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4
An Ecosystem Services Approach to
Damage Assessment
The ecosystem services approach focuses not only on the restoration of
damaged resources but also on establishing and maintaining the value of
benefits derived from ecosystems to the public. This broader view may be
of value for understanding an event of the magnitude, duration, and com-
plexity of the Deepwater Horizon (DWH) spill and may offer more options
for approaches to restoration. Final decisions on restoration projects will, of
course, be an open process that includes stakeholders from local communi-
ties as well as the state and federal natural resources trustees. The incorpora-
tion of an ecosystem services approach to the damage assessment process
should be beneficial in identifying a larger suite of restoration alternatives
that can then be offered as options to the wider group of stakeholders.
In the Statement of Task (see Box S.1) the question “What are the avail-
able methods for identifying and quantifying the ecosystem services in the
Gulf of Mexico (GoM)?” is posed. The committee deconstructed that ques-
tion into the following: “What are the approaches to assessing the impacts
of the DWH oil spill that affect the structure or function of the GoM ecosys-
tem and how can these be translated into changes in quantity and value of
ecosystem services?” In light of ongoing assessment efforts, it is important
to ensure that evaluations of the impacts of human actions on the GoM are
conducted in a systematic and uniform manner so that the results could
be applicable to the ecosystem services analysis as well as to the damage
assessment process. It is likely that some of the wealth of data collected for
the ongoing damage assessment will be readily applicable to the ecosystem
services analysis. A unique opportunity exists to benefit from the application
of new approaches to both available data sets and emerging results from
ongoing and future research to understand the impacts of the DWH oil spill
and large-scale oil spills in general.
Chapter 2 provides a detailed characterization of the approach to evalu-
ating impacts on the value of ecosystem services, including the questions
95
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96 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
that need to be addressed in order to adequately characterize those im-
pacts (see Figure 2.1). These questions—What are the impacts of human
actions on environmental conditions that affect the structure or function of
ecosystems? How do changes in the structure and function of ecosystems
lead to changes in the provision of ecosystem services? How do changes
in the provision of ecosystem services affect human well-being, and how
can the value of the changes in services in terms of human well-being be
quantified?—and the logic behind them set the stage for what is likely to
have been done early in the Natural Resource Damage Assessment (NRDA)
process, whether for the DWH spill or other incidents. Extending this process
to consider how these impacts affect the provision of ecosystem services
and ultimately how this leads to changes in human well-being is discussed
in the following sections of this chapter.
ECOLOGICAL PRODUCTION FUNCTIONS: FROM ECOSYSTEM
STRUCTURE AND FUNCTION TO ECOSYSTEM SERVICES
Production functions are a standard tool used by economists to describe
how inputs can be transformed into outputs. A production function gives
the feasible output of goods and services that can be produced from a given
set of inputs. For example, what is the maximum amount of steel (output)
that can be produced from a given amount of iron ore, energy, machinery,
and labor (inputs)? The notion of production functions applied to ecologi-
cal systems has a long history in agricultural economics (e.g., crop yield
functions) and resource economics (e.g., bioeconomic modeling of fisheries
and forestry). Production functions have also been applied recently to the
provision of ecosystem services (e.g., NRC, 2005a; Barbier, 2007; Daily
et al., 2009; Tallis and Polasky, 2009). An ecological production function
specifies the output of ecosystem services generated by an ecosystem given
its current condition. Changes in ecosystem conditions, either from natural
disturbances such as hurricanes, or from human disturbances such as an
oil spill, will in general alter the amount of various ecosystem services pro-
vided. For example, degradation of coastal marshes may reduce protection
from storm surges and reduce nursery habitat for fish, among other services.
For some ecosystem services, ecological production functions are fairly
well understood and data exist that can be used to quantify the amount of a
service provided. A good example of a fairly well understood and well stud-
ied ecosystem service is carbon sequestration in above-ground biomass for
terrestrial ecosystems, particularly for forests. The U.S. Forest Service collects
data on biomass in forests by stand age and tree species for different areas
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AN ECOSYSTEM SERVICES APPROACH TO DAMAGE ASSESSMENT
of the country (Smith and Smith, 2006). These data, along with knowledge
of the carbon ratio in biomass, can be used to calculate carbon sequestered
in forests. In marine systems, production function approaches have been
used to study the productivity of fisheries as a function of ecosystem con-
ditions (Lynne et al., 1981; Kahn and Kemp, 1985; Ellis and Fisher, 1987;
McConnell and Strand, 1989; Swallow, 1994; Parks and Bonifaz, 1997;
Barbier and Strand, 1998; Barbier, 2000, 2003; Sathirathai and Barbier,
2001; Barbier et al., 2002) although there is far greater uncertainty in the
functional relationship between habitat conditions and fishery productivity.
Table 4.1 expands the basic damage assessment approach presented
in Table 2.1 to include data collection and analyses necessary to establish
ecological production functions for two key ecosystem services in the Gulf
of Mexico, hazard moderation (in the form of storm protection) and food
(in the form of nursery habitat for fisheries). While in general a greater
amount of vegetation or animal material (e.g., mangroves and oyster beds)
will lead to greater dissipation of wave energy and provide more protection
from coastal storms, the degree of protection will depend upon the timing
of storms relative to the tide, height of the storm surge, the direction of the
wind, speed of passage, and other factors. For many marine species, survival
of larvae will depend upon water column conditions and currents at the time
of spawning and quality and quantity of nursery habitat leading to highly
variable recruitment from year to year.
Finding 4.1: Additional sampling and analyses could facilitate an eco-
system services approach by identifying the impacts on ecosystem
function and structure that in turn affect the ecosystem services pro-
vided. The collection of these additional data would set the framework
for establishing the impact of the spill on ecosystem services.
