Keywords

9.1 Introduction

The connection between people and nature leads to the concept of services of the ecosystem. Ecosystem services indicate the paybacks that human beings acquire from ecosystems (MEA 2005). Wetland ecosystems provide a range of services, including retention of water, irrigation for agriculture, flood control, conservation of biodiversity, and micro-climatic regulation, carbon sequestration (Zedler and Kercher 2005; McLaughlin and Cohen 2013). Throughout the world, wetlands cover approximately 12.8 million km2, 8.5 percent of the earth's total land area. Continental wetlands encompass about 9.5 million km2 (Finlayson et al. 1999). Globally, 2193 prominent wetlands are recognized (Ramsar 1971). However, the last century has witnessed a rampant loss of more than 50% of the world's wetland area (UNWWAP 2003). Small water bodies are an essential part of the ecosystem. Ecosystem of the small area also can play a critical role in ecological processes globally. These small ecosystem types show a substantial intensity of many environmental processes. These intense activities can make small ecosystems more dynamic than large water bodies.

Ponds are small wetlands with ecological roles and one of the most crucial water sources available for humans in rural society. According to Shiklomanov and Rodda (2003), globally, 90 percent of liquid water is contained in ponds and lakes. Ponds are the most crucial freshwater habitat, which plays an essential role in biodiversity maintenance. The ecosystem of the ponds directly connects with rural people, but rural ponds are vulnerable to freshwater habitat because people are not aware of their economic benefits. So, proper water management of ponds can mitigate climate change, provide recreation of water and watering of livestock and irrigation support, reduce pollutions, flooding alleviation, and capture the heavy rainfall event. Ecosystem services in small water bodies are most active and globally significant, and so are their contribution and role in the global ecosystem processes. Ponds which have a better quality of water are more economically desirable. The ecosystem of the pond is also essential for rural production and livelihoods sustainability. However, these ponds are also vulnerable and degrading very fast. Proper planning of pond restoration can generate significant benefits in biodiversity conservation, relief from flooding, reduce the impact of pollution and climate change.

The State of West Bengal has an uncountable number of ponds and occupies 7.45% of the total water resources of India. The State also has lots of large ponds, known as ‘Dighi’ and beel. These large ponds serve as the reservoir of rainwater, which can be used during the post-monsoon and the summer seasons. In Sundarbans, since there are no large ponds or natural lakes, the small ponds are crucial for domestic and agricultural purposes. These water bodies are the only source of surface water in the Sundarbans. The demand for freshwater is increasing every day concerning the population growth in the region. In terms of ecosystem services, freshwater storage is the primary ecosystem service of the Ponds because these water bodies provide provisioning and supporting services and very few cultural and regulating services.

Like others assets of capital, the ecosystem is a natural asset. The ecosystem is providing a flow of services by which the consumers are getting benefits. Demand for Ecosystem services’ will be increasing with an increase of community awareness and environmental degradation. According to MEA (2005), economic valuation is a prerequisite to manage an ecosystem. The ecosystem plays a vital role in terms of provisioning, regulating, cultural and other supporting services in the surroundings. However, a wide range of populations is overusing many ecosystem services, and over-exploitation of these ecosystem services is happening due to low awareness about the services. Since human wellbeing is highly dependent on ecosystem services, a consequence of this over-exploitation is affecting the wellbeing of the current and the future generation.

Efforts for the valuation of ecosystem services continued throughout the last few decades. Costanza et al. (1997) assessed the worth of ecosystem services of the entire world to be $33 trillion. According to Costanza et al. (1997), ecosystem services are a bouquet of benefits that the society can retrieve from the ecosystems. These services vary from provisioning and supporting to regulating and cultural services (Costanza et al. 1997). Apart from the restoration of natural resources, enhancement of conservation and management mechanisms of these ecosystems are also necessary; otherwise, we may lose multiple benefits for society. Therefore, to restrict natural resource degradation and associated ecosystem services, the valuation of ecosystem services is highly essential. Ecosystem services evaluation can help us in decision-making by assessing the give and take relationship between human beings and the ecosystems (MEA 2005).

