1. Wetland Overview
1.1. Origin of the Concept of Wetlands
Due to the complexity of wetlands, the diversity of species, and their wide distribution, there are still various opinions and definitions in the disciplinary community [1]. At present, the meaning of wetland that has been temporarily unified around the world is from the Convention on Wetlands, which specifies that wetland is a natural or artificially modified, time-honored, or temporary marsh, peat place, or water geographic zone, containing water carriers that stop or flow, light, semi-salty or brackish water, including the water zone where the depth of water does not exceed 6 m at the lowest tide level [2]. As a broad concept of wetland classification, it can be seen from the conceptual division that wetland are a special transitional type of ecology that are neither water nor land, that include the interweaving of land and water, and the most prominent feature is their ecological system with hydrology, soil, vegetation, and biological environment dominated by water factors.
1.2. Formation of Wetlands
One of the reasons for the existence of wetlands is due to geographical changes in the natural environment, and another reason for their existence is due to urban development, civic development, and other external forces that have contributed to the formation of wetlands. Wetlands are natural sites for sewage purification, and because the entire wetland system has not been fully and completely summarized, the definition of wetlands varies from country to country. Among them, some wetland researchers in China [3] defined wetlands, proposing that wetlands consist of water and various types of substrates that are composed of permanent or temporary organisms, such as aquatic and terrestrial systems, with strong vitality and productivity, resulting in ecosystems of special nature. However, [4] consider wetlands as a living system with environmental landscape value, as well as a habitat for a variety of birds and fish that play an important role in reducing pollution and purifying water. In addition to this, there is a part of the humanities that considers wetlands as terrestrial margins, including all types of natural or man-made bodies of water.
1.3. Wetlands in the City
Urban wetlands is a new term and concept, created in the 21st century. This type of wetland belongs to the urbanization development in response to the urban environmental degradation caused by the activities of urban residents. There are various understandings of the meaning of urban wetlands among the public, but the common view is that they exist within urban areas and are affected by urban human activities, and their ecological service functions are significantly different from natural or man-made wetlands. Due to the diverse types of wetlands, urban wetlands include sea, lakes, rivers, water resource areas, natural and artificially created ponds within the city, as well as sewage treatment facilities in the city and other environmental ecosystems with similar ecological purification, which are wetland ecosystems with certain natural environmental characteristics, recreational environment and scientific research value in the city and surrounding areas, and can be used both for scientific research and as a special area open to the public. Urban wetland park construction has a great role: to protect wetlands (as the main factor), with certain recreational functions, to provide space for human recreation and leisure, to maintain the earth’s ecological environment and the natural ecological environment system stability. Its features reflect the three major values of ecological, social, and economic benefits.
Urban wetlands, urban public open space mainly to improve the human habitat, compared with other “natural wetlands”, have three characteristics: first, social and ecological services are the main function. With the development of society, humans pay more attention to the benefits of non-material output. Second, safety and protection statuses are prominent [5]. Because of the urban population and economic development, urban wetlands play an important role in natural disaster prevention and control and improve the human living environment. Third, the cultural and educational advantages are reflected. Urban wetlands not only provide recreational services, but also have the educational significance of cultivating awareness of ecological and environmental protection to human beings [6]. Therefore, urban wetlands are regarded as urban ecological infrastructure or green infrastructure, building a protective barrier for urban ecological safety and symbolizing a higher level of urban civilization. Urban wetland protection and restoration not only affects the water security and ecological security of cities, but also can fully highlight the characteristics of cities and enhance their cultural taste.
1.4. Research Background
At present, wetland research has attracted the emphasis of wetland researchers internationally, and some developed countries have obtained many valuable theoretical studies and achievements in the research and exploration of wetland parks, and the theoretical and practical studies of wetland parks have gained great achievements under the struggle of researchers in various countries [7]. However, the evolutionary process of wetland parks is relatively short, and there are quite a lot of deficiencies in the construction of core theories. In the research process of wetland parks, it is necessary to insist on the combination of wetland theory and practice, to find loopholes in them, and to study the impact of urbanization development on wetlands from the theories, so as to solve the deficiencies that exist in wetland development.
China’s first national wetland park, Hangzhou Xixi, was built in 2005 [8]; since then, with the passage of time, the number and scale of urban wetland parks have been fairly well-improved and have progressed every year; the above have contributed to the development of China’s wetland conservation system, but also create a basis for the work of wetland conservation. In recent years, the Guangdong has begun making efforts to protect and restore wetland parks, and the achievements are remarkable.
The Guangdong Province, located in the south of China, belongs to the subtropical monsoon climate. The region has many rivers, a unique location and a narrow coastline; Guangdong has become a home to many diverse, large, and widely distributed wetlands, and is one of the strongest biodiversity provinces and regions in China. There are more than 2000 rivers of all sizes in the territory, the coastline of its islands is 1649.50 km long, and the east, west and north rivers converge to form the Pearl River Delta [9]. The interwoven network of rivers and waterways is also the cradle of the breeding and development of Lingnan culture. The Guangdong Province has 1,753,400 hectares of wetlands, of which 1,158,100 hectares are natural wetlands and 595,300 hectares are artificial wetlands. By 2007, twenty-seven national wetland parks were established in the Guangdong Province.
