Environ Manage (2007) 39:301-315
DOI 10.1007/s00267-005-0282-3
Defining Acceptable Levels for Ecological Indicators:
An Approach for Considering Social Values
Robyn L. Smyth Æ Mary C. Watzin Æ Robert E. Manning
Received: 2 September 2005 / Accepted: 3 August 2006
Springer Science+Business Media, Inc. 2007
Abstract Ecological indicators can facilitate an adaptive management approach, but only if acceptable
levels for those indicators have been defined so that the
data collected can be interpreted. Because acceptable
levels are an expression of the desired state of the
ecosystem, the process of establishing acceptable levels
should incorporate not just ecological understanding
but also societal values. The goal of this research was
to explore an approach for defining acceptable levels of
ecological indicators that explicitly considers social
perspectives and values. We used a set of eight
indicators that were related to issues of concern in
the Lake Champlain Basin. Our approach was based
on normative theory. Using a stakeholder survey, we
measured respondent normative evaluations of varying
levels of our indicators. Aggregated social norm curves
were used to determine the level at which indicator
values shifted from acceptable to unacceptable conditions. For seven of the eight indicators, clear preferences were interpretable from these norm curves. For
example, closures of public beaches because of bacterial contamination and days of intense algae bloom
went from acceptable to unacceptable at 7–10 days in a
summer season. Survey respondents also indicated that
the number of fish caught from Lake Champlain that
could be safely consumed each month was unacceptably low and the number of streams draining into the
lake that were impaired by storm water was unacceptably high. If indicators that translate ecological conditions into social consequences are carefully selected,
R. L. Smyth M. C. Watzin (&) R. E. Manning
Rubenstein School of Environment and Natural Resources,
University of Vermont, Burlington, VT 05405, USA
E-mail: mary.watzin@uvm.edu
we believe the normative approach has considerable
merit for defining acceptable levels of valued ecological system components.
Keywords Ecosystem indicators Acceptable levels Normative theory Social norm curves Adaptive
management Lake Champlain Social preferences
Introduction
Ecological indicators programs are being developed to
assist with managing many types of system around the
world, including parks (e.g., Yosemite National Park,
United States and Kruger National Park, South
Africa), transboundary water bodies (e.g., Chesapeake
Bay and the Great Lakes, United States and Lac
Lemond, France), and many categories of natural
habitats. The appeal of indicators is their representative nature and their flexibility; they have been used to
monitor trends in key resources over time, provide
early warning of environmental degradation, diagnose
the cause of an existing problem, and track the
implementation of management actions. How well an
ecological system is described by a suite of indicators
depends on the quantity and diversity of the indicators
and the quality of the data used to develop and
evaluate those indicators. The selection of indicators
should be based on clear criteria, with specific purposes
in mind and careful consideration of the trade-offs
between desirable indicator characteristics. Thoughtfully selected indicators can provide valuable information about both the condition of the ecological system
and the effectiveness of the management actions being
implemented (Bertram and Stadler-Salt 2000; Cairns
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302
and others 1993; Dale and Beyeler 2001; Hunsaker and
Carpenter 1990; The Heinz Center 2002; US GAO
2003).
However, the usefulness of a set of indicators for
decision-makers also depends on defining acceptable
levels for each indicator so that the monitoring data
that is collected can be interpreted. Acceptable levels
should be explicit statements of the desirable range of
measured values for each indicator. They should reflect
management goals, scientific understanding, and social
values. Without information about acceptable levels,
an indicator cannot be used to make management
decisions. Only by systematically separating acceptable
measured values of indicators from unacceptable
values can managers identify those ecosystem components that require management attention (Kelly and
Harwell 1990; Niemi and McDonald 2004; Wiersma
2005).
Unfortunately, the failure to define acceptable levels
is a common shortcoming of many indicator initiatives.
In part, this occurs because the long-term goals and
objectives of many management programs are not
clearly specified (Dale and Beyeler 2001; Niemi and
McDonald 2004). Although a number of studies have
pointed out the need for comparing indicator values to
established benchmarks (Jackson and others 2000;
Niemi and McDonald 2004; OECD 1993; Schaeffer
and others 1988; The Heinz Center 2002; US GAO
2003; Wiersma 2005), few programs have actually
achieved this goal. The overwhelming majority of
indicators programs simply present trends in indicator
values over time (US GAO 2004).
From a purely ecological perspective, acceptable
levels should be based on a scientific assessment of the
range of values that collectively represent a stable and
healthy ecosystem (Niemi and McDonald 2004; Nip and
Uno de Haes 1995; Rogers and Biggs 1999). Ecological
thresholds, levels of ecosystem components that are
irreversible or can trigger major changes in other ecosystem components (Carpenter 2005; Muradian 2001;
Paine and others 1998; Rapport and Whitford 1999;
Scheffer and others 1993, 2001), should also be considered. However, because ecosystems can exist in many
different stable states (Haskell and others 1992; Holling
1973; Perry and Amaranthus 1997; Rapport 1992), this
does not predetermine a particular ecological condition.
Acceptable levels must also be defined from a social
perspective; that is, they must reflect the environmental conditions that are socially desirable or acceptable.
Ecosystem managers can and do target socially desirable ecosystem conditions in order to meet societal
goals. Ideally, social considerations are merged with
scientific understanding to establish an acceptable
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Environ Manage (2007) 39:301-315
level. Water quality standards are a common example
of acceptable levels that are based on a scientific
understanding of the problem, merged with judgments
about acceptable risks to ecological and human health.