According to the Millennium Ecosystem Assessment, a pond can offer several benefits, like regulation, provision, and cultural services (Mace 2008).  Any degradation and conservation changing of wetlands to other land use impact the biodiversity and livelihoods of people living around surrounding ponds. Due to changes in the agricultural activity in Sundarbans, the provisioning services (irrigation, fish farming, and domestic purposes) are declining day by day. Low awareness of the value of ecosystem services and extreme weather events are the main reasons that bar society from reaping benefits from this crucial lentic ecosystem. So to protect the only source of freshwater ecosystem services here, it is high time to assess the value of the services.

The Indian Sundarbans Delta consists of 19 administrative blocks. 13 blocks belong to South-24-Parganas, and 6 to North-24-Parganas. The region is under the coastal zone of the State and high salt-induced landscape. We conducted a focus group discussion and a participatory rural appraisal in February 2021involving the fishers, agricultural farmers, and pond managers (as chalked out by Chambers 1994). The primary data is essential for the valuation of Ponds Ecosystem services. A pre-tested questionnaire should generate the data on ecosystem services and socio-economic aspects, and it has to be specific for the pond ecosystem services. Some secondary data are also crucial from the different government data books like the latest District Statistical Handbook, Economic survey, and Agricultural Statistics.  In the context of increasing demand for irrigation and agricultural management apart  from the valuation of ecosystem services, this paper aims to know the importance of different pond ecosystem services for various stakeholders.

9.2 Challenges and Studies on Valuation of Wetland Ecosystem Services

Ponds can act as a perennial water source, which is an essential ecosystem service. However, a lack of proper assessment of wetland ecosystem services hampered the adoption approach (Crossman et al. 2013; Kull et al. 2015). Earlier pieces of research exclusively focused on the large wetland ecosystems and characterized their services from an economic point of view (Wang et al. 2004; Lai et al. 2013; Howard et al. 2016; Guimaraes and Lowe 2016). Very recently, the assessment of wetland ecosystem services, changes, and patterns of services have become a significant concern globally (Corrigan and Nieuwenhuis 2016; Li and Gao 2016; Li et al. 2016; Hu et al. 2017).

Unlike the giant wetlands, ponds occupy a much smaller surface area. These lentic water bodies are mostly not natural wetlands (constructed), and they are the crucial sources of water in agricultural landscapes (Son et al. 2014; Natsumeda et al. 2015). The pond systems provide many ecosystem services like fish production, supply of water, retention of nutrients, sequestration of carbon, biodiversity, and recreational use (EPCN 2007). However, the developmental activities and urbanization process like construction of the road have seriously degraded wetland areas, mainly ponds (Na et al. 2008; Choi and Bury 2003; Van Dam et al. 2015). Broadly wetlands are of three types- inland, coastal, and constructed. According to the Ramsar convention, 42 specialized sub-categories of wetlands exist (Ramsar 1971). In the conservation program of the U.K. in 1989, an assessment characterized the number, characteristic traits, spatial distribution, and biodiversity of the ponds (Jeffries 2010; Williams et al. 2010; Munns et al. 2016).

According to Céréghino et al. (2014), ponds provide sustainable solutions to the significant environmental problems of climate change and water management. Ponds with fresh water are multifunctional ecosystems that offer a spectrum of economic and social benefits (IUCN 1997; Bekefi and Varadi 2007; EPCN 2007; Downing 2010). They provide multiple services like water retention and diversity of vegetation (Son et al. 2014). The vegetation structure and pond size play a crucial role in regulating the biodiversity of ponds (Feng et al. 2015; Natsumeda et al. 2015; Ouyang et al. 2017). Prach and Tolvanen (2016) discussed the difficulties in the application of programs and pond conservation.

In most of the areas, the conservation and protection of ponds remain most neglected. The demise, abandonment, and pollution of ponds have enhanced continuously over the years (Cirovic et al. 2016; Mupepele et al. 2016). Scotland witnessed the disappearance of more than half of its total ponds due to urban and agricultural encroachment (SEPA 2000). The agricultural ponds of china suffer from intense cultural eutrophication (Martinez et al. 2016). The ponds are capable of providing a bundle of benefits to humankind. However, assessments primarily emphasize a handful of services, like the fish yield, neglecting the other ecological roles (Pechar 2000). Hence a holistic understanding of the ecosystem services from ponds remains poorly constrained (Son et al. 2014; Prach and Tolvanen 2016).