1.5. Purpose and Significance of the Study
A wetland is an area such as a coast, a lake, or a marsh where the land is too wet or where water often accumulates. However, from the viewpoint of ecological conservation, wetlands are defined in a broader scope, covering not only the water surface and the water surface between land areas throughout the year. In 1971, the Convention on Wetlands of International Importance as Waterfowl Habitat (Wetlands Convention) was signed by more than one hundred countries, as well as giving a broad definition. Article 1, paragraph 1 of the Convention defines the following: “A marsh, wetland, peatland, water, with a natural, artificial, permanent or temporary swamp, wetland, peatland, or an area of water with flowing, fresh, brackish or salt water, covering a depth of not more than six meters at low tide.” Wetlands are natural ecosystems with many functions and rich biological diversity on the globe, and are one of the main environments on which people depend for their survival. As an important part of the global ecological environment, urbanized wetlands provide rich environmental and ecological resources for human production and life, and have relatively high ecological value; for example, they produce oxygen, soil erosion, control runoff, store flood water, prevent drought, degrade urban pollution, regulate and control urban climate, and so on. Because of their filter-like function, wetlands are also known as the “kidneys of the earth”. Globally speaking, wetlands cover about 6.4% of the global land area, but store a large amount of organic carbon in the global soil, and most birds cannot survive or reproduce without wetlands; see Figure 1.
We analyzed the main problems faced by urban wetland protection and restoration, and reviewed the research progress of advanced theoretical technologies, key restoration technologies, and the natural ecological design of major urban wetland restoration at home and abroad. We also discuss the problems of biodiversity degradation, frequent destructive production activities of communities, and control governance in two wetlands, Taihu Lake and Poyang Lake. We analyze the successful experiences of urban wetland conservation as well as restoration in terms of adjusting industrial structure, developing circular economies, establishing an ecological compensation mechanism, strengthening regional management of wetlands, and enhancing publicity and education legislation to raise citizens’ awareness. Finally, the research development direction in the field of urban wetland conservation and restoration is foreseen.
In the context of global climate change, wetlands in urbanized areas are equivalent to an ecological barrier naturally constructed for cities, often effectively buffering external damage and impact when extreme weather events such as floods and storm surges are hitting cities. After the tsunami in Japan in 2011, the Japan Institute of Air and Space Technology (JIAT) reassessed the embankment standards of coastal cities in Japan, and after considering the effects of extreme storm surges, ground subsidence, and rising sea levels, it was found that the design standard of one in four hundred years for logs in the Osaka area could actually only cope with extreme tide levels of one in sixty years. The design elevation of one in two hundred years in the Takamatsu area actually only meets the standard of one in ten years. The natural disasters that have occurred in coastal areas around the world have shown us that no artificial or hard dams that are high and strong are infallible, and that what humans need to do is to reflect on the narrow development concept of trying to overcome manipulate nature, and to respect the needs of nature more, seek the ability of nature, leave space for water and nature, and rely on the ability of nature to ensure human safety.
In a typical natural “urban wetland”, although the conservation of wetlands and their important ecological value has been widely recognized by all walks of life, and work has been carried out to protect wetland wildlife, the protection of wildlife is only the first step. The value of estuarine wetlands is by no means limited to the sheltering of wildlife; they are also a natural barrier for coastal cities against extreme weather events such as storm surges and floods, and bear an important responsibility for the ecological safety of the entire city. For example, the 12th Five-Year Plan for Environmental Protection and Ecological Construction in Fuzhou City clearly states: “Implement wetland protection projects, protect and restore wetland ecosystems, and enable wetlands to be reasonably developed and utilized”. Obviously, there is still a deficiency in making wetlands equal in size and area, i.e., working out how to provide space for sustainable urban development while ensuring the least amount of effective land so that urbanized wetlands become an overall ecological security model. A comprehensive understanding of the important ecological service functions beyond land resources, such as safeguarding urban safety, mitigating urban heat island effect, buffering disaster impacts, sheltering wildlife, and supporting agricultural and fisheries development. All the “understanding” and “protection” are based on the familiarity and control of the spatial and temporal dynamic evolution of wetland ecosystem characteristics and laws. Therefore, in the wetland distribution area, it is of great significance for the construction of regional ecological and environmental security to carry out long-term, targeted ecological monitoring. We provide an in-depth study of the spatial and temporal dynamic evolution of key ecological elements in the wetland ecosystem characteristics, and make scientific and objective quantitative assessment to find the ecological and environmental problems of the crux. For a full understanding, we grasp the spatial and temporal evolution of the wetland ecosystem laws to explore the effective prevention of urban wetland area and system function degradation, to strengthen regional, ecological, and environmental security.
