km 2 , and Tongjun Street having the lowest value at about 307,100 CNY/km 2 (Table 9).In 2021, the functional volume of soil conservation in Tonglu County was about 238 million tons, and the value volume of soil conservation was about CNY 1.164 billion.The distribution trend of the functional volume and value volume of soil conservation increases step by step along the outward sides of the Banshui River and the Fuchun River, showing an overall trend of high in the south and low in the north.The highest parts of the value volume are in the Dachishan Forest Park, Tianzidi Scenic Spot, and other places, which are mostly surrounded by mountains (Figure 7).In terms of the division of administrative areas, in terms of the total amount, the total soil conservation value of Baijiang Township, Fengchuan Street, and Fuchunjiang Township ranked as the top three, accounting for 40.64% of the county.In terms of the average amount, the soil conservation value per unit area of each area was about 626,300 CNY/km 2 , with Zhongshan Township having the highest value at about 984,800 CNY/km 2 , and Tongjun Street having the lowest value at about 307,100 CNY/km 2 (Table 9).In 2021, the amount of carbon sequestration function in Tonglu County was about 2.432 million tons and the functional quantity of oxygen release was 176,900 tons; the value quantity of oxygen release was about CNY 2.123 billion.The distribution trend of the functional volume and value volume of oxygen release from carbon sequestration is low on both sides of the Fenshui and Fuchun Rivers, but along both sides, most of the highvalue areas are gathered, and most of the areas have a good level of oxygen sequestration and release (Figure 8).In terms of the division of administrative areas, in terms of the total amount, the total soil conservation values of Baigang Township, Fengchuan Street, and Fuchunjiang Township ranked as the top three, accounting for 40.64% of the whole county.In terms of the average amount, the soil conservation value per unit area between each area was 626,300 CNY/km 2 , of which Zhongshan Township had the highest value at 984,800 CNY/km 2 , and Tongjun Street had the lowest value at 3,071,000 CNY/km 2 (Table 10).In 2021, the amount of carbon sequestration function in Tonglu County was about 2.432 million tons and the functional quantity of oxygen release was 176,900 tons; the value quantity of oxygen release was about CNY 2.123 billion.The distribution trend of the functional volume and value volume of oxygen release from carbon sequestration is low on both sides of the Fenshui and Fuchun Rivers, but along both sides, most of the high-value areas are gathered, and most of the areas have a good level of oxygen sequestration and release (Figure 8).In terms of the division of administrative areas, in terms of the total amount, the total soil conservation values of Baigang Township, Fengchuan Street, and Fuchunjiang Township ranked as the top three, accounting for 40.64% of the whole county.In terms of the average amount, the soil conservation value per unit area between each area was 626,300 CNY/km 2 , of which Zhongshan Township had the highest value at 984,800 CNY/km 2 , and Tongjun Street had the lowest value at 3,071,000 CNY/km 2 (Table 10).

Discussion on the Value Improvement of Ecological Products in Tonglu County
The enhancement of domestic ecological product value often involves employing administrative and economic regulations, among other measures, to encourage individuals, enterprises, and governments in a region to contribute to ecological environmental protection through financial compensation.For instance, Ezhou City's "ecosystem service" ecological compensation follows the principle of "who destroys, who compensates; who protects, who is compensated" [35], establishing a market-based mechanism for realizing ecological value.This approach has yielded positive outcomes.
Internationally, notable examples include the Land Fallow Protection Program in the United States, focusing on ecological protection and restoration [36], and Japan's Forest Recreation and Nutrition Industry, which explores ecological industrialized management [37].These initiatives have significantly contributed to the increased value of ecological products and the economic transformation of ecosystem services.Overall, these endeavors have played a crucial role in promoting the value enhancement and economic transformation of ecological products.
Given the multifaceted nature of the value associated with ecological products, taking forestry resources as an example, which can generate both direct economic value and contribute to climate regulation, it is recommended that Tonglu County pursue a composite ecological product value enhancement path.approach involves comprehensive consideration of the county's abundant forestry resources, leveraging both the direct economic benefits and the value derived from ecological products as carbon sinks.This integrated strategy is proposed for maximizing the value enhancement potential along a composite path.