Previously, several endeavors emphasized designing suitable support systems to safeguard the freshwater ponds and lakes and device effective management strategies (Gutierrez Estrada et al. 2012; Gawne et al. 2012). Soto et al. (2008) devised a mechanism that can effectively identify the services, model their role in the society, and evaluate a composite benefit from several aspects of an ecosystem. According to Newton et al. (2012), cost–benefit analysis (CBA) is an outstanding example to evaluate ecosystem services. This approach calculates the monetary worth of each of the ecosystem services by comparing the costs and benefits. It enables optimizing the management decisions (Costanza et al. 1997). Several economists refer to this approach as environmental CBA (Atkinson and Mourato 2008). This approach considers the associated uncertainties that any natural ecosystem possesses on offering social benefits (Bianchini and Hewage 2012; Karmperis et al. 2012). Newton et al. (2012) calculated that these environmental benefits are highly sensitive to market finance fluctuations.

Further, in environmental management, characterizing risks is a crucial factor. However, there is a limited scope to consider uncertainties in ecological CBAs (Ticehurst et al. 2007; Barton et al. 2008). Several studies have been conducted on the multi-functionality of pond systems (Céréghino et al. 2010; Kloskowski 2011), though the integration of this multi-disciplinary knowledge into practical management suggestions is very rare. However, different studies on pond ecosystem services reveals few investigative reports on the quality of the ecology and environment and the disappearance of ponds in the case of India. In the absence of any good literature on the ecosystem services of ponds, it is hard to analyze the current status of ponds in India and West Bengal.

Discussion with the local people of Sundarbans, provides information on Regulating services (i.e., carbon sequestration, micro-climate regulations), provisioning services (i.e., water retention services, irrigation, fisheries, domestic use), and Cultural (ecotourism) ecosystem services for assessment. Supporting services are very negligible in Sundarbans, so we have not considered them here.

9.3 Evaluation Procedures of Different Services

9.3.1 Assessment of Provisioning Services

The provisioning services of ponds are essential services among all other services the ponds are giving to society. The households of the surrounding ponds are highly dependent on various goods and services of the pond. There are multiple goods like fish, molasses, and leafy vegetables obtained from the ponds.

Apart from the above products, according to our group discussion with the local households, the villagers use the pond water for irrigation purposes. The villagers irrigate their farmlands with the water from the nearest pond, but they do not pay any fees for the water. The local farmers usually deploy a diesel-operated pump set (5 horsepower) to irrigate farmland adjacent to the pond. Farms situated in the vicinity of the pond also occasionally use manually operated lifting devices. Fossil fuel combustion to operate a pump is a cost-intensive endeavor. The multiplicative result of the number of times of the pump operation for irrigation and the average hour of irrigation gives an idea of the tentative cost. Apart from paddy, some vegetables also grow in the pond bed and its peripheral regions. According to the villagers of Sundarbans, surrounding people are highly dependent on the different goods and services of the pond (Table 9.1).

Table 9.1 Types of provisioning service available from the ponds of Indian Sundarbans
Full size table

Water retention, crop production, and fisheries are the central provisioning services of  a Pond in Sundarbans, contributing to the livelihoods of the surrounding population of the villages. The main crop types grown around the ponds are paddy and some vegetables for household consumption and income. However, the vegetables are grown on a small scale. These ponds are also essential for keeping livestock.

9.3.1.1 Assessment Procedure of Water Retention Service

Odgaard et al. (2017) suggested that stock volume acts as a primary indicator while assessing wetland conservation, and it reflects the hydrological regulation service of wetland. In terms of the landscape, the farmland ponds differ from the natural wetlands. After fish farming and irrigational activities, there are significant changes in the downstream runoff of the ponds. So, the yield calculation due to the use of this water from the ecosystem is necessary (Nelson et al. 2011). In the first step, one has to divide the sub-catchment to compute the accumulation of surface runoff. In the next step, subtracting the evaporation of surface water in a pond derives the estimated water retention. The measurement of evaporation from water surface requires a proper methodology and calibration protocol with a conversion factor (Sheng et al. 2007).