2. Domestic and Foreign Research Processes
2.1. Foreign Research Process
Foreign research on wetlands was carried out relatively early, and wetlands prospered in the early days in North America. The development of wetland parks has gradually made greater progress in adopting foreign technical means of wetland landscape planning and construction, while also using wetlands as a comprehensive place for wetland activities, including the development of recreational products, wetland activities, and health care. The currently available research results are insufficient for solving the practical problems encountered in wetlands. Therefore, it is important for researchers around the world to work together to explore the problems encountered in wetland ecology, share the available academic results with each other, and work to maintain the ecology.
Up to now, the theoretical research results achieved in the field of urban wetland research in Western countries, led by the United States, were particularly profound. It is known that the distribution of wetlands in the United States is extensive, and the US ranks among the top in the world in terms of the number of wetlands and wetland parks. Research on wetlands began in the United States in the late twentieth century. The research process has encountered many problems, and most of the current wetland problems have been solved through academic research and practical work, and theoretical research is excellent. These theoretical bases have a very important role in furthering our understanding of wetlands.
There is a certain amount of research and understanding of wetland parks in foreign countries, and a series of policies have been proposed, and good development results have been achieved. However, in the effective use of wetland resources and the rapid development of urban agriculture, the integration of resources and development, as well as the benefits of both ecological and economic aspects, the theoretical basis of the dual-effect theory is not comprehensive enough, and requires continuous exploration and research by academic researchers.
Foreign research on wetland parks lies, on the one hand, in the study of natural wetland parks, mainly on the diversity of aquatic species habitats. In their study of wetland parks, ref. [10] applied the concept of ecological corridors to the conservation planning of wetland systems on the west coast of Taiwan, and proposed the concept of wetland ecosystems for wetland park planning. In their study of natural wetland parks, they used ecological analysis, environmental analysis, and environmental economics, advocating for the application of these methods to wetland parks, arguing that the scientific research value and integrity of wetland ecosystems should be the focus of building wetland parks in non-core urban areas, and in the peripheral areas of nature reserves.
Foreign research on wetland parks, on the other hand, lies in artificial wetlands; ref. [11] proposed that the construction of artificial wetlands helps to restore the surrounding ecological environment. At present, the main research areas of artificial wetlands abroad are urban waste treatment, urban sewage, flood control, urban landscape, and ecological value research. This research considers that artificial wetlands have recreational and economic values and play a very important role in natural ecology and urban functional area improvement.
Developed countries started the planning and construction of wetland parks very early, providing useful reference for the protection, utilization, restoration, and reconstruction of wetland ecosystems. The Beaumont Artificial Wetland in the United States, the Leighton Wetland Garden Wetland, and other wetland parks represented in sewage management are worthy of reference for other wetland parks. Australia’s Newcastle Trane Wetland and Canada’s Nebo Lake Oak Wetland provide habitats for a variety of organisms and provide people with science education and ecotourism services. The London Wetland Park in England is mainly composed of marshes and ponds, and the wetlands have been restored and re-rationalized to form an excellent ecological environment, thus being able to attract a large number of waterfowl to inhabit the park.
2.2. Domestic Research Progress
Against the background of deterioration due to destruction of ecological environment, the importance of protecting the environment has gradually attracted the attention of human beings. Due to the importance of protecting the environment, after the rapid development of international wetland public interest organizations and the 1971 Convention on Wetlands, China joined in 1992 and developed wetland environmental activities in our country (see Figure 2).
China’s research in wetland parks has, relatively, lagged behind; the research on wetland parks began at the founding of the country. Researchers [12] began to dive into the study of wetlands since the founding of New China and in the following decades. In China’s wetland parks, in the academic field of continuous exploration and in the Institute in various areas of wetlands, in-depth discovery and research generally found and realized that wetlands, for the sustainable development of people, have a very important role. In 1992, our country joined the ranks of global wetland conservation and acceded to the “Wetlands Convention”. Since then, China has further studied wetland ecosystems in depth, and applied theories to the conservation and restoration of wetland ecosystems, management, and exploration, providing the basis for the development of wetlands in China.
So far, China’s research on wetland parks is not deep enough. Wetlands are a broad concept that encompass many different fields and disciplines, so they cause the complexity of wetland environments. Now, China lacks some systematic research results on wetland park planning and design theories and methods, while continuing to explore and accumulate practical results and scientific theoretical results. In future scientific research on wetland parks, it will be necessary to continuously explore the academic field of wetlands. At present, there are many sources of ecological deterioration of wetlands as well as solutions waiting for scholars and researchers to explore and study through this process.
In general, there is still a gap in the research and exploration of wetland parks in China compared to the developed countries in the West, and the scientific research institutions and theoretical systems engaged in wetland research are not complete or perfect. Since the completion of the first wetland theme park, theoretical research and practice have complemented each other’s development, and many cities in China have already carried out wetland planning and protection and restoration work. Now under the influence of the sponge city theory, wetland parks reflect the aesthetic, ecological, and cultural integration and other values of conservation and layout of the planning, wetlands and cities have become more closely linked.
