Ann. N.Y. Acad. Sci. ISSN 0077-8923

ANNALS OF THE NEW YORK ACADEMY OF SCIENCES Issue: Ecological Economics Reviews

Valuing ecosystem services Theory, practice, and the need for a transdisciplinary synthesis

Shuang Liu,1 Robert Costanza,1 Stephen Farber,2 and Austin Troy3 1Gund Institute of Ecological Economics and Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, Vermont, USA. 2Graduate School of Public and International Affairs, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. 3Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, Vermont, USA Address for correspondence: Current address: Shuang Liu, GPO Box 1700, Canberra Act 2601, Australia. [email protected]

The concept of ecosystem services has shifted our paradigm of how nature matters to human societies. Instead of viewing the preservation of nature as something for which we have to sacrifice our well-being, we now perceive the environment as natural capital, one of society’s important assets. But ecosystem services are becoming increasingly scarce. In order to stop this trend, the challenge is to provoke society to acknowledge the value of natural capital. Ecosystem services valuation (ESV) is the method to tackle such a challenge. ESV is the process of assessing the contributions of ecosystem services to sustainable scale, fair distribution, and efficient allocation. It is a tool that (1) provides for comparisons of natural capital to physical and human capital in regard to their contributions to human welfare; (2) monitors the quantity and quality of natural capital over time with respect to its contribution to human welfare; and (3) provides for evaluation of projects that will affect natural capital stocks. This review covers: (1) what has been done in ESV research in the last 50 years; (2) how it has been used in ecosystem management; and (3) prospects for the future. Our survey of the literature has shown that over time, there has been movement toward a more transdisciplinary approach to ESV research which is more consistent with the nature of the problems being addressed. On the other hand, the contribution of ESV to ecosystem management has not been as significant as hoped nor as clearly defined. Conclusions drawn from the review are as follows: first, ESV researchers will have to transcend disciplinary boundaries and synthesize tools, skills, and methodologies from various disciplines; second, ESV research has to become more problem-driven rather than tool-driven because ultimately the success of ESV will be judged on how well it facilitates real-world decision making and the conservation of natural capital.

Keywords: natural capital; environmental decision making; ecosystem valuation

Ecosystem services are the benefits people obtain not value.6 Evidence of this is easily seen whereby from ecosystems. These include provisioning ser- weusewords,suchas“priceless”and“invaluable,” vices, such as food and water; regulating services, when discussing the environment and yet this has such as regulation of floods, drought, and disease; proven woefully insufficient in terms of reducing or supporting services, such as soil formation and nu- halting ecosystem degradation. The challenge then trient cycling; and cultural services, such as recre- is to provoke society to acknowledge the value of ational, spiritual, and other nonmaterial benefits.1–4 ecosystem services.7 Ecosystem services valuation On the supply side, ecosystems are experiencing se- (ESV) is the tool that can tackle such a challenge. rious degradation in regard to their capability of providing services. At the same time, the demand Definition and triple goals of ecosystem for ecosystem services is rapidly increasing as pop- services valuation ulations and standards of living increase.5 Ecosystem services are becoming increasingly The concept of ecosystem service is anthropogenic, scarce. This trend is partially due to the lack of valu- as is the process of ESV. For this reason, ESV ation because it is impossible to manage what we do efforts, particularly monetary valuation, have been

54 Ann. N.Y. Acad. Sci. 1185 (2010) 54–78 c 2010 New York Academy of Sciences. Liu et al. Ecosystem service valuation review criticized for conserving ecosystems only for the sake efficient allocation, that is, to allocate scarce ecosys- of humans.8 This argument is misleading for two tem services among competing uses, such as devel- reasons. opment and conservation. But other goals, and thus First, it is important to differentiate ends and other values, are possible. There are at least three means. Monetary valuation, and ESV in general, is broad goals that have been identified as important only a means to communicate the concept of differ- to managing economic systems within the context ence between the two schools of thought concerning of the planet’s ecological life support system:18 ecosystem conservation—for the benefit of man or 1. assessing and ensuring that the scale or magni- the benefit of the entire Earth—is mostly theoretical. tude of human activities within the biosphere In the end, the well-being of people and ecosystems are ecologically sustainable; are interdependent, which is in accord with conser- 2. distributing resources and property rights vation practices today where pluralism between the fairly, both within the current generation of two schools is often the norm.9 humans and between this and future gener- In addition, the fact that ecosystem services have ations, and also between humans and other an economic value does not mean that economic species; and benefits are the only focus for ESV. On the contrary, 3. efficiently allocating the resources constrained nature is vital to human survival and well-being and defined by 1 and 2 above (including both for a myriad of reasons and, therefore, forcing all market and nonmarket resources, and espe- values into a single economic indicator is not real- cially ecosystem services) for the purpose of istic. Recognizing the existence of multiple values maximizing utility or human welfare. and encouraging open and pluralistic discussion of values will lead to new solutions for conservation Because of these multiple goals, valuation must be practice.10 performed from multiple perspectives, using multi- Ecosystems have both intrinsic and utilitarian val- ple methods (including both subjective and objec- ues.a We acknowledge the importance of intrinsic tive), and against multiple goals.13 Furthermore, it is value, yet it is beyond the scope of this paper. This important to recognize that the three goals are not is because ESV is anthropogenic whereas intrinsic “either–or” alternatives. Instead, they are in some value is not. sense independent multiple criteria which must all According to a utilitarian framework, valuation is be satisfied in an integrated fashion to allow human the process of assessing the contribution of a par- life to continue in a desirable way.19 ticularobjectoractiontomeetingaparticulargoal, However, basing valuation on current individual whether or not that contribution is fully perceived preferences and utility maximization alone does not by the individual. A baseball player is valuable to necessarily lead to ecological sustainability or social the extent he contributes to the goal of the team’s fairness,20 or to economic efficiency for that mat- winning. In evolutionary biology, a gene is valuable ter, given the severe market imperfections involved. to the extent it contributes to the survival of the ESV provides a tool that enhances the ability of individuals possessing it and their progeny. In neo- decision makers to evaluate tradeoffs between alter- classical economics, a commodity is valuable to the native ecosystem management regimes in order to extent it contributes to the goal of individual welfare meet a set of goals, namely, sustainable scale, fair as assessed by willingness to pay. The point is that distribution, and efficient allocation.21 one can not state a value without stating the goal being served.13 Framework for ESV ESV is then the process of assessing the contri- bution of ecosystem services to meeting a particular Figure 1 shows an integrated framework devel- goal or goals. In neo-classical economics this goal is oped for ESV (adapted from Ref. 3). It exhibits the pivotal link served by ecosystem services be- tween human and ecological systems. Ecosystem aIn the ESV arena, discussion has been focused on the structures and processes are influenced by bio- difference between intrinsic and utilitarian values and its physical drivers, which in turn create the neces- implication to environmental decision making.5,8,11–17 sary conditions for providing the ecosystem services

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Figure 1. Framework for integrated assessment and valuation of ecosystem goods and services (adapted from de Groot et al.3) (In color in Annals online.) that support human welfare. Through land use servation needs should be price-determining, not management and policy decisions, individuals and price-determined.27 social groups make tradeoffs. In turn, these land use decisions directly modify the ecological struc- tures and processes through engineering and con- Box 1. Ecosystem service valuation methods struction activities and/or indirectly by modifying Monetary valuation (adapted from Farber 15 the physical, biological, and chemical structures and et al. ) processes of the landscape. Revealed-preference approaches • Market methods: Valuations are directly ob- Methodology for ESV tained from what people must be willing to pay for the service or good (e.g., timber har- Many ecosystem services are neither rival nor ex- vest). cludable, so they are subject to market failure • Travel cost: Valuations of site-based ameni- in which the market can not send the correct ties are implied by the costs people incur to price signals to determine the appropriate provi- enjoy them (e.g., cleaner recreational lakes). sion of ecosystem services.22 Aspectrumofnon- • Hedonic methods: The value of a service is market valuation techniques have been developed implied by what people will be willing to pay to value ecosystem services, including both non- for the service through purchases in related monetary valuation methods and environmental markets, such as housing markets (e.g., open- space amenities). economic techniques based on a monetary metric • 23–26 Production approaches: Service values are (Box 1 ). assigned from the impacts of those services The use of a monetary metric assumes that in- on economic outputs (e.g., increased shrimp dividuals are willing to trade the ecosystem service yields from an increased area of wetlands). being valued for other services represented by the metric. The purpose of monetary valuation is to State-preference approaches allow the measurement of the costs or benefits as- • Contingent valuation: People are directly sociated with changes in ecosystem services by cal- asked their willingness to pay or accept com- culating a shadow price. However, caution must be pensation for some change in ecological ser- taken when using this price mechanism to allocate vice (e.g., willingness to pay for cleaner air). ecosystem services, and it has been argued that con-

