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1 Introduction

Wetlands are described as “the lands of transition zone between aquatic and terrestrial ecosystems where the land is covered by shallow water” (Mitsch and Gosselink 1986). The worldwide intergovernmental treaty on wetlands signed at Ramsar, Iran, in 1971 includes marsh, fen, bog, peatland or flowing water, static water, and fresh, salty, or brackish water whether artificial or natural areas of marine water (the depth should be maximum 6 m at low tide) into the wetland (Bowman 2002). However, in the Ramsar Convention, paddy fields, river channels, and anthropogenic water bodies are not comprised in wetland. As wetlands have zoological, ecological, botanical, hydrological, and limnological importance, they are categorized as “wetlands of international importance” underneath the Ramsar Convention (Frazier 1999). The Ramsar Convention published an international report in 2013 in the Economics of Ecosystem and Biodiversity for Water and Wetlands, which emphasizes on the need of shifting our attitude toward wetland. The Ministry of Environment, Forest and Climate Change (MoEFCC) in the notification on 26th September, 2017, has described wetlands as vital bodies of the ecosystems which support abundant biodiversity and help in hydrological cycle. Wetlands provide a broad spectrum of services and resources to the community, such as flood mitigation, water storage and purification, aesthetic enrichment of landscapes, microclimate regulation, and cultural and social activities, for recreational prospects and supporting cultural heritage (Clarkson et al. 2013).

Currently, wetlands are shrinking due to urbanization, population growth, climate change, and land use alteration (Davis and Froend 1999; Ferrati and Canziani 2005; Sebastiá-Frasquet et al. 2014). This might stimulate the qualitative and quantitative characteristics of wetland ecosystems’ functions and services (Erwin 2009). Generally, wetlands are mainly influenced by the social (anthropogenic) pressures such as wastewater discharge, runoff from agriculture, and groundwater depletion by abstraction of groundwater for the utilization of urban water supply and other agricultural practices (Konikow and Kendy 2005). The majority of research has agreed that there is urgency for coordination in an attempt to restore, protect, and manage the wetland ecosystems (Hansson et al. 2005). To find the way for maintaining the sustenance of wetland and the nature, numerous authorities from governmental and nongovernmental levels should coordinate by forming policies and frameworks. In both, the developed and developing nations, various frameworks, policies, and regulations should be implemented to check the degradation of wetland.

1.1 Wetland Type (Ramsar Convention)

Under the umbrella of the Ramsar Convention, wetland types have been defined to aid sharp recognition of the wetland habitats that correspond to every Ramsar site (Table 1.1). Different codes have used to define wetland types. Ramsar sites are dependent upon the Ramsar Classification System for Wetland Type as approved by Recommendation 4.7 and amended by Resolutions VI.5 and VII.11 of the Conference of the Contracting Parties (Table 1.2) (Plans et al. 2009).

Table 1.1 Wetland type and their description
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Table 1.2 Classification of wetlands
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2 Wetlands of India

The wetland of India has been categorized into following types (Prasad et al. 2002).

2.1 Himalayan Wetlands

This type of wetlands includes the parts of Central Himalayas, Eastern Himalayas, Ladakh, and Zanskar (Pangong Tso, Chantau, Tso Moriri, Noorichan, Hanley, and Chushul marshes) and few portions of Kashmir Valley (Dal, Anchar, Haigam, Kranchu, Malgam, Wular, and Haukersar lakes).

2.2 Indo-Gangetic Wetlands

Through the whole stretch from the river Indus at one end of west to Brahmaputra at the other end of east, there lies the largest wetland system in India called the Indo-Gangetic floodplain. The wetlands of the Indo-Gangetic plains and the Himalayan Terai are included in this type of wetlands.

2.3 Coastal Wetlands

The lagoons, mangroves, and massive intertidal expanses are included in the coastal type of wetlands. These are stretched along the 7500 km coastline in West Bengal, Orissa, Tamil Nadu, Andhra Pradesh, Karnataka, Goa, Kerala, Gujarat, and Maharashtra. This category of wetland includes Andaman and Nicobar Islands, Gulf of Mannar, Lakshadweep, Gulf of Kutch, and Sundarbans of West Bengal.

