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date: 27 May 2017

Valuation of Mangrove Restoration

Summary and Keywords

Since the 2004 Indian Ocean tsunami, there has been strong interest globally in restoring mangrove ecosystems and their potential benefits from protecting coastlines and people from damaging storms. However, the net economic gains from mangrove restoration have been variable; there have been some notable project successes but also some prominent failures. There is also an ongoing debate over whether or not the cost of mangrove restoration is justified by the benefits these ecosystems provide. Although the high costs of mangrove restoration and the risk of failure have led to criticism of such schemes, perhaps the more pertinent concern should be whether the ex post option of restoration is economically beneficial compared to preventing irreversible mangrove conversion to alternative land uses. Case studies on mangrove valuation from Brazil and Thailand illustrate the key issues underlying this concern. Since much recent mangrove restoration has been motivated by the trees’ potential storm-protection benefit, a number of studies have valued mangroves for this purpose. However, mangroves are also valued for other important benefits, such as providing collected products for local coastal communities and serving as nursery and breeding grounds for off-shore fisheries. The implications of these benefits for mangrove restoration can be significant. It is also important to understand the appropriate use of benefit transfer when it is difficult to value restored mangroves, methods to incorporate the potential risk of mangrove restoration failure, and assessment of cost-effective mangrove restoration.

Keywords: economic valuation, ecosystem services, mangroves, mangrove restoration, storm protection

Introduction

Around one quarter of the world’s mangroves have been lost due to human impacts, mainly through conversion to aquaculture, agriculture, and urban land uses (Barbier & Cox, 2003; Duke et al., 2007; Friess & Webb, 2014; Spalding, Kanuma, & Collins, 2010). In the early 21st century, estimates suggest that less than 165,000 km2 of mangroves exist globally, and over two-thirds of the remaining area is located in just 20 countries (Giri et al., 2011; Hamilton & Casey, 2016; Spalding et al., 2010). The 20 countries are Indonesia, Brazil, Malaysia, Papua New Guinea, Australia, Mexico, Myanmar, Nigeria, Venezuela, Philippines, Thailand, Bangladesh, Colombia, Cuba, United States, Panama, Mozambique, Cameroon, Gabon, and Ecuador. With the exception of Australia and the United States, these are low- and middle-income economies, which suggests that ongoing development pressures will continue to pose the greatest threat to the world’s remaining mangroves.

However, after the Indian Ocean tsunami in 2004, there was a “sea change” in attitudes toward global mangrove loss because it puts coastlines and coastal communities at risk from flooding and storm events (Alongi, 2008; Barbier, 2014; Braatz, Fortuna, Broadhead, & Leslie, 2007; Cochard et al., 2008; Temmerman et al., 2013). There is particular concern over the increasing vulnerability to climate change of rural populations in the low-elevation coastal zone (LECZ) of developing countries, which is the contiguous area along the coast with less than 10 meters (m) elevation (Barbier, 2015). As mangrove ecosystems disappear or are degraded, there will be less protection against short-lived natural disasters with immediate and often extreme impacts, such as flooding and storm surge, as well as long-term climatic changes with more gradual impacts, such as sea-level rise, saline intrusion, and erosion (Barbier, 2014, 2015; Barbier et al., 2011; Blankespoor, Dasgupta, & Lange, 2016; Intergovernmental Panel on Climate Change [IPCC] Working Group II, 2014; Spalding et al., 2014; Temmerman et al., 2013). In addition, the changes in precipitation, temperature, and hydrology accompanying climate change are likely to threaten the remaining mangrove ecosystems (Dasgupta, Hossain, Huq, & Wheeler, 2014; Dasgupta, Laplante, Murray, & Wheeler, 2011; Doney et al., 2012; Elliott, Cutts, & Trono, 2014; Erwin, 2009; IPCC Working Group II, 2014; Spalding et al., 2014). Thus, understanding the value of mangroves for providing protection against storms, flood damage, and other coastal hazards is important for the broader policy issue of determining the vulnerability of the rural poor in LECZ of the continual loss of mangroves.

Consequently, since the 2004 Indian Ocean tsunami, there has been strong interest globally in both restoring mangrove ecosystems and their ability to protect coastlines and people from damaging storms. However, the past record for mangrove restoration has been variable, with some notable project successes but also prominent failures (Biswas, Mallik, Choudhury, & Nishat, 2009; Lewis, 2005, 2009; United Nations Environmental Programme, 2014). There is also an ongoing debate over whether the cost of mangrove restoration is greater than the value of the coastal-protection service these ecosystems provide (Sandilyan & Kathiresan, 2015). On the other hand, mangrove ecosystems provide important economic benefits other than storm protection, including carbon sequestration, collected wood and nonwood products, and support for off-shore fisheries (Barbier, 2007; Barbier et al., 2011; Huxham et al., 2015; Mukherjee et al., 2014).

