Global values of coastal ecosystem services: A spatial economic analysis of shoreline protection values
Introduction
One third of the world׳s population lives in coastal communities and coastal zones are twice as densely populated as inland areas (Millennium Assessment (MA), 2005, Barbier et al., 2008). Although coastal communities may interact in very different ways with the natural ecosystems they are located in and surrounded by, it is increasingly well understood that natural ecosystems play a crucial role in determining the well-being of human populations (TEEB, 2010). Thus, preserving the continuous flows of benefits is increasingly recognized as one of the most important catalysts for the conservation and sustainable management of natural ecosystems (Chan et al., 2006, Turner and Adger, 1998, Fischer et al., 2009).
Coastal wetlands, mangroves and near-shore coral reefs provide crucial benefits to many coastal communities by protecting them from flooding and storm surges, both seasonal and idiosyncratic storm events. The benefits from this ecosystem service may include prevention of loss of life, damages to housing, infrastructure and food sources, as prevention of saltwater intrusion (Brander et al., 2012). This is particularly important in the case of poor, vulnerable communities, which recent research shows to be often the most critically dependent on the provision of ecosystem services (Ghermandi et al., 2013, McGranahan et al., 2007). A widely accepted common ground in most definitions of vulnerability is the identification of the inability to cope with adverse effects, whether these are natural disasters, war, food shortages, or others (McCarthy et al., 2001, Adger, 2009). Vulnerability may be linked to geographical limitations, which constrain market access, for example. Communities which show in general a more strong direct reliance on ecosystem services and the absence of substitutes are more sensitive to impairment in their provision (WRI, 2005, Ghermandi et al., 2013). One important way to investigate vulnerability and dependence on coastal ecosystem services is to examine their estimated values. While coastal ecosystems offer a wide variety of benefits which are difficult to quantify, making estimations of the value can lead to understanding the drivers of the high and low values, and in turn inform policy. While this is a global analysis, it can be used for informing regional policy as well, especially in areas which are data poor.
Capturing the economic value of ecosystem services in a specific monetary unit or welfare measure is a challenging endeavor. Although valuation research is an active area, the lack of a standardized methodology and common type of unit makes comparisons difficult. Ideally, the determination of the economic values of services should be preceded by the biophysical assessment of their availability, which in turn should be distinguished from their overall provision or availability, to their actual use, in the form of benefits that humans enjoy from the services. This is however rarely the case, and for a number of reasons. First, some ecosystem services are more easily and directly quantified than others. Second, ecosystem services are inherently spatial and assessments need to rely on modeling of their flow in space and time (TEEB, 2010). As a general rule, biophysical assessments are highly dependent on the status of scientific knowledge and data availability, often relying on proxies to identify service provision, as opposed to benefits. This is particularly true in the case where there is lack of consensus on the best/ideal measurement units for these services. Finding a common metric with which to compare a wide variety of studies and management outcomes is however crucial to inform policy decisions, and hence, monetary valuation, even in the absence of biophysical assessment, can be useful as a common language and framework in which the available information can be analyzed and tradeoffs can be evaluated.
Further compounding the difficulty in quantifying and valuing ecosystem services is the fact that many ecosystem services are public goods and as a result, subject to a failure of the market to reflect their economic value.1 This is the case, for instance, of the service of shoreline protection, which, in spite of its significance to human lives, is rarely quantified, valued or taken into account in management decisions (de Groot, 1994). Careful quantification and valuation of the services can lead to better informed policy decisions. For that reason, and in an attempt to address different policy questions, researchers have attempted the valuation of services at different spatial scales of assessment, from local (Badola and Hussain, 2005) to global scale (Costanza et al., 1997, TEEB, de Groot et al., 2012, Ghermandi and Nunes, 2013). These types of studies look at the value of a wide range of ecosystem services, measuring them with a variety of different methods, with the ultimate goal of alleviating the shortcoming associated with the common exclusion of nature׳s values into policy and decision-making.