2.4 Deccan

Several tanks for storing water and numerous trivial and huge reservoirs along with few natural wetlands in nearly each town in the associated region are included in this category of wetland ecosystem (Fig. 1.1).

Fig. 1.1
figure 1

Different types of wetlands of India (a) Indo-Gangetic wetland, (b) coastal wetland, (c) Himalayan wetland

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3 Importance of Wetlands

Wetlands have significant socioeconomic importance like wildlife resource, tourism, energy resource, and water supply. The services and products supported by wetlands are noteworthy. There is a very broad spectrum of services and resources provided by wetlands to humans (Engelhardt and Ritchie 2001). They provide shelter, food, shellfish, livestock fodder, fish and fuel wood, medicinal plants, building materials, honey, beeswax, etc. Straightforwardly or circumstantially wetlands support people by their different functions and values. The biological, environmental, and fiscal values of wetlands are of great importance, which are directly affected by humans. Several valuable operations/services carried out by wetlands are as follows.

3.1 Water Quality

Wetlands have a very dynamic role in storing water and improving the quality of water (Clarkson et al. 2013). They purify water, revive groundwater, and also control the frequency of runoff in urban areas. Many plants growing in wetlands act as filters by doing the cleansing role for the downstream environment (Engelhardt and Ritchie 2002). So, wetlands are regarded as the kidneys of the ecosystem (Mitsch and Gosselink 1986).

3.2 Flood Control

Wetlands help in attenuating flood and decreasing the effect of flood. They maintain the groundwater levels all through the low rainfall periods (Roulet 1990). Riverbanks and shorelines are well stabilized by wetlands of that area. They play a vigorous role in checking coastal erosion by buffering the shorelines against erosion, besides also helping in alleviating the effect of natural disasters by absorbing the tidal forces (Wondie 2010).

3.3 Wildlife Habitat

As every wetland is unique in their climatic and topographic conditions, they have specific environmental conditions which provide vulnerable and endangered communities (Brinson and Malvárez 2002). They are the areas of great importance from the perspective of wildlife habitat as they have no less wildlife species than a forest habitat.

3.4 Recreation, Education, and Resources

As wetlands are the landscapes which add beauty in nature, they provide bird watching, recreational activities of fishing, boating, etc. They play a foremost part in tourism for the recreation of society, for habitat, and for supporting cultural heritage (Clarkson et al. 2013). From the perspective of education, wetlands are interesting environmental resource of carbon sequestration, disaster management, nutrient removal, biodiversity maintenance, and toxic retention (Zedler and Kercher 2005).

4 Growing Threat to Wetland Ecosystem

As wetlands are often depicted as kidneys of the landscape, this directly means it helps in biodiversity maintenance (Mitsch and Gosselink 1986). The change in the physicochemical properties of wetland mainly relies on the climate condition, nutrient availability, and topographic and hydrological conditions. The biotic response depends on the physicochemical modifications in the wetland (Gosselink and Turner 1978). From the past few decades, humans have ignored the importance of wetland ecosystems. The rapid population, land use patterns, and demands of resources have led in the degradation of wetlands. Pollution of wetlands by agricultural runoffs and domestic and industrial wastes have headed towards the major destruction to the wetland ecosystems.

Due to urbanization, demand of resources, and land use changes, wetlands are facing major troubles (Boyer and Polasky 2004). The developmental pressure is increasing day by day leading to the degradation of the wetland ecosystems. The urban water supply demand has led to over withdrawal of underground water which causes salinization and reduction in the water table of the region (Prasad et al. 2002). There are considerable ecological, biological, and economical losses due to unplanned developments. Different anthropogenic activities like agriculture, road construction, industries, residential developments, resource extraction, and disposal of wastes are a main cause of long-term losses and ecological disturbances in the wetland ecosystems (Prasad et al. 2002). The agricultural activities like irrigation by construction of dams, canals, and reservoirs have altered the hydrological conditions of the associated wetlands (Russi et al. 2013). The different hydrological activities like diversion of streams and rivers, transport of water to arid regions, changes in the drainage patterns, and construction of canals have led to the significant degradation of wetlands in the associated regions.