Although the high costs of mangrove restoration and the risk of failure have led to criticism and the debate over whether such schemes should occur, perhaps the more pertinent concern should be whether the ex post option of restoration is economically beneficial relative to preventing irreversible mangrove conversion to alternative land uses. Since much of recent mangrove restoration is motivated by the potential storm-protection benefit, the focus of this article is on valuing mangroves for this purpose. Valuation of mangroves for other important benefits, such as providing collected products (e.g., shellfish, plants, honey, medicines, etc.) for local coastal communities or serving as nursery and breeding grounds for off-shore fisheries and the implications of these benefits for mangrove restoration are also discussed. Several additional issues, such the appropriate use of benefit transfer when it is difficult to value restored mangroves, incorporating the potential risk of mangrove restoration failure, and cost-effective mangrove restoration are also discussed.

Mangrove Restoration

Mangroves grow in sheltered, shallow waters of the tidal zone of coasts and estuaries in tropical and subtropical regions. Mangroves are the only woody plants that can grow in the brackish water of those tidal habitats, and as a consequence, mangrove ecosystems are often rich in biodiversity and provide important ecosystem goods and services. In addition, mangroves are typically established on sloping coastal land areas above mean sea level, and inundated frequently by tidal waters (Lewis, 2005). These variable and complex environmental conditions make the task of restoring mangrove ecosystems difficult and costly.

Ecological restoration involves assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed, typically as a result of human activities (Hobbs & Cramer, 2008; Moreno-Mateos, Meli, Vara-Rodríguez, & Aronson, 2015; Rey-Benayas, Newton, Diaz, & Bullock, 2009). Traditionally, the approach to mangrove restoration “has, unfortunately, emphasized first establishing a mangrove nursery, then planting mangroves at a casually selected site, as the primary tool in restoration, rather than first assessing the reasons for the loss of mangroves in an area and working with the natural recovery processes” (Lewis, 2009, pp. 789–790). At the extreme, this approach has led to many instances of planting single-species stands of mangroves in previously non-mangrove habitats, such as mudflats and seagrass beds, which has contributed to high rates of failure and poor restoration results (Biswas et al., 2009; Gedan & Silliman, 2009; Lewis, 2005, 2009).

To improve success rates and lower costs, subsequent efforts focused on enhancing natural seed propagation and recovery, provided that normal tidal hydrology is not disrupted and that there are sufficient waterborne seeds or seedlings of mangroves from adjacent forests (Lewis, 2009). However, the recovery of mangrove forests may take considerable time, or even fail, if native mangrove tree seeds or seedlings are not artificially reintroduced, because the high energy of tides prevents their spontaneous recruitment in bare sediments (Bosire, Dahdouh-Guebas, Kairo, & Koedam, 2003; Moreno-Mateos et al., 2015). In addition, as noted by Field (1998, p. 387), “if the degraded site is a disused shrimp pond there may be accelerated soil erosion due to increased surface run-off, a decrease in soil water storage capacity, a reduction in the biodiversity of soil fauna, a depletion of soil organic matter, the presence of acid sulphate soils and the addition of toxic chemicals.” In such abandoned and degraded areas, considerable and costly treatment of the site is required before any mangrove restoration can begin.

As a consequence, mangrove restoration has had varying degrees of success at different locations around the world. A survey of 10 mangrove restoration projects comprising 24 sites in six countries (the United Arab Emirates, Madagascar, Kenya, Senegal, the Solomon Islands, and Indonesia) confirms that success in mangrove recovery is improving, but problems still persist in some locations (UNEP, 2014). Half the projects were very successful in terms of enhancing vegetation coverage; 20% were successful; 20% showed limited or no change; and in one project, mangroves actually declined. In addition, mangrove restoration may fail for economic and social reasons. Evidence from Thailand indicates that poor coastal households are less willing to participate in mangrove replanting schemes, even though they are aware of the storm-protection benefits of mangroves, because of the high opportunity cost of their labor and lack of community control over the management of the restored mangroves (Barbier, 2008). The inability to match ecological, economic, and social goals appears to be a consistent problem constraining successful mangrove restoration throughout Southeast Asia and other regions (Adame, Hermoso, Perhans, Lovelock, & Herrera-Silviera, 2015; Biswas et al., 2009).

Even successful mangrove restoration can be expensive, and costs can vary considerably depending on the amount of human assistance to natural recovery and upfront investment required. Lewis (2005) found that mangrove restoration costs globally could range from US$225 to US$216,000 per hectare (ha), excluding the costs of the land, and Narayan et al. (2016) suggest that costs vary from US$500 to $54,300 per hectare. However, most estimates appear to be around US$5,000 to US$10,000 per hectare. For example, in the Caribbean, restoration-site costs are US$5,077 per hectare (Adame et al., 2015); and in Thailand, US$8,812 to US$9,318 per hectare (Barbier, 2007).