56 Ann. N.Y. Acad. Sci. 1185 (2010) 54–78 c 2010 New York Academy of Sciences. Liu et al. Ecosystem service valuation review

erences. As a result these cost figures should not be • Conjoint analysis: People are asked to choose on the benefit side of a benefit-cost balance sheet.b or rank different service scenarios or ecolog- Conducting original valuation research is expen- ical conditions that differ in the mix of those sive and time-consuming. Benefit transfer has been conditions (e.g., choosing between wetlands applied as a “second-best” strategy, where decision scenarios with differing levels of flood pro- makers seek a timely and cost-effective way to value tection and fishery yields). ecosystem services.30 It involves obtaining an esti- Cost-based approaches mate for the value of ecosystem services through the • Replacement cost: The loss of a natu- analysis of a single study or group of studies that ral system service is evaluated in terms of have been previously carried out to value “similar” what it would cost to replace that ser- goods or services in “similar” locations. The trans- vice (e.g., tertiary treatment values of wet- fer itself refers to the application of derived values lands if the cost of replacement is less and other information from the original “study site” than the value society places on tertiary to a “policy site,” which can vary across geographic treatment). space and/or time.31,32 • Avoidance cost: A service is valued on the ba- The ability to transfer values from one context sis of costs avoided, or of the extent to which it to another is service-specific. Some ecosystem ser- allows the avoidance of costly averting behav- vices, such as carbon sequestration, may be provided iors, including mitigation (e.g., clean water at a scale for which benefits are easily transferable. reduces costly incidents of diarrhea). By contrast, values of local-scale services, such as Benefit transfer: The adaptation of existing ESV flood control, may have limited transferability. Table information or data to new policy contexts that 1 provides guidance for transferring service values have little or no data (e.g., ecosystem service values from one context to another.33 obtained by tourists viewing wildlife in one park Similarly, Table 1 also illustrates some valuation used to estimate that from viewing wildlife in a tools that are more appropriate for some ecosys- different park). Nonmonetizing valuation or assessment34 tem services than for others. For example, Travel Measures of attitudes, preferences, and intentions Cost (TC) is primarily used for calculating recre- Civic valuation ation values while Hedonic Pricing (HP), for esti- Decision science approaches mating property values, is associated with the aes- Ecosystem benefit indicators thetic qualities of natural ecosystems. Contingent Biophysical ranking methods Valuation (CV) and Conjoint Analysis (CA) are the only methods by which measurements can be ob- tained for nonuse values, such as the existence value For an environmental economist, the principle of wildlife. distinction among monetary valuation methods is Finally, nonmonetary methods do not require based on the data source, that is, whether it derives valuation results expressed in a single monetary from observations of human behavior in the real unit.34 For instance, group valuation (GV), a type of world (i.e., revealed-preference approaches)orfrom civic valuation, is a more recent addition to the val- human responses to hypothetical questions (state- uation literature and addresses the need to measure , preference approaches) such as, “How much would social values directly in a group context.35 36 An- you be willing to pay for...?” or “What would you other novel approach has emerged which estimates do if...?” individuals’ subjective happiness as a function of When an ecosystem service is difficult to value us- factors, such as ecosystem services and income.26 ing the above two approaches, researchers—mainly ecologists—have resorted to the method of replace- ment or avoided cost. However, economists believe that such a cost-based approach should be used only bSimilarly, one should differentiate the concept of Cost of , , with great caution.25 28 29 For them, any value esti- Policy Inaction and the value of ecosystem services. The mate derived from this approach is not a measure former is the economic loss in the absence of additional of economic value because it is not based on pref- policy or policy revision.6

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Table 1. Categories of ecosystem services and economic methods for valuation (Farber et al.33)

Amenability to Most appropriate Transferability Ecosystem service economic valuation method for valuation across sites

Gas regulation Medium CV, AC, RC High Climate regulation Low CV High Disturbance regulation High AC Medium Biological regulation Medium AC, P High Water regulation High M, AC, RC, H, P, CV Medium Soil retention Medium AC, RC, H Medium Waste regulation High RC, AC, CV Medium to high Nutrient regulation Medium AC, CV Medium Water supply High AC, RC, M,TC Medium Food High M, P High Raw materials High M, P High Genetic resources Low M, AC Low Medicinal resources High AC, RC, P High Ornamental resources High AC, RC, H Medium Recreation High TC, CV, ranking Low Aesthetics High H, CV, TC, ranking Low Science and education Low Ranking High Spiritual and historic Low CV ranking Low

AC, avoided cost; CV, contingent valuation; H, hedonic pricing; M, market pricing; P, production approach; RC, replacement cost; TC, travel cost.

History of ESV research presented by the transdisciplinary nature of ESV re- search. In the 1960s, for instance, there was relatively This section provides an historical perspective on little work that transcended disciplinary boundaries ESV research. The initial impetus for ESV was the on ESV. In later years, this situation gradually im- emergence of environmentalism in the 1960s. How- proved. Transdisciplinary approaches are required ever, this is not to say that the foundations of for ESV in which practitioners (1) perceive disci- ESV were not present before that. For instance, plinary boundaries as academic constructs irrele- Hotelling’s discussion of the value of parks implied vant outside of the university, and (2) allow the by travel costs signaled the start of the travel cost problem being studied to determine the tools, rather valuation era.37 Similarly, suggestions by Ciriacy- than vice versa. Wantrup in the late 1940s led to the use of stated We frequently see ESV research in which teams preference techniques.38 Such early efforts demon- of researchers trained in different disciplines sep- strate that economists started to consider evaluat- arately tackle a single problem and then strive to ing the contribution of nature to human well-being, combine their results. This is known as multidis- even though the concept of ecosystem services was ciplinary research, but the result is much like the not developed for almost another 50 years. blind men who examine an elephant, each describ- Our approach to the history of advances in ESV ing the elephant according to the single body part will not be a method by method literature review.c they touch. The difference is that the blind men Rather, we focus on how people faced the challenge can readily pool their information, while different academic disciplines lack even a common language with which their practitioners can communicate.42 c Several reviews of the published ESV literature have been Interdisciplinary research, in which researchers from developed elsewhere.23,24,39–41 different disciplines work together from the start to

58 Ann. N.Y. Acad. Sci. 1185 (2010) 54–78 c 2010 New York Academy of Sciences. Liu et al. Ecosystem service valuation review jointly tackle a problem and reduce the language value, or the value of maintaining opportunities to barrier as they go, is a step in the right direction learn about the costs and benefits of avoiding pos- toward the transdisciplinary path. sibly irreversible future states.48 Discussions in this paper focus primarily on the In most cases, willingness to pay for these newly United States due to the comparative wealth of case recognized values could not be derived via market studies. It could be true that the development of ESV transactions because most of the ecosystem services research and practice are quite different in other in question are not traded in actual markets. Thus, parts of the world.43 new valuation methods were also proposed, includ- We arbitrarily divide the last 50 years (1960 to ing travel cost,49 contingent valuation,50 and hedonic present) into four periods. Influential contributions pricing.51 during each period are marked as milestones in Fig- In the meantime, ecologists also proposed their ure 2. The chart is meant to be illustrative, not com- own valuation methods. For example, “energy anal- prehensive, as space prohibits showing all important ysis” is based on thermodynamic principles in which contributions and milestones. solar energy is considered to be the only primary input to the global ecosystem.52 This biophysical method does not assume that value is determined by 1960s—Common challenge, separate individual preferences, but rather attempts a more answers “objective” assessment of ecosystem contributions The 1960s are remembered as the decade of early to human welfare. environmentalism. Main social events include pub- lication of Rachel Carson’s Silent Spring in 1962, 1970s—Breaking the disciplinary boundary passage of the 1970 Clean Air Act, and formation of the U.S. Environmental Protection Agency (EPA) in The existence of “limits to growth” was the main that same year. message in the environmental literature during the In response to increasing public interest in 1970s.53 The Arab oil embargo in 1973 emphasized environmental problems, such as pollution and dra- this message. matic population increase, economists began re- “Steady-state economics”asananswertothe thinking the role of the environment in their pro- growth limit was proposed by economist Herman duction models and identified new types of surplus Daly, who emphasized that the economy is only a for inclusion in their welfare measure.44 subsystem of the finite global ecosystem.54 Thus, Economist Kenneth Boulding compared the the economy can not grow forever, and ultimately “cowboy economy” model, which views the envi- a sustainable steady state is desired. Daly was in- ronment as a limitless resource, with the “spaceship spired by his graduate-school mentor, Nicholas economy” view of the environment’s essential lim- Georgescu-Roegen. In The Entropy Law and the Eco- its.45 His work included recognition of the ecosys- nomic Process, Georgescu-Roggen elaborates exten- tem service of waste assimilation to the production sively on the implications of the entropy law for model, where before, ecosystems had mainly been economic processes and how economic theory could regarded as a source of provisioning services. be grounded in biophysical reality.55 Consideration of cultural services in an economic Georgescu-Roegen was not the only scientist to analysis began with Krutilla’s seminal observation break the disciplinary boundary in the 1970s. Ecol- that many people value natural wonders simply for ogist H. T. Odum published his influential book their existence. Krutilla argued that these people ob- Environment, Power, and Society in 1971, where he tain utility through vicarious enjoyment of natural summarized his insights from studying the energet- areas and, as a result, had a positive willingness to ics of ecological systems and applying them to social pay for the government to exercise good stewardship issues.56 of the land.46 Along with these early efforts, a heated de- In addition to existence value, other types of eco- bate between ecologists and economists highlighted nomic value were also considered. These include their differences regarding concepts of value. The option value, or the value of avoiding commitments economists of the day objected strenuously to the that are costly to reverse.47 Thereisalsoquasi-option energetic approach. They contended that value and