Wetlands are also largely affected by deforestation, as it leads in the removal of the topmost layer of the earth leading to soil erosion and siltation problems (Smith et al. 2016; Zhao et al. 2006). Besides, the unrestricted dumping of toxic wastes from industries and sewage has led in the deterioration of physiochemical properties of wetlands, giving rise to eutrophication and destruction of aquatic ecosystem of the related wetland (Russi et al. 2013). Climate change like the change in precipitation patterns, global warming, increased CO2, increase in the occurrence of storm floods and droughts, and sea level rise could also badly affect the wetland ecosystems (Chen et al. 2003). The plant species like water hyacinth and Salvinia has threatened the Indian wetlands, as these species absorb the underground water and also clog the waterways (Prasad et al. 2002).

5 Strategies of Restoration and Conservation

Wetlands are considered as one of the most fertile but endangered ecosystems of the world (Cherry 2012; Maltby 1991). Extensive uses, as well as exponential population growth, have made this ecosystem more deteriorating and vulnerable to environmental changes (Zedler 2003). Anthropogenic pressure (i.e., land use change, inappropriate use of water resources, burgeoning development projects) is the well-known reason of the decline in wetland resources (Ducks Unlimited Canada 2010). In contemporary time, wetlands are modifying continuously for the human needs, and the current wetland’s declining rate in India can move toward severe environmental consequences. Around 74% of the rural populations (Anon 1994) are reliant on resources coming from the wetland. Land use conversion from wetland to agricultural, industrial, and various urban development results in substantial losses in the form of hydrological perturbations, pollution, and their effects (Turner et al. 1994). In the context of Indian biodiversity, numerous flora and fauna are reliant on wetlands or their products (Prasad et al. 2002).

To control these problems, restoration practices are not the only options but the ultimate necessity. Along with various biological restoration practices, the practices of natural hydrological conditions of wetlands are able to reconstruct the physicochemical properties like the degree of the substrate, pH, nutrient availability, anoxia, sediment properties, and soil salinity (Prasad et al. 2002). These modifications lead to a change in physicochemical environment, which also promotes to change in biotic feedback in the wetland (Gosselink and Turner 1978). Hydrological conditions in wetlands modify even slightly which can lead toward huge change in response to biota richness, species composition, and ecosystem productivity. There are some restoration methodologies for wetland as described by various authors (Pfadenhauer and Klötzli 1996; Klimkowska et al. 2007):

  1. i.

    Fen depth: Fen depth has been necessary since we assumed that most of the organic material will soon be lost anyway at peat depths of less than 1 m.

  2. ii.

    Rewetting potential: The rewetting potential is chosen as a criterion because one has to be sure that sufficient water is available in the area to allow permanent flooding and the purpose of a wetland as a sink can be restored. Assessment of rewetting potential is specifically important and must include the entire catchment area of the wetland to be restored.

  3. iii.

    Presence of suitable target species: The third major criterion, the occurrence of target species, is more relevant when areas cannot be rewetted sufficiently. In that case, the existence of characteristic fen or fen meadow species is important for carrying out a more flexible plan, in which several development goals must be pursued simultaneously. It may take some time before the site conditions of the restoration area meet the requirements of the target species.

5.1 Use of GIS and Remote Sensing in Wetland Management

Remote sensing data accomplished with geographic information system (GIS) is a significant tool for wetland restoration and management. The application encloses water resource assessment, flood management, hydrologic modeling, reservoir capacity surveys, water quality mapping and monitoring, and assessment and monitoring of the environmental effects of water resources project (Adam et al. 2010; Jonna 1999).

  1. i.

    Water Resource Management

Abundant of thematic maps on the hydro-geomorphological features, slope, elevation, surface water bodies, and land use are performed by remote sensing and GIS. It has been initiated for the action plan for water source development (Adam et al. 2010; Ozesmi and Bauer 2002). The result may also reveal that the underground potential basin is moderate to good (Rao 1997). Utilization of satellite remote sensing data and aerial photointerpretation impressively support in planning groundwater reconnaissance and help in discovering the sources by recognition of geomorphological units.

  1. ii.

    Flood Zonation Mapping

Satellite data source is utilized for the demarcation of flood-risk zone and flood-inundated regions. Temporal data promote to get correct ground facts about the status of restoration and conservation projects of wetland. IRS 1 C/D WIFS data having 180 km spatial resolution and high temporal consecutiveness has helped in demarcating the zonation of flooding areas of large river bodies. This helps in designing for basin- and state-wise flood inventories.