Assessing Mangrove Restoration Benefits

Given the high and variable costs of mangrove restoration, and the risk of failure, it is important to ensure that restoration is worthwhile. In addition, whether restoration is economically beneficial depends on comparing the option to the alternative, which is preventing irreversible mangrove conversion and degradation. Both of these approaches to assessing mangrove-restoration benefits can be seen in examples from Brazil and Thailand, respectively.

Because mangrove restoration requires significant upfront costs and the full benefits are not realized until the restoration is completed, it is difficult to know ex ante whether the benefits justify the costs. As demonstrated by de Rezende, Kahn, Passareli, and Vásquez (2015), one way of resolving this issue is to employ choice experiments to determine the preferences of potential beneficiaries for different restoration outcomes. The authors apply this analysis to northern Rio de Janeiro (state) in Brazil, which contains approximately 725 ha of mangroves that have declined as the result of deforestation, drainage for pasture, urban expansion, dredging, erosion, and siltation. To determine preferences for restoration, the choice experiment offered several options, which varied in terms of the level of restoration (minimal, moderate, or complete), time required for each option, monthly cost of restoration, and weekly time commitment for volunteering for the restoration effort.

The main findings of de Rezende et al. (2015) are that, out of the nine scenarios investigated, respondents prefer a moderate restoration in less than 10 years, which improves the health of remaining mangroves and reduces erosion somewhat but includes only minimal support for crab and other fisheries. There also is a strong preference for complete restoration in 11 to 20 years, which not only improves the health of existing mangroves but also extends mangrove forest area by 20%. The authors also estimate that, based on ten years of monthly payments, respondents are willing to pay between US$17.98 and US$108.07 per month for moderate restoration, and US$6 to US$99.35 monthly for complete restoration. Even if complete restoration takes 30 years, respondents were willing to make 10-year payments amounting to US$82.89 per month. The opportunity of volunteering time to a restoration project is estimated to be about $0.50 per hour, or around 26% to 52% of typical hourly wages. Overall, the results suggest that potential beneficiaries in northern Rio de Janeiro state, Brazil prefer moderate and complete mangrove restoration, and do not consider the opportunity cost of their time assisting in local restoration projects to be prohibitive.

As shown by Barbier (2007), the economic decision to restore mangrove ecosystems in Thailand that have been lost to aquaculture expansion must address two policy choices: do the net economic returns to shrimp farming justify further mangrove conversion to aquaculture, and is it worth investing in mangrove restoration in abandoned shrimp-farm areas? These questions are important for Thailand; from 1961 through the early 2000s, the country lost around 1,500 to 2,000 km2 of coastal mangroves, or about 50%–60% of the original area (Food and Agricultural Organization of the United Nations [FAO], 2003). Over 1975 to 1996, 50% to 65% of Thailand’s mangroves were lost to shrimp-farm conversion alone (Aksornkoae & Tokrisna, 2004). Although this conversion has been declining since the 1990s, the conversion of mangroves to shrimp-farm ponds and other commercial coastal development continues to be a major threat to Thailand’s remaining mangrove areas. More importantly, if Thailand wants to restore mangrove ecosystems, then then coastal areas that previously contained mangroves but are now covered with abandoned shrimp farms should be the main focus.

Figure 1 summarizes the analysis by Barbier (2007) of, first, a comparison of the economic returns of shrimp farming to the benefits provided by a mangrove ecosystem, and second, the comparison of both options to the costs of mangrove restoration. Although the overall commercial profitability of shrimp aquaculture in Thailand has attracted substantial private investment, subsidies to fertilizer, feed, credit, and other inputs used in shrimp-pond operations have artificially increased the private returns to shrimp farming. The actual net economic returns to shrimp farming, which are calculated once the estimated subsidies are removed, yield a net present value of US$1,078 to US$1,220 per hectare. In contrast, as Figure 1 shows, the net present value of mangrove goods and services amount to US$10,158 to US$12,392 per hectare , which is 10 times greater than the value of shrimp farming. The net economic returns are even less for shrimp-farm operations if they generate substantial problems of local water pollution from the continuous flushing of chemicals and waste from the ponds. These additional costs of water pollution (not indicated in Figure 1) lower the net present value returns from shrimp aquaculture by another $1,000 per hectare (Barbier, 2007).

Valuation of Mangrove RestorationClick to view larger

Figure 1. Valuing the Tradeoffs in Mangrove Land Use Options, Thailand.

Note: All values in net present values per hectare (10%–15% discount rate, US$1996).

Source: Barbier (2007).

There is also the problem of the highly degraded state of abandoned shrimp ponds after their productive life is over, which can be in just three to eight years. Across Thailand those areas with abandoned shrimp ponds degenerate rapidly into wasteland, since the soil becomes very acidic, compacted, and too poor in quality to be put to any other productive use, such as agriculture. Rehabilitating an abandoned shrimp-farm site requires treating and detoxifying the soil, replanting mangrove forests or assisting natural seeding, and then maintaining and protecting the mangrove seedlings for several years. As Figure 1 indicates, these restoration costs are considerable, $8,812 to $9,318 per hectare in net present value terms. This reflects the fact that converting mangroves to establish shrimp farms is almost an “irreversible” land use, and that without considerable additional investment in restoration, these areas do not regenerate into mangrove forests.