$${\text{WR }} = {\text{ P}}_{{\text{i}}} + {\text{ W}}_{{\text{s}}} + {\text{ min }}\left( {{\text{R}}_{{\text{i}}} ,{\text{R}}_{{\text{c}}} } \right) \, {-}{\text{ E}}_{{\text{i}}}$$
(9.1)

where W.R. is the water retention potential of the pond (m3), Pi is the annual rainfall (m3), Ws denotes the supply of water (m3), Ri denotes the runoff in the pond catchment (m3), Ei is the evaporation of water surface volume (m3), and Rc is the pond volume (m3). To calculate the minimum value of the pond and the amount of runoff, it may be assumed that all the ponds are maintained at a steady water level.

$${\text{R}}_{{\text{i}}} { = }\mathop \sum \limits_{{{\text{i}} = 1}}^{{\text{n}}} \left( {{\text{WaterYieldi}} \times \frac{{{\text{Aw}}}}{{{\text{Ap}}}}} \right)$$
(9.2)

where Ri is the accumulated runoff, WaterYield denotes runoff in unit area land (mm/a), Aw is the total catchment area of the pond, and Ap is the water body area.

The required parameters for this model have to be collected from field surveys and the published secondary references as benefit transfer. In this model, the other parameters will be calculated by using the FAO guide for irrigation (Allen et al. 1998). The valuation of water retention services is based on the current market price and availability of water.

9.3.1.2 Assessment of Irrigation Water

We can assume that due to irrigation, the crop yield enhances by ΔY from the rain-fed yield Yr (tons/ha) to the irrigated yield Yi, which means Yi = Yr + ΔY. We further presume that the cost of labor and materials (land, seeds, fertilizer, and use of machinery) are the same in irrigated and rain-fed conditions. Hence, the value of irrigation water from the pond in crop production is anticipated not more than the increased value of crop production.

We can adopt the Doorenbos and Kassam formula to evaluate the crop yield as a function of evapotranspiration. This method is one of the standard methods vividly used by FAO (Steduto et al. 2009), which is based on the assumption that yields are linearly related to the water consumption by different crops. Thus, the rain-fed yield, Yr, is a segment of the irrigated crop yield Yi. Therefore, the Yr can be calculated as a function of the actual evapotranspiration (ETa) in the rain-fed situation, and PET is the potential evapotranspiration of crops.

$${Y}_{r}={Y}_{i} (1-{k}_{y})(1-\frac{{ET}_{a}}{PET})$$

Ky is the crop yield response factor that captures the linkages between production and water use by a crop. The above equation is the water production function that can be applied to all crops of Sundarbans.

Hence the water productivity is the difference between maximum irrigated crop yield and rain-fed yield:

$$\Delta {\text{Y}} = \,{\text{Yi}} - \,{\text{Yr}}$$

Accurate estimation of actual crop evapotranspiration is very difficult. According to FAO ETa can be estimated from data tables on evapotranspiration rate, available soil water, and wetting intervals. These tables are also complicated to get the value of ETa, and later these tables were replaced by more precise ETa estimations based on water balance estimations. Potential evapotranspiration, PET (ET. rate in the presence of adequate irrigation) can be evaluated by solving a vertical soil water balance equation. The crop-specific PET values can be estimated as ETa estimation, but we have to assume that there is no limitation of water availability to calculate PET values.

Irrigation water requirements (IWR) is the difference between crop water requirement (CWR) and rain-fed crop water consumption, CWCr. This can be calculated through the cumulative PET and the cumulative ETa during the respective crop's lifetime. Thus, IWR can be expressed as

$$IWR=\frac{\left(CWR- {CWC}_{r}\right)}{e} , ({m}^{3}/ha)$$

where e implies irrigation efficiency, the ratio of irrigation water taking out from the pond, and water consumption for irrigation (i.e., the amount of water leakage at the time of irrigation). The types of irrigation systems can estimate the values of e.

Therefore the rise in production, ΔY (tons ha−1), meets the expense of irrigation which is nothing but an amount of irrigation water, i.e. IWR (m3 ha−1).