  1. iii.

    Water Quality Analysis and Modeling

Water quality analysis has been proceeded through using the relationship between chlorophyll-a, reflectance, and suspended solid concentration. Remote sensing data is utilized for the analysis of water quality factors and modeling. In the near-infrared wavelength range, the quantity of suspended solids content is directly proportional to the reflectance. Due to the temporal and spatial resolution of satellite data information of the point of discharge and source of pollution, the inflow of sewage can be regularly examined. By means of IRS LISS-II data, the suspended load in estuarine waters was inspected (Adam et al. 2010; Sasmal and Raju 1996).

There was some program initiated by WWFs for the conservation and restoration of wetland which helps to improve water access, efficiency, and allocation for people and the environment. This program promotes water stewardship, climate change adaptation, and water safety and mainly emphasizes habitat protection. Working with the Ramsar Convention, international river basin, national governments, nongovernmental organization, and institutions play a dynamic role for wetlands includes (WWF):

  • Assisting execution of international agreements and treaties on biodiversity and wetlands

  • Encouraging payments for environmental services (PES) for funding freshwater ecosystem facilities

  • Evaluating and growing the representativeness of freshwater habitats in protected area systems

  • Forming freshwater conservation setups

  • Restoring serious freshwater habitats

5.2 Specific Techniques for Conservation

Wetland restoration technique involves modification in hydric soil condition, hydrophytic plant communities, and hydrologic conditions. Wetland functions that happened on fragmented wetland site before to moderation to the extent operable. Wetland conservation strategies involve restoring endemic, native plant and animal communities (Faulkner et al. 2011). Minimization of soil erosion is the primary reason of the most commonly applied practice, residue management, conservation crop management, no-tillage/strip tillage, conservation cover, afforestation, reduction of land use change, reduction of overgrazing, and increase in vegetative cover and irrigation (Faulkner et al. 2011).

Degradation and depletion of sea grass in a coastal wetland, which is often caused by erosion which leads to eutrophication or dredge-and-fill activities, is commonly restored by transplantation (Burkholder et al. 2007; Fonseca et al. 1994). The suitable place and donor population for replacement should receive more focus on the significant expense (Bastyan and Cambridge 2008). Along with that, seeding techniques and mechanical planting have also been used as a possible solution to restore sea grass loss (Paling et al. 2009; Van Katwijk et al. 2009).

To resolve the complication of degraded wetlands caused by Spartina alterniflora invasions in the Yangtze River Delta, some are the examples especially in Chongming Dongtan wetland; methods that involve breaking of rhizomes, cutting, digging and tillage, and waterlogging as well as biological substitution with Phragmites australis proved effective (Liu et al. 2013; Yuan et al. 2008).

6 Preparation Needed Before Starting a Restoration Project

Before beginning a restoration project, pre-preparation step should be needed enlisting of this first one: locate the degraded wetland and identify the key indicators to decide the potential of replacement, restoration, and regulation. Along with ecological restoration, elemental method should be acknowledged to estimate the feasibility of conserving the damaged ecological, hydrological, and chemical processes. The social feasibility and ecological rationality should be used to predict and identify the crucial regions and pattern of ecological conservation and restoration (Zhao et al. 2016).

Ecological restoration endeavors are frequent part of an international framework that purposes to achieve local and global restoration targets (such as the Aichi Biodiversity Targets and EU biodiversity targets), for which inhabitants afford the expense (Adams et al. 2010; Kari and Korhonen-Kurki 2013). In literature related to conservation, the idea has been referred to as the “parks versus people” debate, where safeguarding global biodiversity through so-called fortress restoration. This fortress restoration is on one end of the spectrum, and a focus on refining local people is at the other end (Miller et al. 2011; Southworth et al. 2006). To safeguard nature restoration and conservation areas from resource exhaustion of resource are necessary. Because of such limitations, people have been moved or denied access to the resources, frightening their rights and livings (Brockington and Wilkie 2015).