An example of an ecological production function for a key ecosystem
service provided by coastal wetlands—hazard moderation (via storm surge
protection)—is provided below (Box 4.1). This example outlines the chal-
lenges faced by those seeking to capture the full suite of ecosystem services
in a complex environment, as well as the potential benefits of this broader
view in assessing the impact of damages to the environment.
For many other ecosystem services, there is either a lack of mechanistic
understanding, a lack of data, or both that prevents accurate quantification of
ecosystem services as a function of ecosystem condition. Marine ecosystems
are complex with many interacting processes and complex food-web dy-
namics. Such complexity makes it difficult to understand how disturbances
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98
TABLE 4.1 An Expansion of Table 2.1 to Illustrate the Data and Methods Needed for an Ecological Production Function
Approach for the Ecosystem Services of Hazard Moderation and Food from Coastal Wetlands.
Assessment Process for Ecosystem Services Approach
Ecological
Data Typical Approach Production Type of Data Needed for
Category Resource to the Assessment Ecosystem Service Type of Data Needed Function Ecosystem Service
Biological Wetland Determine spatial Hazard 1. Plant type (or 1. Relationship 1. Collecting data on (1),
extent of vegetation Moderation species), height between plant (3), and (4). Data on
oiled; collect and (reduction in and density. type, height, wetland extent and
document any dead storm surges; see 2. Percentage of area density, and amount oiled would be
or oiled wildlife. Box 4.1). likely to experience areal extent of collected in a standard
acute toxicity and vegetation and NRDA but other data
die off. reduction of would likely not be.
3. Cross-shore and wave energy. 2. Building the functional
along-shore extent 2. Relationship relationships to
of wetland harmed. of reduction in translate from data on
4. Estimates of ability wave energy to plant height, density
of the wetland likely reduction and extent to likely
to reestablish in storm surge. height of storm surge.
with and This may be done via
without human empirical relationships
intervention. and/or modeling.
Food (production 1. Measures of fishery 1. Relationship 1. Collecting data on (2)
from commercial landings. between and (3).
and recreational 2. Measures of wetland 2. Building the functional
fisheries; see fishery stock and condition relationship between
Box 4.2) recruitment. and fishery wetland condition and
3. Estimates of productivity fishery productivity.
the ability of This may be done via
wetlands to re- empirical relationships
establish with and and/or modeling.
without human
intervention.
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AN ECOSYSTEM SERVICES APPROACH TO DAMAGE ASSESSMENT
BOX 4.1 HAZARD MODERATION (STORM SURGE PROTECTION): REGULATING SERVICE
Coastal wetlands include salt marshes and mangroves and can reduce the damaging effects
of hurricanes on coastal communities (Badola and Husain, 2005; Danielsen et al., 2005; Das and
Vincent, 2009).
Our knowledge of fluid dynamics and of the physical processes that govern the behavior
of waves has advanced to the point where we can explain why wetlands reduce wave energy
and protect coastal infrastructure (Massel et al., 1999; Narayan and Singh, 2006; Quartel et al.,
2007; Vosse, 2008; Krauss et al., 2009). Reduction of wave energy depends on the structure of the
plant canopy, its height and density, and the cross-shore and along-shore extent of the wetland
(Narayan and Singh, 2006; Koch et al., 2009; Massel et al., 1999). The velocity of water traveling
within a plant canopy is relatively lower than flow velocities above the canopy. Canopy height in
relation to water depth is relevant because flow through the vegetation encounters a different
level of friction than the water above the vegetation. Therefore, the total friction in the water
column will be different as a function of depth for vegetated and non-vegetated areas. Because
a mangrove canopy is taller and exerts more drag than a salt marsh community, mangroves are
more effective at reducing wave energy than salt marshes. Quartel et al. (2007) suggested that
the drag force exerted by a mangrove forest is a function of the projected cross-sectional area of
the submerged canopy (denoted as A in the equation CD = 0.6e0.15A). For the same muddy surface
without mangroves the drag is a constant 0.6. Mazda et al. (1997) observed that 100 m2 of man-
grove forest was capable of reducing wave energy by 20 percent. Reduction in water levels across
a mangrove area in Florida was 9.4 cm km–1 (Krauss et al., 2009). The dissipation of wave energy
is also affected by topography. In a modeling study of sea-level rise and storm surge across the
Louisiana coast, Vosse (2008) found that when the relative land elevation was decreased by 20
cm, wave heights increased 5-10 cm across the model domain, and when relative land elevation
decreased 50 cm, wave heights increased 10-20 cm. The conclusion is that friction by the plant
canopy dissipates energy and reduces wave heights, but the effect of the wetland surface de-
pends on water depth. In the future, the effect of wetland surge dissipation will depend on the
survival of the wetlands, because wetland survival will have a great effect on the height of the
storm surge relative to mean sea level.
to an ecosystem will reverberate through the system and ultimately lead
to changes in the provision of ecosystem services. A further complication
in predicting the provision of ecosystem services arises from variability in
environmental conditions that are characteristic of many coastal and marine
ecosystems (Koch et al., 2009).
Ideally, a thorough ecosystem services analysis would be based on a
mechanistic understanding of, and model for, the complex linkages and
interdependencies of the ecosystem being studied. Such a model would al-
low for predicting the provision of ecosystem services given the state of the
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100 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
ecosystem (i.e., the ecological production function). Establishing such an
ecosystem model is perhaps the greatest challenge facing the application of
an ecosystem services approach for damage assessment. One complicating
aspect is that the damage assessment process does not lend itself to collect-
ing data that would better inform our basic understanding of variability in
biological processes across the GoM. Because of this and other factors, a
complete ecosystem model for the Gulf of Mexico has yet to be developed.