Impact of Urbanization on Wetland Ecosystem
There are significant differences between urban and non-urban environments in terms of natural environment and biological characteristics. With the continuous development of urban construction, the hydrological properties of urban wetlands have changed, which has a direct impact on the structure and function of wetlands. For example, the construction of municipal infrastructures such as roads, sewers, and river surges will have an impact on the hydrological properties of rivers, which in turn will lead to a chain effect on the wetland and terrestrial ecology in the surrounding areas. Urbanization has caused changes in the biological and chemical properties of wetlands, resulting in changes in their species assemblages, dispersal capabilities, and interactions. Specific, rare, and special forests are limited in the region. The size, morphology, and hydrological conditions of patches are the main factors affecting the ecology of plant and animal growth and reproduction.
In the process of urbanization, the changes in wetland morphology are influenced by the combination of both natural and human aspects, i.e., the combined action of man and man. The natural force belongs to the eternal, which is always present in the process; the human dynamics, that is, the transformation and utilization of wetlands by man, changes from weak to strong, and more and more widely and profoundly changes the morphology of wetlands, making them the main force of the whole ecosystem in a certain period of time. Especially in the case of a combination of natural and human dynamics, wetlands have been severely damaged, leading to the collapse of entire ecosystems. Studies have shown that the historical variability of wetlands in arid regions, as well as the progressively changing dry and hot climate, are important factors in creating this variability, as shown in Table 1, Table 2, Table 3 and Table 4 and Figure 3.
2.3. Impact of Urbanization on Wetland Area
The decrease in wetland area due to urbanization is mainly due to sedimentation, lake and beach reclamation, and landfills, and the filling, occupation, and modification of wetlands by urban construction and transportation. The USDA survey shows that the reduction of wetland area in the U.S. watershed is mainly due to the urbanization process. Urbanization has led to a loss of 58% of wetlands in the United States, 55% of wetlands in the Netherlands since 1950, 90% of wetlands in New Zealand since 1850, and 60% of wetlands in Spain. Our wetlands decreased by 33% from 1978 to 2008. The second national wetland survey in 2009 showed that the total area of wetlands in China was 53,602,600 hm2, a decrease of 3,396,300 hm2 compared to the first survey completed in 2003, with a decrease of 8.82%. The wetland area of urban lakes in Wuhan City reduced by 52.3 percent from the 1950s to the early 21st century. The Xixi wetland in Hangzhou has rapidly declined in area due to rapid urbanization, especially in the eastern part of the wetland, where the area of the water body declined from 29.50 percent in 1990 to 4.45 percent in 2010. Urban expansion in areas such as Beijing, Tianjin, Wuhan, Jinan, Shanghai, and Lhasa has resulted in the permanent disappearance of surrounding wetlands, as shown in Table 5 and Figure 4.
2.4. Impact of Urbanization on Wetland Biodiversity
Wetland habitat fragmentation induced by urbanization can adversely affect native flora and fauna, leading to changes in species richness and distribution, population composition, and ecosystem function. This is because the shift in land use types during urbanization can lead to a reduction in plant and animal habitat, habitat fragmentation, and decrease in environmental quality. The enhancement of boundary habitats and their boundary effects can limit pollen and fruit dispersal, increasing the number of soil plots susceptible to invasive species and enhancing species invasion. Researchers [13] found that urbanization increased the loss of native species and invasion of exotic species in Atlantic white fir Chamaecyparis thyoides wetlands, preventing the development of wetlands. It was also found that sediment accumulation from urban runoff and frequent streambed disturbance limit algal blooms, and that sediment metal accumulation in streambeds has devastating effects on algae [14]. The evolution of the original wetland plant communities in Dongting Lake to artificial communities has accelerated along with the urbanization process. The reduction and loss of biodiversity will seriously affect the stability and ecological balance of the wetland ecosystem, damage soil fertility and water quality, affect food sources and industrial and agricultural resources, and ultimately affect ecological security and sustainable human development, as shown in Figure 5.
3. Effect of Wetland on Ecological Environment
Urban wetlands are an ecological and landscape type with a mosaic pattern of water bodies, banks, and land, and have long been an ideal place for people to live because of their unique resources and environmental conditions. Wetland areas exist in many of China’s most important tourist and scenic areas, and urban wetlands are generally the least active areas for human activity, and their beautiful natural landscapes are ideal for citizens and tourists. Even a walk, bike ride, etc. in a wetland park can be a refreshing experience. Today, people pursue a healthier lifestyle and often go to wetland parks as a family to release stress and build up their strength to pursue a better life.
Some wetlands have preserved historical relics, reflecting their profound humanistic heritage and rich material cultural heritage, and are an important place for studying history and culture [15]. Due to long-term human activities, they have become not just a physical landscape but a cultural landscape [16]. Under the guidance of relevant national conservation policies and development policies, the cultural ecology of the city can be effectively protected and preserved by tapping and renewing the unique cultural resources of wetlands. The waterfront landscape created by using wetlands can produce a strong visual effect and combining it with real buildings can form a spatial sequence with a sense of rhythm, thus making the wetlands and the city one in spatial structure.
3.1. Cultural and Scientific Values
Wetlands are not only the main ecological environment that people rely on, but also contain a rich variety of biology and a highly productive ecosystem. Urban wetlands are valuable because they have many ecological services that cannot be replaced by other factors, and are a barrier to urban ecological security, which is indispensable for sustainable urban development.