However, the social judgments imbedded in these
acceptable levels are sometimes ‘‘hidden’’ from the
public by scientific experts and water quality managers
and might or might not reflect the values of the
stakeholders using the water body. Public support for
ecosystem management would be enhanced if these
judgments are made more visible and explicit and
managers defined their benchmarks in terms that
laypeople can understand and support (Anderson and
others 2001; Harwell and others 1999; Karr 1992;
Rapport 1992; Stankey and others 2005; Watzin 2004).
Some indicator programs have tried to incorporate
social perspectives into selection of acceptable levels.
In the realm of US park and wilderness management,
indicators have been used to evaluate a range of
resource and social conditions such as trampling of
soils and trailside vegetation, crowding, and conflicting
uses (Hammitt and Cole 1998; Manning 1999; Manning
and Lawson 2002; Manning and others 1996, 2004,
2005; Shelby and others 1988). The acceptable levels,
or standards of quality, established for these indicators
represent thresholds in impacts caused by visitor use
and are most commonly generated using visitor surveys
(Manning 1999; Manning and Lawson 2002; Manning
and others 1996, 2000, 2002, 2003). These acceptable
levels focus on user perspectives and the social values
they represent.
The Chesapeake Bay Program (2002) has likewise
defined management end points that serve as acceptable levels for a number of the indicators that they use.
These acceptable levels have been defined based on
both ecological consideration and social perspectives.
The best of the Chesapeake Bay Program Indicators
express ecological conditions in measures that laypeople understand. For example, the innovative ‘‘Bernie
Fowler Sneaker Index’’ of water clarity is similar to a
Secchi Disk reading but is expressed in terms of the
depth that a wader can go into the water and still see a
white pair of sneakers. The acceptable level has been
set based on the public’s expectation that water clarity
will return to previous levels, levels that are also
associated with healthy seagrass communities.
The goal of this research was to explore an approach
for defining acceptable levels of ecological system
indicators that explicitly considers social perspectives
and values. To bring together ecological characteristics
and social values, we used a set of indicators that
translated environmental conditions into measures
people understand. Our approach is based on normative
Environ Manage (2007) 39:301-315
theory, which provides a theoretical and empirical
foundation for developing acceptable levels from the
social perspective. We applied this approach to management of the Lake Champlain Ecosystem in the
northeastern United States and Canada.
A Normative Approach to Defining Acceptable Levels
of Ecosystem Indicators
Norms are a theoretical construct that have a long
tradition and are widely used in sociology. As the term
suggests, norms represent what is considered ‘‘normal’’
or generally accepted within a cultural context. In a
more technical sense, norms are cultural rules that
guide behavior. Those behaviors are a function of a
sense of obligation to abide by the norm and the
related belief that sanctions (rewards and/or punishments) are possible depending on whether or not the
norms are followed. It is this sense of obligation and its
associated sanctions that make norms different from
and potentially more powerful than attitudes. Attitudes are positive or negative evaluations of behavior,
whereas norms define what behavior should be. Sanctions associated with norms can range from informal
and internally imposed (e.g., feeling guilty) to formal
and externally imposed (e.g., being publicly ostracized). When norms apply to behaviors that are
important to society and for which there is wide
agreement, they can ultimately be codified into public
policy or even law (e.g., vehicles must be driven on the
right side of the road).
Much of the sociological work on norms has been
driven by development of the return potential model
(Jackson 1965). This model is built using responses
given to survey questions that evaluate the acceptability of a range of behaviors. The response data are
graphed so that behaviors are displayed on a horizontal
axis and evaluations of those impacts are displayed on
a vertical axis. The resulting line connecting the
evaluation scores is called a ‘‘norm curve.’’
Norms can be measured for both individuals (personal norms) and groups (social norms). As the terms
suggest, personal norms are measures of the standards
or evaluations of individuals, whereas social norms
represent shared standards or evaluations of a group.
Social norms are measured by aggregating and plotting
the evaluation data for a group. The resulting line is
called a ‘‘social norm curve.’’ Normative data can be
especially useful in helping to formulate acceptable
levels for environmental conditions.
Applications of normative theory and methods to
the environmental context involve an extension of
303
normative theory and methods as originally conceived
(Roggenbuck and others 1991; Shelby and Vaske 1991;
Vaske and Whittaker 2004). Many of these applications address the acceptability of environmental and
social conditions, not behavior. Unlike behavior,
resource and social conditions might not be subject to
sanctions or entail an explicit notion of obligation on
the part of individuals. However, environmental
impacts are a direct consequence of human behavior,
and the decision to allow such impacts to accumulate to
socially unacceptable levels represents institutional
behavior of management agencies. These agencies
have an obligation to manage the environment to
meet the needs of society and, ultimately, can be
subject to sanctions (public disapproval, legal challenge) if they fail to live up to this obligation. This
extension of normative theory allows application of
norms to environmental issues.
In the environmental arena, normative theory and
methods have been applied most in the field of park
and outdoor recreation management (Manning 1999;
Shelby and Heberlein 1986; Shelby and others 1996;
Vaske and others 1986). These applications have
addressed both ecological and social conditions in
parks, including soil erosion and destruction of vegetation along trails and at campsites (Manning and
others 2004; Shelby and others 1988) and crowding and
conflicting uses (Heberlein and others 1986; Manning
2001; Manning and Valliere 2002; Manning and others
1996, 1999, 2001, 2002; Shelby 1981; Vaske and others
1986; Whittaker and Shelby 1988).
