Recreation Monitoring at Acadia National Park
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Recreation Monitoring at Acadia National Park
Robert Manning, Charles Jacobi, and Jeffrey L. Marion
Introduction
ACADIA NATIONAL PARK IS ONE OF THE MOST INTENSIVELY USED NATIONAL PARKS in the
United States. While its annual visitation (2.2 million visits in 2004) does not rise to the lev-
els of some of the “crown jewel” western national parks (Yellowstone National Park, for
example, accommodated 2.9 million visits in 2004), visits to Acadia are concentrated on its
comparatively small size of less than 50,000 acres. Yellowstone, by comparison, is spread
across 2.2 million acres. Given the intensive character of visitor use at Acadia, it is vital to
monitor recreational use and its associated impacts to help ensure protection of important
park resources and the quality of the visitor experience.
Over the past decade, Acadia has tem. These indicators and standards give
undertaken an expanding program of recre- focus to the monitoring program, enhanc-
ation-related monitoring and associated ing its efficiency and effectiveness. Second,
activities. This program has been guided by computer-based simulation modeling has
the National Park Service (NPS) Visitor Ex- been used to help conduct the monitoring
perience and Resource Protection (VERP) program. Simulation models can be used to
framework (NPS 1997; Manning 2001). estimate park conditions (as defined by
VERP was designed by the NPS to address indicator variables), reducing the need for
carrying capacity and related recreation on-the-ground monitoring, and can be used
management issues. The underlying ration- as a more “proactive” monitoring approach
ale of the VERP framework is to (1) define by estimating the maximum amount of visi-
desired resource and social conditions in tor use that can be accommodated without
terms of empirically based indicators and violating standards. Third, several issues
standards, (2) monitor indicator variables, associated with monitoring on the carriage
and (3) apply management actions to roads are described. These issues have aris-
ensure that standards have been main- en over several years of experience with this
tained. Thus, monitoring resource and monitoring program. Finally, the recreation
social conditions at Acadia has become an monitoring program at Acadia is expanding
important part of park planning and man- to address other areas of the park. A pro-
agement. gram of natural and social science research
This paper describes four aspects of has been undertaken to help guide this
the monitoring program applied to Acadia. monitoring. The final section of the paper
First, a suite of indicators and associated briefly describes this program of research as
standards was initially formulated to guide it applies to resource-based impacts of
monitoring of the park’s carriage road sys- recreation, including societal judgments
Volume 23 • Number 2 (2006) 59Visitor Impact Monitoring
about appropriate standards for such than 50 mi of unpaved roads constructed at
impacts. the direction of John D. Rockefeller, Jr., in
the early 1900s, represent one of the most
Indicators and standards to guide significant resources in the park. Originally
monitoring built for horse-drawn carriages, the carriage
Parks are complex resource and social roads are now used primarily for hiking and
systems that can be characterized by a mul- biking and have become extremely popular.
titude of ecological and experiential vari- However, increased use has created con-
ables. However, monitoring such variables cern for the quality of the recreation experi-
can be time-consuming and expensive. ence. In response to this concern, a pro-
Therefore, monitoring programs must be gram of research was initiated to help for-
designed carefully to ensure that they focus mulate indicators and standards for the car-
on a relatively small number of indicator riage-road experience.
variables that best meet selected criteria or A first phase of research focused on
characteristics (Schomaker 1984; Stankey identifying potential indicators. A survey of
et al. 1985; Marion 1991; Merigliano 1990; a representative sample of carriage road vis-
Whittaker and Shelby 1992; National Park itors was conducted. Using both open- and
Service 1997; Manning 1999). closed-ended questions, visitors were asked
Moreover, within the context of the to report on what added to or detracted
VERP framework, standards must be for- from the quality of their experience on the
mulated for indicator variables. Standards carriage roads. Two types of indicators were
are generally defined as the minimum identified: one was crowding-related and
acceptable condition of indicator variables concerned the number of visitors seen on
(National Park Service 1997; Manning the carriage roads; the other was conflict-
1999). Standards provide vital reference related and addressed several “problem
points for monitoring programs. Within the behaviors” experienced on the carriage
VERP framework, standards are thresholds roads, including bicycles passing from
that define when and where management behind without warning, excessive bicycle
action is needed. Without such standards, speed, people obstructing the carriage
findings from monitoring programs are dif- roads by walking abreast or stopping in
ficult to interpret and provide little direct groups, and dogs being off leash.