As pointed out by Barbier (2007), what should happen is that before the decision to allow shrimp farming is made, the restoration costs could be treated as one measure of the “user cost” of converting mangroves irreversibly, and these costs should be deducted from the estimation of the net returns to shrimp aquaculture. As the restoration costs exceed the net economic returns per hectare, the decision should be to prevent the shrimp aquaculture operation from occurring. Unfortunately, past land-use policy in Thailand has ignored the user costs of shrimp farming, and as a result, substantial mangrove areas were converted for aquaculture. Many short-lived shrimp farms in these areas have also long since fallen unproductive and are now abandoned.

Thus, an important issue for Thailand is whether it is worth restoring mangroves in these abandoned areas. If the benefits of ecosystem goods and services are not large, then mangrove restoration may not be justified. Figure 1 indicates that the net present value of three mangrove ecosystem benefits—the net income from local mangrove forest products, habitat–fishery linkages, and storm protection—do exceed the costs of restoration. This suggests that mangrove restoration may be worthwhile, despite the high costs. However, the value of the storm protection (US$8,966 to US$10,821 per hectare) is critical to the decision about whether to restore mangrove ecosystems in abandoned pond areas. Mangrove restoration is an economically feasible land-use option only if restoration succeeds in generating a significant storm-protection benefit. However, the latter benefit just covers the cost of restoration, which suggests that generating income from collecting forest products and support for off-shore fisheries are important for ensuring that mangrove restoration is worthwhile. Consequently, the Thailand case-study illustrates that coastal protection by mangroves may not necessarily be sufficient for justifying the high costs of restoration, as some of the debates suggest (Sandilyan & Kathiresan, 2015), and that other benefits may be smaller but important to the overall decision about whether or not to invest in mangrove restoration.

Storm-Protection Benefits

As much emphasis has been placed on restoring mangroves for their storm-protection benefits, it is worth reviewing the evidence on this value from various studies. To date, there are still only a few economic studies that estimate the protective value of mangrove ecosystems, but more estimates have been emerging. Table 1 provides a representative selection of recent studies from tropical developing countries. Although many more studies exist than are listed in Table 1, there are problems of reliability in the estimates of protection benefits produced by some studies because of the arbitrary valuation methods often employed (Barbier, 2007, 2012).

As Table 1 indicates, the protective value of mangrove ecosystems is directly related to their ability to attenuate, or reduce the height, of the storm surges and waves as they approach shorelines. Mangrove trees also have the capacity to buffer winds, an often overlooked but nonetheless very important benefit (Das & Crépin, 2013). The value of mangroves in providing such protection against storm-surge flooding and high-speed winds is why their storm-protection benefits are often cited as an important justification for mangrove restoration globally. The studies listed in Table 1 provide an indication of the economic importance of these benefits of mangrove ecosystems.

Table 1. Selected Valuation Studies of the Storm Protection Benefit of Mangroves.

Ecosystem structure and function

Ecosystem service

Valuation examples

Valuation method

Attenuates and/or dissipates waves, buffers wind

Protection of coastal communities against property damage, loss of life and/or injuries.

Badola and Hussain (2005), India Barbier (2007), Thailand Das and Crépin (2013), India Das and Vincent (2009), India Huxham et al. (2015), Kenya Laso Bayas et al. (2011), Indonesia Sathirathai and Barbier (2001), Thailand Narayan et al. (2016), various

  • Damage cost avoided

  • Expected damage function

  • Expected damage function

  • Storm-related deaths avoided

  • Replacement cost

  • Deaths and damages avoided

  • Replacement cost

  • Replacement cost ratio

For example, mangroves significantly reduced the number of deaths and damages to property, livestock, agriculture, fisheries, and other assets during the 1999 cyclone that struck Orissa, India (Badola & Hussain, 2005; Das & Vincent, 2009). Statistical analysis indicates that there would have been 1.72 additional deaths per village within 10 km of the coast if mangroves had been absent (Das & Vincent, 2009). Economic losses incurred per household were greater (US$154) in a village that was protected by a constructed embankment compared to those (US$33) in a village protected by mangrove forests (Badola & Hussain, 2005).

In a definitive study for one of the regions worst affected by the 2004 Indian Ocean tsunami, Aceh, Indonesia, Laso Bayas et al. (2011) confirm that not only coastal topography and near-shore bathymetry but also vegetation, including the presence of mangroves, plantations and other coastal forests, were effective in reducing the deaths and damage caused by the tsunami. Mangroves, forests, and plantations situated between villages and the coastline may have decreased loss of life by 3% to 8%, as the trees appear to have slowed or diverted the waves. If these natural barriers were located behind the villages, casualties increased by 3% to 6%, because the debris from the trees increased the risk of death.

