robert manning, charles jacobi, and jeffrey l. marion manning.pdf · carriage roads (manning et al....

Over the past decade, Acadia hasundertaken an expanding program of recre-ation-related monitoring and associatedactivities. This program has been guided bythe National Park Service (NPS) Visitor Ex-perience and Resource Protection (VERP)framework (NPS 1997; Manning 2001).VERP was designed by the NPS to addresscarrying capacity and related recreationmanagement issues. The underlying ration-ale of the VERP framework is to (1) definedesired resource and social conditions interms of empirically based indicators andstandards, (2) monitor indicator variables,and (3) apply management actions toensure that standards have been main-tained. Thus, monitoring resource andsocial conditions at Acadia has become animportant part of park planning and man-agement.

This paper describes four aspects ofthe monitoring program applied to Acadia.First, a suite of indicators and associatedstandards was initially formulated to guidemonitoring of the park’s carriage road sys-

tem. These indicators and standards givefocus to the monitoring program, enhanc-ing its efficiency and effectiveness. Second,computer-based simulation modeling hasbeen used to help conduct the monitoringprogram. Simulation models can be used toestimate park conditions (as defined byindicator variables), reducing the need foron-the-ground monitoring, and can be usedas a more “proactive” monitoring approachby estimating the maximum amount of visi-tor use that can be accommodated withoutviolating standards. Third, several issuesassociated with monitoring on the carriageroads are described. These issues have aris-en over several years of experience with thismonitoring program. Finally, the recreationmonitoring program at Acadia is expandingto address other areas of the park. A pro-gram of natural and social science researchhas been undertaken to help guide thismonitoring. The final section of the paperbriefly describes this program of research asit applies to resource-based impacts ofrecreation, including societal judgments

Volume 23 • Number 2 (2006) 59

Recreation Monitoring at Acadia National Park

Robert Manning, Charles Jacobi, and Jeffrey L. Marion

IntroductionACADIA NATIONAL PARK IS ONE OF THE MOST INTENSIVELY USED NATIONAL PARKS in theUnited 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, forexample, accommodated 2.9 million visits in 2004), visits to Acadia are concentrated on itscomparatively small size of less than 50,000 acres. Yellowstone, by comparison, is spreadacross 2.2 million acres. Given the intensive character of visitor use at Acadia, it is vital tomonitor recreational use and its associated impacts to help ensure protection of importantpark resources and the quality of the visitor experience.

about appropriate standards for suchimpacts.

Indicators and standards to guidemonitoring

Parks are complex resource and socialsystems that can be characterized by a mul-titude of ecological and experiential vari-ables. However, monitoring such variablescan be time-consuming and expensive.Therefore, monitoring programs must bedesigned carefully to ensure that they focuson a relatively small number of indicatorvariables that best meet selected criteria orcharacteristics (Schomaker 1984; Stankeyet al. 1985; Marion 1991; Merigliano 1990;Whittaker and Shelby 1992; National ParkService 1997; Manning 1999).

Moreover, within the context of theVERP framework, standards must be for-mulated for indicator variables. Standardsare generally defined as the minimumacceptable condition of indicator variables(National Park Service 1997; Manning1999). Standards provide vital referencepoints for monitoring programs. Within theVERP framework, standards are thresholdsthat define when and where managementaction is needed. Without such standards,findings from monitoring programs are dif-ficult to interpret and provide little directguidance to managers.

For these reasons, the recreation-relat-ed monitoring program at Acadia beganwith an effort to formulate a suite of indica-tors and standards. This work was initiatedin the mid-1990s on the park’s system ofcarriage roads (Manning et al. 1998; Jacobiand Manning 1999) and has expanded toinclude all major visitor use areas within thepark. The initial application to the carriageroads will be used to illustrate this work.

The carriage roads, a system of more

than 50 mi of unpaved roads constructed atthe direction of John D. Rockefeller, Jr., inthe early 1900s, represent one of the mostsignificant resources in the park. Originallybuilt for horse-drawn carriages, the carriageroads are now used primarily for hiking andbiking and have become extremely popular.However, increased use has created con-cern for the quality of the recreation experi-ence. In response to this concern, a pro-gram of research was initiated to help for-mulate indicators and standards for the car-riage-road experience.

A first phase of research focused onidentifying potential indicators. A survey ofa representative sample of carriage road vis-itors was conducted. Using both open- andclosed-ended questions, visitors were askedto report on what added to or detractedfrom the quality of their experience on thecarriage roads. Two types of indicators wereidentified: one was crowding-related andconcerned the number of visitors seen onthe carriage roads; the other was conflict-related and addressed several “problembehaviors” experienced on the carriageroads, including bicycles passing frombehind without warning, excessive bicyclespeed, people obstructing the carriageroads by walking abreast or stopping ingroups, and dogs being off leash.