guidance to managers. The first phase of research also docu-
For these reasons, the recreation-relat- mented existing patterns of use on the car-
ed monitoring program at Acadia began riage roads and visitor attitudes toward a
with an effort to formulate a suite of indica- variety of management alternatives. The
tors and standards. This work was initiated carriage roads support a diversity of recre-
in the mid-1990s on the park’s system of ation opportunities defined both spatially
carriage roads (Manning et al. 1998; Jacobi and temporally. Some areas and times are
and Manning 1999) and has expanded to relatively heavily used, while others accom-
include all major visitor use areas within the modate relatively light levels of use. Despite
park. The initial application to the carriage the problem behaviors noted above, most
roads will be used to illustrate this work. visitors supported maintaining the current
The carriage roads, a system of more mix of carriage road users—hikers, bikers,
60 The George Wright ForumVisitor Impact Monitoring
and equestrians. Based on these findings, Visitors were shown the photographs
park management decided to maintain a in random order and asked to rate their
diversity of carriage road experiences by acceptability on a scale from –4 (“very un-
establishing two types of recreation oppor- acceptable”) to +4 (“very acceptable”).
tunity “zones” for the carriage roads as Study findings are shown in Figure 2. This
defined by location, time of day, and time of figure is called a social norm curve (or
year. However, both of these zones would impact acceptability curve) and represents
continue to accommodate all types of visi- the aggregate acceptability ratings for the
tors. The two carriage road zones would be sample of visitors. The norm curve docu-
defined by the same indicators, but different ments the relationship between increasing
standards would be set. use levels and the quality of the visitor expe-
A second phase of research focused on rience.
formulating standards for indicator vari- Two other sources of information were
ables. This research also used a survey of a developed to help formulate standards for
representative sample of carriage road visi- crowding on the carriage roads. The survey
tors and adopted normative theory and using the photographs described above was
related empirical techniques (Shelby and administered to a representative sample of
Heberlein 1986; Vaske et al. 1986; Man- residents of communities surrounding the
ning 1999). As applied in outdoor recre- park, and a computer-based simulation
ation, norms are generally defined as stan- model of visitor use on the carriage roads
dards that individuals and groups use to (described in the next section) was devel-
evaluate social and environmental condi- oped to provide more detailed information
tions in parks and related areas (Shelby and on the relationship between total daily use
Vaske 1991). If visitors have normative stan- level of the carriage roads and PPV condi-
dards concerning relevant aspects of recre- tions. Based on all of this information, stan-
ation experiences, then such norms can be dards were formulated for the indicator
studied and used as a basis for formulating variable of PPV conditions.
standards. Standards were also formulated for the
Because of the relatively large number four problem behaviors described above.
of visitors on the carriage roads, crowding Visitors were asked to report the maximum
was measured in terms of persons-per- number of times it would be acceptable to
viewscape (PPV), incorporating a visually experience each of these behaviors during a
based measurement approach (Manning et trip on the carriage roads. The resulting
al. 1996; Manning and Freimund 2005). norms were used as a basis of formulating
The viewscape for the carriage roads (the standards.
length of carriage road that can be seen at After indicators and standards for the
any one time) averages approximately 100 carriage road experience were formulated, a
m. A series of photographs was prepared similar program of work has been conduct-
that showed a range of zero to 30 visitors on ed in all other major visitor use areas of the
a typical 100-m section of the carriage park; indicators and standards are now
roads. The photographs were prepared being formulated for these areas. Examples
using digital photo-editing software. of the range of resource and social indica-
Sample photographs are shown in Figure 1. tors being formulated at Acadia include trail
Volume 23 • Number 2 (2006) 61Visitor Impact Monitoring
1a 1b
1c 1d
1e 1f
Figure 1. Sample study photographs showing a range of visitor use on the carriage roads.
Figure 2. Social norm curve for PPV on the carriage roads.
62 The George Wright ForumVisitor Impact Monitoring
width and erosion, visitor encounters along can be accommodated on the carriage roads
trails, number of visitors at one time at without violating crowding-related (PPV)
attraction areas, and number of cars on park standards. Finally, the model can also be
roads. used to facilitate a program of adaptive
management (Lee 1993; Stankey et al.