The greater the diversity of organisms, the more stable the urban ecosystem. Wetlands are key to maintaining urban biodiversity as a major component of the ecosystem on which many wildlife species depend for survival and reproduction [17]. At the same time, the biodiversity of urban wetlands also makes them an important genetic gene pool, which is of great significance for the conservation of wildlife germplasm resources and the cultivation and improvement of economic species. The complex ecosystems, rich flora and fauna, and species richness of urban wetlands provide valuable practice sites for conducting scientific education and research.
3.2. Benefits Embodied in Wetlands
3.2.1. Economic Benefits
In addition to the capital investment required to operate wetlands, they also have their own economic value. Firstly, artificial wetlands purify wastewater, a method that saves a lot of money and works better than conventional wastewater treatment methods, and they also store water. Secondly, Qionghai wetlands usually have a landscape effect and can be visited by tourists to gain economic benefits [18]. In addition, economic benefits can be gained from the plants and animals in these wetlands, such as fish, shrimp, crabs, algae, lotus roots, and rhizomes, which can be processed and sold as food, as shown in Figure 6.
3.2.2. Socio-Cultural Benefits
The wetlands themselves are a small biosphere, rich in biological resources and are an indispensable component of the environment. In the later stages of their development, the wetlands were developed in different styles according to their characteristics, thus adding artificial natural scenery to the city [19]. In beautifying the environment, they also create a good environment for humans to relax, exercise, rest, and release social stress. In addition, the wetland itself provides a good natural environment to cultivate people’s sentiment and inspire themselves, which has an irreplaceable value.
The biological chains, biomes, ecosystems, and ecospheres composed of many kinds of organisms in wetlands have educational and scientific significance, not only providing materials, but also serving as test bases for people to study and research.
In summary, the benefits that wetlands bring to a society can be summarized in the following areas. Wetland benefits include, but are not limited to: 1. maintenance of biodiversity; 2. floodwater storage; 3. natural disaster prevention; 4. degradation of pollutants; 5. regulation of climate; 6. prevention of saline leaching into coastal aquifers and water bodies; 7. wildlife habitat; 8. provision of abundant plant and animal products; 9. supply of water resources; 10. supply of mineral resources; 11. provision of energy; 12. provision of water transport; 13. provision of gene pools; 14. tourism and travel; 15. socio-cultural significance; 16. educational and scientific research value; 17. maintainence of natural systems and existing processes.
4. Wetland Conservation Issues and Measures
4.1. Difficulties and Problems Revealed in Wetland Conservation
Since the development of wetland parks in China is still in its infancy and various areas are not fully mature, there are very many difficulties and problems that need to be faced in the process of urbanization and development. The key points of performance are as follows.
4.1.1. To Establish a Sound Professional Management Body
At present, China’s exploration in the construction and protection of wetland parks is in its infancy, and the accumulation of experience, as well as practical exploration, are lacking [20]. It is necessary to integrate technical forces to build management institutions for the construction and protection of wetland parks, which is the most urgent task to accelerate the construction of wetland parks [21]. In addition, there has never been a sound system of technical research in the construction of wetland parks, nor has there been a perfect evaluation method of wetland parks, which obviously increases the risk of failure for relevant technical research.
4.1.2. Unscientific Planning and Design
At present, many wetland parks in construction lack the guidance of relevant scientific theory. They are completely copied from park/waterpark planning and design, and do not highlight the special characteristics of the wetland landscape.
Failure to create a structurally stable, species-diverse, and functional ecosystem has led to many problems in planning and design.
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Unreasonable design of land selection, in order to pursue a large area for the site to create pressure.
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Unclear division of functional zoning and unclear division of the core protection boundary, without highlighting the regional characteristics.
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Too much artificial change interference, the construction of too many squares and artificial buildings so that people do not appreciate the natural wetland scenery.
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Landscape design is too formalized, changing the long-established landscape pattern of natural and humanistic integration of wetlands, etc.
4.1.3. Policies and Systems Need to Be Improved
At this stage, many international countries have already formulated laws and regulations on wetland protection, but because the development of wetlands in China is relatively slow and late, and at the same time, the relevant domestic laws and regulations are not yet sound and perfect, there is a lack of protection laws in this area. The lack of laws and systems makes the park ecological environmental protection lack relevant laws as a basis [22]. At the same time, because the paid protection of wetlands has not been fully implemented, farmers are unable to obtain proper economic compensation due to the closure of grazing and the return of farmland to the swamp, which makes their enthusiasm for wetland protection very much negatively affected.
4.1.4. Management and Scientific Research Need to Be Strengthened
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The management system needs to be rationalized. At present, the management system of China’s wetland parks is relatively complex, involving many aspects of management issues, and the management efficiency is relatively low.
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Weak technology research lags behind. Because the current technical support for wetland protection is weak, the research in ecosystem restoration technology and wetland protection lags behind. This means that wetland park resource surveys, database construction, and other aspects of the work cannot be implemented.