Quantification and Trading Mechanism of Forest Stock Ownership
The ownership of forest land and forest trees uniformly managed by village collective economic organizations should be quantified to households, and the ownership of property rights of village collective economic organizations should be clarified.The equity held by village collective economic organizations, units, or individual forest farmers should be issued by state-owned forestry enterprises and institutions according to the proportion of investment required for cooperative afforestation mountain farms [38].According to the population of villagers in village collective economic organizations, the villagers' equity and number of forest tickets should be calculated after integer quantification (the value of villagers' individual share equity tickets is 100), among which the forest tickets held by village collective economic organizations can continue to be held by village collective economic organizations (30%) according to the requirements of the reform of rural collective property rights systems.A portion should be quantified and distributed to all villagers (70%).Using the "human base, households as the unit" assumption, equity certificates should be issued and equity management should proceed in accordance with the principle of "quantification to people, power to households, internal circulation, dynamic management" to maintain the relative stability of equity.
As a kind of equity certificate with the power of securities, Lin Piao itself has the power of trading, pledging, cashing, etc., which makes Lin Piao marketable.The forest tickets held by the members of the village collective economic organization and social capital can be listed and traded on the compliant property rights trading platform, and the future equity income of the cooperative operation of the mountain farm is cashed in advance through the transaction.Individual foresters can apply for pledged loans through holding forest tickets, increase the credit line, and increase forestry investment.In the forest ticket trading link, the state-owned forestry enterprises and institutions guarantee the forest ticket issued by the unit.If the members of the village collective economic organization and social investors plan to withdraw from the cooperative investment, the state-owned forestry enterprises and institutions will buy back the forest ticket investment amount plus the annual simple interest rate of 3% of the cooperative operation [39].

Production-Storage-Trading Mechanisms for Carbon Sinks
With reference to the expected transaction price information of the National Carbon Sinks Trading Platform, Zhejiang Province Emission Right Trading Network, and other markets, the future income of the forest land pledged by the foresters as carbon sinks will be measured on the basis of the carbon sinks generated by their above-ground biomass and below-ground biomass in the next 10 years and the average annual emission reduction [40].Upon completion of the calculation, the bank will register and publicize the pledge of forestry carbon sinks in the Unified Registration and Publication System for Movable Property Financing of the People's Bank of China Credit Center.
Carbon sinks proceed from production to storage and trading channels and "can be measured, can be mortgaged, can be traded, can be realized".Farmers' forestry rights are transferred to the village professional cooperatives in a unified way, unified management is implemented, and carbon sinks are formed into carbon sink product packages after certification, which are stored and traded through the platform.