Computer simulation modeling as a 2005) by estimating (“monitoring”) the
monitoring tool effects on PPV levels of alternative manage-
As noted earlier, monitoring indicator ment practices, such as redistributing use
variables can be time consuming and costly. over time and space and altering the mix of
Moreover, some indicators, like PPV condi- carriage roads users (Lawson et al. 2003).
tions along the carriage roads, can be inher-
ently difficult to observe. Simulation mod- Monitoring recreation on Acadia’s
els offer a potentially attractive alternative to carriage roads
on-the-ground monitoring. Once a simula- Based on the research described above,
tion model is developed, it can be used to several indicators were established for the
estimate the condition of indicator vari- quality of the carriage road experience,
ables. including PPV levels and problem behav-
A simulation model of carriage road iors. Standards were then formulated for
use was developed in the 1990s (Manning these indicator variables. For PPV levels,
et al. 1998; Wang and Manning 1999; Ja- the simulation model of carriage road use
cobi and Manning 1999; Manning and estimated that the carriage roads could
Wang 2005). The model was constructed accommodate up to 3,000 visitors per day
using diary reports by visitors of their travel without violating the PPV standards that
routes and times along the carriage roads were formulated. Because total daily use of
and counts of the number of visitors enter- the carriage roads was potentially easier to
ing each of the 11 major access points to the monitor than PPV levels, this became a
carriage roads. These and related data were focus of the recreation monitoring program.
processed using the general purpose simu- Total daily use of the carriage roads is mon-
lation software, Extend. The model was itored by means of an electronic trail count-
designed to estimate PPV levels along the er. Over a period of several years, a series of
carriage roads and can be run at any daily one-day censuses of carriage road use were
use level of the carriage road system. The conducted by stationing volunteer ob-
park’s monitoring program measures daily servers at each of the 11 major carriage road
use of the carriage roads through an elec- entrances. Resulting counts of total daily
tronic trail counter and uses the simulation carriage road use were correlated with
model to estimate PPV levels (the crowd- simultaneous trail counter readings, and a
ing-related indicator variable) to ensure that strong correlation was found. Based on this
crowding-related standards are not violat- analysis, PPV levels are monitored on an
ed. Moreover, the model has been used in a annual basis using trail counter readings.
more “proactive monitoring” approach Trail counter readings from 1997 through
(Lawson et al. 2003). The model was run at 2004 suggest that carriage road use has
increasing levels of daily carriage road use remained relatively stable and that PPV-
to estimate the maximum daily use level that related standards have not been violated.
Volume 23 • Number 2 (2006) 63Visitor Impact Monitoring
In addition to the monitoring de- undesignated (visitor-created) trails on
scribed above, actual PPV counts are con- Little Moose Island (LMI) and designated
ducted every three years at selected loca- trails on Isle au Haut (IAH). Research has
tions and times. An observer records the been directed at selecting appropriate indi-
number of visitors on 100-m viewscapes at cators of resource impacts and developing
15-second intervals. These counts help protocols for monitoring these indicators.
“ground truth” and validate the PPV esti- This work has integrated natural and social
mates derived from the trail counter and science studies to yield indicators and asso-
computer simulation model. ciated standards that are both ecologically
Monitoring of problem behaviors on and experientially meaningful. This work
the carriage roads is conducted by means of will be extended to undesignated and desig-
a short visitor survey conducted every three nated trails on Mount Desert Island in
years. Respondents are asked to report how 2007.
many of the four problem behaviors they The creation and proliferation of
have experienced. Resulting data suggest undesignated trails is a common problem in
that standards are being violated for two parks that can directly affect sensitive plant
problem behaviors despite enactment of communities, rare flora and fauna, and
several management practices (promulga- wildlife habitats (Leung and Marion 2000).
tion of “rules-of-the-road” for the carriage Visitors seeking to access scenic overlooks,
roads, “courtesy” patrols of the carriage water resources, or merely to explore, often
roads, and production of an educational trample vegetation sufficiently to create ex-
video shown at local bicycle rental shops) tensive informal trail systems. Resource de-
designed to address this issue. If data from gradation on these trails is often severe due
the next monitoring cycle in 2006 suggest to lack of professional trail design, con-
that standards are still being violated, a struction, and maintenance. Such un-
decision will be made to either take addi- planned trail networks generally receive no
tional management actions to reduce the environmental reviews, yet they cause
incidences of problem behaviors (e.g., edu- direct trampling and resource degradation,
cate visitors, adopt behavioral regulations, habitat fragmentation, and can further
limit carriage road use) or formulate spread invasive species. While some degree
revised, more realistic standards. of visitor impact is unavoidable, excessive
trail impacts threaten natural resource val-
Monitoring resource impacts ues, visitor safety, and the quality of recre-
Acadia National Park visitors partici- ation experiences.