A series of studies for Thailand also indicate a significant protective value of mangroves against the damages caused by frequent storm events. Sathirathai and Barbier (2001) employed the replacement cost method to estimate the value of coastal protection and stabilization provided by mangroves in Surat Thani Province, Thailand. Using the cost of constructing breakwaters to replace protection by mangroves, the authors calculate that the present value over 20 years of mangrove protection and stabilization service is $12,263 per hectare. The contribution of mangrove deforestation to economic damages of storms was estimated for 39 coastal storm events affecting Southern Thailand from 1975 to 2004 (Barbier, 2007). Over 1979 to 1996, the marginal effect of a 1 square kilometer (km2) loss of mangrove area was an increase in expected storm damages of about US$585,000 per km2, and from 1996 to 2004, the expected increase in damages from a 1 km2 loss in mangroves was around US$187,898 per km2. Barbier (2012) used spatial simulation to further show how declining wave-attenuation function inward from the seaward edge affects the mangrove conversion decision, including the optimal location of shrimp ponds in the mangrove ecosystem, as well as the risk of ecological collapse.

In Kenya, Huxham et al. (2015) showed that the protective benefit of mangroves is one of the several regulating services that are currently mostly without markets yet have some of the most substantial values from a range of mangrove ecosystem services. What is more, this protective benefit is important to the “triple win” coastal strategy that integrates economic development, environmental conservation, and adaptation to climate change.

Despite the importance of the coastal protection service of mangroves, the geographic coverage of valuation studies remains limited (see Table 1). Moreover, even recent studies (e.g., Huxham et al., 2015) have continued to employ ad hoc valuation methods such as benefit transfer and replacement cost that have been criticized for their lack of reliability (see Barbier, 2007; Plummer, 2009; World Bank, 2016). The overall consensus is that the replacement-cost approach should be used with caution in estimating value of ecosystem services such as storm protection because, first, it essentially means estimating a benefit (e.g., storm protection) by a cost (e.g., the costs of constructing seawalls, breakwaters, dykes, groins, and other structures); and second, the human-built alternative is rarely the most cost-effective means of providing the service (Barbier, 2007; Freeman, Herriges, & Kling, 2014; World Bank, 2016).

Instead of the replacement-cost method, some valuation studies have used the expected damage function approach to estimate the protective value of mangroves (see Table 1). In such cases, the mangrove ecosystem may be thought of as producing a nonmarketed service, such as “protection” of economic activity, property and even human lives, which benefits individuals through limiting damages. As a result, the expected damage function approach is an adaptation of the production function methodology of valuing the environment as an input into a final benefit (Barbier, 2007; Barbier & Enchelmeyer, 2014). Utilizing this approach requires modeling the “production” of this protection service and estimating its value as an environmental input in terms of the expected damages avoided.

But the expected damage function has its own limitations, especially when households are risk averse, and in such circumstances does not necessarily capture the entire ex ante willingness to pay to reduce or avoid the risk from storm damages from mangrove restoration. As pointed out by Barbier (2016), when assessing the storm-protection benefits arising from the restoration of mangroves and other estuarine and coastal systems, the reduction in expected storm surge damages is only one component of the marginal willingness-to-pay for any restoration. This ex ante willingness-to-pay will also depend on avoiding or lowering the risks associated with the storm, which may be substantial for risk-averse households. However, to date, most studies of the protective benefit arising from either conserving existing mangrove ecosystems or restoring degraded mangroves do not estimate any resulting impacts on either the disutility from risk aversion or the risk of possible injury, illness or death from any potential damaging storms. Nevertheless, despite its limitations, the expected damage function is a direct compensation surplus measure for estimating an important component of the protective value of mangrove ecosystems, and thus can be considered a lower-bound estimate of this benefit arising from mangrove restoration.

A comparison of using an expected damage function approach and replacement cost method of estimating the welfare impacts of a loss of the storm-protection service due to mangrove deforestation in Thailand confirms that the latter method tends to produce extremely high estimates (Barbier, 2007). Similarly, Narayan et al. (2016) compare the cost of building submerged breakwater compared to natural-based defense provided by mangrove restoration projects. They find that the costs of building artificial breakwaters is on average five time more expensive (ranging from 3.1 times to 6.9 times more expensive across the sample) in providing the same level of storm protection as restored mangroves. Increasingly, it is recognized that in remote and inaccessible sheltered bays where mangroves are normally found, artificial barriers, breakwaters and seawalls are not the least-cost options for providing storm-protection benefits, especially when compared to mangroves.