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• Georgescu -Roegen (1971 ) • • Clawson (1959 ) Travel cost Just and others (1982) ‘The entropy law and • Davis (1963 ) Factor income the economic process’ Contingent Valuation • Daly (1977 ) • • Weisbrod (1964 ) Costanza (1980) ‘Embodied ‘Steady -state economy’ Option value energy and economic valuation’ • • Arrow and Fisher (1974 ) • Ehrlich and Ehrlich (1981 ) EPA ESV Forum (1991 ~ 1992 ) • Krutilla (1967) • Quasi -option value Concept of ‘Ecosystem Services’ NCEAS ESV workshop Existence value • ( 1999 ~ 2001 ) Costanza and Daly (1982 ) • • Odum (1971 ) Concept of ‘Natural Capital’ Millennium Ecosystem • Odum (1967 ) Assessment (2001 ~2006) ‘Environment , power • Farber and Costanza (1987 ) Energy Analysis • NRC report 2004 and society’ 1 st coauthored paper

1960 - 1970 1970 - 1980 1980 - 1990 1991 - 2010

Common challenge , Era of concerted efforts separate answers

Figure 2. Milestones in the history of ecosystem service valuation. (In color in Annals online.) price were determined solely by people’s “will- However, in later years this distinction between nat- ingness to pay” and not by the amount of en- ural resources and the environment has been chal- ergy required to produce a service. H. T. Odum lenged as artificial and thus no longer meaningful and his brother E. P. Odum and economists or useful.23 Leonard Shabman and Sandra Batie engaged in a point–counterpoint discussion of this difference 1980s—Moving beyond multidisciplinary ESV in the pages of the Coastal Zone Management research Journal.28,57,58 Though unrealized at the time, a new method In the 1980s, two government regulations created called the production function approach became one a tremendous demand for valuation research. The way to bring together the views of ecologists and first was the 1980 Comprehensive, Environmental Re- economists. This method is used to estimate the eco- sponses, Compensation and Liability Act (CERCLA), nomic value of ecosystem services that contribute to commonly known as Superfund, which established the production of marketed goods. It is applied in liability for damages to natural resources from toxic cases where ecosystem services are used, along with releases. In promulgating its rules for such Natural other inputs, to produce a market good.59,60 Resource Damage Assessments (NRDA), the U.S. Early contributions in the area include works Department of Interior interpreted these damages from Anderson,61 Schmalensee,62 and Just and and the required compensation within a welfare– Hueth.63 Just and his colleagues provided a rigor- economics paradigm, measuring damages as lost ous analysis of how to measure changes in welfare consumer surplus. The regulations also describe due to price distortions in factor and product mar- protocols that are based on various economic valu- 65 kets. These models provide a basis for analyzing the ation methods. effects of productivity-induced changes in product The role of ecosystem valuation increased in im- and factor prices.64 portance in the United States with President Rea- Thefieldofenvironmentalandresourceeco- gan’s Executive Order 12911, issued in 1981, requir- nomics grew rapidly from the beginning of the ing that all new major regulations be subject to a 66 1970s. The field became institutionalized in 1974 cost-benefit analysis (CBA). d with the establishment of the Journal of Environ- As shown in Figure 3, the 1980s witnessed dra- mental Economics and Management (JEEM). The matic increases in the number of publications, objects of analysis for natural-resource economists have typically been resources, such as forests, ore de- dThesearchwasconductedforfourgeneraltypesofen- posits, and fish species, that provided provisioning tities relevant to ecosystem services, including ecological services to the economy. On the other hand, the en- functions, extractive uses, nonextractive uses, and pas- vironment itself is viewed more as a medium tainted sive uses. We excluded valuation publications on human by the externalities associated with air, noise, and health and the built environment from EVRI because they water pollution, as well as the source of amenities. are not relevant to ESV.

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87-sector input–output model of the U.S. economy for 1963, 1967, and 1973, modified to include house- holds and governments as endogenous sectors, to investigate the relationship between direct and in- direct energy consumption (embodied energyf )and the dollar value of output by sector. They found that the dollar value of sector output was highly corre- lated with embodied energy, though not with di- rect energy consumption or with embodied energy calculated excluding labor and government energy Figure 3. Number of ESV publications in EVRI over time costs. (accessed Feb. 10, 2007). (In color in Annals online.) Differences of opinion between ecologists and economists still existed in the 1980s in terms of the relationship between energy inputs, prices, and val- including peer-reviewed papers, book chapters, ues.72 But the decade also witnessed the first paper governmental reports, and theses on the topic of coauthored by an ecologist and an economist on ecosystem valuation.e These results are based on a ecosystem valuation.73 Though the idea of the pa- search of the Environmental Valuation Reference per was simply to compare the results from two InventoryTM (EVRI), the world’s largest online val- separate studies using different methods, the paper uation database (http://www.evri.ca/). also represented the first instance of an ecologist and The 1989 Exxon Valdez oil spill was the first economist overcoming their disciplinary differences case where nonuse value estimated by contingent and working together. valuation was considered in a quantitative assess- The term ecosystem services first appeared in ment of damages. In March of that year, the Exxon Ehrlich and Ehrlich’s work (198174). The creation of Valdez accidentally spilled 11 million gallons of oil the concept represents an attempt to build a com- into Alaska’s pristine Prince William Sound. Four mon language for discussing linked ecological and months later, the District of Columbia Circuit of economic systems. Using “ecosystem services” and the U.S. Court of Appeals held that nonuse value “environmental services” as key words, a search in should be part of the economic damages due to re- the ISI Web of Knowledge shows the total number leases of oil or hazardous substances that injure nat- of papers published and the number of disciplinary ural resources. Moreover, the decision found that categories in which they occur over time (Fig. 4). For CV was a reliable method for undertaking such example, the curves indicate that by July 2007, more estimates. Prior to the spill, CV was not a well- than 200 papers per year were being published on developed area of research. After the widely pub- ecosystem services in about 50 subdisciplines. The licized oil spill, the attention given to the concep- two exponential curves show the increasing use of tual underpinnings and estimation techniques for the term over time and the fact that it has been nonuse value increased dramatically.68 In the same embraced quickly by many different disciplines, in- year, two leading researchers, Mitchell and Carson, cluding those that appear at first glance to be not published their substantive work on CV.69 so relevant, such as computer science, pharmacy, At the same time, ecologists began to compare business, law, and demography. their results based on energy analysis with con- ventionally derived economic values. For example, Costanza70 and Costanza and Herendeen71 used an f The energy embodied in a good or service is defined as the total direct energy used in the production process plus all the indirect energy used in all the upstream production eThe drop of the number of publications in some recent processes used to produce the other inputs to the process. years is probably due to artificial effect, i.e., EVRI has not For example, auto manufacturing uses energy directly, but included all the publications. According to a similar analy- it also uses energy indirectly to produce the steel, rubber, sis by Adamowicz, the amount of peer-reviewed literature plastic, labor, and other inputs needed to produce the in environmental valuation has increased over time.67 car.