The first phase of research also docu-mented existing patterns of use on the car-riage roads and visitor attitudes toward avariety of management alternatives. Thecarriage roads support a diversity of recre-ation opportunities defined both spatiallyand temporally. Some areas and times arerelatively heavily used, while others accom-modate relatively light levels of use. Despitethe problem behaviors noted above, mostvisitors supported maintaining the currentmix of carriage road users—hikers, bikers,

Visitor Impact Monitoring

The George Wright Forum60

and equestrians. Based on these findings,park management decided to maintain adiversity of carriage road experiences byestablishing two types of recreation oppor-tunity “zones” for the carriage roads asdefined by location, time of day, and time ofyear. However, both of these zones wouldcontinue to accommodate all types of visi-tors. The two carriage road zones would bedefined by the same indicators, but differentstandards would be set.

A second phase of research focused onformulating standards for indicator vari-ables. This research also used a survey of arepresentative sample of carriage road visi-tors and adopted normative theory andrelated empirical techniques (Shelby andHeberlein 1986; Vaske et al. 1986; Man-ning 1999). As applied in outdoor recre-ation, norms are generally defined as stan-dards that individuals and groups use toevaluate social and environmental condi-tions in parks and related areas (Shelby andVaske 1991). If visitors have normative stan-dards concerning relevant aspects of recre-ation experiences, then such norms can bestudied and used as a basis for formulatingstandards.

Because of the relatively large numberof visitors on the carriage roads, crowdingwas measured in terms of persons-per-viewscape (PPV), incorporating a visuallybased measurement approach (Manning etal. 1996; Manning and Freimund 2005).The viewscape for the carriage roads (thelength of carriage road that can be seen atany one time) averages approximately 100m. A series of photographs was preparedthat showed a range of zero to 30 visitors ona typical 100-m section of the carriageroads. The photographs were preparedusing digital photo-editing software.Sample photographs are shown in Figure 1.

Visitors were shown the photographsin random order and asked to rate theiracceptability on a scale from –4 (“very un-acceptable”) to +4 (“very acceptable”).Study findings are shown in Figure 2. Thisfigure is called a social norm curve (orimpact acceptability curve) and representsthe aggregate acceptability ratings for thesample of visitors. The norm curve docu-ments the relationship between increasinguse levels and the quality of the visitor expe-rience.

Two other sources of information weredeveloped to help formulate standards forcrowding on the carriage roads. The surveyusing the photographs described above wasadministered to a representative sample ofresidents of communities surrounding thepark, and a computer-based simulationmodel of visitor use on the carriage roads(described in the next section) was devel-oped to provide more detailed informationon the relationship between total daily uselevel of the carriage roads and PPV condi-tions. Based on all of this information, stan-dards were formulated for the indicatorvariable of PPV conditions.

Standards were also formulated for thefour problem behaviors described above.Visitors were asked to report the maximumnumber of times it would be acceptable toexperience each of these behaviors during atrip on the carriage roads. The resultingnorms were used as a basis of formulatingstandards.

After indicators and standards for thecarriage road experience were formulated, asimilar program of work has been conduct-ed in all other major visitor use areas of thepark; indicators and standards are nowbeing formulated for these areas. Examplesof the range of resource and social indica-tors being formulated at Acadia include trail



Figure 2. Social norm curve for PPV on the carriage roads.



1a 1b

1c 1d

1e 1f

Figure 1. Sample study photographs showing a range of visitor use on the carriage roads.

width and erosion, visitor encounters alongtrails, number of visitors at one time atattraction areas, and number of cars on parkroads.

Computer simulation modeling as amonitoring tool

As noted earlier, monitoring indicatorvariables can be time consuming and costly.Moreover, some indicators, like PPV condi-tions along the carriage roads, can be inher-ently difficult to observe. Simulation mod-els offer a potentially attractive alternative toon-the-ground monitoring. Once a simula-tion model is developed, it can be used toestimate the condition of indicator vari-ables.

