Shenzhen Futian Mangrove Nature Reserve is located on the north bank of Shenzhen Bay. The area ranges from 22°30′–22°32′ north latitude to 113°56′–114°3′ longitude east, with a total area of 3.68 km2 (as shown in Figure 1). The region belongs to the East Asian monsoon region and the South Asian subtropical monsoon maritime climate region. The average annual temperature is 22.4°C. January is the coldest month. The lowest extreme temperature is 0.2°C. July is the hottest month. The highest extreme temperature is 38.7°C. The average annual rainfall is 1,700–1,900 mm, and rainfall is received mainly from April to September. The annual evaporation capacity is 1,500–1,800 mm. The average annual relative humidity is 80%. The annual sunshine hours are about 2000 d [1, 2]. It is the only mangrove wetland in the world located in the centre of the city, which is also an important ‘transit station’ and ‘gas station’ on the international migratory bird passage of the Eastern Hemisphere [3]. It is an important object of biodiversity and wetland ecological protection in the world [4].
Futian Nature Reserve is mainly composed of mangroves, fish ponds surrounded by dam, tidal flats, rivers, land, sea area and so on. Mangrove accounts for the largest area. The area of mangroves is mostly strip-shaped, the community appearance is relatively simple, and the region of mangroves mainly contains shrubs and small arbour trees. The canopy is relatively neat and generally 4–6 m high [5]. Mangrove plants mainly include
During the 30 years of rapid economic development in Shenzhen, the Futian mangrove wetland ecosystem was seriously affected by urban expansion and environmental pollution. Mangrove wetlands were shrinking, and mud deposits of the tidal flats were increasing the level of the seabed. A forest of tall buildings blocked the passage of birds. Ecological problems such as the death of fish and shrimp caused by water pollution became rampant. The wide spread of alien species such as
For environmental problems, the PSR framework model has a very clear causal relationship, i.e. human activities exert a certain amount of pressure on the environment. Resultantly, the state of the environment has changed to a certain extent, and human society should respond to the changes to restore environmental quality and prevent environmental degradation [12, 13]. These three links exactly constitute the entire process of decision-making and formulating countermeasures. Figure 2 shows the PSR model logic diagram.
This paper divides the ecosystem pressure of the mangrove wetland into natural pressure and anthropic pressure. Based on the actual natural conditions and current environmental characteristics of the wetland in the Futian Mangrove Nature Reserve, several indexes from both natural and anthropic factors will be selected as evaluation elements. The specific selected indexes are shown in Table 1.
Evaluation index selection of the pressure subsystem.
Pressure subsystem | Anthropic pressure | Density of population |
Per capita GDP | ||
Urbanisation rate | ||
Noise pollution | ||
Light pollution | ||
Natural pressure | Mangrove pest | |
Extreme temperature weather per year |
Ecosystem refers to a unified whole system formed by the continuous process of material circulation and energy flow between all creatures living together in a certain space and their environment. Ecosystem health assessments take into account changes in composition and structure and pattern under the influence of anthropic and natural factors. In this paper, the state subsystem is divided into three aspects, which are assessed individually: environment quality, biology and ecology and biological productivity. Specific indexes are selected as shown in Table 2.
Evaluation index selection of the state subsystem.
State subsystem | Biology and ecology | Diversity of species |
Environmental quality | Water quality | |
Biological productivity | Conversion between nutrient levels | |
Total energy conversion |
Response criterion level should cover two factor levels: natural response and social response. The natural response of the ecosystem mainly reflects the changes and trends of various environmental and biological indexes under pressure. However, in the process of the state subsystem evaluation, this paper will analyse and explain the current situation of various indexes by comparing historical data. Therefore, the response subsystems are no longer repeatedly discussed. Only the response activities related to social factors are evaluated. Specific indexes are selected as shown in Table 3.
Evaluation index selection of response subsystem.
Response subsystem | Social response | Proportion of the tertiary industry |
Education level of the population | ||
Investment in environmental pollution | ||
Planning regulations and policies | ||
Degree of public participation |
The ecosystem of the Futian mangrove wetland is a comprehensive system composed of several subsystems. The index system for comprehensive evaluation is a collection of indexes from various aspects based on the components of the ecosystem of the Futian mangrove wetland, which have functions and characteristics such as time, space, level and quantity. Therefore, in order to analyse the structural mechanism of complex ecosystem, it is necessary to carry out hierarchical analysis on the index system. Based on the screening principle of indexes, this paper uses the thought of system analysis to decompose the complex problems of the ecosystem into a number of interrelated and different order levels and then combines the actual situation to decompose the system into four levels: objective level, criterion level, factor level and index level [14, 15]. Figure 3 provides further details.