pate in a variety of recreation activities, On LMI four types of monitoring pro-
including driving, boating, hiking, horse cedures have been experimentally applied:
riding, and biking, and these activities have (1) global positioning system (GPS) surveys
an array of effects or “impacts” on natural of the location and extent of visitor-created
resources, including vegetation, soils, water, trails, (2) trail condition class assessments
and wildlife. To date, resource-related mon- based on vegetation and soil loss, (3) photo-
itoring and associated research has focused graphic monitoring from permanent GPS-
on hiking and camping impacts to vegeta- mapped photopoints, and (4) a point sam-
tion and soils, including assessments of pling method with a systematic sampling
64 The George Wright ForumVisitor Impact Monitoring
interval of 300 ft following a randomized (54.8% of the total) were classified as hav-
start. LMI is a very small, pristine island ing impacts that were barely distinguishable
located off the Schoodic Peninsula and is or being in a lightly impacted condition
only accessible to hikers during low tide. (Class 0 or 1), 2,864 ft (18.3%) were
The GPS and condition class surveys assessed as being heavily impacted with
revealed a surprisingly large network of vis- eroded treads (Class 5) (Table 1). These
itor-created trails, totaling 15,618 ft (2.96 procedures and data illustrate the most effi-
mi) (Figure 3 & Table 1). While 8,552 ft cient methods for tracking the proliferation
Figure 3. Trails on Little Moose Island.
Volume 23 • Number 2 (2006) 65Visitor Impact Monitoring
Table 1. Condition class and length of visitor-created trails on Little Moose Island in 1996.
and degradation of undesignated trails. cover of vegetation, organic litter, exposed
Park staff analyzed and employed these data soil, rock, and roots). This type of data is
to define a limited subset of 1.09 mi of des- presented for illustration purposes in the
ignated trails, a 63% reduction, that retain next section on IAH.
access to the island’s principal destination On IAH two trail condition assessment
sites. These trails received subtle mainte- methodologies, the point sampling and
nance work to facilitate their use, while 1.86 problem census methods, were integrated
mi of trail were closed to use with brush and to provide quantitative data describing con-
small trail closure/revegetation signs. A ditions for several impact indicators. A
trailhead sign with a Leave No Trace mes- point sampling method with a systematic
sage was installed asking visitors to protect sampling interval of 500 ft, following a ran-
sensitive vegetation by staying on the main domized start, was the primary method
trails or rock ledges. (Leung and Marion 1999b; Marion and
Photopoint monitoring can be easily Leung 2001). Data assessed for a subset of
added to GPS surveys to provide a visual the indicators are reported here, including
documentation of changing trail conditions. tread width, maximum tread incision, and a
Park staff purposely identified and took new, more efficient variable interval method
photos at 24 photopoints in 2001 and for determining cross-sectional area (CSA)
2003, including points along the newly des- of soil loss (see Figure 4). While more time-
ignated trail system and along the trails consuming than maximum incision, CSA
identified for closure. Few changes in vege- provides an accurate measure of trail soil
tation cover were detectable along the des- erosion that can be extrapolated to provide
ignated trails but photos revealed substan- an estimate of total soil loss from each trail.
tial recovery beginning along the closed A problem census method integrated
trails. Finally, the point sampling survey into the monitoring procedures provided
provided additional quantitative transect census information on three specific trail
data on indicators such as tread width, soil impact problems: excessive erosion (>5 in),
loss, and tread substrates (e.g., percent excessive muddiness, and number of infor-
66 The George Wright ForumVisitor Impact Monitoring
Figure 4. Diagram of the cross-sectional area method (variable intervals) for assessing soil erosion on trails.
mal trails branching from the formal trail which equates to a loss of about 55 truck-
since the last sample point (Leung and loads of soil. Problem assessment data
Marion 1999a). As they hiked, field staff (Table 3) also reveal very few occurrences of
looked for and recorded the beginning and excessive soil erosion and muddiness, with
ending distances from the starting point for a lineal extent of only 368 and 292 ft/mi,
all occurrences of these problems. In con- respectively. These data illustrate the capa-
trast to point sampling, this method pro- bility of more measurement-based trail
vides census data on the extent and location assessment protocols that provide quantita-
of specific pre-defined problems, facilitat- tive data for tracking degradation.