However, several marine ecosystem models have been developed that
could be useful for analysis of ecosystem services in the Gulf of Mexico
such as Atlantis (Fulton et al., 2011), Ecopath with Ecosim,1 and Marine In-
VEST (Guerry et al., 20112). These models, and others, span a range of data
requirements and modeling sophistication. Application of these models to
a system as complex as the Gulf of Mexico in order to analyze the impact
of an event of the magnitude of the DWH oil spill would require extensive
data collection, model testing, and verification. Given the magnitude of the
impacts and the importance of many GoM ecosystem services, however,
such efforts may be justified. Models for specific ecosystem services (e.g.,
fisheries) or components of the ecosystem (e.g., wetlands) are more readily
available and more easily applied and do not necessarily require extensive
ecosystem modeling efforts in order to be successful. There may also be
cases where the lack of scientific understanding, paucity of data, or the
degree of environmental variability may be simply too great at this time to
afford much confidence in predicting the quantity or value of ecosystem
services generated. That said, utilizing the extensive data that have been
collected for the damage assessment process in the GoM and the existing
ecosystem models for the GoM presents a unique opportunity for enhancing
our understanding of ecological production functions and the provision of
ecosystem services in the GoM.
Finding 4.2: An ecosystem services approach to damage assessment
and valuation offers great promise but accurate estimates may be
limited to cases in which there is a mechanistic understanding of the
service’s production function and environmental conditions are not
highly variable. In other cases, however, the lack of scientific under-
standing, paucity of data, or great environmental variability may pre-
clude quantification of ecosystem services with reasonable confidence.
See http://www.ecopath.org/.
1
See http://www.naturalcapitalproject.org/InVEST.html.
2
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AN ECOSYSTEM SERVICES APPROACH TO DAMAGE ASSESSMENT
APPROACHES TO VALUING ECOSYSTEM SERVICES
In Chapter 2 we addressed the question “what are the impacts of human
actions on environmental conditions that affect the structure or function
of ecosystems?” In the section above we discussed ecological production
functions and their role in addressing “how do changes in the structure and
function of ecosystems lead to changes in the provision of ecosystem ser-
vices?” The next component of the ecosystem services approach focuses on
establishing the value of ecosystem services. The value of an ecosystem ser-
vice is the contribution of the service to human well-being. Ideally, valuation
methods can provide a quantitative measure in a common metric to facilitate
comparisons across services that indicates how much the availability of the
service contributes to the improvement in human well-being. For example,
how much money would people be willing to give up in exchange for restor-
ing a coastal ecosystem? Answering this question involves identifying what
ecosystem services might be affected by the restoration and by how much.
For example, restoration might lead to improved fishing, improvement in
water quality, and greater storm protection. Economic methods can then be
applied to assess how valuable these changes in services are. Improved fish-
ing may be quite valuable for commercial fishermen and avid recreational
fishermen (and possibly for those who eat a lot of fish), but may be relatively
unimportant for those who do not fish or consume seafood. Alternatively,
in the case of damage to the environment that reduces services, valuation
methods can be applied to assess how much value has been lost.
Economics provides well-developed methods grounded in established
economic theory to measure values (see Freeman, 2003 for a thorough dis-
cussion of economic approaches to valuation and Chapter 4 in NRC, 2005a
for a discussion of economic valuation techniques applied to ecosystem
services). Economic analysis of ecosystem services can generate estimates
of the value of services in terms of a common (monetary) metric. The eco-
nomic approach to valuation begins with individuals and the tradeoffs they
are willing to make. Economists assume that individuals have well-defined
and stable preferences. Given preferences, the value of an ecosystem service
can be measured in terms of what the individual would be willing to give
up to get more of the ecosystem service. By measuring what an individual
is willing to give up in terms of a common monetary metric, the economic
approach to valuation generates measures of the relative value of goods
and services.
Valuing multiple ecosystem services at one time with one survey is not
commonly undertaken primarily to avoid survey respondent fatigue. The
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102 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
more questions and text, and the greater complexity of the valuation sce-
nario due to multiple services, the less reliable the answers will be for a given
survey. Given the spatial extent of the DWH spill and the varied habitats
impacted, there are numerous ecosystem services that could potentially be
affected. The scope of the ecosystem services valuation exercises for a spill
of this size could be challenging for the current practice of stated preference
methods. Many ecosystem services are public goods. In economic terms,
public goods are “non-rival” in consumption (one person’s use of a public
good does not diminish the use of another) and “non-excludable” (once it
is supplied it is freely available to everyone). For example, the light from
a lighthouse is a public good. The light provides navigation services to all
ships that pass within sight of it. Similarly, coastal ecosystem restoration may
provide public goods of storm protection services and water purification
services, which are then freely available to all nearby residents.
To assess the value of a public good requires adding up the value to
all beneficiaries of the public good. Assessing the value of public goods is
complicated by the fact that there is often no direct signal of value for many
of the beneficiaries. For example, how can a public agency assess the value
of the navigation service provided by the lighthouse or storm protection
and water purification services provided by a coastal ecosystem? Closely
related to the concept of public goods is the concept of common property
resources. Common property resources, like oyster beds or fisheries, are
resources subject to use by multiple parties. Because each user does not
typically take into account the negative effect of their use on others, com-
mon property resources often suffer from over-use. In the extreme, when
there are no limits on who can exploit the resource (“open access”), severe
over-harvesting can occur, a result known as the “tragedy of the commons.”
