Ecological risk assessment method based on ecological system service

Abstract

The invention belongs to the technical field of ecological system service and evaluation, and particularly relates to an ecological risk evaluation method based on ecological system service. The method specifically comprises the steps of (1) determining a target range; (2) determining an ecological system service; (3) selecting typical representative years, and evaluating the ecosystem service within the target range in each representative year; (4) calculating a regional ecological risk index under each typical representative year; and (5) results obtained in the step (3) and the step (4) are combined with five ecological system services of the target range region in each typical year to comprehensively evaluate the ecological risk of the target range. According to the method, theoretical guidance and practical reference can be provided for improvement of ecological system service in a target range and functional division of the ecological system.

Description

Technical Field

[0001] The present invention belongs to the technical field of ecosystem services and assessment, and specifically is an ecological risk assessment method based on ecosystem services. Background Art

[0002] Ecosystems provide a series of services and values ​​for human activities. However, the rapid development of industrialization and urbanization has led to profound changes in ecosystems. The degradation of ecosystems has aggravated ecological risks and seriously hindered the sustainable development of human activities. Ecological risk refers to the adverse effects of ecosystems and their subsystems when they are exposed to multiple risk sources. Ecological risk assessment (ERA) is a method to assess the adverse effects of one or more stress factors on the study area. Ecological risk assessment is of great significance to the protection of ecosystems and scientific management. However, the existing ecosystem assessment framework ignores factors such as assessment endpoints and uncertainty, which weakens its reliability and practicality. Ecosystem services refer to ecological characteristics, functions and processes that directly or indirectly promote human well-being, or more specifically, the benefits people obtain from ecosystems. They are usually considered to be a bridge connecting human well-being and ecosystem processes. Therefore, ecosystem services can be appropriately used as the endpoint of ecological risk assessment. Introducing the value of ecological services into ecological risk assessment for improvement and development has become a hot topic in current regional ecological risk research. At the same time, ecological risks are affected by future uncertainties. Ecological risk assessment based on multi-scenario simulation of land use and ecosystem service value is also of great significance to ecological management. Summary of the invention

[0003] To solve the above problems, the present invention provides a method for analyzing ecological risks based on ecosystem services. The method uses the ecosystem service value as the end point of ecological risk assessment and improves the ecological risk assessment method.

[0004] The technical solution of the present invention:

[0005] An ecological risk assessment method based on ecosystem services includes the following steps:

[0006] (1) Determine the target scope: Consider the assessment needs and assessment objectives to first determine the target scope of the assessment. The target scope is divided according to the river basin scope or administrative area scope.

[0007] (2) Determination of ecosystem services: The selected ecosystem services include water conservation, carbon storage and sequestration, soil conservation, water purification and habitat quality.

[0008] (3) Select typical representative years and evaluate the ecosystem services within the target range in each representative year: obtain the data required for ecosystem service evaluation, including land use data, climate and environmental data, DEM data, socioeconomic data, etc.; use ArcGIS software to process the acquired data into data with the same resolution and coordinate system; use the processed data to evaluate ecosystem services. The system service evaluation specifically uses the carbon sequestration module of the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model to evaluate carbon storage and sequestration, the habitat quality module to evaluate habitat quality, the nutrient transport ratio module to evaluate water purification, the water balance equation to evaluate water conservation, and the soil and water loss equation to evaluate soil conservation.

[0009] (4) Calculate the ecological risk index for each typical representative year. Divide the target area into risk units of m km × n km using the equally spaced systematic sampling method. Calculate the ecological risk index of each risk unit and use it as the ecological risk level of the center point of the risk unit. Based on the ecosystem structure of the target area, select the landscape disturbance index, vulnerability index, and loss index to construct a comprehensive ecological risk index, and analyze the size and changes of the regional ecological risk index within the target area.

[0010] Based on the landscape characteristics within the target range, the target range is divided into six landscape types: cultivated land, forest land, grassland, water area, construction land and unused land, according to the method of distinguishing differences and summarizing commonalities.