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250 of a judicial process of damage assessment, includ- ing lost passive-use values” (p. 64)75 (i.e., nonuse

# of paper value). 200 # of category At the same time, the controversy about CV also stimulated a substantial body of transdisciplinary 150 ESV research. Highlights include conjoint analysis, Meta-Analysis (MA), group valuation, and Multiple Criterion Decision Analysis (MCDA). 100 Insights from psychology have proven fruitful in structuring and interpreting CV studies.76 Anew

50 approach that gained popularity in the 1990s was conjoint analysis. This technique allowed researchers to identify the marginal value of changes in the char- 0 1982 1992 2002 acteristics of environmental resources, as opposed to asking direct CV questions. Respondents are asked Figure 4. Number of peer-reviewed ecosystem service to choose the most preferred alternative (or, to rank papers and their related sub-categories over time listed the alternatives in order of preference, or to rate in the ISI Web of Science (accessed June 29, 2007). (In them on some scale) among a given set of hypo- color in Annals online.) thetical alternatives, each depicting a different bun- dle of environmental attributes. Responses to these The concept of ecosystem services and the related questions can then be analyzed to determine the concept of “natural capitalg ” have enhanced our un- marginal rates of substitution between any pair of derstanding of how the natural environment mat- attributes that differentiate the alternatives. If one ters to human societies. It is now believed that the of the characteristics has a monetary price, then it is natural environment and the ecosystems within can possible to compute the respondent’s willingness to be defined as natural capital, and along with phys- pay for the other attributes.77–80 ical, human, and social capital, these four together While subject to the same concern as CV regard- comprise society’s precious assets. ing the hypothetical nature of valuation, the con- joint analysis approach offers some advantages.81 1990s ∼ present: Moving toward For example, it creates the opportunity to determine transdisciplinary ESV research tradeoffs in environmental conditions through its emphasis on discovering whole preference structures Not only attention but also controversy was drawn and not just monetary valuation. This may be espe- to the CV approach after its application to the Exxon cially important when valuing ecosystems, which Valdez case, when it became known that a major provide a multitude of joint goods and services. In component of the legal claims for damages was likely addition, it more reasonably reflects multi-attribute to be based on CV estimates of lost nonuse or exis- choice than the typical one-dimensional CV. tence value. The concerns about the reliability of the A well-developed approach in psychological, ed- CV approach led the National Oceanic and Atmo- ucational, and ecological research, MA was in- spheric Administration (NOAA) to convene a panel troduced to the ESV field by Walsh and col- of eminent experts co-chaired by Nobel Prize win- leagues in the late 1980s and early 1990s.82–84 ners Kenneth Arrow and Robert Solow to examine MA is a technique that is increasingly used to the issue. In January 1993, the panel issued a re- understand the influence of methodological and port which concluded that “CV studies can produce study-specific factors on research outcomes and to estimates reliable enough to be the starting point synthesize past research. Recent applications include MA of air quality,85 endangered species,86 and wet- lands.87,88 A more recent use of MA is the sys- g Natural capital is defined as the stock of ecosystem tematic utilization of the existing value estimates structure that produces the flow of ecosystem goods and from the source literature for the purpose of value services. transfer.89–91

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Mainly derived from political theory, discourse- “the challenge of improving ecosystem valuation based valuation is founded on the principles of methods presents an opportunity for partnership— deliberative democracy and the assumption that partnership between ecologists, economists, and public decision making should result, not from other social scientists and policy communities. In- the aggregation of separately measured individual terdisciplinary dialogue is essential to the task of preferences, but from a process of open public developing improved methods for valuing ecosys- debate.92,93 This method is extremely useful in ESV tem attributes" (p. 90).42 In a paper compar- as it can address the fairness goal of ESV.35,36 ing economics and ecological concepts for valu- MCDA techniques originated over three decades ing ecosystem services, participants from the second ago in the fields of mathematics and opera- workshop concluded that “there is clearly not one tions research and are well-developed and well- ‘correct’ set of concepts or techniques. Rather there documented.94 These provide a structured frame- is a need for conceptual pluralism and thinking ‘out- work for decision analysis, which involves definition side the box’ ” (p. 390). 15 of goals and objectives, identification of the set of This call for cross-disciplinary research is echoed decision options, selection of criteria for measuring by a recent National Research Council study on as- performance relative to objectives, determination of sessing and valuing the ecosystem services of aquatic weights for the various criteria, and application of and related terrestrial ecosystems. In their final re- procedures and mathematical algorithms for rank- porth a team composed of 11 experts from the ing options. fields of ecology, economics, and philosophy offered Compared to CBA, MCDA has at least these guidelines for ESV including: “Economists and ecol- three advantages95,96: (1) by definition MCDA is ogists should work together from the very beginning multidimensional and can consider different and to ensure the output from any an ecological model is incommensurable objectives, such as sustainability, in a form that can be used as input for an economic equity, and efficiency at the same time; (2) MCDA model” (p. 220).25 is much more flexible in structure as well as ag- Two interdisciplinary publications drew gregation procedures. For instance all indicators do widespread attention to ESV and stimulated a con- nothavetobevaluedinmonetaryterms.Instead, tinuing controversy between ecological economists the original measurement units could be kept or and traditional “neoclassical” economists. Costanza normalized in different ways, which makes room and his colleagues (ecologists and economists) for subjective components of the analysis; and (3) published an often-cited paper in Nature on valuing MCDA has the capacity to take into account qual- the services provided by global ecosystems. They itative variables. This is especially useful when un- estimated that the annual value of 17 ecosystem certainty is an issue. For instance, the effect of global services for the entire biosphere was US$33 trillion.1 warming on species diversity is uncertain but can be The journal Ecological Economics contributed a expressed qualitatively. Of course, MCDA also has special issue in 1998, which included a series of 13 it own limitations, such as (1) a multicriteria prob- commentaries on the Nature paper. lem is by definition mathematically ill-structured, The first book dedicated to ecosystem services was i.e., it has no objective solution. This is also the pri- also published in 1997.2 Nature’s Services brought mary reason for proliferation of so many different together world-renowned scientists from a variety theories and models; and (2) various aggregation of disciplines to examine the character and value of procedures exist for MCDA which could make the ecosystem services, the damage that has been done, valuation process less transparent. and the consequent implications for human soci- The emergence of these new interdisciplinary ety. Contributors including Paul R. Ehrlich, Don- methods can be attributed in part to two work- ald Kennedy, Pamela A. Matson, Robert Costanza, shops in the 1990s which brought together ESV re- Gary Paul Nabhan, Jane Lubchenco, Sandra searchers from different disciplines (EPA 1991 and National Center for Ecological Analysis and Synthe- sis (NCEAS) 1997, summarized in special issues of hTheir report titled “Valuing ecosystem services: toward Ecological Economics in 1995 and 1998, respectively). better environmental decision-making” is available online The organizers of the first workshop believed that at http://books.nap.edu/books/030909318X/html.