Below we describe some methods economists use to estimate the value of
ecosystem services focusing on tools for “non-market” valuation that are
particularly relevant to ecosystem services.
The economic approach to valuation of ecosystem services has its critics
(e.g., McCauley, 2006; Norton and Noonan, 2007). Some environmental
philosophers argue that nature has intrinsic value, i.e., value in and of itself,
regardless of whether or not nature contributes to human well-being through
the provision of ecosystem services (e.g., Norton, 1986; Rolston, 1988), and
that humans have inherent obligations to protect and conserve nature. These
duties cannot be avoided merely because some individual or group would
benefit by doing so. Other critics of economic approaches to valuation
question the accuracy of standard assumptions in economic models. Psy-
chologists question the assumption that people have well-defined, stable and
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AN ECOSYSTEM SERVICES APPROACH TO DAMAGE ASSESSMENT
consistent preferences that they bring to decision making. A body of work
in both psychology and behavioral economics has documented systematic
departures from classic assumptions of rational behavior (e.g., Kahneman
and Tversky, 1979; Ariely, 2009). A body of experimental evidence suggests
that people often construct their preferences when called upon to make
decisions and are therefore sensitive to the context and framing of decisions
(e.g., Lichtenstein and Slovic, 2006). Sociologists question the central focus
on individuals and individual decisions, which they feel does not give proper
consideration to how values are shaped by larger groups, norms, and cul-
ture. Despite these criticisms, virtually all valuation of ecosystem services to
date has used the economic approach to quantify values. Other approaches
to valuation of ecosystem services exist and these are briefly discussed later
in this chapter in the section “Other Methods” (and see also EPA SAB, 2009
for a review of both economic and non-economic approaches).
ECONOMIC VALUATION METHODS
Economists have developed a variety of methods to quantify values of
environmental and natural resources. Although some natural resources are
traded in markets where prices can be used to value these resources, most
elements of environmental quality are not traded in markets and have no
direct measure of value. Economists have developed methods of non-market
valuation over the last several decades that can be applied to value environ-
mental quality and resources not traded in markets (Freeman, 2003). These
methods were developed long before ecosystem services were part of the
vernacular of how one describes the relationship between the environment
and humans.
To assess the value of changes in ecosystem services from environmen-
tal impacts such as an oil spill, economic valuation methods need to be
combined with ecological assessments of impacts. For example, changes
in marsh, seagrass, oyster reefs, mangroves, and other habitats impacted by
the oil spill could have a direct impact on ecosystem services supplied by
these systems. Analysis of impacts on the supply of services combined with
economic valuation methods can generate estimates of the value of changes
in ecosystem services as a result of environmental changes. For example,
Bell (1997) linked recreational catch to fishing effort and the contribution
of wetlands to fishing productivity to estimate the value of wetlands in sup-
porting recreational fishing. Lynne et al. (1981) related blue crab productivity
and value to salt marsh along Florida’s Gulf Coast and found that the mar-
ginal value productivity of marsh varies with marsh area and fishing effort.
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104 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
There are three main types of valuation methods applied to ecosystem
services:
• revealed preference based on observed economic behavior,
• stated preference based on responses to survey questions, and
• cost-based methods such as avoided damages and replacement cost.
Revealed preference and stated preference methods generate estimates
of benefits consistent with economic notions of what individuals would be
willing to give up in terms of other goods or services to get more of an eco-
system service. Avoided damage, though labeled as a cost-based method,
can also be thought of as measuring benefits. Damages are a cost while
avoided damages are a benefit. For example, typically the marginal benefit
of pollution abatement is viewed as equivalent to the marginal damages
from pollution, i.e., the benefit of not polluting is not incurring the associ-
ated damages. Replacement cost, however, is a measure of costs rather
than benefits. Because replacement costs measures costs not benefits, some
economists do not include these approaches as a valid way to measure the
value of ecosystem services. However, many economists view replacement
costs as a valid approach to measuring what is lost when ecosystem services
are lost or diminished as long as certain restrictive conditions, discussed
below, are met.
Revealed Preference Methods
Under the broad heading of revealed preference methods, which infer
economic values based on observed behavior, are various methods of both
market and non-market valuation. For goods and services traded in mar-
kets, data on the amount bought and sold at various prices can be used to
establish estimates of demand (willingness-to-pay) functions that measure
the value of the goods and services to consumers. The value of a good or
service can be measured by what an individual would be willing to pay
to get more of the good or service. Market prices are what an individual
actually has to pay to get more of the good or service. The gap between
the individual’s willingness to pay and what they have to pay (price) is
called consumer surplus and represents a monetary value of the gain in
welfare to the individual from purchasing the good or service. An estimate
of the willingness-to-pay can be derived from market data by noting that
people should be willing to purchase the good up to the point at which
willingness-to-pay is equal to price. By observing how much of each good
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AN ECOSYSTEM SERVICES APPROACH TO DAMAGE ASSESSMENT
or service is purchased at different prices one can recover an estimate of
the willingness-to-pay for different amounts of the good or service (see
Freeman, 2003 for a more complete discussion). Some marine ecosystem
services produce marketed goods for which market prices can be used for
purposes of valuation. Commercial fisheries are a prime example. The most
difficult part of measuring the impact of the DWH oil spill on commercial
fisheries is not the valuation component to understand willingness-to-pay,
but rather, measuring the impact of the spill on fishery productivity. Get-
ting an estimate on the impact of the spill on fishery productivity requires
estimating the change in productivity through time and not just the initial
impact. That said, there remain challenges to valuation even with observable
market prices. When consumers are uninformed about actual environmental
conditions their choices may not accurately reflect their preferences (this
issue is a concern for all valuation methods). Other issues related specifi-
cally to the commercial fishing example include uncertainty over how much
and how long fears of contamination will depress demand for fish from the
GoM and the difficulty of getting accurate cost data with which to estimate
economic rents.