This study is the first systematic attempt to examine and map the economic value of shoreline protection as provided by three major coastal ecosystem types – coastal wetlands, mangroves and coral reefs—worldwide. We examine the available information on their economic value and investigate their dependence from a series of study-, site- and context-specific driving factors in a geographically explicit manner by means of meta-analysis. Identifying and understanding the drivers of the ecosystem services values for specific services is a first step towards their eventual integration into governmental policies and accounting. Next, the results of the meta-analytic regression are used to infer an estimate of the value of ecosystem services in other areas for which direct valuation has not been performed and produce a map of the worldwide distribution of shoreline protection values from the considered ecosystems. Finally, we discuss how the results of this study can be interpreted for the Caribbean region, with specific respect to coastal conservation and development policy.
One ecosystem service provided by mangroves, coral reefs and coastal marshes in wide coastal areas worldwide devoid of other, artificial defenses, is storm regulation or coastal protection. All three ecosystems mitigate the full effect of the storm surges, slowing or preventing them from reaching coastal human populations.
In general, when reefs and mangroves are damaged or destroyed, the absence of this natural barrier has been shown to increase the damage to coastal communities from normal wave action and violent storms. This storm protection that coastal ecosystems provide prevents both the loss of life and property for communities living in near-shore areas. The roots of mangrove plants help to hold the sediment in place (Orth et al., 2006). Mangrove forests protect inland communities and freshwater resources from saltwater intrusion during storms, and they protect near shore settlements from erosion (Semesi, 1998, Badola and Hussain, 2005). The root systems of mangroves prevent the resuspension of sediment and slow water flow in areas where the protection of shoreline-based activities are important (Spaninks and van Beukering,, Gilbert and Janssen, 1998). Mangroves protect areas from storms, have some recreational and fishing service value, and protect water quality (Aburto-Oropeza et al., 2008). In general, mangroves serve as “natural barriers” to protect life, infrastructure and property of coastal communities (Badola and Hussain, 2005). In addition the protection of property and infrastructure will indirectly benefit the tourism and recreation industries, but this indirect effect is not measured in this study. Valuation of mangroves has primarily focused on their storm protection services, though there is a small growing literature on the direct uses of mangroves. In major storms, research has shown that coastal communities experienced greater damage and higher mortality rates from many types of natural disasters when mangroves had been removed, and the value of these damages ranges widely (Danielsen et al., 2005, Barbier, 2007a, Barbier, 2007b, Das and Vincent, 2009).
Coral reefs (and mangroves) also minimize the impact of storms by reducing wind action, wave action, and currents and coral reef structures buffer shorelines against waves, storms and floods (Done et al., 1996, Moberg and Folke, 1999, Adger et al., 2005). In general, the structure of coral reefs provides a significant barrier to storm surges (UNEP-WCMC, 2006). They are increasingly under human and climatic threat to due to water pollution, sea temperature rise and ocean acidification (Bruno and Bertness, 2001), and regional studies have shown that the threats that coral reefs are facing affect their ability to provide ecosystem services (Bruno and Selig, 2007). Coral reefs are generally undervalued due to their open-access nature and to the fact that the ecosystem service of storm protection they provide is a (quasi) public good, and as a result, often disregarded in policy and decision-making contexts (Brander et al., 2007). Economic studies on coral reefs have included their diverse uses, which include direct uses such as fishing and diving, as well as indirect uses such as storm protection.
Wetlands found in coastal areas also function as storm buffers distinctly from how open water or land dissipates storm energy (Simpson and Riehl, 1981). This mechanism reduces the area of open water over which wind can form waves and simultaneously decreasing the storm surge, and absorbing the energy of waves (Costanza et al., 2006, Costanza et al., 2008). Moreover, coastal wetlands provide a physical barrier for storm protection. They also serve functions such as water purification, habitat for birds and fish, as well as the prevention of saltwater intrusion from sea water. Wetland ecosystem service studies have been performed more extensively than those from the previous two ecosystems, perhaps due to the wide range of services they provide, as well as possibly because they serve as a link of freshwater—marine systems. Research has been performed on a site scale, and several meta-analyses have been recently published (Brouwer et al., 1999, Woodward and Wui, 2001, Brander et al., 2006, Ghermandi et al., 2010). This study adds value to the current meta-analysis literature in two ways. First, it provides a first global and spatially explicit analysis of the economic value of coastal ecosystems for shoreline protection, which may constitute an important tool in the hands of coastal and marine planners and managers. Second, the integration with Geographic Information Systems helps to put the values elicited in primary valuation studies into their context, a dimension which is often lacking in primary valuation study reporting.