The factors affecting the Futian mangrove wetland ecosystem can be quantifiable, i.e. its fuzziness can be transformed into the membership degree relative to the stability level. According to the actual situation of the evaluation system studied, the evaluation index system of fuzzy comprehensive evaluation is established from the perspective of representativeness, systematicness and applicability. The fuzzy evaluation matrix of relative membership of a single evaluation index is established from the sample data of each evaluation index.
It is assumed that
The standardised treatment formula of the index ‘the larger the better’ can be written as follows:
The standardised treatment formula of the index ‘the smaller the better’ can be written as follows:
The standardised treatment formula of the index ‘the more medium the better’ can be written as follows:
Fuzzy evaluation matrix
The fuzzy evaluation matrix
The hierarchical structure model is constructed to pre-process the data of the index level, and the relatively reliable membership degree is obtained through calculation, analysis and comparison. The membership degree is taken as the index level. According to the practical problems, the factors in the indicator level are denoted as follows:
Then, the maximum eigen root of the judgement matrix and its corresponding eigenvectors are solved. We calculate the product of each row of the judgement matrix, as follows:
Then, we calculate the NTH root of
Next, we normalise vector
It is assumed that
To test the consistency of the judgement matrix, its consistency should be calculated as follows:
In order to test whether the judgement matrix has satisfactory consistency, the consistency index
The judgement matrix has satisfactory consistency. Otherwise, the judgement matrix needs to be adjusted until it is satisfied.
The calculation method of the Futian mangrove wetland ecosystem evaluation index is as follows:
In the formula,
The determination of environmental standards in this paper mainly refers to the following terms: (1) national, industrial and local standards, including environmental quality standards for surface water (GB3838-2002) and classification standards for nutritional state of lakes (reservoirs); secondary water quality standards of marine water quality standards (GB3097-1997); soil environmental quality standards (GB15618-1995) etc. (2) grading criteria for wetland ecosystem evaluation provided by Sun Longqi [16].
According to the biodiversity monitoring report data of the Futian Mangrove Reserve for the past 3 years, the calculation is as follows:
According to the above analytic hierarchy process, the characteristic vector of the judgement matrix is written as follows:
According to consistency check,
From the comparison of the weights of the pressure subsystems in Figure 4, it can be seen that the weighted score of natural pressure is 0.01988, whereas the anthropic weighted score is 0.28706. The lower the score, the less stress the system is under and the more stable the ecosystem is. Therefore, the score indicates that anthropic pressure in the Futian mangrove wetland in Shenzhen is higher than that of natural pressure. With the development of society and economy, the exploitation and utilisation of resources by humans has exerted a great influence on the ecological environment of the sea area, and the influence of humans has exceeded the influence of natural ecological disasters on the environment.
As for natural pressure, in terms of the weighted score of third-level indexes, the annual extreme temperature weather score is the lowest, amounting to 0.00100. This indicates that the Futian mangrove wetland in Shenzhen has a lower pressure effect on the ecosystem than other pressure indexes. The study shows that annual extreme temperature weather in the sea area does not cause stress. However, the impact of mangrove pests on the whole ecosystem is much greater than that of annual extreme temperature weather. For anthropic pressure, the weighted scores of population density, per capita GDP, urbanisation rate, light pollution and noise pollution are 0.02630, 0.09873, 0.06322, 0.06322 and 0.03559, respectively. Socio-economic indexes indirectly reflect the frequency of human socio-economic activities. According to the weighted scores of these five indexes, the population and economy of Futian, Shenzhen, have a great influence on the coastal ecosystem. Furthermore, the influence of human activities on the marine ecological environment is on the increase.
In order to reflect the comprehensive situation of all factors more intuitively, Figure 5 presents a comparison diagram of the weighted scores of each indicator of the state subsystem, and the figure indicates that the weighted scores of species diversity and water quality between total energy conversion and nutrient level are 0.05531, 0.04446, 0.00100 and 0.03559, respectively. In addition, energy conversion and infringement score lowest, which indicates that the ecosystem of mangrove wetland in Shenzhen is damaged due to human activities, and in particular to the discharge of domestic sewage. The structure of the intertidal community is unstable, and the energy flow and material circulation of the ecosystem are broken, both of which lead to the reduction of species diversity and serious damage to the ecosystem.
According to the weighted score of the response subsystem in Figure 6, the highest weighted score of the tertiary industry is 0.09873, which shows that the country attaches great importance to economic development. However, the education level of the population, environmental pollution investment and public participation index scores are significantly low, which indicates that there is still room for promotion and improvement in the local social response. The good state of the ecosystem is closely related to the importance of the state, the efforts of local government departments in policies and management, the educational level of the population and the importance of people to the environment. Therefore, the establishment of a sound system of laws and regulations, lax management measures, and strict and effective administrative law enforcement can play a decisive role in mangrove wetland protection.