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Postel, and Norman Myers present a detailed syn- has a strong influence in stimulating awareness of thesis of the latest understanding of a suite of ecosys- the costs and gains stemming from environmental tem services and a preliminary assessment of their decisions and often plays a major role in influenc- economic value. ing the choice among competing regulatory alter- As of April 2001, more than 2000 experts have natives.104,105 been involved in a 4-year effort to survey the health In Europe, the extent of both research and applied of the world’s ecosystems and the threats posed by workinESVis much more limitedthaninthe United human activities. The Millennium Assessmenti has States. Usually, environmental effects are not valued fundamentally changed the landscape in ecosystem in monetary terms within the European Union. Up service research by switching attention from ecolog- until around 1990 the European Commission did ical processes and function to the service itself.97 not use CBA or related procedures in its formulation of new directives.105,106 ESV in practice NextwewillfocusonESV’srolesin(1)NRDA,(2) CBA/CEA (cost-effectiveness analysis), (3) natural In the area of ESV research and application, most capital accounting, and (4) payment for ecosystem demands originate from policy makers and public services (PES). Because there are no specific mech- agencies.j To what extent, however, is ESV actually anisms that track the process of how and when re- used to make real environmental decisions? search becomes policy, we have to rely on examples The answer to this question is contingent upon and, therefore, offer an anecdotal overview. the specific areas of environmental policy which are of concern. There are a few areas in which ESV is well established. These include NRDA cases, CBA ESV in Natural Resource Damage of water and forest resource-use planning in the Assessments United States.67 In a number of European countries CBA has been used as a decision tool in public work NRDA is the process of collecting, compiling, and schemes, especially in road construction.98 In other analyzing information to determine the extent of areas, however, there have been relatively few doc- injuries to natural resources from hazardous sub- umented applications of ESV whereby it was used stance releases or oil discharges, and to determine as the sole or even the principal justification for en- appropriate ways of restoring the damaged resources vironmental decisions, and this is especially true in and compensating for those injuries. Two environ- the natural resources planning area (though cf. Mc- mental statutes provide the principal sources of fed- Collum99 for some examples). A recent survey of 14 eral authority over natural resource damages: the case studies showed the interaction of ESV research Comprehensive Environmental Response, CERCLA, and policy ranging from “no action” all the way to and the Oil Pollution Act (OPA). Although other “influencing federal policy design” (p. 2064).100 examples of federal legislation addressing natural A number of factors have limited the use of ESV resource damages do exist, these two statutes are as a major justification for environmental decisions. the most generally applicable and provide a consis- These include methodological problems that affect tent framework in which to discuss natural resource the credibility of the valuation estimates, legisla- damage litigation. tive standards that preclude consideration of cost- Under the Department of Interior regulations, benefit criteria, and lack of consensus about the role valuation methodologies are used to calculate “com- that efficiency and other criteria should play in the pensable values” for interim lost public uses. Val- design of environment regulations (see later sec- uation methodologies include both market-based tion for details on debates on ESV). However, while methods (e.g., market price and/or appraisal) and environmental decisions may not always be made nonmarket methodologies (e.g., factor income, solely or mainly on the basis of net benefits, ESV travel cost, hedonic pricing, and CV). Under the OPA, trustees for natural resources base damages iThe synthesis report is now available at http://www. for interim lost use on the cost of “compensatory millenniumassessment.org/en/index.aspx. restoration” actions. Trustees can determine the jOther reviews of the use of ESV in policy include Refs. scale of these actions through methodologies that 67,98,99,101–103. measure the loss of services over time or through

64 Ann. N.Y. Acad. Sci. 1185 (2010) 54–78 c 2010 New York Academy of Sciences. Liu et al. Ecosystem service valuation review valuation methodologies. In any case, NRDA poses whole?). By recovering the costs of compensatory a big challenge for ESV as a dollar value estimate restoration actions (costs of resource compensa- of total damages is required and valuing multiple tion) rather than the value of the interim losses ecosystem services typically multiplies the difficulty (monetary compensation), the revised format de- of evaluation. flects some of the public controversy about eco- Although statutory authorities existed prior to nomic methods. However, some researchers argue, the 1989 Exxon Valdez oil spill, the spill was a sin- for instance, that money can not be removed from gular event in the development of trustee NRDA NRDA for the simple reason that failure to consider programs. In the years following the spill, NRDA moneyleavestrusteesunabletojudgetheadequacy has been at the forefront of ESV use in litigation. of compensating restoration.111 The prospect of extensive use of nonmarket meth- ods in NRDA has generated extensive controversy, ESV in a Cost Benefit Analysis–Cost particularly among potentially responsible parties Effectiveness Analysis framework (cf. Hanemann107 and Diamond and Hausman108 for differing viewpoints on the reliability of the use CBA is characterized by a fairly strict decision mak- of CV in NRDA as well as in CBA in general). ing structure that includes defining the project, In the Exxon Valdez case, a team of CV researchers identifying impacts that are economically relevant, was hired by the State of Alaska to conduct a study physically quantifying impacts as benefits or costs, of the lost “passive use value” caused by the spill, and then calculating a summary monetary valua- and the team produced a conservative assessment tion.112 CEA has a rather similar structure, although of 2.8 billion dollars.k,109 Exxon’s own consultants only the costs of alternative means of achieving a published a contrasting critical account of CV ar- previously defined set of objectives are analyzed. guing that the method can not be used to estimate CBA provides an answer to “whether to do,” and passive-use values. Their criticism mainly focused CEA answers “how to do.” on situations where respondents have little experi- When the Reagan administration came to power, ence using the ecosystem service that is to be altered it attempted to change the government’s role in the and when the source of the economic value is not private affairs of households and firms. Regulatory the result of some in-site use.l,110 reform was a prominent component of its platform. This argument led to the previously mentioned President Reagan’s Executive Order No. 12291 re- NOAA panel, which, after a lengthy public hearing quired a CBA for all new major regulations whose and review of numerous written submissions, issued annual impact on the economy was estimated to ex- a report that cautiously accepted the reliability of ceed $100 million.66 The aim of this Executive Order CV.75 was to develop more effective and less costly regula- In the context of the wide-ranging public debate tion. It is believed that the impact of EO 12291 fell that continued after the Exxon Valdez case, NOAA disproportionately on environmental regulation.98 reframed the interim lost value component from a President Bush Sr. used the same executive or- monetary compensation measure (how much money der. President Clinton issued Executive Order 12866, does the public require to make it whole?)toare- which is similar to Reagan’s order but changes some source compensation measure (how much compen- requirements. The order requires agencies to pro- satory restoration does the public require to make it mulgate regulations if the benefits “justify” the costs. This language is generally perceived as more flexi- ble than Reagan’s order, which required the benefits kThis compares to the 1 billion dollars in natural resource to “outweigh” the costs. Clinton’s order also places damages and restitution for injuries settled in court and greater emphasis on distributional concerns.m,113 over 2 billion dollars Exxon spent on oil-spill response and restoration.68 In 2008, however, a divided high court cut punitive damages in the case to $507.5 million. mAs one reviewer pointed out, the policy change with lMuch of this debate could be reconciled if the critiques Clinton’s order indicated a switch to a social welfare func- distinguished concerns about the CV itself from a belief tion that differs from Bergson-Sammelson function of that CV estimates do not measure economic values be- individualistic welfare maximization, on which a CBA is cause they are not the result of an economic choice.40 based.106

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The use of CBA analysis in environmental policy 10 years, giving an internal rate of return of 90– making under the George W. Bush administration 170% and a payback period of 4–7 years. This remains controversial. At the core of the contro- return is an order of magnitude higher than is versy was the growing influence of the White House usually available, particularly on relatively risk-free and its perceived responsibility for cost-benefit re- investments.115 view: the Office of Information and Regulatory Af- fairs (OIRA), within the Office of Management and ESV in natural capital accounting Budget. Traditionally, OIRA has had fairly mini- mal interaction with submitting agencies as they Though closely related, “Green” gross domestic prepared CBAs. But under administrator John Gra- product (GDP) accounting and natural capital ac- ham, OIRA became intimately involved in all as- counting are different. GDP aggregates all sources of pects of the cost-benefit process. During the 8 years well-being, including all market goods and services, of the Clinton administration, OIRA sent 16 rules into a single index. Green GDP adds missing eco- back to agencies for rewriting. In his first year alone, logical elements to conventional GDP by including Graham sent back 19 rules (not all of which were nonmarket contributions to welfare. Natural capital environmental). accounting, in contrast, usually separately accounts Originally, CBAs primarily reflected market ben- for all of nature’s contributions to welfare, includ- efits such as, job creation and added retail sales. ing those captured in GDP as intermediate prod- More recently, attempts have been made to incor- ucts, such as pollination’s contribution to increased porate the environmental impacts of projects and agricultural output. Proposals have been made to policies within CBA to improve the quality of gov- integrate the results of natural capital accounting ernment decision making. The use of ESV allows into Green GDP, although researchers have cau- CBA to be more comprehensive in scope by incor- tioned against double accounting and the simple porating environmental values and placing them on add-up approach.116 So far, a handful of studies the same footing as traditional economic values. have attempted to plug ESV results into Green GDP The EPA’s National Center for Environmental accounting—117,118 for example, using the supply Economics’ online library has been an integral re- side of the input–output model to avoid double ac- source in the CBAs conducted over the years. The counting.119 most common ESV application by the EPA involves This paper will focus only on natural capital ac- analyses of the benefits of specific regulations as part counting, which was popularized by the effort to of Regulatory Impact Analyses (RIAs). Although value the ecosystem services and natural capital on a RIAs—and hence ESV—have been done on numer- global scale.1 Since then, there have been numerous ous regulations, the scope and quality of the ESV in studies to value natural capital at a national level120 these RIAs has varied widely. A review of 15 RIAs and at the state/regional levels.121–123 Attempting to performed by the EPAbetween 1981 and 1986 found include the value of all ecosystem services, these that only six of the 15 RIAs addressed by the study studies used benefit transfer of results from the presented a complete analysis of monetized benefits empirical valuation literature. Recent trends in- and net benefits.114 The 1987 study notes that many clude combining the transferred results with Geo- regulations were improved by the analysis of benefits graphical Information Systems (GIS) and ecosystem and costs, even where benefits were not monetized modeling. andnetbenefitswerenotcalculated. GIS has been used to increase the context speci- One famous example of the use of CEA is the ficity of value transfer.124,125 The value-transfer pro- 1996 New York Catskills Mountains Watershed case cess is augmented with a set of spatially explicit fac- where New York City administrators decided that tors so that geographical similarities between the investment in restoring the ecological integrity of policy site and the study site are more easily de- the watershed would be less costly in the long tected. In addition, the ability to present and cal- run than constructing a new water filtration plant. ibrate economic valuation data in map form of- New York City invested between $1 billion and fers a powerful means for expressing environmental $1.5 billion in restoratory activities in the expec- and economic information on multiple scales to tation of realizing cost savings of $6–$8 billion over stakeholders.