Finally, it should be pointed out that mangrove restoration and artificial protection may also be complementary at the early stages of restoration efforts, and fully restored mangroves may also reinforce the effectiveness of artificial storm barriers, such as dykes and seawalls. The latter combination of “green” and “grey” infrastructure may be the most effective way of protecting vulnerable coasts from the variability of sea level rise, increased frequency and intensity of storms, and the risks of climate change (Barbier, 2014; Sandilyan & Kathiresan, 2015; World Bank, 2016). When mangrove tree seeds or seedlings are artificially reintroduced or naturally propagated, both frequent storms and the high energy of tides in coastal zones can prevent the establishment of young mangrove trees in bare sediments (Bosire et al., 2003; Moreno-Mateos et al., 2015). In Vietnam, this problem was solved by establishing bamboo T-fences to reduce coastal erosion and protect the sediment balance necessary for natural regeneration of mangroves (Albers & Schmitt, 2015). At US$50– US $60 per meter (m), such low-cost and temporary fencing (they last on average 5–7 years) is a relatively inexpensive way to improve the success of mangrove restoration at its crucial early stages of tree establishment. After successful restoration of sites suitable for mangrove growth, natural regeneration of mangroves will occur and the forest area expand. If artificial dykes are constructed inshore from the restored mangroves, then protection of coastal populations and property from sea level rise and the increasing frequency and intensity of storms is further enhanced. This is especially important in developing countries such as Vietnam, as the construction of dykes is expensive (US$2,270 per meter for a 3.5 meter high concrete dyke), and the possibility of increasing dyke height is limited due to the load-bearing capacity of the soil (Albers & Schmitt, 2015).

Other Benefits

Of course restored mangrove ecosystems can also provide benefits other than storm protection, including income and subsistence benefits from collecting products from the mangroves, nursery and breeding habitats for off-shore fisheries, and carbon sequestration. As the Thailand case study (Figure 1) illustrated, these additional benefits might be smaller compared to storm-protection benefits but important to the overall decision about whether or not to invest in mangrove restoration. In addition, products collected directly from the mangroves and also the artisanal fisheries supported by them may also be important in terms of the food security and subsistence needs of local coastal communities (Andrew et al., 2007; Béné, Hersoug, & Allison, 2010; Nfotabong, Din, Longonje, Koedam, & Dahdouh-Guebas, 2009; Sarntisart & Sathirathai, 2004; Walters et al., 2008).

For example, Figure 1 indicates that the net present value in terms of income to local coastal communities in Thailand from collected mangrove products range from US$484 to US$584 per hectare (ha). The net present value of mangroves as breeding and nursery habitat in support of off-shore artisanal fisheries ranged from US$708 to US$987 per hectare. Such benefits are considerable when compared to the average incomes of coastal households; a survey of four mangrove-dependent communities in two different coastal provinces of Thailand indicates that the average household income per village ranged from US$2,606 to US$6,623 per annum, and the overall incidence of poverty (corresponding to an annual income of US$180 or lower) in all but three villages exceeded the average incidence rate of 8% found across all rural areas of Thailand (Sarntisart & Sathirathai, 2004). The authors also found that excluding the income from collecting mangrove forest products would have raised the incidence of poverty to 55.3% and 48.1% in two of the villages, and to 20.7% and 13.64% in the other two communities.

The Thailand example is not unusual; poor households across the developing world typically benefit from the support to economic livelihoods provided by mangroves (Badola & Hussain, 2005; Bandaranayake, 1998; Barbier et al., 2011; Hassan & Crafford, 2015; Huxham et al., 2015; Naylor & Drew, 1998; Mukherjee et al., 2014; Nfotabong et al., 2009; Rönnbäck, Crona, & Ingwall, 2007; Walters et al., 2008; Walton et al., 2006). In addition, coastal people often associate important cultural values with local mangroves. A contingent valuation study of mangrove-dependent coastal communities in Micronesia demonstrated that the communities “place some value on the existence and ecosystem functions of mangroves over and above the value of mangroves’ marketable products” (Naylor & Drew, 1998, p. 488).

These livelihood benefits to local communities can be critical not only to the success of mangrove restoration but also to whether local cooperation in projects is forthcoming (Barbier, 2008; Rönnbäck et al., 2007; Walton et al., 2006). For example, Walton et al. (2006) found that restoring mangroves in the Philippines can have a significant impact on the lives of coastal communities, leading to 98% of surveyed local people expressing support for protecting the mangroves. In Kenya, natural mangroves were rated more highly than plantations by local people in terms of the number, range, and quality of products, with the exception of mangrove poles; however, 71% of respondents were still positive toward the plantations because they believe the forests will eventually be more beneficial to livelihoods (Rönnbäck et al., 2007).

Several studies of restoring mangroves in Thailand illustrate the connection between improved mangrove benefits to local coastal communities, their willingness and ability to participate in restoration projects, and their involvement in the long-run management of restored mangroves for these benefits. An analysis of four coastal communities reveals that awareness of community conservation efforts, community-imposed utilization rules and of the environmental damages imposed by shrimp farms are key motivating factors in the decision by male and female members of mangrove-dependent households to participate in restoration activities (Barbier, 2008). As a consequence, there may be more willingness to participate in mangrove restoration as a means to combat mangrove loss due to shrimp-farm expansion and other developments, but equally important is the degree of control the community has over managing the restored mangroves and their utilization. Similarly, in a mangrove forest rehabilitation project in Pattani Bay, local ownership of the project and effective community participation by three surrounding villages were crucial to the successful restoration of degraded mangroves (Erftemeijer & Bualuang, 2002). Community surveys throughout Thailand have confirmed that where local villages have been allowed to design and maintain well-defined governance structures over mangroves, stand structure was superior these community-managed forests than in open-access state forests (Sudtongkong & Webb, 2008). The lessons learned from these and similar studies of the motivation of local communities to participate in local mangrove restoration projects should be applied to designing the correct institutions and incentives for the larger mangrove rehabilitation schemes planned for many coastal areas across Southeast Asia and other tropical regions (Barbier, 2008; Biswas et al., 2009).