Conclusions
Based on the assessment of ecosystem service functions, in this accounting study, we have discussed the concept, theoretical basis, and accounting methods with respect to the gross ecosystem product.We took Tonglu County as an example to estimate the county-wide gross ecosystem product in 2021, the total value of which was about CNY 55.129 billion, i.e., 1.33 times the county's GDP in that year.The following conclusions can be drawn: (1) The existing ecological environment monitoring data can basically support the accounting of GEP and ecological assets; (2) The GEP can reflect the ecosystem of a region's ecosystems' contribution to the local residents and the neighboring areas and ecological benefits.The changes in GEP and ecological assets can reflect the effectiveness of ecological protection and the coordination between development and protection in an area; (3) The results of GEP and ecological asset accounting can provide a basis for further research on the mechanism of realizing the value of ecological products and transforming the ecological value of ecological products into economic benefits.
The study shows that the ecosystem of Tonglu County not only provides products necessary for life to the local area and its neighboring areas, but also provides a large number of regulating services and cultural services.It is an important ecological barrier and an important ecological safety guarantee area in the western part of Hangzhou, and its ecological location provides great ecological benefit to the whole of Hangzhou province and Zhejiang province.Finally, building on the accounting of forestry resources as an example, we propose a targeted approach to enhance the composite ecological product value.By giving due consideration to forestry resources and carbon sinks, we aim to amplify the value of ecological products through an integrated enhancement pathway.This study contributes to the examination of the county-level ecosystem gross product with a nuanced perspective and precise data, addressing a gap in the research conducted within Tonglu County.It provides guidance on the practical implementation of ecological civilization construction and the pursuit of sustainable development in Tonglu County.Moreover, the study serves as a directive for broader societal involvement in ecosystem protection, the restoration of ecological service functions, and the prevention of further deterioration of the living environment.By encouraging people to perceive the relationship between ecosystems and humanity from a fresh visual perspective, we aim to foster a comprehensive understanding of the paramount importance of ecosystems.
This study has some limitations, which need to be improved upon in subsequent studies: (1) Due to the difficulty of obtaining some basic data, this study accounts for the gross ecosystem product of Tonglu County based on the year 2021.Some data, such as the total phosphorus in pollutants, tourism data in cultural services, etc., are missing, resulting in some items not being used in the normal accounting.In addition, some parameter data are missing, such as the sediment siltation coefficient, average runoff coefficient, evaporation coefficient, etc. Further, the selection of the year was undertaken relatively early and cannot accurately reflect the base year.As the data are not based on field measurements, this will also create errors, affecting the ecological value of ecosystems in Tonglu County.In further research, we should establish good cooperation with regional and national ecological monitoring stations, incorporate the indicators and parameters required by ecological asset accounting into long-term monitoring, and update the data once a year so as to carry out the research with reliable and stable data sources, and thus carry out a more comprehensive assessment of ecosystem service functions in Tonglu County.(2) Ecosystem services have spatial and temporal variability, i.e., "lag effect".At present, the alternative cost method is mostly used for assessment, but it is assessed from the perspective of cost rather than value, which is less relevant, and the accounting results may have certain bias.In future studies, more research should be conducted based on the market and existing literature should be analyzed to determine the true amount of value of each ecosystem service.The findings of this study represent a conservative estimate of the gross ecosystem value in Tonglu County.However, it is sufficient to indicate the substantial ecological benefits of Tonglu County's ecosystem.This information can reflect the ecological status of the area and quantify the advancements in ecological civilization construction, thereby promoting the development of ecological civilization in Tonglu County.

Figure 1 .
Figure 1.Location of the study area.

Figure 1 .
Figure 1.Location of the study area.

Figure 3 .
Figure 3. Technical roadmap of ecological product value accounting.

Figure 3 .
Figure 3. Technical roadmap of ecological product value accounting.

Sustainability 2024 , 25 Figure 4 .
Figure 4. Distribution of the total value of each regulating service in different administrative districts of Tonglu County in 2021.

Figure 4 .
Figure 4. Distribution of the total value of each regulating service in different administrative districts of Tonglu County in 2021.

Figure 4 .
Figure 4. Distribution of the total value of each regulating service in different administrative districts of Tonglu County in 2021.

Figure 5 .
Figure 5. Distribution of average value volume of regulated services by different boroughs in Tonglu County, 2021.

Figure 5 .
Figure 5. Distribution of average value volume of regulated services by different boroughs in Tonglu County, 2021.

Figure 6 .
Figure 6.Distribution of water conservation values in Tonglu County in 2021.

Figure 6 .
Figure 6.Distribution of water conservation values in Tonglu County in 2021.

Figure 7 .
Figure 7. Distribution of soil conservation values in Tonglu County in 2021.

Figure 7 .
Figure 7. Distribution of soil conservation values in Tonglu County in 2021.

Figure 8 .
Figure 8. Distribution of carbon sequestration and oxygen release values in Tonglu County in 2021.

Figure 8 .
Figure 8. Distribution of carbon sequestration and oxygen release values in Tonglu County in 2021.

Table 2 .
Quality and value of ecosystem provisioning products in Tonglu County, 2021.

Table 3 .
Quality and value of ecosystem provisioning products in Tonglu County, 2021.

Table 4 .
Quality and value of ecosystem regulation services in Tonglu County, 2021.

Table 5 .
Composition of gross ecosystem product in Tonglu County, 2021.

Table 6 .
Gross ecosystem product for different ecosystems in Tonglu County.

Table 7 .
Gross ecosystem product for different ecosystems in Tonglu County.

Table 8 .
Total water conservation values of different administrative districts in Tonglu County in 2021.

Table 8 .
Total water conservation values of different administrative districts in Tonglu County in 2021.

Table 9 .
Total soil conservation values for different boroughs in Tonglu County, 2021.

Table 9 .
Total soil conservation values for different boroughs in Tonglu County, 2021.

Table 10 .
Total value of carbon sequestration and oxygen release in different boroughs in Tonglu County in 2021.