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The EcoValue Project,n for example, draws from Integrated with ecosystem modeling, an ESV study recent developments in ESV, database design, inter- under CVES concluded that a proposed flood net technology, and spatial analysis techniques to abatement project in the Lent area could pro- create a web-accessible GIS decision support sys- vide more than $30 million in public benefits tem. The site uses empirical studies from the pub- over a 100-year timeframe. And five ecosystem ser- lished literature which are then used to estimate the vices would increase in productivity as a result economic value of ecosystem services. Using water- of floodplain function improvements and riparian sheds as the primary unit of spatial aggregation, the restoration.127 project provides ecosystem service value estimates Modeling has also been combined with GIS to un- for the State of Maryland and the four state North- derstand and value the spatial dynamics of ecosys- ern Forest regions, including New York, Vermont, tem services. An example of this application was a New Hampshire, and Maine. The end result is a study of the 2352 km2 Patuxent River watershed in GIS value transfer platform capable of providing Maryland.128,129 This model was used to address the the best available valuation data to researchers, de- effects of both the magnitude and spatial patterns cision makers, and public stakeholders throughout of human settlements and agricultural practices on the world. hydrology, plant productivity, and nutrient cycling In a study using a similar technique, Constanza in the landscape, and the value of ecosystem ser- and colleagues estimated the value of ecosystem vices related to these ecosystem functions. Several services in New Jersey using benefit transfer tech- historical and future scenarios of development pat- niques.123 The aggregate total for the state ranged ternswereevaluatedintermsoftheireffectsonboth from $11.6 to $19.6 billion/year depending on the the biophysical dynamics of ecosystem services and criteria used. In addition to calculating the range, the value of those services. A recent efforto in- mean and standard deviation for each of 12 ecosys- volves the use of spatially explicit dynamic modeling tems services for 11 Land Use/Land Cover (LULC) to integrate our understanding of ecosystem func- types, they also mapped these values by assuming tioning, ecosystem services, and human well-being an average value for each LULC in GIS. across a range of spatial scales. Recognizing the value of ecosystem services, de- cision makers have started to adopt ex ante ESV re- ESV in payment for ecosystem services search linked with computer modeling. An example of this was an integrated modeling and valuation PES is “a voluntary transaction where a well-defined study of fynbos ecosystems in South Africa.126 In environmental service is being bought by a service buyer from a service provider if and only if the ser- this example, a cross-section of stakeholders con- 130 cerned about the invasion of fynbos ecosystems by vice provider secures service provision” (p. 664). European pine trees worked together to produce There are multiple ways to classify PES. In terms of a simulation model of the dynamics and value of the ecosystem commodities conserved, PES could the ecosystem services provided by the system. The be grouped as payments in the carbon market, wa- model allowed the user to vary assumptions and ter market, biodiversity market, and bundled service values for each of the services and observe the re- market. According to payment types, most PES falls into one of these three categories: voluntary, compli- sulting behavior and value of the ecosystem services 131 from the system. This model was subsequently used ant, or government mediated. By function, PES by park managers to design and justify containment programs are divided into those for pollution con- and removal of the pine trees. trol, for conservation, and for generating environ- In a more recent example, the city of Port- mental amenities. Finally, from the perspective of service providers, a distinction is made between land land’s Watershed Management Program spon- p. 132 sored a Comparative Valuation of Ecosystem Ser- diversion and working-land PES programs. vices (CVES) analysis in order to understand the tradeoffs between different flood control plans. ohttp://www.uvm.edu/giee/mimes/. pThe term PES has been used, especially by practi- nhttp://ecovalue.uvm.edu. tioners, in a much boarder sense for any kind of

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PES is a field fast expanding both inside and out- the market, equity concerns in program design, and side academia. In 2008 alone, two special issues of lack of information on benefit estimates. Ecological Economics and Environment and Develop- First, the market for ecosystem services is often ment Economics were dedicated to PES. Recently, not competitive. In theory, the price for an ecosys- the U.S. Department of Agriculture also estab- tem service is determined by the buyer’s willing- lished an Office of Ecosystem Services and Markets ness to pay and the service provider’s willingness to develop “new technical guidelines and science- to accept. In reality, potential supply often outstrips based methods to assess environmental service demand in markets for ecosystem services, which benefits which will in turn promote markets for results in low prices.140 ecosystem services including carbon trading to mit- For voluntary markets, price is negotiated and igate climate change.”134 the PES programs are more tailored to local con- Indeed, one would imagine that ESV, the process ditions. For instance, the Vittel PES program de- of assessing the benefits of environmental services, veloped customized pricing for each farm.141 By must have been applied widely to guide PES. By contrast, in government-mediated markets, prices definition a buyer offers payments to those who are often set at the average cost of producing the provide ecosystem services, which benefit the buyer. service, as opposed to marginal cost, which means Naturally, the amount of the payment should be that service providers do not make any profit. Most determined on the basis of the ecosystem service government-mediated programs for land diversion delivered (output based) and how much the buyer haveafixedpaymentperlandunitandaredesigned has benefited (benefit based). to attract the least profitable lands while maximizing In practice, however, ESV results have rarely been the area enrolled.132 applied in setting payment amounts. An input- Second, equity concerns partially explain the rea- based (or cost-based) approach is dominant, and son why government-mediated PES programs pay most PES programs base payments on the cost of the uniform rates; in this sense they can be difficult to seller’s adoption of particular land uses or manage- differentiate from traditional subsidy programs.139 ment activities.130 In the former case, it is sufficient However, PES programs can not always serve the to compensate service providers for the opportu- goals of equity and conservation at the same nity cost of foregoing alternative land uses. When time.142,143 Alix-Garcia et al. found that the most additional management activities, such as reforesta- egalitarian approach—paying a flat rate per hectare tion are involved, the PES payment equals the sum per year with a cap on the number of allowable of opportunity cost, transaction cost, and conserva- hectares per recipient—was the least efficient strat- tion cost.135 egy in terms of environmental benefits per dollar Benefit-based PES program do exist, but they are spent.144 exceptions rather than the rule.130 Proxies of ben- The third reason for the popularity of the cost- efits, such as land cover type,136,137 spatial location based approach is the lack of information on benefit of service providers’ land,138 and level of manage- estimates.137 Conducting original ESV research of- ment activities (e.g., area reforested combined with ten requires a great amount of time and resources, a minimum tree-survival rate139), are used instead. and existing studies are often not designed and re- Yet the linkages between such proxies and the ecosys- ported with benefit transfer in mind. For instance, tem services conserved are often uncertain, and the the payment amount per unit land area is more degree of uncertainty varies depending on the ser- useful for PES purposes, yet most CV estimates are vice.139 reported in per household or per individual terms. So why have ESV estimates rarely been applied By contrast, costs are more straightforward to esti- in PES programs? Several reasons may factor into mate. the equation, including the uncompetitiveness of A major problem with the cost- or input-based approach is underpayment, whereby the payment is not high enough to attract potential providers to the market-based mechanism for conservation including eco- most important areas of ecosystem service conser- labeling certified forest product, conservation easements, vation. In the United Kingdom’s Environmentally ecotourism—even entrance fees to national parks.133 Sensitive Areas program, for instance, the payment,