For most ecosystem services, however, markets do not exist, making
estimation of values from ecosystem services more difficult. Without market
prices other non-market methods must be used as proxies for prices. In some
cases, the value of these non-marketed ecosystem services can be estimated
using data on observed behavior of how much of a service is utilized and
the cost to the individual of utilizing the service (e.g., travel cost methods),
or by using data on related goods and services such as housing values (e.g.,
hedonic property price methods).
Travel cost studies (see example in Box 4.2) use information on trips
that individuals make to recreational sites and the expenditures of time and
money involved in making the trip (Freeman, 2003). Travel cost studies
typically use “random utility models” in which the value (utility) of a visit
to a given recreational site is a function of distance from sites, site access
fees, observable site characteristics (environmental quality, site facilities,
etc.), observable characteristics of individuals (income, education, etc.), as
well as unobservable characteristics of the individual (idiosyncratic prefer-
ences). Travel cost methods allow an analyst to trace out a demand function
for site visits by varying the implicit price of a visit (travel cost plus access
fees) faced by individuals and observing the number of trips taken. Further,
by looking at sites of varying environmental quality, the value of improved
environmental quality can be estimated.
A number of studies have used travel cost methods in the Gulf region
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110 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
graded. There are two sorts of cost-based methods that are commonly used
in valuing ecosystem services—avoided damages and replacement costs.
An avoided damaged approach estimates how damages would increase
if the ecosystem service were diminished or absent. Replacement costs
estimates the cost of providing the service via some alternative means. The
method of avoided damages to value an ecosystem services uses estimates
of likely damages that would be incurred with and without the ecosystem
service. Avoided damages from maintaining an ecosystem that provides
protection against storms, floods or other natural disasters are a measure of
benefits provided by the ecosystem. This method is probably the most com-
mon method used to value coastal protection (Badola and Husain, 2005;
Danielsen et al., 2005; Costanza, 2008; Das and Vincent, 2009). The value
of coastal protection afforded by coastal wetlands is estimated by finding
the difference in likely damages to coastal communities from a hurricane or
other storm event in the case with intact coastal marshes versus degraded
or no coastal marshes to absorb wave energy and reduce storm surge. For
example, Costanza et al. (2008) used a regression model to analyze the
damages from 34 major U.S. hurricanes since 1980. While wind speed was
an important variable in estimating damage, they also found that wetlands
helped to reduce damages. The estimated yearly marginal value of wetlands
in the Gulf region in their analysis ranged from a low of $126 ha–1yr–1 in
Louisiana to a high of $14,155 ha–1yr–1 in Alabama.
Another commonly used cost-based method to generate a value for
ecosystem services is replacement cost, which is the cost of providing the
service an alternative way such as replacing the service provided by eco-
systems with a human-engineered approach. For example, clean drinking
water can be provided by natural processes in intact watersheds or provided
through a water filtration system. The most commonly cited example for
the value of ecosystem services is the Catskills watershed providing clean
drinking water for New York City. Replacing the clean water provided by
the watersheds with a water filtration plan was estimated to cost $6 to $8
billion (Chichilnisky and Heal, 1998).
Many economists are skeptical of the use of replacement cost as a meth-
od of valuation, even though it is often used in valuing ecosystem services.
The main reason for skepticism is that replacement cost is about cost rather
than directly a measure of benefits. However, replacement cost can address
the value of ecosystem provision of a service in certain instances (NRC,
2005a; EPA, 2009). To be a valid measure of the value of what an ecosystem
provides, three conditions must be met (Shabman and Batie, 1978):
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AN ECOSYSTEM SERVICES APPROACH TO DAMAGE ASSESSMENT
• there is a human-engineered solution that provides equivalent
quality/quantity of the service provided by the ecosystem,
• the human-engineered solution is the least cost alternative of pro-
viding the service, and
• individuals in aggregate would be willing to incur the cost if the
ecosystem service were not available.
If these conditions are satisfied, then the cost of replacement represents
a lower bound of the value of what is lost when the ecosystem service is
diminished or lost.
Benefit Transfer
Undertaking revealed, preference or stated, preference studies often
involves expenditure of considerable time and resources. In cases where the
time frame of analysis is short and the questions at stake are small in magni-
tude it may not be worthwhile undertaking original research to estimate en-
vironmental benefits. In such cases, benefit transfer can be used and in fact
has been widely applied (EPA, 2009). Benefit transfer uses existing estimates
of value from primary studies conducted in one location and applies them to
a different location. In this sense, benefit transfer is not a valuation method in
the same vein as those discussed above because it merely offers guidance on
existing estimates that might be used in a new setting. There are two benefits
transfer approaches commonly used: single point or average transfer, and
function transfer. The single point or average transfer takes estimates from
existing studies and applies those values to the new policy site. A function
transfer can customize a value for the policy site using an estimated equation
derived from the statistical relationship between the willingness-to-pay of
individuals and their socio-economic characteristics (Freeman, 2003; NRC,
2005a). The function transfer is likely to be superior unless the application
site is highly similar to the site where the original study was undertaken in
all observable dimensions. In the case of the DWH spill and the impacted
areas of the Gulf, it is unlikely that there are study sites of the appropriate
scale and complexity that would be appropriate for comparison and transfer.