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Educational functions need to be strengthened. Because of deviations in understanding, or because many are driven by economic interests, wetland park ecological protection may be seriously diluted and the contradiction between construction and wetland protection emerges. There is an overuse of development, leading to a loss of the original natural ecological functions of wetlands.
4.2. Suggested Measures for Wetland Convention Construction and Protection
4.2.1. Wetland Natural Ecological Design
The natural ecology of wetlands and scientific design is an important way to restore and adjust wetlands. Wetland ecosystems require the use of the basic principles and methods of ecology to build, restore, and adjust the wetland, so that the normal operation of the wetland and sustainable development of the ecosystem are mantained [19]. In the “Discussion on Several Basic Issues of Wetland Ecological Design”, the basic principles of its design, indicators of design, and types of design are discussed in more detail. This is of great guidance for the restoration and regulation of wetlands in China. It is believed that it will be of pivotal importance to the restoration and adjustment of wetlands in China.
4.2.2. Agreements Related to Wetland Conservation in China
Wetland conservation rate as shown in Figure 7. Our country has cooperated with international organizations, such as the International Fund for Nature, the United Nations Development Programme, the IUCN, and the International Crane Foundation, in the fields of wetland conservation and survey, natural area construction, and talent cultivation. At the same time, China has acceded to several international conventions. The reference conventions are listed in the Table 6.
5. Poyang Lake Wetland Ecological Restoration Case
This research team uses the successful restoration examples of Taihu Lake and Poyang Lake as the typical wetland ecological restoration cases in China shown in this project.
5.1. Introduction to Poyang Lake
Poyang Lake is a large-scale freshwater lake in China, geographically located in the middle and lower reaches of Yangtze River, spanning six provinces, including Jiangxi, Anhui, Zhejiang, Fujian, Guangdong, and Hunan, with a total of 84 counties and 23 districts, and nine percent of the Yangtze River area. Poyang Lake is a typical basin-type natural depression in the north of Jiangxi Province, which is connected with Ganjiang River area, Fei River area, Xinjiang River area, Rao River area, Xiushui area, and many other tributaries, and is an important overwater, throughput, and seasonal shallow lake of the Yangtze River.
5.2. Contamination before Remediation
After the 1980s, there was still a large amount of deforestation in the Poyang Lake area. The main forest resources in this basin are mainly coniferous forests, seventy-seven percent of coniferous forests and 76% of coniferous forests, and only twenty-three percent of leafy broad forests. Due to the acidification of coniferous forest soil, it is difficult for many plants to grow and very difficult to form a water and soil conservation system with supporting trees, irrigation, and grasses. The understory vegetation is very homogeneous and the forest floor surface cover is less, containing mainly acidic coniferous and humus, which makes it difficult to form effective water storage and water storage and to form effective ecological protection.
Jiangxi is the province with the most serious soil erosion in the south of China, and the soil erosion is focused on the middle and upper reaches of “Five Rivers” basin and the Poyang Lake basin represented by the Poyang Lake; the soil erosion area reaches 336.12 × 105 thousand square meters at present, accounting for 95.5% of the total soil erosion in China. The 210,104 × 104 t of suspended matter separated from the sloping cultivated land and sparse residual forest leads to the siltation of the lake; 315.6 × 104 t of sediment produced by the waste earth from mining, road construction, and natural scouring leads to the siltation of the middle and upper reaches and ponds, reservoirs, weirs, and dams. In addition, the total siltation of the lakes in the Yangtze River is 104.5 × 104 t from July to September every year; many places are turned into land.
From the ecological environment condition of Poyang Lake, its ecological environment problems are.
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(1). The reclamation of the enclosed lake leads to the reduction of the lake area and the decrease of the fishery production.
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(2). Water pollution and water level change will affect the life of aquatic plants and animals, thus affecting the biodiversity of wetland.
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(3). Changes in the wetland landscape and a decline in plant and animal species and numbers will have a direct impact on the development of ecotourism and economic income
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(4). Flooding has a huge impact on the regional economy.
In 1990, the arable land in Poyang Lake area was 412,236,000 hm2, and in 2003, the arable land in the whole area was only 376,193,000 hm2. The main reasons for the continuous decrease of arable land in the lake area are: (1) farmers occupy the land for building houses; (2) soil erosion and floods destroy the arable land; (3) farmers burn bricks and destroy the fields. At present, the quantity of destroyed fields by burning bricks reaches 4,670,000 hm2 every year, and this phenomenon can be seen everywhere in Poyang Lake area.
The research results show that the clean soil in the agricultural soil of the Poyang Lake area accounts for 1.57% of the total area. The clearer and cleaner soil accounts for 74.34%. The starting polluted soil accounts for 20.44%. Significantly polluted soil accounts for 3.43%. Severely contaminated soil accounts for 0.22%. Nearly 1/4 of the agricultural soils are contaminated. Over the last two decades, at least 50 to 60% of the agricultural soils in the Lake District are currently contaminated.