Indicators for the Lake Champlain Ecosystem
The Lake Champlain ecosystem is a large transboundary lake and watershed system with substantial
ecological, recreational, economic, and historical values. Before 1990, a variety of independent federal,
state, and provincial agencies and institutions with
diverse interests and expertise were implementing a
variety of management programs on the lake and in
its watershed with varying degrees of coordination
(Watzin 2004). In November 1990, the US Congress
passed the Lake Champlain Special Designation Act,
which led to the creation of the Lake Champlain Basin
Program (LCBP) in the following year. In 1996, the
first edition of a comprehensive management plan for
the ecosystem, Opportunities for Action: An Evolving
Plan for the Future of the Lake Champlain Basin, was
completed and released to the public (LCMC 1996).
Updated in 2003 (LCSC 2003), this management plan
consists of 11 goals that include reducing phosphorus
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304
pollution, toxic contamination, and non-native nuisance species; protecting human health, fish and
wildlife communities, wetlands, and stream and riparian habitats; enhancing recreational activities and
appreciation of the basin’s cultural heritage resources;
and maintaining a vital economy. These goals are all
focused on ensuring that the lake and its basin will be
protected, restored, and maintained so that future
generations will enjoy its full benefits.
After focus-group meetings with stakeholders in
both Vermont and New York and in consultation with
the Lake Champlain Basin Program, we selected a
preliminary set of eight indicators related to the goals
of Opportunities for Action (Table 1) for our analyses.
These indicators, described more fully below, included
the number of days of intense algae blooms in the lake,
the number of days that public beaches were closed
because of bacterial contamination, the number of fish
caught from Lake Champlain that can be safely
consumed, the number of sea lamprey wounds found
on a fish caught from Lake Champlain, the number of
streams draining to Lake Champlain that are impaired
by stormwater, the rate of land development in the
Lake Champlain Basin, the extent of water chestnut
infestation in the lake, and the number of public access
sites around the lake.
Lake Champlain is a naturally mesotrophic lake that
is threatened by anthropogenic nutrient (phosphorus)
enrichment (LCSC 2003, 2005). Much of the management focus of the LCBP is on phosphorus reduction
and control. The stakeholder community around Lake
Champlain might care little about phosphorus per se,
but it is concerned about increases in the algae blooms
that can result from phosphorus enrichment because
these algae blooms interfere with recreational use and
enjoyment of the lake (Watzin and others 2006).
Therefore, we selected ‘‘days of intense algae blooms’’
as an indicator of phosphorus conditions in the lake. As
with algae blooms, public beach closure resulting from
coliform bacteria contamination is a problem affecting
human use and enjoyment of the lake, and this
problem is also a high priority for management. Each
summer leading up to our study, popular beaches were
closed periodically because of bacterial contamination.
Safe fish consumption was emphasized as an important concern during focus-group meetings held during
the initial project development. Polychlorinated biphenyls (PCBs) and mercury are the major bioaccumulating toxins triggering fish consumption advisories for
Lake Champlain (LCSC 2003). Although the advisories
issued for Lake Champlain by the Health Departments
of the state of New York, the state of Vermont, and the
province of Quebec differ, all three jurisdictions advise
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that children and women of childbearing age should
limit their consumption of fish, particularly walleye and
lake trout, from Lake Champlain (LCSC 2005).
Basin land-use distribution was selected because it is
an indicator of many pressures impacting Lake
Champlain ecosystem characteristics of concern. Agricultural land, ~16% of the Lake Champlain Basin,
contributes phosphorus, bacteria, sediment, and pesticide waste to Lake Champlain (Hegman and others
1999). Urban and suburban land, at least 6% of the
basin and growing, contributes more phosphorus per
acre than agricultural land and is also a source of
bacteria and toxin-laden stormwater and sediments
(Budd and Meals 1994). By altering the pollutant load
and the flow regime to the lake, changes in land-use
distribution can have cumulative impacts on the
biological community (Watzin and McIntosh 1999).
Water chestnut is one major non-native nuisance
species in Lake Champlain that can be measurably
reduced through management. It is primarily found in
the southernmost lake segment and has historically
advanced northward from Whitehall, New York.
Twenty years of data collection show that the spread
of water chestnut can be adequately controlled, given
sufficient management expenditure for harvesting
(Hunt and Crawford 2002).
Sea lamprey control is a major focus of fisheries
management on Lake Champlain (Lake Champlain
Fish and Wildlife Management Cooperative, Fisheries
Technical Committee 1999). This parasite attaches to
and preys primarily upon salmonid fishes, such as lake
trout and landlocked Atlantic salmon, causing unsightly
sores, reduced growth, and increased mortality of these
fishes. At this time, sea lampreys are primarily managed
through the application of a chemical lampricide
3-trifluoromethyl-4-nitrophenol (TFM) to lamprey
spawning streams in the Champlain Basin. The use of
TFM is controversial because of potential impacts to
nontarget species, such as amphibians and mollusks.
Stormwater is a source of water pollution for Lake
Champlain and its tributaries. Although stormwater
discharge permits are required of all new developments,
many stream reaches are already impaired by developments that predate the permitting system or that are not
in compliance with their original permits. Because of
the variety of pollutants found in stormwater, these
impaired streams pose a threat to Lake Champlain
(LCSC 2005). As forest and other natural land types
and agricultural land are converted into urban and
suburban land cover, the likelihood of stream impairment resulting from stormwater runoff will increase.