Benefit transfer has a number of limitations and is not a good substitute for
conducting primary research at the policy site of interest. For the Gulf of
Mexico an additional major limitation of using benefit transfer is the lack
of primary studies applicable to the habitats and ecosystem services for the
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112 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
region.3 A special issue of Ecological Economics (Wilson and Hoehn, 2006)
outlines the challenges of applying benefit transfer. Some benefit transfer
studies have been conducted in the Gulf region focusing on the services
provided by saltwater and freshwater wetlands, such as recreation, waste
regulation, and gas regulation (Kazmierczak, 2001; Jenkins et al., 2010).
Finding 4.3: Primary research on the values of ecosystem services
would provide additional grounding for the DWH damage assessment.
Valuation Studies of Previous Oil Spills
Valuation studies of previous oil spills provide a foundation from which
to discuss valuation methodologies for ecosystem services potentially im-
pacted by the DWH spill. The Exxon Valdez spill was the starting point
for the application and evaluation of non-market valuation techniques for
natural resource damage impacts. The national study conducted after the
Exxon Valdez oil spill (Carson et al., 1997, 2003) to assess the damage to
passive use values focused a debate on the appropriateness of CVMs to
estimate damages. As a result NOAA formed its “blue ribbon panel” to as-
sess the use of the CVM for passive use values and concluded that “useful
information” conveyed for damage assessment (Arrow et al., 1993). Similar
studies followed the 2002 Prestige oil spill in Europe. Loureiro et al. (2009)
conducted a contingent valuation study, the first in Europe after a large oil
spill, and found that the environmental and passive use losses for Spanish
society was around 574 million euros. Other research was conducted on
“what-if” scenarios, taking advantage of the notoriety of the Prestige spill.
Van Biervliet et al. (2005, 2006) conducted an economic assessment of the
loss of non-use values resulting from oil spill scenarios along the Belgian
coast. Estimation results suggest that welfare losses might range from 120
million euros to 606 million euros and a program targeted at the prevention
of oil spills could easily be defended as long as costs are no higher than
120 million euros.
Because oil spills may affect the livelihoods of those directly tied to the
coast and sea, a number of studies have looked at these impacts, specifically.
Hausman et al. (1995) modeled recreational demand behavior in Alaska to
estimate welfare losses suffered by recreational users as a result of the Exxon
Valdez oil spill. They found the loss to be less than $5 million. The social
costs from a diminished commercial fishery in south-central Alaska, an
important economic engine, was determined using a market model with an
See www.GecoServ.org for a gap analysis of valuation studies.
3
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upper bound of the first-year social costs of $108 million and second-year
effects as high as $47 million (Cohen, 1995). Garza-Gil et al. (2006) estimate
the short-term economic damages from the Prestige oil spill in the Galician
fishing and tourist activities could have reached five times more than the
applicable limit of compensations. Utilizing landings in a purely market ap-
proach, Negro et al. (2009) show that some species landings increased after
the spill while others decreased, relative to landings before the spill. They
note the limitations of this approach in linking changes on landings to the
Prestige oil spill and conclude that landings are sensitive to fishing effort,
predator-prey interaction, and species sensitivity to oil.
Finding 4.4: Both market and non-market approaches to valuing eco-
system services have become accepted and established practice over
the past two decades since the Exxon Valdez oil spill. When appropri-
ately applied, these techniques can generate valid estimates of value
for ecosystem services lost due to human-caused and natural events.
Other Methods
There are a number of additional methods that are outside the traditional
environmental and natural resource economics toolkit. Many of these other
methods are reviewed in a recent study published by the U.S. EPA’s Science
Advisory Board (EPA, 2009). These methods include social-psychological
approaches that measure attitudes, preferences, and intentions; methods that
involve individual narratives or focus groups; and behavioral observation
methods. Additionally, civic valuation measures values when people consider
their role as “citizen,” while referenda and initiatives provide information on
how members of the voting public value action involving the environment,
and citizen valuation juries measure stated values. Studies of voting on refer-
enda and citizen valuation juries can provide information useful in estimating
values (e.g., Vossler et al., 2003) but other methods are further afield and are
not necessarily consistent with the economic approach to valuation. Several
methods mentioned in the U.S. EPA Science Advisory Board study (EPA, 2009)
focus more on the ecological function of habitats rather than on economic
valuation of ecosystem services and so are more similar to HEA and REA.
These methods include ecosystem benefit indicators, conservation valuation,
energy analysis, and ecological footprint analysis. These latter approaches are
generally not consistent with an economic valuation approach and would
need additional justification before being adopted.
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TABLE 4.2 Examples of GoM Ecosystem Services Values
Adjusted
Habitat Service Values (2008) Units Method Author
Beach Recreation $144 per visit Travel cost Freeman (1995)
Beach Recreation $70 per person/ Travel cost Bell & Leeworthy
per day (1990)
Coral Reefs Recreation $635 per person/ Travel cost Bhat (2003)
per day
Saltwater Recreation $30 per hectare/ Travel cost Farber & Costanza
Wetland per year (1987)
Saltwater Food $3 per hectare Market prices Lynne et al. (1981)
Wetland
Saltwater Recreation $19,300 per hectare/ Contigent Bell (1997)
Wetland per year valuation
Saltwater Recreation $216 per hectare/ Contigent Bergstrom et al.
Wetland per year valuation (1990)
Saltwater Waste $681 per hectare/ Benefit transfer Kazmierczak (2001)
Wetland Regulation per year
Valuation Methods Applied to the Gulf of Mexico
Table 4.2 summarizes some of the studies mentioned above and pro-
vides a limited number of examples and results of where monetary valuation
techniques have been used in the GoM region. These examples are by no
means a complete list of studies conducted in the Gulf or an endorsement of
these particular findings but are reported for illustrative purposes. It should
be noted that the values generated from these studies are dependent on
place and situation and thus are driven in a large part by the socio-economic
characteristics of the respondents. However, these studies provide an im-
portant foundation from which additional Gulf-specific studies can be built.