68 Ann. N.Y. Acad. Sci. 1185 (2010) 54–78 c 2010 New York Academy of Sciences. Liu et al. Ecosystem service valuation review which is smaller than ESV estimates based on CV, tions of ESV. In particular, “monetary reduction- did not offer enough incentives to attract enroll- ism,” illustrated by the willingness-to-pay criterion, ment in the intensive farming areas.145 Similarly, is strongly rejected by those who claim that ecosys- U.S. farmers enrolled in the Conservation Reserve tems are not economic assets and that it is therefore Program spurned guaranteed annual payments to immoral to measure them in monetary terms.8,149 cash in during the recent commodity market boom Based exclusively on an individual’s preferences, the because the government payments were no longer principle of utility maximization is judged to be comparable to what they could make by working too reductionist a basis on which to make decisions their land.146 involving environmental assets, irreversibility, and A future direction for PES is to establish ben- future generations.150,151 efit and output-based systems supported by ESV. Practitioners of ESV argue that the ESV concept is Lacking guidance from ESV research, many PES much more complex and nuanced than these objec- programs are based on a shaky scientific founda- tions acknowledge. Monetization is simply a conve- tion. One example is for similar activities programs nient means of expressing the relative values that so- that pay for multiple services do not pay more than ciety places on different ecosystem services. If these those paying for a single service.139 The benefit values are represented solely in physical terms—so and output-based approach could possibly elimi- much less provision for clean water, perhaps, and so nate uncertainty between the input (e.g., land and much more for production of crops—then the clas- labor) and the output of ecosystem services. It is also sic problem of comparing apples and oranges ap- more efficient to pay farmers per unit of ecosystem plies. The purpose of monetary valuation is to sim- services provided rather than per area of land re- ply create a setting whereby the disparate services gardless of the services provided.147 provided by ecosystems are able to be compared to each other using a common metric. Alternative Debate on the use of ESV common metrics exist (including energy units and land units, i.e., the “ecological footprint”), but in There are multiple policy purposes and uses of ESV. the end, the choice of metric is not critical because, Theseusesinclude: given appropriate conversion factors, one could al- 1. to provide for comparisons of natural capital ways translate results of the underlying tradeoffs to physical and human capital in regard to their from one metric to another. contributions to human welfare. Thekeyissueherecomesdowntotradeoffs.If 2. to monitor the quantity and quality of natural onedoesnothavetomaketradeoffsbetweenecosys- capital over time with respect to its contribu- tem services and other things, then valuation is not tion to human welfare an issue. If however,onedoeshavetomakesuch 3. to provide for evaluation of projects that pro- tradeoffs, then valuation will occur, whether it is pose to change (enhance or degrade) natural explicitly recognized or not.152 Given this, it seems capital. better that the tradeoffs be made explicit. The practicality lies in the fact that ESV uses eas- Much of the debate about the use of ESV has to ily understood and accepted rules to reduce complex do with not appreciating this range of purposes. In clusters of effects and phenomena to single-valued addition, there are a range of other obstacles and commensurate magnitudes—that is, to dollars. The objections to the use of ESV. In summarizing ex- value of the benefit-cost framework lies in its ability periences of ESV use from six countries, Barde and to organize and simplify certain types of informa- Pearce mentioned three main categories of obsta- tion into commensurate measures.153 cles: (1) ethical and philosophical, (2) political, and While we believe that there is a strong case in favor (3) methodological and technical. Below we discuss of monetary valuation as a decision aid to help make each of these in greater detail.148 tradeoffs more explicit, we also recognize that there are limits to its use. Expanding ESV toward sustain- Ethical and philosophical debate ability and fairness goals (on top of the traditional Ethical and philosophical obstacles arise from a crit- efficiency goal) will help expand the boundaries of icism of the neoclassical welfare economics founda- those limits.21 An MCDA system that incorporates

Ann. N.Y. Acad. Sci. 1185 (2010) 54–78 c 2010 New York Academy of Sciences. 69 Ecosystem service valuation review Liu et al. the triple goals might appear to alleviate the lim- itations of monetary valuation, but in fact it does not. If there are real tradeoffs in the system, those tradeoffs will have to be evaluated one way or the other. An MCDA facilitates greater public participa- tion and collaborative decision making, and allows consideration of multiple attributes,154 but it does not eliminate the need to assess tradeoffs, and, as we have said, conversion to monetary units is only one way of expressing these tradeoffs and all forms Figure 5. A model of ecosystem service valuation. of value may and should ultimately contribute to decisions regarding the environment.155 of information from a range of alternative courses Political debate of action. The usefulness of value estimates must be assessed in the context of this framework for The very objective and virtue of ESV is to make arraying information.23 policy objectives and decision criteria explicit, e.g., The more frank and open decision makers are what are the actual benefits of a given course of ac- about the problems of making choices and the values tion? What is the best alternative? Is the government involved, and the more information they have about making efficient use of environmental resources and the implications of their choices, the better their public funds? Introducing a public debate on such choices are likely to be. issues is often unattractive to technical experts and decision makers and may significantly reduce their Methodological and technical debate margin of action and decision autonomy. Therefore, there may be some reluctance to introduce ESV into ESV has also been criticized on methodological and political or regulatory debates. technical grounds. There are a range of issues here Notwithstanding this, humanity will have to which are covered in detail elsewhere.29,152 For the make choices and tradeoffs concerning ecosystem purposes of this discussion, we will focus on two services, and, as mentioned above, this implies and major issues which seem to underlie much of the requires “valuation” because any choice between debate: purpose and accuracy. competing alternatives implies that the one cho- One line of criticism aimed at ESV is it can only be sen is more highly “valued.” Practitioners of ESV used to evaluate changes in ecosystem service values. argue that society can make better choices about For example, Bockstael et al. contended that assess- ecosystems if the valuation issue is made as ex- ing the total value of global-, national-, or state-level plicit as possible. This means taking advantage of ecosystem services is meaningless because it does the best information available, making the uncer- not relate to changes in services, and one would not tainties in that information explicit, and developing really consider the possibility of eliminating the en- new and better ways to make good decisions in the tire ecosystem at these scales.29 But, as mentioned face of uncertainties. Ultimately, it means being ex- earlier, there are at least three purposes for ESV, plicit about our goals as a society, both in the short and this critique has to do with confusing purpose and the long term, and understanding the complex #3 (assessing changes) with purpose #1 (compar- relationships between current activities and policies ing the contributions of natural capital to human and their ability to achieve these goals.13 welfare with those of physical and human capital). As Arrow and colleagues argued, valuation should To better understand this distinction, the follow- be considered as a framework and a set of procedures ing is helpful (Fig. 5): to help organize available information.153 Viewed The Demand for Services reflects the Marginal in this light, benefit-cost analysis does not dictate Valuations of increasing service levels. The Quantity choices, nor does it replace the ultimate authority of Services available determines the Average Valu- and responsibility of decision makers. It is simply ation of that service over its entire range. Conse- a tool for organizing and expressing certain kinds quently, Average Value x Quantity would represent

70 Ann. N.Y. Acad. Sci. 1185 (2010) 54–78 c 2010 New York Academy of Sciences. Liu et al. Ecosystem service valuation review a “Quasi-market Valuation” of that service level. In a market value” could only be determined through restricted sense, if there were a market for the service, full scale ecologic-economic modeling. While mod- this would be the revenue obtained from the service, eling of this type is under way,157 it is costly and comparable to an indicator like the sales volume of difficult, and meanwhile decisions must be made. the retail sector. It would be directly comparable and “Quasi-market value” is thus a reasonable first- analogous to the valuation of income flows from order approximation for policy and public discourse physical capital, and could be capitalized to reflect purposes if we want to compare the contributions of the market value of natural capital and compared to natural capital to the contributions of other forms similarly capitalized values for physical investment. of capital to human welfare. Furthermore, changes in the volume or value of this ESV can also be used to assess the impact of spe- service could be capitalized to reflect the value of cific changes or projects. Balmford et al. is a recent new natural capital investment/disinvestment, just example of the use of ESV at global scale. In this as we measure new investment and depreciation in study, the costs and benefits of expanding the global physical capital at the macro level.156 nature reserve network to encompass 15% of the ter- This “quasi-market value” has a restricted mean- restrial biosphere and 30% of the marine biosphere ing. Of course, it does not reflect the “full value” were evaluated, concluding that the benefit-cost ra- of the service to human welfare because full value tio of this investment was approximately 100:1.158 is the sum of marginal values; i.e., the area under In these circumstances, Average Value x Qislikely the demand curve. However, the more substitutes to be a reasonable measure of the economic value of there are available for the service, the less the dif- the change in services; an overestimate of benefits ference between “full value” and this quasi-market for service increases, and an underestimate of costs value. In addition, this quasi-market value is more for service decreases. The degree of over- or under- directly comparable with the quasi-market value of estimation depends again on the replaceability of the physical and human capital contributors to hu- the service being gained or lost. man welfare as measured in aggregate indicators like Beyond the confusion concerning purposes, the GDP. So, if one’s purpose is to compare contribu- accuracy of ESV is also sometimes questioned. Dia- tions of natural capital to human welfare with those mond and Hausman, for instance, asked the ques- of physical and human capital (as estimated in GDP, tion, “[In] contingent valuation–is some number bet- for example), then this is an appropriate (albeit not ter than no numbers?” (p. 45).108 perfect) measure. The answer to this question depends on the in- Furthermore, if there really were a market for the tended use of the ESV result and the corresponding service, and economies actually had to pay for it, the accuracy required.31,32 AsFigure6shows,wecan entire economics of many markets directly or indi- think of accuracy as existing along a continuum rectly impacted by the service would be altered.152 whereby the minimum degree of accuracy needed is For example, electricity would become more costly, related to the cost of making a wrong decision based altering its use and the use of energy sources, in turn on the ESV result. altering the costs and prices of energy using goods For example, using ESV to assist an environmen- and services. The changes in markets would likely tal policy decision maker in setting broad prior- reflect back onto the demand for the ecosystem ser- ities for assessment and possible action may re- vice, increasing or decreasing it, depending on the quire a moderate level of accuracy. In this regard, service and its economic implications. The “true any detriment resulting from minor inaccuracies is