Lake Champlain is a popular recreational site
for both basin residents and tourists, generating an
Environ Manage (2007) 39:301-315
305
Table 1 Ecological indicators selected, the current condition for this indicator, and the alternative levels evaluated by survey
respondents
Indicator
Current condition
Days of intense algae blooms during
the summer
Varies by shoreline location from 0 days to more than 0 days,
30 days
3–4 days,
7–10 days,
14–21 days,
30 days or more
Days that public beaches are closed
because of bacterial contamination
during the summer
Varies by beach from 0 days to the entire summer
season
0 days,
3 days,
7 days,
10 days,
14 days,
21 days
Number of fish caught from Lake
Champlain that can be safely
consumed
0–1 fish per month for some sport fish
(lake trout, walleye, small mouth bass)
0 fish/month,
1 fish/month,
3 fish/month,
6 fish/month,
10 fish/month,
Unlimited fish
Number of sea lamprey wounds found
on fish caught from Lake
Champlain
Most salmonid fish have 3–4 wounds; other species have No wounds,
lower wounding rates
Half the fish have 1 wound,
Most fish have 1 wound,
Most fish have 2–3 wounds,
Most fish have 4–5 wounds,
Most fish have more than 5 wounds
Number of streams draining to Lake
Champlain that are impaired by
stormwater
At last assessment, there were 27 streams in the
Lake Champlain Basin impaired by stormwater.
Rate of land development in the Lake
Champlain Basin
Currently, at least 6% of the basin is developed (about Less than 1% increase per year
300,000 acres); rates of development vary by region,
(3000 acres/year),
with highest rates in Chittenden County, VT
About 3% increase per year,
About 5% increase per year,
About 10% increase per year,
About 15% increase per year
Extent of water chestnut
infestation in Lake Champlain
Water chestnut infestation in Lake Champlain has
spread over a 55-mile range from Whitehall, NY
north to Charlotte, VT
0 miles from Whitehall, NY,
20 miles from Whitehall, NY,
40 miles from Whitehall, NY,
55 miles from Whitehall, NY,
70 miles from Whitehall, NY,
90 miles from Whitehall, NY
Number of public access sites around
the lake
There are at least 681 sites of all types in the Lake
Champlain Basin
Current public access adequate,
Improve existing public access
areas,
Increase public access by 10%,
Increase public access by 15%,
Increase public access by 20%
estimated $3.8 billion from tourism in 1998–1999
(LCSC 2003). Developing and enhancing public access
to Lake Champlain for diverse recreational uses is a
high priority of the LCBP. Public access with minimal
congestion and user conflict is an important element of
sustainable tourism and resident satisfaction with the
management of Lake Champlain.
Levels evaluated
0 impaired streams,
9 impaired streams,
18 impaired streams,
27 impaired streams,
36 impaired streams,
45 impaired streams
Using a Normative Method to Understand Social
Values/Preferences
The social norm analyses we conducted followed
methods developed by Jackson (1965). The data
necessary to develop social norm curves were collected
through a survey of Lake Champlain stakeholders. The
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Table 2 Example social norm curve question
Very Unacceptable
0 impaired streams
9 impaired streams
18 impaired streams
27 impaired streams
36 impaired streams
45 impaired streams
–3
–3
–3
–3
–3
–3
–2
–2
–2
–2
–2
–2
Very Acceptable
–1
–1
–3
–1
–1
–1
0
0
0
0
0
0
+1
+1
+1
+1
+1
+1
+2
+2
+2
+2
+2
+2
+3
+3
+3
+3
+3
+3
Urbanization in the Lake Champlain Basin can have negative impacts on streams which discharge into Lake Champlain. Currently,
there are at least 27 streams in the Lake Champlain Basin impaired by stormwater. We would like to know what you think is an
acceptable number of impaired streams. Please rate each of the number of impaired streams in the table above by circling a number on
the scale from –3 to +3. A rating of –3 means that the number of impaired streams is very unacceptable and a rating of +3 means that
the number of impaired streams is very acceptable.
norms of individuals were measured with questions
that asked respondents to rate the acceptability of a
range of potential conditions for the eight ecological
indicators addressed in the study. The range of
conditions presented for each indicator is shown in
Table 1. In order to keep the length of the questionnaire reasonable, norm questions were blocked such
that two indicator variables were included in each
version of the questionnaire (Manning and Lawson
2002). An example of the norm questions associated
with one of these indicator variables is shown in
Table 2. A limited amount of information about the
current condition of the lake or basin was provided
with each question for context.
For each question, respondents were asked to rate
the acceptability of a range of potential conditions
represented by five or six discrete levels of each
indicator variable. Acceptability was measured on an
ordinal scale that ranged from –3 to +3, where –3 is
very unacceptable, 0 is neutral, and +3 is very acceptable (see Table 2). A mean acceptability rating and
standard error were calculated for each level of the
indicator variables from all of the individual ratings for
each level. Aggregated social norm curves were
created by plotting these mean acceptability ratings
across the ranges of discrete levels examined for each
indicator.
Survey Implementation and Results
The population of interest for this study was the
stakeholders of the Lake Champlain ecosystem: residents of the basin that had some knowledge of and
interest in Lake Champlain. However, this is not a
readily accessible population for survey purposes. The
LCBP is the central authority responsible for coordinating management, education, and public outreach
for Lake Champlain. A random sample of the mailing
list of the LCBP was used as the study population.
123
Similarly, Boxall and Macnab (2000) used the member
list of a natural history organization as a surrogate for
wildlife viewers in a study comparing their preferences
to those of hunters. The LCBP appeals to a broad
spectrum of Lake Champlain stakeholders, making it a
better surrogate population than a random sample of
basin residents or more specialized subpopulations
such as basin residents with fishing licenses, members
of paddling clubs, or marina members. Because this
population consisted of individuals with some knowledge and interest in the lake, they were also more
likely to complete the questionnaire successfully.