Then the irrigation water use efficiency of a specific crop can be estimated as IWUE = ΔY/IWR (tons m−3). If the farm gate price of that particular crop is Pc (Rs/ton), then the maximum value of water (Vw) for that crop can be estimated as

$${\text{V}}.{\text{W}}.\, = \,{\text{Pc}}\, \times \,{\text{IWUE}}\, = \,{\text{Pc}}\, \times \,\Delta {\text{YIWR}}$$

9.3.1.3 Assessment of Fish and Shellfishes

Several studies reported the aquatic, wetland-dependent, and wetland-associated fauna from ponds of Sundarbans. The freshwater wetlands are inhabited by a wide diversity of vertebrate and invertebrate faunal components. Therefore, only those genuinely aquatic or those associated with or directly dependent upon the wetlands were included in this estimation. A total of more than 20 species of fish have been identified from various ponds of Sundarbans. The Family Cyprinidae is represented by 17 species among the different families, including Indian major and minor carps and weed fishes. Some catfishes, mussels, and mud eels are quite common in occurrence in ponds of two districts of Sundarbans.

Fishes are the marketed products, and their per unit (kg) value is well defined. So overall production values of the fishes can be measured through the market transaction method. However, this is a conservative estimate as we do not take into account the costs of seeds, feed cost, cost of collection, etc., which are spent from the previous year's savings. Therefore, the estimation of beneficiaries of the pond is not exact. Also, it is revealed that no such feed is used and the total value of fisheries is equal to {total production value—(cost of Seed + Cost of Collection)}. Some people surrounding the pond collecting small fish and shellfishes from the wetland. Most of the households collect small fish and shellfishes from ponds except during the rainy season. According to our Focus Group Discussion (FGD) on an average of over 8 months per year, the households collect mollusks which save on an average a cost of Rs. 360 per month per household. In some cases, the villagers revealed that people from lower strata of the society collect mollusks and sell them in the local market at a remunerative price. Villagers were asked to reveal the amount that they have to pay to purchase those items that they collect from the pond. The well-defined market price made it easier for them to tell the amount they save each month by collecting various small fishes and shellfishes from the pond.

9.3.1.4 Domestic Use

Ponds in Sundarbans serve as a primary source of water for the surrounding villages. Apart from the pond, other open water sources like bore wells, tube wells are mostly saline. According to the villagers, the pond water is supporting domestic uses in the surrounding houses. The weighted average cost for filtered water in a treatment plant is Rs.1.38/kiloliter. To estimate the value of domestic water at the household level, we can use this treatment cost multiplied by the average daily per capita water consumption in the household.

9.3.2 Assessment of Regulating Services

9.3.2.1 Carbon Sequestration

Globally, wetland ecosystems are recognized as important carbon sinks (Maltby and Immirzi 1993; Page et al. 2011). However, there is less information regarding the carbon dynamics of wetland types, such as coastal wetlands. Water allocations are increasing to maintain the ecological health of regulated floodplain wetlands. The wetlands store almost 20–25% of the world's soil organic carbon, out of which the terrestrial wetlands hold a larger proportion than their marine counterparts (Gorham 1991). In addition, wetlands contribute near about 40% of the global methane emissions, which have the highest carbon density among terrestrial ecosystems and have greater carbon sequestration capacities (Pant et al. 2003).

Apart from that, the greenery catchment also serves as a carbon sink. The figures for carbon sequestration were considered by Eid and Shaltout (2013), who reported that per hectare carbon sequestration benefit ranged from 14.9 and 8.6 g Carbon per m2 per year. Considering the current land use and land cover (LULC) of Sundarbans, we can go for a conservative estimation of carbon sequestration. Since certified emission reduction (CER) markets are depressed and not a fair reflection of the importance of carbon sequestration to the human community, the European Union Voluntary Emission Reduction (EU VER) price of 10 USD/CER around 700 INR per ton of carbon was calculated here (Forest Trends Ecosystem Marketplace 2020).

9.3.2.2 Microclimate Regulation

Micro-climate regulation is an important ecosystem service of wetlands. The wetland essentially regulates the climatic conditions in its vicinity by improving the evaporation-transpiration process. Existing literature suggests that the monetary worth of micro-climate regulation service from wetlands ranged from INR 3300 to 29,040 per hectare (Costanza et al. 1997; Torras 2000; Pearce 2001). Based on the above literature, by using the mean value of the service, we can  use a conservative estimation of the microclimate regulation for the ponds of Sundarbans.