Due to the rapid development of agriculture, agricultural production, and urbanization, the pollutants brought by the lake runoff and the Yangtze River basin have caused serious pollution to the local water bodies and have formed a very great impact on the survival and reproduction of the organisms living and growing in the water. The water quality of some waters from rivers into the lake exceeds the standard, and the detection rate is one hundred percent; it has a significant impact on the eutrophication process of Poyang Lake.
5.3. Wetland Restoration Project Construction Practices
5.3.1. Strictly Enforce the Control of the Development Area of Wetlands to Preserve the Habitat Space for Wildlife
The unscientific and unreasonable expansion and development, excessive reclamation, and development degrade the function of wetland and deteriorate the ecological environment. “According to local conditions” should be the important guideline for the development and utilization of Poyang Lake wetland in the future. In recent years, the development of County Yang Lake wetland has already had a certain scale; in the future, the construction should be carried out in stages according to the specific situation, and the ecological restoration and reconstruction should be carried out in the area that has been changed, and corresponding measures should be taken. At the same time, we should gradually realize the development of industry, agriculture, and the expansion of urbanization, gradually establish a reasonable land layout, implement the return of farmland to grass in areas that have caused serious damage to the ecological environment, change the use of wetland resources to compensate for the decline in the area of arable land, impose strict restrictions on the main wildlife habitats, and require the preservation of wetland organisms to have a living space sufficient to live and breed.
5.3.2. Increase Financial Investment to Strengthen Research on Biodiversity
The wetland biological resources in Poyang Lake are rich and play a pivotal role in reservoirs and flood control, etc. Various effective financing methods should be adopted to increase the investment and input, especially using modern technology to monitor the ecological environment of Poyang Lake comprehensively and establish the database of the wetland ecosystem of Poyang Lake, and investigate further. The database of the ecosystem of Poyang Lake, various types of species, ecological environment system investigation and collection, protection and identification, etc. will be integrated into the unified management and service, and based on this, a wildlife breeding and protection center for Poyang Lake wetland will be established, and the wildlife species and quantity of Poyang Lake will be improved gradually through advanced breeding technology, so as to explore a new way of scientific and reasonable sustainable development.
5.3.3. Reasonable Development of Wetland Resources of Poyang Lake
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Resolutely level the dike and flood, and return the farming to the lake. Restore the wetland area of Poyang Lake and gradually restore the wetland ecosystem.
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Develop and utilize the famous and excellent wild plant resources in the lake area in an organized and high-level way, introduce excellent varieties, and establish an artificial cultivation base.
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Protect the water environment: industrial sewage, slag dust, pesticides and fertilizers, and snail control agents discharged into the lake should be strictly managed, controlled, and prevented from pollution according to the national permitted standards.
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Srictly conserve the natural vegetation of the sandbar in the lake area, absolutely prohibit grazing, deforestation and woodcutting on the sandbar. To rationalize layout, plant trees and grasses, and establish a system of wind and sand control forests.
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To protect the natural forest vegetation of five major rivers into the lake, fully implementing the natural forest protection project in the Yangtze River basin and preventing soil erosion is the key to protect the ecology of Poyang Lake wetland.
5.3.4. Launching Publicity and Education Legislation to Raise Public Awareness
Making citizens understand and participate in wetland work is the main influential significance for the protection of various organisms in urbanized wetlands. At present, the publicity and education of the ecological environment of Poyang Lake wetland is still very backward, and the popularity is far from enough, due to the cultural quality of local people and the gap in local economic development, which leads to problems such as a lack of public awareness and frequent actions of damaging wetland. On this basis, we should further strengthen communication and exchange with the surrounding areas of Poyang Lake to make the public realize the importance of biodiversity protection, so as to enhance the public awareness of ecological environment, and promote the protection and development of Poyang Lake wetland through special laws and regulations.
5.3.5. Status of Restoration of Poyang Lake
Poyang Lake Wetland Park is the largest one in the country, with one thousand and sixty-seven lakes; the fish in the lake are fresh and delicious, especially the various delicious fishes such as the three fresh Poyang fish. As the most characteristic wetland scientific research base in China, Poyang Lake National Wetland Park has built Poyang Lake Wetland Science Park based on the natural conditions of Poyang Lake, which fully displays the largest wetland resources in China. It dedicates a most intuitive, and easy, as well as effective, understanding platform for the general public to understand wetlands and promote wetland conservation by collecting, collecting, displaying, and studying the physical objects of wetland ecology and wetland cultural heritage. The establishment of the Science Park has served the function of public learning. In the vast wetland area, there are many kinds of vegetation, which release a large amount of carbon dioxide gas through photosynthesis. Poyang Lake National Wetland Park has rich wildlife resources, including 249 species of wild vertebrates; 141 species of vascular wetland plants; 108 species of fish; 132 species of birds, accounting for 98% of the total number of wetland migratory birds in the world, and more than 4000 white cranes; 98% of white cranes and hundreds of swans choose to spend winter in Poyang Lake every winter, which is a spectacular sight. It is called “Paradise of cranes and hometown of swans”. (see Table 7).