There were over 7000 addresses in this mailing list,
including people from Vermont, New York, and
Quebec (although the number of Quebec addresses
was considerably less than those from the other two
jurisdictions).
The questionnaire design and multiple contact
survey implementation followed procedures recommended by Dillman (2000). Two thousand questionnaires were sent out in August 2002. Postcard
reminders were sent to nonrespondents 3 weeks after
the questionnaire mailing, and replacement questionnaires were sent to ~80% (because of budget limitations) of the nonrespondents 4 weeks after the postcard
reminder. There were 798 surveys returned from a final
pool of 1867 surveys that were successfully delivered,
generating a response rate of 42.7%. Although the
sample was drawn from a mailing list, the sample is
diverse with respect to the demographic information
obtained from survey respondents (Table 3). Compared to 2000 US census data for Vermont (because a
majority of the population of Vermont resides in the
basin, unlike New York), survey respondents were a
little older and more educated than the general
population.
The average number of visits by survey respondents
to Lake Champlain during the summer was nine per
month. When asked how the lake has changed over the
last 5 years, 41.4% reported that the condition of the
Environ Manage (2007) 39:301-315
307
Table 3 Summary of sample demographic characteristics (percent of the populations showing various characteristics)
Age
<25
1.2%
25–35
5.7%
36–50
32.4%
>50
56.3%
No response
4.4%
Total
100%
Graduate School
49.0%
No response
4.6%
Total
100%
Other
11.6%
No response
7.7%
Total
100%
Education
< High School
0.9%
High School
5.1%
Some college
9.5%
College
30.9%
Occupation
Business/technical
32.6%
Retired
19.5%
Educator
17.6%
Government/nonprofit
11%
lake has declined over the last 5 years, 29.2% thought
that it has stayed the same, 19.7% reported improved
lake condition, and 9.7% did not answer the question.
The sample population included participants in all
major lake recreational activities, including viewing
and picnicking, swimming, angling, paddling, motorboating, sailing, and scuba diving.
Norm Curves for Ecosystem Indicators
The social norm curves derived from the survey data
trace the average acceptability ratings of the sample
population across the range of levels of the eight
ecosystem indicator variables examined (Figures 1 and
2). All levels for which the y value is greater than zero
can be considered acceptable, with the peak of the
curve representing the optimal condition according to
the responses. The point at which the curve crosses the
zero point of the acceptability scale represents one
potential threshold or acceptable level for an indicator
because it is the point at which aggregate ratings fall
out of the acceptable range and into the unacceptable
range (Manning 1999; Manning and Lawson 2002). The
spread of the curve about the y axis is a measure
of norm intensity or salience (importance) of the
indicator, and the variability of responses about the
mean, called crystallization, is a measure of consensus
about the norm among the group sampled (Manning
and Lawson 2002).
Overall, the direction of the slopes of the norm
curves was as expected. The variability in responses
tended to be largest around the minimum acceptable
condition and smallest for levels furthest away from
the minimum acceptable condition. This signifies less
consensus about where the condition shifts from
minimally acceptable to minimally unacceptable than
there is regarding the acceptability of the extreme
values in the range of the conditions presented.
The norm curve for public beach closure had high
salience, as indicated by a wide range of y values
(Figure 1). This curve shows that, on average, 7 or
more days of public beach closure during the summer
is unacceptable. During the summer of 2002, Blanchard Beach in Burlington, Vermont was closed for the
entire swimming season, clearly exceeding this measure of acceptability. Other beaches showed a greater
range in the number of days of closure, and many
public swimming areas along Lake Champlain fully
complied with this acceptable level of performance
(Watzin and others 2005). Algae blooms, which also
impact recreational use and enjoyment along the shore
of Lake Champlain, show a similar norm curve shape
(Figure 1). Although these questions appeared in
different questionnaire versions, the shift from acceptable to unacceptable conditions occurs at approximately 7 days for both public beach closure and days of
intense algae blooms.
In the written comments and in a choice experiment
also included in the survey (Watzin and others 2005),
public beach closures appeared to be a relatively
greater concern in Vermont compared to New York. In
part, this might reflect the differences in the bacteria
standards and beach closure frequency in Vermont
compared to New York rather than an actual difference in societal values and associated norms. In
Vermont, the standard for beach closure is considerably stricter than in New York, 77 Escherichia coli per
100 ml compared to 1000 total coliform bacteria in a
single sample (Dorfman 2002) or 200 total coliforms in
a 3-day average. Quebec uses 200 total coliforms per
100 ml as their standard. In the interest of managing
Lake Champlain as one ecosystem, implementation of
a consistent monitoring and closure policy for all Lake
Champlain beaches could clarify what could be a
confusing message to the users of Lake Champlain
beaches.
The norm curve for safe fish consumption showed
less salience than the curves generated for other
indicators (Figure 1). However, the range of conditions
presented in the question for this indicator was more
constrained than the ranges used for other indicators.
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Environ Manage (2007) 39:301-315
3
3
A
B
2
2
Acceptability
Acceptability
1
0
-1
0
-1
-2
-3
1
-2
0
3
10
7
14
-3
21
0
3-4
Days of Beac h Clos ure per Seas on
14-21
7-10
30+
Days of Algae Bloom per Season
3
3
C
D
2
2
Acceptability
Acceptability
1
0
-1
1
0
-1
-2
-2
-3
-3
0
1
3
6
10
15
Number of Fish Safely Consumed per Month
None
1/2 with 1
1
2-3
4-5
>5
Number of Sea Lamprey per Fish
Fig. 1 Social norm curves for beach closures, days of algae bloom, safe fish consumption, and sea lamprey wounds. Social norm curves
are shown with one-sided standard error bars for each of the mean acceptability ratings
As with bacteria standards, the fish consumption
advisories for Lake Champlain issued by the state of
New York and the state of Vermont differ slightly. The
current fish consumption advisories suggest that adults
limit their intake of lake trout and walleye to about one
meal per month. The advisories are more restrictive for
children and women of childbearing age and less
restrictive with regard to other fish species caught in
the lake. Nevertheless, there appears to be little public
tolerance for substantial limitations on safe fish consumption based on this norm curve.