[0011] Landscape disturbance index E i It reflects the degree of external interference to the ecosystems represented by different landscapes. Its expression is:

[0012] E i =aC i +bN i +cD i

[0013] in:

[0014] Fragmentation index

[0015]

[0016] Separation index

[0017]

[0018] Dominance Index

[0019]

[0020] Where: n i is the number of patches of landscape type i, A i is the area of ​​landscape type i, A is the total area of ​​the target range, Q i is the number of risk units in landscape type i, M i is the number of patches of landscape type i, L i is the area of ​​landscape type i. a, b, and c are C i , N i , D i , and a+b+c=1. According to relevant references, a, b, and c can be assigned weights of 0.5, 0.3, and 0.2, respectively.

[0021] Vulnerability Index F i It represents the vulnerability of the internal structure of the ecosystem represented by different landscapes, and can reflect the resistance of different landscape types to external disturbances. The smaller the ability to resist external disturbances, the greater the vulnerability and the greater the ecological risk. According to the actual situation of the target range, the vulnerability of the landscape types within the target range is divided into 6 levels, and the vulnerability index of each land use type is: unused land = 6, water area = 5, cultivated land = 4, grassland = 3, forest land = 2, construction land = 1. After normalization, the vulnerability index of each landscape type is obtained, which is used to calculate the loss index; the vulnerability index of each land use type after normalization is: unused land = 0.286, water area = 0.238, cultivated land = 0.190, grassland = 0.142, forest land = 0.095, construction land = 0.048.

[0022] Loss Index R i It is used to reflect the degree of loss of natural attributes of ecosystems represented by different landscape types under the dual interference of natural and human factors. Its expression is:

[0023] R i =E i ×F i

[0024] The ecological risk index ERIx is expressed as:

[0025]

[0026] Where: ERIx is the ecological risk index of the x-th risk unit, Ax i is the area of ​​landscape type i in the x-th risk unit, Ax is the area of ​​the x-th risk unit, R i is the loss index of the i-th type of landscape.

[0027] (5) Based on the results obtained from steps (3) and (4), and combined with the five ecosystem services in the target area in each typical year, a comprehensive assessment of the ecological risk of the target area is conducted.

[0028] Beneficial effects of the present invention:

[0029] The present invention combines models and spatial mapping methods to analyze the distribution patterns of five ecosystem services (water conservation, carbon storage and sequestration, soil conservation, water purification, and habitat quality) in different time and space; and uses landscape fragmentation, landscape isolation, landscape dominance, and landscape loss indexes to calculate the total ecological risk index of each risk unit, and finally visualizes the calculation results to form a regional ecological risk spatiotemporal distribution map of the target assessment range. The present invention can provide theoretical guidance and practical reference for the improvement of ecosystem services and ecosystem function zoning in the target range, and provide basic support for the optimization of national land space pattern, propose more targeted and accurate ecological protection policies, and provide a scientific basis for coordinating ecosystem service functions and promoting the balanced development of ecology and social economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flow chart of the method of the present invention;

[0031] Figure 2(a) to Figure 2(e) 2(a) is a spatiotemporal distribution diagram of ecosystem services in each typical year in the embodiment of the present invention; wherein, FIG2(a) is a spatiotemporal distribution diagram of water yield, FIG2(b) is a spatiotemporal distribution diagram of carbon storage, FIG2(c) is a spatiotemporal distribution diagram of soil conservation, FIG2(d) is a spatiotemporal distribution diagram of total nitrogen, and FIG2(e) is a spatiotemporal distribution diagram of habitat quality;

[0032] Figure 3 It is a spatial distribution map of regional ecological risks in each typical year in the embodiment of the present invention. Specific implementation plan

[0033] The specific implementation scheme of the present invention is further explained in combination with the technical scheme and the accompanying drawings.

[0034] (1) Determine the target range. In this embodiment, a certain place is selected as the target range of this embodiment.

[0035] (2) Determine ecosystem services. Five ecosystem services were analyzed: water conservation, carbon storage and sequestration, soil conservation, water purification, and habitat quality.

[0036] (3) Select typical representative years. 2000, 2010 and 2020 were selected as typical representative years, and the five ecosystem services in the target range were evaluated in the three typical representative years (as shown in Figure 2).