ing management efforts to rectify such Preliminary standards of quality have been
impacts. Both methods can be applied con- selected for tread width and maximum inci-
currently at an assessment rate of approxi- sion, and monitoring will be replicated to
mately one mile/hour by two surveyors. evaluate these approximately every five
All 12 NPS trails on IAH were years.
assessed; trail length ranged from 0.16 to An associated program of social sci-
3.99 mi, with a mean of 1.56 mi and a total ence research was also conducted on trail-
of 20.1 mi. Use data were developed for related impacts at IAH. Trail widening and
each trail based on trail use monitoring and erosion, visitor-created trails, and vegeta-
development of a simulation model of visi- tion loss affect park resources, but these
tor use (Manning et al. 2004). Based on nat- impacts can also degrade the quality of the
ural breaks in the use data, IAH trails were visitor experience. At what point do such
classified as low-use (0.3–1.0 encoun- impacts become unacceptable from an
ters/mi), moderate-use (4.0–6.0 encoun- experiential perspective? To help answer
ters/mi), and high use (10.0–11.0 encoun- this question, two series of photographs
ters/mi). were prepared illustrating a range of recre-
Table 2 presents point sampling data ation-related trail impacts on IAH, includ-
for each trail with summaries by level of trail ing trail erosion and proliferation of visitor-
use and for the entire island. Results reveal created trails (Manning et al. 2004).
increasing degradation with use level, Preparation of these photographs was guid-
though conditions on even the high-use ed by the assessment of trail conditions
trails are good—which we attribute to rela- described above. The photographs for visi-
tively low use, good design, and durable tor-created trails are shown in Figure 5. As
substrates. However, even with a mean max- with the photographs of visitor use on the
imum incision value of 1.4 in, estimated soil carriage roads described earlier, these pho-
loss for the entire trail system totals 553 yd3, tographs of resource impacts were incorpo-
Volume 23 • Number 2 (2006) 67Visitor Impact Monitoring
Table 2. Point sampling data for tread width and soil loss.
rated into a survey of visitors to IAH. The dards. Indicators provide a focus for the
resulting social norm curve for visitor-creat- monitoring program and standards provide
ed trails is shown in Figure 6. These and reference points that inform interpretation
related data are also being used to help for- of resulting monitoring data and ultimately
mulate standards for recreation-caused guide management action. Identification of
resource impacts. indicators and formulation of standards is
informed by a continuing program of natu-
Conclusion ral and social science research.
Recreation monitoring is an expand- Monitoring of recreation at Acadia
ing, evolving, and increasingly important includes both resource and experiential
element of park management at Acadia. variables. The monitoring program, and the
This monitoring program is conducted research upon which it is based, explicitly
within the context of the NPS VERP frame- recognize the interrelationships that can
work, which requires identification of indi- characterize the resource and social dimen-
cators and formulation of associated stan- sions of park and recreation management.
68 The George Wright ForumVisitor Impact Monitoring
Table 3. Problem assessment data for number of occurrences and lineal distance of excessive soil erosion and muddi-
ness.
For example, natural science research helps designed to maximize efficiency and pro-
document the ecological impacts of recre- vide measures of cross-validation where
ation and how these impacts progress over possible.
time, while social science research helps Recreation monitoring began at Acadia
understand the degree to which these nearly 10 years ago, but was relatively nar-
impacts degrade the quality of the visitor rowly focused on the quality of the visitor
experience. An integrated program of natu- experience on the carriage roads.
ral and social science research can help Monitoring has since been extended to
develop a more comprehensive and coordi- other areas of the park and to both experi-
nated suite of recreation-related indicators ential and resource-related visitor impacts.
and standards. Ultimately, a suite of resource and experien-
Recreation monitoring at Acadia is tial indicators and standards will be formu-
conducted through a combination of field- lated for all major areas of the park, and
based measurements (e.g., measures of trail management of recreation use and related
width and erosion, direct observation of impacts will be guided by data derived from
PPV levels, visitor surveys), remote sensing the park’s program of recreation monitor-
(trail counters), and computer simulation ing.
modeling. This combination of methods is
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Robert Manning, University of Vermont, 356 Aiken Center, Burlington, Vermont 05405;
robert.manning@uvm.edu
Charles Jacobi, Acadia National Park, P.O. Box 177, Bar Harbor, Maine 04609-0177; char-
lie_jacobi@nps.gov
Jeffrey L. Marion, U.S. Geological Survey, Patuxent Wildlife Research Center, Virginia
Tech, Forestry (0324), Blacksburg, Virginia 24061; jmarion@vt.edu
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