There are currently at least 27 streams impaired by
stormwater in the Champlain Basin. This is beyond the
generally acceptable condition based on the norm
curve for impaired streams (Figure 2). In this curve,
the mean ratings for all levels except the first are in the
less than zero, or unacceptable, range, and crystallization around the means increases steadily for each level
beyond nine impaired streams. This suggests that
123
management attention is necessary to improve stream
conditions in the basin.
The social norm curves for land development and
stream impairment (Figure 2) have a similar pattern
with decreasing variability about the means in the
unacceptable range. To measure the social norm curve
for basin development, respondents were told that
there were at least 300,000 acres of developed land in
the Champlain Basin. They were then asked to rate the
acceptability of a range of increases in developed land
per year. The results clearly indicate that substantial
increases in developed land are not favored. Rates of
land development vary across the basin; growth in
Chittenden County, Vermont might be outside the
range of acceptability, but rates of land development
are lower in other areas of the basin, particularly in
New York.
Currently, water chestnut in Lake Champlain
extends about 55 miles north of Whitehall, New York
Environ Manage (2007) 39:301-315
309
3
3
B
2
2
1
1
Acceptability
Acceptability
A
0
-1
-2
0
-1
-2
-3
0
9
18
27
36
-3
45
1
3
10
5
15
20
Percent of Land Developed in Basin per Year
Number of Streams Impaired in Basin
3
3
D
2
2
1
1
Acceptability
Acceptability
C
0
-1
-2
-3
0
-1
-2
0
20
40
55
70
90
Miles of Water Chestnut Infestation
-3
Current
Improve
10%
15%
20%
Changes in Public Access
Fig. 2 Social norm curves for number of streams impacted by stormwater, rate of basin land development, spread of water chestnut,
and public access to Lake Champlain. Social norm curves are shown with one-sided standard error bars for each of the mean
acceptability ratings
and this condition is not generally acceptable
(Figure 2). The LCBP currently has an aggressive
program for water chestnut harvesting that is successfully moving this extent southward. The norm curve
suggests that the public would like to see the extent of
water chestnut halved and, therefore, supports continuing this management action.
One or more sea lamprey wounds on fish caught
from Lake Champlain was generally not acceptable
(Figure 1). Currently, wounding rates vary considerably by fish species, fish size, and lake segment (Lake
Champlain Fish and Wildlife Management Cooperative, Fisheries Technical Committee 1999), but most
fish have at least one wound. To achieve a lower level
of lamprey wounding, a higher level of lamprey control
will be needed. This means greater use of the controversial chemical lampricides in Lake Champlain tributaries or greater implementation of alternative
management actions.
Both the sea lamprey and water chestnut indicator
norm curves support continued management of these
nuisance species. However, written comments qualita-
tively demonstrate concern over the use of chemicals in
the treatment of nuisance species. Several respondents
commented that they were unaware of the water
chestnut problem and others stated that they would not
support management to reduce water chestnut if it
involved the application of chemicals. There was also
concern expressed about the use of lampricides in the
watershed. These results are consistent with the findings for safe fish consumption and, in sum, suggest that
the use and presence of toxic chemicals in Lake
Champlain, no matter what the source or purpose, is
a concern for many respondents.
The final norm curve generated was for public access
(Figure 2). This curve shows the smallest range in
acceptability ratings and is the most difficult to
interpret. Although improving existing public access
areas received the highest acceptability rankings, there
was little difference between the rankings of any of the
management options. Similarly, a study of recreation
areas along Green Bay, Wisconsin found very limited
interest in adding park acreage (Breffle and Rowe
2002). We were surprised by this result, however,
123
310
because public access is generally considered an
important issue for Lake Champlain. In a separate
question, respondents were asked to rate the importance of public access, and 82% of the respondents
indicated that public access was ‘‘very important’’ or
‘‘important.’’ Public access was also commonly mentioned in the comment section of the questionnaire.
The reasons why the norm curve results and other
survey comments about public access were inconsistent
are not clear. Because the potential conditions listed as
choices in this question were not ordinal, as with the
other social norm questions, this question might have
been more difficult for respondents to answer. Another
potential explanation is that the ability to access the
lake is highly valued (hence, the high importance
ranking), but there is general satisfaction with the
current level of public access (as shown by the social
norm curve). The LCBP has been active in both
improving existing access and developing additional
access sites throughout its tenure. Once again, the
social norm analyses supports continuing this management action.
Using Social Norms for Indicators in an Adaptive
Management Approach
Adaptive management is based on the premise that if
appropriate information is gathered as management
actions are implemented, managers can learn as they
go (Holling 1978; Lee 1993; Stankey and others 2005;
Walters 1986). Changes in measured indicator levels
can provide that information, including not just information about ecosystem condition and the effectiveness of the management actions but also information
about the validity of the hypotheses upon which the
management actions were based. By specifying acceptable levels for indicators, managers articulate their
desired outcomes and thereby provide means for
evaluating the effectiveness of their management
priorities and approaches. By organizing indicators in
an adaptive management approach, managers can
increase their understanding of the ecosystem regardless of the outcomes of management. Improved
understanding also reduces uncertainty, thereby
enhancing the likelihood that future management
strategies will be successful.