6. Conclusions
China only started wetland research in the 1950s, but still no sound theory has been formed so far, and the progress of research is uneven for various different types of wetland ecosystems. We suggest that in the future, in addition to the application of high technology, research on different aspects should be strengthened, and new progress is expected to be made.
In this study, we examine wetland conservation methods, wetland restoration and wetland reconstruction methods, sustainable development methods, governance methods, and the relationship with drought. We found that the concept and division of wetlands have not yet formed a relatively complete definition and related classification system; we also comprehensively survey and compile wetlands and their resources, and scientifically map urbanized wetlands. At present, the productivity and carrying capacity of wetlands in our country are still in the initial stage of development and need to be further improved and improved.
Conceptualization, Z.L. and D.G.; Data curation, L.M.; Investigation, B.X.; Methodology, Q.H.; Resources, L.F.; Visualization, D.G. All authors have read and agreed to the published version of the manuscript.
Not applicable.
Not applicable.
The experimental data used to support the findings of this study are available from the corresponding author upon request.
The authors declare no conflict of interest.
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National and sub-source chemical oxygen demand emissions in 2020.
| Project | Total | Industrial Source | Agricultural Source | Source of Life | Centralized Pollution Control Facilities |
|---|---|---|---|---|---|
| Emissions/million tons | 2564.8 | 49.7 | 1593.2 | 918.9 | 2.9 |
| Proportion (%) | - | 1.9 | 62.1 | 35.8 | 0.1 |
National and sub-source total nitrogen emissions in 2020.
| Project | Total | Industrial Source | Agricultural Source | Source of Life | Centralized Pollution Control Facilities |
|---|---|---|---|---|---|
| Emissions/million tons | 322.3 | 11.4 | 158.9 | 151.6 | 0.4 |
| Proportion (%) | - | 3.5 | 49.3 | 47.0 | 0.1 |
National and sub-source ammonia nitrogen emissions in 2020.
| Project | Total | Industrial Source | Agricultural Source | Source of Life | Centralized Pollution Control Facilities |
|---|---|---|---|---|---|
| Emissions/million tons | 98.4 | 2.1 | 25.4 | 70.7 | 0.2 |
| Proportion (%) | - | 2.2 | 25.8 | 71.8 | 0.2 |
National and sub-source total phosphorus emissions in 2020.
| Project | Total | Industrial Source | Agricultural Source | Source of Life | Centralized Pollution Control Facilities |
|---|---|---|---|---|---|
| Emissions/million tons | 33.7 | 0.4 | 24.6 | 8.7 | 0.01 |
| Proportion (%) | - | 1.1 | 73.2 | 25.7 | 0.03 |
Actual urbanization rate in China, 2010–2019 (%).
| Year | Urbanization Rate of Resident Population | Urbanization Rate of China’s Urbanized Household Population | Actual Urbanization | Urbanization Rate of Middle and High-Income Countries | Actual Deviation |
|---|---|---|---|---|---|
| 2010 | 49.95 | 34.17 | 45.69 | 58.86 | −13.17 |
| 2011 | 51.27 | 34.71 | 46.80 | 59.74 | −12.94 |
| 2012 | 52.57 | 35.33 | 47.92 | 60.60 | −12.68 |
| 2013 | 53.73 | 35.93 | 48.92 | 61.46 | −12.54 |
| 2014 | 54.77 | 36.63 | 49.87 | 62.30 | −12.43 |
| 2015 | 56.10 | 39.90 | 51.73 | 63.14 | −11.41 |
| 2016 | 57.35 | 41.20 | 52.99 | 63.96 | −10.97 |
| 2017 | 58.52 | 42.35 | 54.15 | 64.78 | −10.63 |
| 2018 | 59.58 | 43.30 | 55.18 | 65.57 | −10.39 |
| 2019 | 60.60 | 44.38 | 56.22 | 66.35 | −10.13 |
International Convention on Wetlands.
| A | Convention on Wetlands of International Importance especially as Waterfowl Habitat |
| B | Convention on international trade in endangered species of Wild Fauna and Flora |
| C | United Nations Convention on the Law of the Sea |
| D | Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter |
| E | United Nations Convention to Combat Desertification |
| F | Convention on Biological Diversity |
| G | United Nations Framework Convention on Climate Change |
List of wetland types in Poyang Lake National Wetland Park.
| Land Type | Area (ha) | Proportion in Total Wetland Area (%) | Proportion in Total Land Area (%) | |
|---|---|---|---|---|
| Natural wetland | Lake | 12,920.9 | 36.8 | 35.6 |
| Rivers | 1125.8 | 3.2 | 3.1 | |
| Grass island | 4312.2 | 12.3 | 11.9 | |
| Mudflat | 13,624.5 | 38.8 | 37.5 | |
| Island | 276.0 | 0.8 | 0.8 | |
| Inundation | 1866.6 | 5.3 | 5.1 | |
| Constructed wetland | Pond | 275.9 | 0.8 | 0.8 |
| Irrigated land | 714.2 | 2.0 | 0.8 | |
| Woodland | 27.5 | - | 0.1 | |
| Other land | 1141.4 | - | 3.1 | |
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