Using the health index formula, the health index and comprehensive health index of the ecosystem stress, state and response in the protected area were calculated. (Table 4 indicates the corresponding health level.) The results are shown in Table 10.
Mean random consistency index.
0 | 0 | 0.58 | 0.90 | 1.12 | 1.24 | 1.32 | 1.41 | 1.45 |
Classification criteria and definitions of Futian mangrove wetland ecosystem evaluation.
I | ≥0.8 | A | The ecosystem has stable structure and function, and the system has adequate strength to recover and regenerate. |
II | 0.6–0.8 | B | The ecosystem function is relatively perfect, and can recover after being commonly disturbed. |
III | 0.4–0.6 | C | Although damaged to a certain extent, the ecosystem can still maintain its basic functions. |
IV | 0.2–0.4 | D | The structure and function of the ecosystem are degraded, biodiversity declines and environmental problems are serious. |
V | ≤0.2 | E | The structure and function of the ecosystem have almost collapsed, and the ecological environment has become seriously damaged. |
Noise evaluation criteria of mangrove reserve (day).
0 | 50 | 0 |
1 | 55 | 0.2 |
2 | 60 | 0.5 |
3 | 65 | 0.7 |
4 | 70 | 1.0 |
Classification of pressure evaluation.
0–0.2 | Mild stress |
0.2–0.4 | Small pressure |
0.4–0.6 | Medium pressure |
0.6–0.8 | High pressure |
0.8–1.0 | Extreme pressure |
Classification of state evaluation.
0.8–1.0 | A | The ecosystem has stable structure and function, and the system possesses adequate strength to recover and regenerate. |
0.6–0.8 | B | The ecosystem function is relatively perfect, and can recover after being commonly disturbed. |
0.4–0.6 | C | Although damaged to a certain extent, the ecosystem can still maintain its basic functions. |
0.2–0.4 | D | The structure and function of the ecosystem are degraded, biodiversity declines and environmental problems are serious. |
0–0.2 | E | The structure and function of the ecosystem have almost collapsed, and the ecological environment has become seriously damaged. |
Weight of each index.
Pressure subsystem 0.41173 | Anthropic pressure 0.36391 | Density of population | 0.55 | 0.04782 | 0.02630 |
Per capita GDP | 1 | 0.09873 | 0.09873 | ||
Urbanisation rate | 0.8 | 0.07902 | 0.06322 | ||
Noise pollution | 0.6 | 0.05932 | 0.03559 | ||
Light pollution | 0.8 | 0.07902 | 0.06322 | ||
Natural pressure 0.04782 | Mangrove pest | 0.5 | 0.03776 | 0.01888 | |
Extreme temperature weather per year | 0.1 | 0.01006 | 0.00100 | ||
State subsystem 0.20301 | Biology and ecology 0.07902 | Diversity of species | 0.7 | 0.07902 | 0.05531 |
Environmental quality 0.07410 | Water quality | 0.6 | 0.07410 | 0.04446 | |
Biological productivity 0.06938 | Conversion between nutrient levels | 0.6 | 0.05932 | 0.03559 | |
Total energy conversion | 0.1 | 0.01006 | 0.00100 | ||
Response subsystem 0.38526 | Social response 0.38526 | Proportion of the tertiary industry | 1 | 0.09873 | 0.09873 |
Education level of the population | 0.8 | 0.07902 | 0.06322 | ||
Investment in environmental pollution | 0.7 | 0.06917 | 0.04842 | ||
Planning regulations and policies | 0.7 | 0.06917 | 0.04842 | ||
Degree of public participation | 0.7 | 0.06917 | 0.04842 |
Ecosystem health index and level of the reserve.
Health index | 0.256962 | 0.140323 | 0.307203 | 0.25262 |
Health level | IV | V | IV | IV |
It is calculated that the mangrove wetland ecosystem is in a poor state (level IV). Its ecosystem structure and function are degraded. There has been a radical decline in biodiversity, and environmental problems are serious.
Based on the PSR model, the ecological health evaluation system of Futian Mangrove Reserve in Shenzhen was established. The AHP model was used to evaluate the health state of the reserve. The results showed that the proportion of pressure, state and response in the system was 41.17%, 20.3% and 38.53%, respectively. The health index was 0.256962, 0.140323 and 0.307203, respectively. The comprehensive health index of the reserve is 0.25262, which indicates health grade IV (poor state). The main reasons for the above results are as follows: (1) in the past 30 years, urbanisation has led to the loss of a significant portion of the ecological functions of the reserve ecosystem and the continuous decline of the health level; (2) water pollution, artificial introduction of plants and pests, and so on have inflicted great external pressure on the protection area; and (3) construction and other human activities affect the restoration of the natural state of the reserve.