Norm curves suggest which ecological conditions
people desire for the Lake Champlain Basin, but
decision-makers must also consider the implications of
society’s choices and consider the management strategies necessary to support the acceptable levels
suggested by these curves. Because the existing eco-
123
Environ Manage (2007) 39:301-315
logical datasets for Lake Champlain are limited,
acceptable levels should logically be approached within
the context of adaptive management (Watzin and
others 2005). Further ecological studies will continue to
shed new light on the mechanisms of action in
ecosystems and suggest new and innovative management strategies. Preliminary judgments can then be
modified as additional data, including economic data,
become available. A regular cycle of indicator evaluation will help focus on the most appropriate levels in
the most efficient and effective manner.
The social norm curves that we generated offer a
number of suggestions for decision-makers in the Lake
Champlain Basin. For example, there seems to be
some public consensus that more than about 7 days of
closure of public beaches because of bacteria contamination passed a threshold of acceptability. In order to
bring those beaches that exceed this level closer to it,
environmental managers must consider bacterial
sources and transport pathways and identify additional
controls and treatment for runoff from farmlands and
urban/suburban land.
When we administered our survey, beach closures
along Lake Champlain occurred solely as a result of
bacterial contamination. Since then, beach closures
and restrictions of recreational activities as a result of
toxic cyanobacteria blooms have become increasingly
common (Watzin and others 2005). Toxins in public
waters are usually managed through the use of water
quality criteria that are based on risks of exposure and
adverse health effects (US EPA 1986). The World
Health Organization (1998, 2003) has recommended
guidelines for some cyanotoxins in drinking water and
recreational waters. However, these guidelines provide
little advice on controlling cyanobacteria in Lake
Champlain or any water body; they simply indicate
when risks to human health become significant. They
are also based on risk thresholds that are rarely shared
with the public.
From an ecological perspective, there is great
uncertainty about what triggers cyanobacterial dominance and toxin production in lakes (Huisman and
others 2005; Wilhelm and others 2003). Phosphorus is
considered the primary limiting nutrient in Lake
Champlain and there is generally a positive relationship between total phosphorus concentration and both
total algal and cyanobacteria abundance in lakes
(Huzsar and Caraco 1998; Paerl and others 2001;
Raikow and others 2004), but other studies show that
nitrogen might be equally important (Downing and
others 2001; Elser 1999; Jensen and others 1994;
Scheffer and others 1997; Smith 1983), and some
evidence suggests that human-induced eutrophication
Environ Manage (2007) 39:301-315
in lakes might be irreversible if phosphorus reductions
are the only management approach taken (Carpenter
and others 1999).
The LCBP has an extensive monitoring program for
phosphorus and also monitors chlorophyll-a concentration, a measure of overall algal abundance. It does
not compile information on rates of beach closure
because of toxic algae blooms. We believe that this
indicator might be a more representative measure of
public perceptions about lake condition than measures
of either phosphorus or chlorophyll-a concentration.
Although further ecological analysis is needed to
determine the water quality necessary to achieve
acceptable levels of beach closure, an algae bloom
beach-closure indicator might serve to integrate societal desires with these conditions.
Both land use in the basin and the number of
streams impaired by stormwater influence the number
of days of beach closure and algae bloom in the lake.
Our norm curve analyses clearly indicate that the
number of streams impaired by stormwater is unacceptable to the public and suggest that current rates of
land development are only marginally acceptable. If
additional management actions are taken to control
soil erosion and runoff from both agricultural and
developed land and appropriate development controls
are implemented, there should be fewer days of algae
bloom and beach closure in the future as well as fewer
impaired streams. A mechanistic understanding of
land-use impacts could help in designing land-use
management strategies that decrease soil erosion and
thereby also decrease the potential for phosphorus
runoff to surface waters (Bennett and others 2001;
Sharpley and others 1994).
Our sea lamprey and water chestnut indicator
results suggest that more aggressive action is necessary
in order to manage for the impacts of nuisance species.
In Lake Champlain, an ecological threshold was
probably passed when native salmonids were extirpated from the lake in the late 1800s. The fish
community now will likely never regain its native
composition, and the increase in the sea lamprey
population has probably significantly altered the
potential stable states of the fish community (Aron
and Smith 1971). In the last several decades, a number
of new exotic species have invaded the lake, including
extremely prolific populations of zebra mussels
(Dreissena polymorpha) and white perch (Morone
americana). Because exotic species alter resource
flows, trophic structure, and, potentially, the disturbance regime, they can also alter the stable state of a
community (Vitousek 1990). Additional research
will be necessary to determine what community
311
composition will be stable and resilient, given the
lake’s current trophic state and the suite of exotic
species that are now part of the ecosystem.
The social norm results presented here support
continuing many management actions already implemented by the LCBP (e.g., nuisance species control,
public access improvements, and phosphorus reductions) but also indicate a desire for more aggressive
management in other areas (e.g., toxic contamination
and stream impairment). They also indicate potentially
conflicting interests (e.g., the application of TFM, a
toxic substance, for the control of sea lamprey, a
nuisance species). Managers must balance many societal values along with ecological constraints in deciding
which management strategies to implement. Social
science research, such as choice experiments (Breffle
and Rowe 2002; Lawson and Manning 2002, 2003;
Watzin and others 2005) and decision analysis (Anderson and others 2001), can help evaluate the trade-offs
among choices and preferences under various potential
management scenarios. Although social norm analyses
can provide critical information about the levels of
various ecosystem characteristics that people desire,
these analyses do not force respondents to prioritize or
make any trade-offs among potential management
issues and actions; therefore, they might need to be
supplemented with other information to help managers
deal with the resource constraints and conflicting use
demands that always exist in ecosystem management
programs.