Many services, especially those of a provisional or cultural nature,
can have a monetary impact well beyond their immediate environs. These
“economic impacts” from the oil spill can disrupt whole industries as is il-
lustrated by the discussion on charter fishing in Box 4.2. Here the monetary
impact is felt not only by the charter boat operators but also the supplier of
fuel, lodging, food services, tackle, and equipment and by the employees
of these establishments whose paychecks might be reduced. The same sort
of impacts could be felt in any of the industries that were disrupted by the
spill including commercial fishing, tourism, and oil and gas exploration and
production as well as for industries that rely on products from the GoM yet
are based outside the GoM region.
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The theoretical foundations and the practical application of both re-
vealed and stated preference approaches are well grounded in a rich litera-
ture. Cost-based approaches do not have the same grounding. Nonetheless,
an avoided damages approach may be useful in estimating the value of
coastal protection. Replacement cost might also be used but only if certain
conditions described above are satisfied. The appropriate valuation methods
to employ are dependent upon what ecosystem services are being measured,
which is equivalent to saying it is important to have the right equipment
for the sport in which you are participating. Travel cost approaches are
most commonly used for measuring the value of recreational opportuni-
ties. Hedonic property price studies could be used to measure changes in
values to coastal communities as a result of the DWH oil spill, but their use
is limited to capturing only the impacts felt by property owners in coastal
communities. Stated-preference methods can be used for virtually any eco-
system service, including nutrient regulation, storm protection, and erosion
control, but careful attention needs to be paid to survey design to get reli-
able answers to valuation questions. Given the scope and scale of impact,
the NRDA process would require rigorously derived values of ecosystem
services impacted by the oil spill which would necessitate original valuation
studies rather than relying on benefits transfer. However, values from previ-
ous work can be an important check on the validity of values estimated in
oil spill-specific studies.
All of the economic valuation methods identified above can be effec-
tive in measuring value when applied appropriately and employing “best
practices.” The NOAA Blue Ribbon panel (Arrow et al., 1993), for example,
discusses at length a “best-practices” approach when utilizing a contingent
valuation in order to generate useful information for damage assessment.
Examples for the Extension of an Ecosystem
Services Approach to Include Valuation
Having discussed both the data and methods for assessing impact and
quantifying the provision of ecosystem services for the case of wetlands
and the ecosystem services of coastal protection and fisheries in the Gulf
of Mexico (Table 4.1), we now extend these examples to include the valu-
ation of ecosystem services (Table 4.3). To reiterate, the examples shown in
Table 4.3 are meant to illustrate how an ecosystem services approach could
be incorporated into the existing NRDA process; they are not intended to
capture the full complexity of the three component steps involved in the
ecosystem services approach or the ongoing NRDA process.
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TABLE 4.3 Provision and Valuation for Coastal Wetlands for the Services of Hazard
Moderation, Food, and Recreation
Methodology for the Provision and Valuation of the
Damage Assessment Practices Ecosystem Services Approach
Type of data needed for
Typical approach to the ecological production
Data category Resource assessment Ecosystem Service function
Biological Wetland Determine exposure Hazard Moderation 1. Plant type, (or species),
pathway and spatial (reduction in storm height and density.
extent of vegetation surges; see Box 4.1) 2. Percentage of area likely
oiled; collect and to experience acute
document any dead toxicity and die off.
or oiled wildlife. 3. Cross-shore and along-
shore extent of wetland
harmed.
4. Estimates of ability
of the wetland to
reestablish with
and without human
intervention.
Food 1. Measures of fishery
(commercial fisheries) landings.
2. Measures of fishery
stock and recruitment.
3. Estimates of the
ability of wetlands
to reestablish with
and without human
intervention.
Recreation 1. Measures of fishery
(Recreational fisheries) landings.
2. Measures of fishery
stock and recruitment.
3. Estimates of the
ability of wetlands
to reestablish with
and without human
intervention.
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Type of data needed for
Ecological production Type of data needed for valuation of ecosystem
function valuation Valuation method service
1. Relationship between 1. Location of structures, Avoided cost: calculate 1. Collecting data on (1),
plant type, height, infrastructure, the expected damages (3), and (4). Data on
density, and areal agriculture, etc. near associated with storm wetland extent and
extent of vegetation the coast. surge. amount oiled would be
and reduction of 2. Value of structures, The value of the collected in a standard
wave energy. infrastructure. ecosystem service is NRDA but other data
2. Relationship of equal to the reduction would likely not be.
reduction in wave in expected damages. 2. Building the functional
energy to likely relationships to translate
reduction in storm from data on plant
surge. height, density and
extent to likely height
of storm surge. This may
be done via empirical
relationships and/or
modeling.
3. Building the functional
relationship that
translates height of
storm surge to expected
damage.
1. Relationship 1. Market price of Market valuation: 1. Collecting data on (2)
between wetland commercial fish. calculate profit from and (3).
condition and fishery 2. Fishing cost per unit fishing. Use market price 2. Building the functional
productivity. effort (capital, labor, and harvest data to relationship between
fuel). calculate revenue. Use wetland condition and
cost data along with fishery productivity.
revenue calculation to This may be done via
calculate profit. empirical relationships
and/or modeling.