Figure 6. Accuracy continuum for the ESV (adapted from Desvousges et al.165).

Ann. N.Y. Acad. Sci. 1185 (2010) 54–78 c 2010 New York Academy of Sciences. 71 Ecosystem service valuation review Liu et al.

Figure 7. EVRI peer-reviewed valuation data by ecosystem services (total data point = 730, accessed Feb. 10, 2007). (In color in Annals online.) adequately offset by the potential gains. This use What is needed are ESV studies which encompass of ESV represents an increase of knowledge which all the components mentioned earlier in Figure 1, in- costs society relatively little if the ESV results are later cluding ecological structures and processes, ecolog- found to be inaccurate. However, if ESV is used as ical functions, ecosystem services, human welfare, a basis for a management decision which involves land-use decisions, and the dynamic feedback be- irreversibility, the costs to society of a wrong deci- tween them. To our knowledge, there have been few sion can be quite high. In this case, it can be argued such studies to date, although several recent projects that the accuracy of a value transfer should be very are moving in this direction, including Valuing high. the Arc,q Nature Capital Project,r and Multi-scale Models of Ecosystem Services. It is just this type of study that is of greatest relevance to decision makers and it looks to be the way forward.159 Findings and directions for the future Figure 7 indicated how little effort has gone into ESV is multidimentional and socially contentious. understanding the linkages between ecological func- In contrast, traditional ESV research involves the tions, services, and human welfare. Among 675 work of experts from separate disciplines, and these peer-reviewed ESV studies (with a total of 730 data studies often turn out to be overly simple, uni- points) published in the past 35 years, most effort dimensional, and “value-free.” Our survey of the has gone into the understanding of human prefer- literature has shown that over time there has been ences for ecosystem services which are directly con- movement toward a more transdisciplinary ap- sumed, including 34% valuing recreation benefits proach to ESV research, an approach more con- and 18% valuing water quality change. In compar- sistent with the nature of the problems being ison, most supporting and regulating services are addressed. undervalued if they are valued at all. The truly transdisciplinary approach ultimately Obviously there has been great progress in ecol- required for ESV is one in which practitioners must ogy and in understanding ecosystem processes and accept that disciplinary boundaries are academic functions, and in the economics of developing and constructs irrelevant outside of the university, and must also allow the problem being studied to deter- mine the appropriate set of tools, rather than vice qhttp://valuingthearc.org/about˙us/index.html. versa. r http://www.naturalcapitalproject.org/joinourteam.html.

72 Ann. N.Y. Acad. Sci. 1185 (2010) 54–78 c 2010 New York Academy of Sciences. Liu et al. Ecosystem service valuation review applying nonmarket techniques for valuation; how- ital” from the New Jersey Department of Envi- ever, there remains a gap between the two. To quote ronmental Protection. We thank William Mates, a recent ESV report by an interdisciplinary group Matthew Wilson, Marta Ceroni, Kerry Turner, and of ecologists, economists, and philosophers, ‘‘...the Brendan Fisher for valuable discussions, and three fundamental challenge of valuing ecosystem services anonymous reviewers for their suggestions. lies in providing an explicit description and ade- quate assessment of the links between the structure Conflicts of interest and functions of natural systems, the benefits (i.e., goods and services) derived by humanity, and their The authors declare no conflicts of interest. subsequent values” (pp. 2–3).25 Nevertheless, some useful integrated studies are References emerging to bridge the gap between ecosystem func- 1.Costanza,R.,R.d’Arge,R.deGroot,et al. 1997. The tions and services, including those valuing biological value of the world’s ecosystem services and natural cap- control160 and pollination services.161–163 ital. Nature 387: 253–260. This paper also attempted to quantify ESV’s con- 2. Daily, G. 1997. Nature’s Services: Societal Dependence tribution to environmental policy making by an- on Natural Ecosystems. Island Press. Washington, DC. swering questions, such as “to what extent is ESV 3. de Groot, R.S., M.A. Wilson & R.M.J. Boumans. 2002. actually used to make real decisions?” However, A typology for the classification, description and valu- it was soon realized that this goal was too ambi- ation of ecosystem functions, goods and services. Ecol. tious. Instead, along with other reviewers,64,102 it Econ. 41: 393–408. was found that the contribution of ESV to ecosystem 4. Millennium Ecosystem Assessment. 2003. Ecosystems managementhasnotbeenaslargeashopednoras and Human Well-being: A Framework for Assessment. clear as imagined. This requires ESV researchers to Island Press. Washington, DC. do more than simply develop good ideas to influence 5. Millennium Ecosystem Assessment. 2005. Ecosystems policy. They need to understand how the political and Human Well-being: Current States and Trends.Is- process affects outcomes and actively market the use land Press. Washington, DC. of appropriate and feasible methodologies for pro- 6. Sukhdev, P. 2008. The Economics of Ecosystems and Bio- moting environmental policy. In other words, ESV diversity: An Interim Report. European Communities. research has to become more problem driven rather A Banson Production. Cambridge, UK. than tool driven.113 7. Ehrlich, P.R. & R.M. Pringle. 2008. Where does biodi- We discussed the three types of obstacles to the versity go from here? A grim business-as-usual forecast use of ESV in policy making. While there is a strong and a hopeful portfolio of partial solutions. Proc. Natl. case in favor of monetary valuation as a decision Acad. Sci. USA 105: 11579–11586. aid, we also recognize that there are limits to its use. 8. McCauley, D.J. 2006. Selling out on nature. Nature 443: These limitations are due to the complexity of both 27–28. ecological systems and values, which could be more 9. Armsworth, P.R., K.M.A. Chan, G.C. Daily, et al. 2007. adequately incorporated by the triple-goal ESV sys- Ecosystem-service science and the way forward for con- tem. Valuing ecosystem services with not only effi- servation. Conserv. Biol. 21: 1383–1384. ciency, but also fairness and sustainability as goals, 10. Norton, B.G. & D. Noonan. 2007. Ecology and valua- is the next step needed to promote the use of ESV tion: big changes needed. Ecol. Econ. 63: 664–675. in ecosystem management and environmental pol- 11. Brown, T.C. 1984. The concept of value in resource- icy making. This new system can be well supported allocation. Land Econ. 60: 231–246. by current transdisciplinary methodologies, such as 12. Norton, B., Costanza, R. & R.C. Bishop. 1998. The evo- participatory assessment,164 group valuation,35,36,92 lution of preferences—Why ‘sovereign’ preferences may and the practice of integrating ESV with GIS and not lead to sustainable policies and what to do about it. ecosystem modeling.128,129,157 Ecol. Econ. 24: 193–211 13. Costanza, R. 2000. Social goals and the valuation of Acknowledgments ecosystem services. Ecosystems 3: 4–10. This work was supported in part by Contract No. 14. Ludwig, D. 2000. Limitations of economic valuation of SR04–075, “Valuation of New Jersey’s Natural Cap- ecosystems. Ecosystems 3: 31–35.

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