The 11 goals in the LCBP’s management plan,
Opportunities for Action (LCSC 2003), convey information about the desired state of some of the components of the ecosystem and, therefore, can help guide
the development of acceptable levels. However, all of
the goals in the plan might likewise not be fully
compatible. For example, the phosphorus reduction
goal establishes target phosphorus concentrations that
should prevent nuisance algal blooms in the future.
Actions that will reduce phosphorus are the primary
focus of this section of the plan. The recreation
management goals are to promote sustainable tourism
and increase public access to the lake. Increases in
tourism and recreational use of the lake could increase
phosphorus loading to the lake unless more aggressive
management actions are taken to offset this load.
In a similar vein, both phosphorus concentration and
recreational use will affect the living resources in the
lake, but these linkages are not considered in the
current management strategies. The phosphorus goals
in the LCBP’s plan were developed based solely on
consideration of the links between phosphorus and
recreational use and enjoyment of the lake (Smeltzer
123
312
and Quinn 1996). However, these criteria also have
implications for the biota in the lake. The living
resource goal is to restore and maintain a healthy and
diverse community of fish and wildlife (LCSC 2003);
this goal cannot be achieved without consideration of
the phosphorus, toxic substances, and habitat management actions presented elsewhere in the plan. The
fisheries objectives emphasize abundant angling opportunities. The size of the fish community is directly
dependent on the productivity of the lake and, therefore, its phosphorus concentrations.
Unfortunately, neither the living resource goal nor
the fisheries objectives fully articulate the desired
biological community in Lake Champlain; therefore, it
is difficult to determine what level of productivity is
necessary to support it. Likewise, no estimate of the
productive capacity of the Lake Champlain ecosystem,
either in its current trophic state or after phosphorus
reductions are achieved, has been made. Such an
estimate is prerequisite to predicting the overall
carrying capacity in major lake segments. Although
productivity estimates could be developed in the
future, they will take time, and the articulation of the
desired biological community is, in essence, a social
choice.
For more than a decade, the LCBP has been
conducting a large-scale experiment on Lake Champlain without collecting the data that are needed to
interpret it. At the top of the food web, managers have
been changing fish abundances by stocking sport fish
and reducing sea lamprey. At the bottom of the food
web, managers have been reducing phosphorus, which
controls the growth of the algae. Somewhere in the
middle, through the introduction of zebra mussels and
other exotic species, a host of connections both up and
down the food web have been altered. Very clearly,
adaptive management could provide a context for
addressing these unknowns if a set of indicators are
adopted and the monitoring data to quantify them are
collected over time.
As Opportunities for Action continues to evolve, the
linkages between sections of the plan should be
explicitly addressed so that an overall desired ecosystem state can be more fully articulated. As this is done,
it will also be possible to more fully consider both the
social and the ecological factors that must be examined
and balanced in establishing acceptable levels for
ecological system indicators. This will occur only if
there is greater collaboration between social scientists
and natural scientists in the region. Natural scientists
must help translate ecological conditions (e.g., phosphorus concentrations and fish productivity) into social
consequences (e.g., days of algae blooms, potential
123
Environ Manage (2007) 39:301-315
angling success), and social scientists must identify and
measure societal values in a way that is useful in
developing numeric ecological benchmarks.
Clearly, there is also room within adaptive management for public understanding of the trade-offs
inherent in decision-making. As the citizens and stakeholders in the basin become more aware of how they
affect and are affected by the environment over time,
this might change how they react to the trade-offs
inherent in setting management goals and establishing
management priorities. This might also lead to changes
in social norms and ongoing redefinition of acceptable
levels of the ecological system indicators.
Conclusions
We believe that ecological indicators have enormous
potential for improving management decision-making,
but only if they are chosen with awareness of societal
values. Once appropriate indicators are selected, they
must be made interpretable by establishing acceptable
levels that balance social preferences with ecological
integrity. The social judgments that are implicit in
formulating ecological benchmarks are often ‘‘hidden’’ from the public by scientific experts and
managers. The normative approach offers one way
to help make these judgments more visible and
explicit. Likewise, the importance of integrating social
values and enhancing public support for ecosystem
management is discussed at length in the literature.
However, there is little consensus about how to
accomplish this.
The techniques presented here have considerable
potential for quantitatively assessing social preferences
for valued ecosystem characteristics, regardless of the
ecological system. We encourage applications of these
methods in other systems and suggest that if indicator
programs are to reach their full potential, greater focus
must be brought to bear on specifying acceptable levels
that can be used as management targets. If information
about social preferences can be combined with related
information about ecological condition and function,
then a truly integrated and holistic approach for
interpretation and use of indicators information within
an adaptive ecosystem management framework is
possible.
Acknowledgments Many people helped with this project,
including staff at the Lake Champlain Basin Program and all
of the partner federal, state, and provincial agencies. We
especially thank Bill Howland, Miranda Lescaze, Colleen
Hickey, Craig Martin, Eric Smeltzer, and Martin Mimeault.
Environ Manage (2007) 39:301-315
We also thank Kim Locke for editorial assistance with the
manuscript. Funding for this project was provided by the US
Environmental Protection Agency, through the New England
Interstate Water Pollution Control Commission and the Lake
Champlain Basin Program.
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