[0037] Figure 2 (a) is a spatial distribution map of water conservation. The water production shows a spatial characteristic of high in the south and low in the north. The water production in coastal areas is significantly higher than that in inland areas. The fluctuation of water production is closely related to precipitation, evapotranspiration and land use change. The carbon storage of forests (Figure 2 (b)) is an important component of the carbon storage of the entire region, resulting in a large difference in the spatial distribution of carbon storage, among which the carbon storage in the northwest and southeast is the highest. Soil conservation (Figure 2 (c)) is an important indicator for measuring the function of ecosystems. Its spatial pattern distribution and change trend are crucial to the quality of regional ecological environment. The spatial pattern of soil conservation during this period did not change significantly, but the soil conservation showed an increasing trend overall, which to a certain extent also reflects the enhanced ecological environmental protection awareness of the government and society in recent years. Water purification service (Figure 2 (d)) is used to evaluate the water purification function of soil and vegetation. Because soil can intercept and transfer nitrogen and phosphorus, the degree of water purification is usually expressed by the output of nitrogen and phosphorus nutrients. In the present invention, the amount of nitrogen on the surface and underground of the basin is used as a key indicator to measure the degree of water purification. From the spatial distribution map of total nitrogen in the target range, we can see that areas with high nitrogen content are mainly concentrated in rivers and lakes. In general, the nitrogen content shows a trend of first increasing and then decreasing. Habitat quality (Figure 2 (e)) is represented by the biodiversity index, which is the ability of the ecosystem to provide living and reproductive conditions for biological populations. The closer the habitat quality index is to 1, the richer the biodiversity in the area. As can be seen from the figure, the area of ​​low-value areas of biodiversity is gradually increasing, which reflects that the problem of ecological destruction has become more serious in recent years, reminding us that we must attach great importance to ecological protection and restoration.

[0038] (4) Calculate the regional ecological risk index for each typical representative year, and combine it with the ecosystem service assessment in step (3) to further explore the comprehensive relationship between ecological risk and ecosystem services.

[0039] In order to spatialize the ecological risk index, the study area was divided into 8477 risk assessment units of 10km×10km, and risk center points were generated based on the scope and workload of the study area. Fragstats4.2 was used to calculate the ecological risk index of the center point of each risk unit, and the Kriging interpolation method was used to obtain the distribution characteristics of the ecological risk in the target range.

[0040] Regional ecological risk analysis was achieved using geological statistical methods and GIS technology. The ecological risk index was assigned to the center point of 8477 cells. On this basis, the ecological risk index was interpolated to the entire study area using the semivariogram method, and finally the ecological risk index distribution map of the entire study area was obtained (see Figure 2). Figure 3 shown).

[0041]

[0042] Where: γ(h) is the variation function, h is the step size; N(h) is the number of sample points when the interval distance is h, Z(x i ) and Z(x i +h) are the landscape ecological risk index at spatial location x i and x i +h spatial observations.

[0043] With the help of the natural breakpoint method provided by ArcGIS, the ecological risk is divided into five levels: low risk area (ERI < 0.10), medium-low risk area (0.10 < ERI < 0.15), medium risk area (0.15 < ERI < 0.20), medium-high risk area (0.20 < ERI < 0.25), and high risk area (0.30 < ERI). The experimental semivariogram is calculated using the geological statistical method provided by ArcGIS. The theoretical semivariogram is fitted, and on this basis, the Kriging interpolation method is used to obtain the watershed ecological risk level map. The spatial distribution of the ecological risk index in the target range shows the characteristics of "high in the east and west, low in the middle". Generally speaking, the low-risk area occupies the largest proportion of the area, mainly distributed in the northern and southern forests, with low vulnerability and separation; the medium-risk area is mainly distributed in the eastern cultivated land area; the high-risk area and high-risk area are mainly distributed in the water bodies and construction land distribution areas with high landscape fragmentation and separation.