9.3.3 Assessment of Cultural Services

9.3.3.1 Ecotourism

If marketed correctly, these sites have immense possibilities to appear as a significant Eco tourism support. It has all attributes that define ecotourism sites. Assuming that tourism here would be confined to West Bengal for the time being, we estimated a significant chunk of the population spending a substantial amount of money on Sundarbans tourism. Further, we calculated that once the ecotourism developed, 2000 groups of tourists would visit these sites once a year (multiple visits were ruled out, as we were making a conservative estimate). Thus, each tourist (or group) might spend 5% of their annual tourism budget to visit the ecotourism of Sundarbans. Therefore, based on these very conservative assumptions, considerable tourism earnings can be an additional benefit. This gave us a significant part of the total economic benefit from tourism. We, however, did not concern ourselves with the cost of developing institutional mechanisms and infrastructure, apart from depreciation and operations and maintenance.

9.4 Discussion

Natural resource management is one of the biggest challenges in developing countries. In the coastal area, we have a lot of sources of water but mostly saltwater. The pond is an important wetland in the coastal region that can support freshwater for domestic and other uses. So proper valuation of these wetlands is necessary. This paper aims to identify the essential services that determine wetland values and how to estimate the values of the different services. Here we have identified how the ponds influence human welfare the various benefits and characteristics of the pond and valuation methods. It has been observed that the pond size is much essential in terms of the valuation of water retention service. Sundarbans’ rural ponds produce locally traded goods and services that are more valuable than other regional wetlands in West Bengal. We have identified that the ponds that provide water regulation and habitation for biodiversity are more valuable in the Sundarbans than cultural services. This means that the conversion of the pond into a supporting service for tourism development can reduce their valuation, even though the conservation may increase valuation.

According to the literature review, it has been found that there are very few studies on the valuation of pond ecosystem services. If we consider other wetland systems, then the review observed that most of the studies on wetland ecosystem services mainly focused on supporting and regulating services. If we compare different ecosystem services, it has been observed that the valuation of provisioning and cultural services is not estimated like the other two services. It is also true that wetland ecosystems are giving more supporting and regulating services than provisioning and cultural services (de Groot et al. 2012). Lack of data and the complexity in understanding services identification are the main reasons to take less initiative for calculating the provisioning and cultural services (Fish et al. 2016). Due to a lack of data and monitoring capacities, most researchers from developing countries are using the benefit-transfer method (de Groot et al. 2012; Xu et al. 2018). Though the benefit transfer is one of the cost-effective methods for policymaking in developing countries, the benefits transfer function may create a lower value than the actual one if we are not aware of the proper application process. Therefore, one must be careful about applying benefit transfer for future policy development and keep in mind space, time, and other dimensions when we are pooling values for different wetland services from different countries. It has been observed that anthropogenic factors are the major drivers to determining pond ecosystem services’ valuation. The  concept of ecosystem services valuation backed by human wellbeing, and if the ecosystem services are not providing any benefits to human wellbeing, then they have no value (MEA 2005). Like manufactured products and services, humans can change ecosystem services value through land-use change, ecosystem management and utilization rate, and extraction of Ecosystem services (de Groot et al. 2010; Jones et al. 2016). To estimate the valuation of pond Ecosystem services, policymakers must consider the role of anthropogenic factors for changes in economic values due to human activities.

9.5 Conclusion

Valuation of pond ecosystem services is precious because it helps to decide how to enhance the quality of life for those who are exclusively dependent on these crucial lentic water bodies. Valuation of pond ecosystem services gives us a platform to illustrate the concept of market failure and knowledge on why the sustainable use of natural resources is necessary. Market efficiency cannot be taken for granted. Valuation of pond ecosystem services has to begin with the nature of sustainability, based on justice to users. On the other hand, it should be kept in mind that the values of different services should be maximized. In conclusion, we can say that the economic valuation of pond ecosystem services should be based on normative values, should not have error of double-counting, and should follow scientific objectivity. However, the economic evaluation of the ponds of Indian Sundarbans from several standpoints is in its infancy. A vast scope of research lies for the economists to reveal the ecosystem services of these crucial ecosystems.