To stimulate support for wetland restoration and foster sustainable use of wetland restore areas, an intended approach is obligatory. Increasing realization of the problem and enhancing awareness can be a needful strategy to promote public sensitization for wetland conservation. Reflecting upon the concept of Festinger (1957), Kollmuss and Agyeman (2002) suggest the proposal that the public may show a conflict against nonconforming information, meaning that “information that boosts our current values and conceptual frameworks is readily acknowledged, whereas information that controverts or excavate our thoughts and beliefs are avoided or not able to recognize at all.” This means that the pros and cons of wetland restoration should be “framed” in ways that reverberate with the people (Groffman et al. 2010).

The public may be empathetic toward the restoration and conservation of wetland and its ecosystem. In reality, when it comes to daily practice and actual environmental behavior, activities that conflict with biodiversity conservation still gain priority (Samantha et al. 2016). This emphasizes the importance of wetland restoration projects to identify trade-offs and collaboration, making them better capable of dealing with both competing and complementary targets (Mitsch and Gooselink 2000). As expressed by McShane et al. (2011), by actively involving with scientists, regional users and environmentalists can raise sensitization for wetland restoration projects, which is expected to enhance the accomplishment of wetland restoration and conservation (Cooke et al. 2013).

7 Constructed Wetland (CW): An Attempt to Optimize Wildlife Conservation and Restoration

Generally, for treating wastewater, constructed and engineered wetlands are designed in such a way to look like natural wetland to remove various contaminants or improve the water quality along with conservation of resources (Vymazal 2013; Saeed and Sun 2012). These systems chiefly encompass substrates, vegetation, water, soil, and microorganisms (Badhe et al. 2014). They employ complex processes involving physicochemical and biological mechanisms (Upadhyay et al. 2016). It has been noticed since long that the CW treat a variety of wastewater with the help of plants and microbes. On the basis of macrophytes present in the wetland, it can be categorized as under (Brix 1993):

  1. 1.

    Free-floating macrophyte-based systems: In this type of CW, free-floating plants remove the pollutants which are present in dissolved form (Upadhyay et al. 2016).

  2. 2.

    Emergent macrophyte-based systems: This system plays a critical role as the rhizomes of the plant produce suitable required environment for nutrient removal process (Hofmann 1991). The rhizome helps in bacterial growth by providing surface for filtration of solids. The aerenchymatous rhizomes supply oxygen and create oxidized microenvironment in anoxic soil that subsequently increases decomposition of organic matter and nitrification.

  3. 3.

    Submerged macrophyte-based systems: These systems are less suited for the treatment of raw sewage and therefore utilized as tertiary treatment step for improving the effluent quality or treating eutrophic natural water. The species that have been employed for the above purposes are Ulva lactuca, Ceratophyllum spp., Elodea canadensis, Cladophora spp., Myriophyllum spp., E. nuttalli, Enteromorpha spp., Egeria densa, Potamogeton spp., etc.

The designing of CW is based on the flow of water, i.e., vertical flow (VF), horizontal flow (HF), surface flow, and subsurface flow (Ali et al. 2013). The water hydrology and the substrates used in CW (clay, sand, rock, peat, zeolite, gravel, etc.) provide a wider range of habitat for the growth of different types of microorganism like bacteria, fungi, and algae (Cui et al. 2010; Wu et al. 2014). The microorganism growing in the designed CW ultimately degrades the pollutants present in wastewater, thereby releasing large amounts of nitrogen, phosphorus, and other organic and inorganic contaminants. These contaminants were further utilized by plants for their growth and development (Rai et al. 2013). The growth of plants acts as a house of different wildlife animals. The conservation and restoration of wetland through CW can be dealt with the following points:

  • CW facilitates the growth of different groups of microorganisms in a single habitable niche.

  • CW purifies a variety of wastewater coming from different resources which directly affects the nature of natural wetland.

  • The growth of plants may act as nesting sites for birds and other insects.

  • CW may recharge groundwater and inhibits soil erosion.

  • CW may assist in flood control and vegetation loss and provide shelter to different wildlife animals.

8 Conclusions

In the past few decades, scientists and managers have identified the multiple values and functions of wetlands. Wetlands have generally been called as “kidneys of the landscape” because of their capability to transmute and store organic content. For this reason, various types of constructed wetland are employed to deal with wide range of wastewater all over the world. Many efforts are put into investigation in the advancement and refinement of CW technology. Further researches are needed to optimize design criteria for all sorts of CWs. Also, scientific studies are much needed for the improvement of long-term performance capabilities and operational problems related with the systems.