1. Relationship 1. Survey information Travel cost. Use 1. Collecting data on (2)
between wetland on fishing trips. information on and (3).
condition and fishery recreation trips, time 2. Building the functional
productivity. and resource costs relationship between
of trips to calculate wetland condition and
willingness-to-pay for fishery productivity.
recreational fishing trips. This may be done via
empirical relationships
and/or modeling.
3. Estimation of value using
travel cost (random
utility model).
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Finding 4.5: Measurements and analysis such as illustrated in Table
4.3 would allow for the determination of the impact of the DWH spill
related to the ecosystem function and structure of coastal wetlands
and to quantify the impact on key ecosystem services. Further research
is needed to determine the required measurements for the assessment
of other ecosystem services and habitats.
SUMMARY
While the committee strongly believes that an ecosystem services ap-
proach has great potential, we also understand that it would be often difficult
to implement due to limited understanding and limited data. The linkages
between human actions, ecosystem structure and function, and the provi-
sion of ecosystem services are complex owing to system dynamics in which
there is seldom a single impact and the fact that the occurrence of multiple
impacts often results in non-linear changes. There are large gaps in current
understanding of ecosystems and their provision of services, and often a
paucity of data to quantify these services (Chee, 2004). There may also be
unidentified links and feedbacks in ecosystems (Walker et al., 2009). In the
context of the DWH spill, complex and interconnected system dynamics
can make it difficult to isolate the impact of a single decision or action on
overall system behavior. In addition, because of complex interconnections
in systems, the impact of an action or decision at a particular place at a par-
ticular time can have impacts over large spatial and temporal scales (Boyd,
2010), further complicating the challenge of characterizing and projecting
into the future the spatial and temporal human and ecological impacts from
the DWH spill.
Ideally, one would like to have a fully developed and proven “end-to-
end” ecosystem model that explicitly describes all important interactions.
However, ecosystem models capable of incorporating complex system dy-
namics are still early in their evolution (Allen and Fulton, 2010). Such mod-
els do not exist for most ecosystems including the Gulf of Mexico. While
complete ecosystem models might be ideal, they are not essential for making
progress on evaluating ecosystem services. As a practical matter, reasonable
estimates of ecosystem services can be made with simpler existing models
that focus on particular aspects of ecosystems. Even though these models
will omit some interconnections, if done in a thoughtful manner they may
be able to capture the most important linkages and generate reasonable
estimates of ecosystem service provision and value. The committee will
explore these models in the final report.
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In addition to understanding the provision of services, understanding
the value of services in terms of human well-being also poses a number of
issues. Economic approaches to valuation offer the promise of measuring
benefits from ecosystem services in a common metric (money). However,
some ecosystem service benefits are extremely difficult to accurately assess
in monetary terms (e.g., spiritual, cultural, and aesthetic values). There are
additional concerns over distributional equity: who benefits and who is
harmed by changes in ecosystem conditions? Making the public whole via
restoration is not simply a matter of making sure that aggregate net benefits
with restoration are greater or equal to aggregate net benefits before the oil
spill. Making the public whole also involves making sure that aggregate net
benefits to various groups within society do not decline. Since many services
emanate from public resources, for example national parks for recreation
and oyster beds for food, it is important that the benefits of ecosystem ser-
vices are enjoyed by as many as possible without excluding or negatively
impacting one segment of the population.
An ecosystem services approach focuses not only on the restoration
of damaged resources, but also on maintaining the usefulness of those re-
sources to the public. On the other hand, an ecosystem services approach
that restores the value of the services but does so via human-engineered
substitutes (e.g., building a dyke or water filtration plant) will not result in
making the environment whole. Some portions of the public may not view
such actions as adequate restoration even though the value of services is
made equivalent. There is also the danger that an ecosystem services ap-
proach will focus on a small subset of services and may not restore the
full suite of ecosystem services valued by the public given the difficulty of
valuing the complete set of ecosystem services (NRC, 2005a). To the extent
that the public values the existence of habitat and species, regardless of
the extent that these lead to provision of other ecosystem services beyond
existence, the gap in practice between restoring ecosystem services and
restoring habitat and species will be reduced. High existence values may
mean making the environment whole would be necessary for making the
public whole.
We also caution that our discussions have not touched on the issue of
public involvement or review of any potential restoration project. It is clear
that for the DWH spill public involvement and review will be a key ele-
ment of decisions on restoration projects. It is likely that the value placed on
particular habitats, restoration projects, or natural resources will vary with
the community involved, which will add complexity to the overall process.
Furthermore, improvements that increase the benefits from one ecosystem
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service may come at the expense of another ecosystem service. What may
be acceptable to one community may not be acceptable to another, and
what is valued as a project by one state agency may not be valued in the
same way by another. Much has been written about how best to make
environmental decisions that affect broad communities within society (e.g.,
Cash et al., 2003; NRC, 2005b, 2008). Technical analyses of the value of
ecosystem services should fit within a larger consultative process that in-
volves affected communities.
Despite these limitations, shortcomings and uncertainties, the commit-
tee believes that attempts to incorporate an ecosystem services approach to
understanding the impacts of the DWH spill would inevitably offer a much
more comprehensive and realistic assessment. The tremendous amount of
data that has been and will continue to be collected in connection with the
DWH spill will facilitate such attempts. While the toolbox is not complete,
especially for the complexities of the DWH oil spill, techniques and models
are available to value ecosystem services, and research and application of
new approaches are ripe for development. The committee will continue to
explore the issues associated with potential benefits (and shortcomings) of
applying an ecosystem services approach to damage assessment, as well as
those associated with restoring (and perhaps increasing) ecosystem resil-
ience for GoM, will be a focus in the production of its final report.