[0044] (5) Comprehensive analysis:

[0045] The current evaluation system emphasizes the trade-off and synergistic relationship between ecosystem services, and largely ignores the comprehensive relationship between the security of the landscape pattern and ecosystem services. The present invention conducts a comprehensive assessment of the ecological risk of the target range on the basis of ecosystem services. It can be seen from the spatiotemporal distribution map of the ecosystem service system and the ecological risk distribution map that the low-value areas of ecological risk are distributed in the forests in the north and south, which are the high-value areas of carbon storage and habitat quality, and the amount of soil and water loss is low, the total nitrogen content in the basin is low, and the degree of eutrophication of water bodies is low. Most of the high values ​​of the ecological risk index are distributed in the east of the target range, where the carbon storage is low, the habitat quality index is low, the biodiversity is low, the human activities in the basin are intense, the ecological vulnerability is high, and the ecological risk index is high. There is a corresponding relationship between the distribution of ecological risks and ecosystem services. The ecological risk assessment framework guided by ecosystem services can reduce the error between the loss of ecosystem services and the management of complex ecological risks.

Claims

1. An ecological risk assessment method based on ecosystem services, characterized in that: The following steps are involved: (1) Determine the target scope: Consider the assessment needs and assessment objectives to first determine the target scope of the assessment. The target scope is divided according to the river basin scope or administrative area scope; (2) Determine ecosystem services: The selected ecosystem services include water conservation, carbon storage and sequestration, soil conservation, water purification, and habitat quality; (3) Select typical representative years and evaluate the ecosystem services within the target range in each representative year: obtain the data required for ecosystem service evaluation, including land use data, climate and environmental data, DEM data, and socioeconomic data; use ArcGIS software to process the acquired data into data with the same resolution and coordinate system; use the processed data to evaluate ecosystem services; the system service evaluation specifically uses the comprehensive evaluation model of ecosystem services InVEST's carbon sequestration module to evaluate carbon storage and sequestration, the habitat quality module to evaluate habitat quality, and the nutrient delivery ratio module to evaluate water purification; use the water balance equation to evaluate water conservation, and use the soil erosion equation to evaluate soil conservation; (4) Calculate the ecological risk index for each typical representative year; divide the target area into risk units of m km × n km using the equal-interval systematic sampling method; Calculate the ecological risk index of each risk unit and use it as the ecological risk level of the center point of the risk unit; Starting from the ecosystem structure of the target range, select the landscape disturbance index, vulnerability index and loss index to construct a comprehensive ecological risk index, and analyze the size and change of the regional ecological risk index within the target range; Combined with the landscape characteristics within the target area, the target area is divided into six landscape types: cultivated land, forest land, grassland, water area, construction land and unused land, by distinguishing differences and summarizing commonalities. Landscape disturbance index E i Reflects the extent to which the ecosystems represented by different landscapes have been disturbed by external factors; Its expression is: E i =aC i +bN i + cD i in: Fragmentation index Separation index Dominance Index Where: n i is the number of patches of landscape type i, A i is the area of ​​landscape type i, A is the total area of ​​the target range, Q i is the number of risk units in landscape type i, M i is the number of patches of landscape type i, L i is the area of ​​landscape type i; a, b, c are i , N i , D i The weight of , and a+b+c=1; Vulnerability Index F i It represents the vulnerability of the internal structure of the ecosystem represented by different landscapes, and can reflect the resistance of different landscape types to external interference. The vulnerability of landscape types within the target range is divided into 6 levels, and the vulnerability index of each land use type is: unused land = 6, water area = 5, cultivated land = 4, grassland = 3, forest land = 2, and construction land = 1. After normalization, the vulnerability index of each landscape type is obtained, which is used to calculate the loss index. The vulnerability index of each land use type after normalization is: unused land = 0.286, water area = 0.238, cultivated land = 0.190, grassland = 0.142, forest land = 0.095, and construction land = 0.

048. Loss Index R i It is used to reflect the degree of loss of natural attributes of ecosystems represented by different landscape types under the dual interference of natural and human factors; its expression is: R i =E i ×F i The ecological risk index ERIx is expressed as: Where: ERIx is the ecological risk index of the x-th risk unit, Ax i is the area of ​​landscape type i in the x-th risk unit, Ax is the area of ​​the x-th risk unit, R i is the loss index of the i-th type of landscape; (5) Based on the results obtained from steps (3) and (4), and combined with the five ecosystem services in the target area in each typical year, a comprehensive assessment of the ecological risk of the target area is conducted.

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