Common methods for assessment of shoreline protection values are based on market prices, revealed preference analysis, stated preference surveys, avoided damage, and replacement cost. Different methods are applicable to different ecosystem services, and the results of different valuation techniques will differ depending on the welfare measure used (Freeman, 2003), and some methods do not have a sound foundation in welfare theory, which may lead to either over- or underestimation (Brander et al., 2006). In the shoreline protection literature, avoided damages and replacement cost are very common methods used for shoreline protection studies (Vo et al., 2012).
Many site level studies have examined the value of shoreline protection provided by coral reefs, mangroves, and coastal wetlands around the world, often coming up with very wide ranges of values.2 The statistical analysis of this wide range of studies and research outcomes through meta-regression analysis can be a useful tool to help pointing out the principal drivers of value for this ecosystem service. Although such exercise cannot in general replace the more precise and site-specific information that can be obtained from a primary valuation study, it can provide the policy- and decision-makers with a suitable framework within which to evaluate the complex multi-dimensional aspects involved in the management of these coastal ecosystems. Moreover, the meta-analytical framework can be used as a cost-effective tool to draw generalized conclusions and transfer ecosystem service value estimates to policy sites for which primary valuation studies are not available. This is often the case in less-developed regions, including those where ecosystems such as mangroves and coastal wetlands are more abundant. There is by now a large number of studies that have used meta-regression analysis of ecosystem values for such purposes (for a comprehensive overview see Nelson and Kennedy, 2009).
Section snippets
Collection of primary valuations of shoreline protection
A wide variety of studies were examined during the phase of literature review for this study. The studies were focused on shoreline protection by coral reefs, mangroves and wetlands.3 The studies used were all economic valuation studies which were associated with a specific site. The studies were from a variety of coastal sites, including
Results: general results
In terms of characteristics of the studies used in the meta-analysis, observations from Indonesia, the United States, and Thailand occur the most frequently, at 17, 18, and 7 times, respectively. Fifty observations come from Asia, eighteen observations from the Americas, twelve observations from Caribbean, seven observations from Oceania, three from Africa and two from Europe. Thirty-four of the observations come from peer reviewed journals, and 58 are from “gray literature,” working papers or
Discussion
The negative and significant correlation between the economic value of coastal ecosystem and the size of ecosystem, suggests the presence of diminishing marginal returns to ecosystem size. The reason for this finding could illustrate an issue of scarcity of the ecosystem resource; the smaller the resource, the more it is valued in terms of providing critical ecosystem benefits. Other studies, primarily of wetlands, have shown that the size of the ecosystem has a negative correlation with the
Conclusions
This study presented the novel use of meta-analytic regression and benefit transfer to examine issues of ecosystem service values associated with coastal ecosystems, and the benefits that accrue to coastal populations. After performing a meta-analytic regression of the economic value of coastal and shoreline protection, the results show that size, level of development, GDP, type of ecosystem, wind speed, storm frequency, and method all affect the economic value of the ecosystem service.
Acknowledgments
The authors would like to thank Conservation International for support of this work, as well as Leah Karrer and Emily Pidgeon. The authors also thank Keith Alger, Paulo Nunes, Laura Onofri, Elizabeth Selig, Fabiano Godoy, Andres Cano, Erica Ashkenazi, Kellee Koenig, Karyn Tabor, Andre Boustany, John Fay, and Venetia Hargreaves-Allen for methodological, technical and editorial support.
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