Risk of Failure, Benefit Transfer, and Cost-Effective Mangrove Restoration

No matter how well-designed, mangrove restoration projects always carry a risk of potential failure. Assessing the benefits of such projects must always consider taking such risks into account. This is especially important if mangrove restoration occurs on a large scale and involves phased implementation of restoration projects over many years.

Using the example of marsh creation in Louisiana, United States, Barbier (2016) has shown that it is relatively straightforward to adjust the current benefits of restoration and any capitalized land values if there is a risk of restoration failure. Incorporating such risks was important, given that the marsh-restoration plans in coastal Louisiana called for high rates of annual implementation during the first five-year phase, from 2013 to 2017, which, in turn, increases the risk of failure. Overall, the results showed that the risk of marsh-creation failure costs each individual in Louisiana about US$4 in total net wealth generated. With the costs of the risk of failure included, the cumulative asset wealth produced through creating marsh for protective benefits amounts to less than 0.1% of Louisiana’s 2012 gross domestic product per capita in constant 2005 US$.

Another frequent problem encountered in assessing the various benefits of mangrove restoration is how to overcome the difficulty of valuing them. One approach may be to use the Delphi technique to elicit values from experts with long experience with mangrove ecosystems, especially for those ecosystem services that have proven difficult to value (Mukherjee et al., 2014). However, a more common approach is to use benefit, or value, transfer. This method involves taking estimates of economic value from one site and “transferring” them to a similar location elsewhere (Johnston & Rosenberger, 2010; Plummer, 2009; Richardson, Loomis, Kroeger, & Casey, 2015; Rosenberger & Stanley, 2006; Troy & Wilson, 2006). In the benefit transfer literature, the location from which the valuation estimates are taken is called the “study” site, because it has already been “studied” in some way to obtain the original valuation estimate. The location to which the estimates are applied is called the “policy” site.

Plummer (2009) reviews the extensive environmental economics literature on the limits of implementing benefit transfer, especially in the context of the various goods and services provided by coastal and marine ecosystems, including mangroves. He concludes that the errors in applying this technique can be minimized provided there is sufficient ecological and economic correspondence between the study and policy sites. Plummer (2009) suggests that “lack of correspondence” can be reduced when

  • the ecosystem at the study site is a good match for the ecosystem under consideration at the policy site (i.e., ecological correspondence), or;

  • the respective populations of the study and policy sites do not differ considerably in terms of income levels, benefits derived from the ecosystem, preferences, employment and economic opportunities, household characteristics (e.g., occupation, education, number of adults and children, etc.), and other attributes that would cause wide variances in willingness-to-pay estimates between populations at the study site and populations at the policy site (i.e., economic correspondence).

The advancement in benefit transfer methods and modeling techniques, including the application of geographical information systems (GIS) and meta-regression analysis, means that there are more opportunities to use these methods as a way of extrapolating and transferring estimated ecosystem service values from one location, population, and time to other locations, populations, and periods. However, this technique is not a substitute for reliability. If there is a lack of economic and ecological correspondence between the study and policy sites, transferring values between the two sites through GIS and other methods will simply lead to inaccurate valuation estimates (Troy & Wilson, 2006).

Similarly, applying benefit transfer through meta-analysis regression has potential drawbacks. It requires knowledge of the values of the independent variables for the policy site of interest, and assumes that the statistical relationship between the dependent and independent variables is the same between the study and policy sites (Richardson et al., 2015; Rosenberger & Stanley, 2006). If one can statistically control for these differences in ecological and economic correspondence, it reduces the benefit transfer errors. In addition, there needs to be a sufficient number and variety of reliable policy-site valuation studies to make the meta-analysis regression applicable in the first place. For example, as Table 1 shows, only a handful of valuation studies of the protective benefits of mangroves may serve this purpose. Unfortunately, this suggests that benefit transfers may be less helpful in overcoming the lack of reliable estimates for the benefits associated with the coastal and storm protection provided by mangroves.

An alternative to transferring values when benefits are difficult to measure may be to focus on the cost-effectiveness of mangrove restoration. It has long been emphasized that appropriate site selection is crucial to improving the ecological success of mangrove restoration (Albers & Schmitt, 2015; Biswas et al., 2009; Lewis, 2005, 2009). Selection of areas for restoration based on cost-effectiveness can also ensure that a limited budget can be used to attain the maximum and improve the allocation of funds for restoration projects (Adame et al., 2015).

Adame et al. (2015) have illustrated the use of cost-effectiveness analysis for selecting sites for mangrove restoration in the Caribbean based on three benefits: carbon storage, water purification, and coastal protection. By examining the trade-offs between the provision of these ecosystem services and the cost of restoration, the authors were able to determine which restoration areas could deliver the three services at the lowest cost, thereby ensuring the maximum benefits from the fixed restoration budget. In addition, selecting cost-effective areas for restoration of mangroves on the basis of carbon sequestration often guaranteed the provision of coastal protection and water purification. This suggests that there may not be tradeoffs among the various mangrove benefits provided through cost-effective selection of restoration sites in the case-study area.

Conclusion

Concerns over the rapid decline in remaining mangrove areas and the increasing vulnerability of coastal populations have led to growing worldwide interest in restoring mangrove ecosystems. As a consequence, many countries are engaging in ambitious plans to invest and expand mangrove-restoration projects. However, mangrove restoration is expensive, funds are limited, and the risk of failure is a pervasive problem. Determining whether the cost and risk of mangrove restoration yields sufficient overall benefits is therefore increasingly relevant to restoration decisions.

Although much of the early-21st-century mangrove restoration is motivated by the potential storm-protection benefit, valuation of mangroves for other important benefits, such as providing collected wood and nonwood products (e.g., shellfish, plants, honey, medicines, etc.) to local coastal communities and nursery and breeding grounds for offshore fisheries, is also significant to restoration efforts. These other benefits may be smaller compared to storm-protection benefits but important to the overall decision about whether or not to invest in mangrove restoration. In particular, the connection between improved mangrove benefits to local coastal communities, their willingness and ability to participate in restoration projects, and their involvement in the long-term management of restored mangroves for these benefits needs to be explored in further research.

There are a number of other ways in which future research can improve approaches to valuing mangrove restoration. First, approaches to estimating the protective benefit of mangroves need to be extended to include any resulting impacts on either the disutility from risk aversion or the risk of possible injury, illness, or death from any potential damaging storms. Second, because mangrove restoration is occurring on larger scales and involves more ambitious targets, assessing the benefits of such restoration and the implications for capitalized land values should incorporate the risk of restoration failure. Finally, further progress needs to be made in developing more effective valuation approaches as alternatives to the second-best methods that are currently used too frequently, such as replacement-cost and benefits transfers. Improving the valuation of mangrove restoration may prove important in ensuring better restoration decisions and more successful projects and schemes.

Suggested Readings

Adame, M. F., Hermoso, V., Perhans, K., Lovelock, C. E., & Herrera-Silviera, J. A. (2015). Selecting cost-effective areas for restoration of ecosystem services. Conservation Biology, 29, 493–501.Find this resource:

Barbier, E. B. (2007). Valuing ecosystem services as productive inputs. Economic Policy, 22, 177–229.Find this resource:

Barbier, E. B. (2008). In the wake of the tsunami: Lessons learned from the household decision to replant mangroves in Thailand. Resource and Energy Economics, 30, 229–249.Find this resource:

Barbier, E. B. (2016). The protective value of estuarine and coastal ecosystem services in a wealth accounting framework. Environmental and Resource Economics, 64, 37–58.Find this resource:

Biswas, S. R., Mallik, A. U., Choudhury, J. K., & Nishat, A. (2009). A unified framework for the restoration of Southeast Asian mangroves: Bridging ecology, society and economics. Wetlands Ecology and Management, 17, 365–383.Find this resource:

Lewis, R. R., III. (2005). Ecological engineering for successful management and restoration of mangrove forests. Ecological Engineering, 24, 403–418.Find this resource:

Plummer, M. L. (2009). Assessing benefit transfer for the valuation of ecosystem services. Frontiers in Ecology and Environment, 7(1), 38–45.Find this resource:

de Rezende, C. E., Kahn, J. R., Passareli, L., & Vásquez, W. F. (2015). An economic valuation of mangrove restoration in Brazil. Ecological Economics, 120, 296–302.Find this resource:

Sandilyan, S., & Kathiresan, K. (2015). Mangroves as bioshields: an undisputed fact. Ocean and Coastal Management, 103, 94–96.Find this resource:

Walton, M. E., Giselle, M., Samonte-Tan, P. B., Primavera, J. H., Edwards-Jones, G., & Le Vay, L. (2006). Are mangroves worth replanting? The direct economic benefits of a community-based reforestation project. Environmental Conservation, 33(4), 335–343.Find this resource:

World Bank. (2016). Managing coasts with natural solutions: Guidelines for measuring and valuing the coastal protection services of mangroves and coral reefs. In M. W. Beck & G-M. Lange (Eds.), Wealth Accounting and the Valuation of Ecosystem Services Partnership (WAVES), World Bank, Washington, DC.Find this resource:

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