A simulation model of carriage roaduse was developed in the 1990s (Manninget al. 1998; Wang and Manning 1999; Ja-cobi and Manning 1999; Manning andWang 2005). The model was constructedusing diary reports by visitors of their travelroutes and times along the carriage roadsand counts of the number of visitors enter-ing each of the 11 major access points to thecarriage roads. These and related data wereprocessed using the general purpose simu-lation software, Extend. The model wasdesigned to estimate PPV levels along thecarriage roads and can be run at any dailyuse level of the carriage road system. Thepark’s monitoring program measures dailyuse of the carriage roads through an elec-tronic trail counter and uses the simulationmodel to estimate PPV levels (the crowd-ing-related indicator variable) to ensure thatcrowding-related standards are not violat-ed. Moreover, the model has been used in amore “proactive monitoring” approach(Lawson et al. 2003). The model was run atincreasing levels of daily carriage road useto estimate the maximum daily use level that

can be accommodated on the carriage roadswithout violating crowding-related (PPV)standards. Finally, the model can also beused to facilitate a program of adaptivemanagement (Lee 1993; Stankey et al.2005) by estimating (“monitoring”) theeffects on PPV levels of alternative manage-ment practices, such as redistributing useover time and space and altering the mix ofcarriage roads users (Lawson et al. 2003).

Monitoring recreation on Acadia’s carriage roads

Based on the research described above,several indicators were established for thequality of the carriage road experience,including PPV levels and problem behav-iors. Standards were then formulated forthese indicator variables. For PPV levels,the simulation model of carriage road useestimated that the carriage roads couldaccommodate up to 3,000 visitors per daywithout violating the PPV standards thatwere formulated. Because total daily use ofthe carriage roads was potentially easier tomonitor than PPV levels, this became afocus of the recreation monitoring program.Total daily use of the carriage roads is mon-itored by means of an electronic trail count-er. Over a period of several years, a series ofone-day censuses of carriage road use wereconducted by stationing volunteer ob-servers at each of the 11 major carriage roadentrances. Resulting counts of total dailycarriage road use were correlated withsimultaneous trail counter readings, and astrong correlation was found. Based on thisanalysis, PPV levels are monitored on anannual basis using trail counter readings.Trail counter readings from 1997 through2004 suggest that carriage road use hasremained relatively stable and that PPV-related standards have not been violated.



In addition to the monitoring de-scribed above, actual PPV counts are con-ducted every three years at selected loca-tions and times. An observer records thenumber of visitors on 100-m viewscapes at15-second intervals. These counts help“ground truth” and validate the PPV esti-mates derived from the trail counter andcomputer simulation model.

Monitoring of problem behaviors onthe carriage roads is conducted by means ofa short visitor survey conducted every threeyears. Respondents are asked to report howmany of the four problem behaviors theyhave experienced. Resulting data suggestthat standards are being violated for twoproblem behaviors despite enactment ofseveral management practices (promulga-tion of “rules-of-the-road” for the carriageroads, “courtesy” patrols of the carriageroads, and production of an educationalvideo shown at local bicycle rental shops)designed to address this issue. If data fromthe next monitoring cycle in 2006 suggestthat standards are still being violated, adecision will be made to either take addi-tional management actions to reduce theincidences of problem behaviors (e.g., edu-cate visitors, adopt behavioral regulations,limit carriage road use) or formulaterevised, more realistic standards.

Monitoring resource impactsAcadia National Park visitors partici-

pate in a variety of recreation activities,including driving, boating, hiking, horseriding, and biking, and these activities havean array of effects or “impacts” on naturalresources, including vegetation, soils, water,and wildlife. To date, resource-related mon-itoring and associated research has focusedon hiking and camping impacts to vegeta-tion and soils, including assessments of

undesignated (visitor-created) trails onLittle Moose Island (LMI) and designatedtrails on Isle au Haut (IAH). Research hasbeen directed at selecting appropriate indi-cators of resource impacts and developingprotocols for monitoring these indicators.This work has integrated natural and socialscience studies to yield indicators and asso-ciated standards that are both ecologicallyand experientially meaningful. This workwill be extended to undesignated and desig-nated trails on Mount Desert Island in2007.

The creation and proliferation ofundesignated trails is a common problem inparks that can directly affect sensitive plantcommunities, rare flora and fauna, andwildlife habitats (Leung and Marion 2000).Visitors seeking to access scenic overlooks,water resources, or merely to explore, oftentrample vegetation sufficiently to create ex-tensive informal trail systems. Resource de-gradation on these trails is often severe dueto lack of professional trail design, con-struction, and maintenance. Such un-planned trail networks generally receive noenvironmental reviews, yet they causedirect trampling and resource degradation,habitat fragmentation, and can furtherspread invasive species. While some degreeof visitor impact is unavoidable, excessivetrail impacts threaten natural resource val-ues, visitor safety, and the quality of recre-ation experiences.

On LMI four types of monitoring pro-cedures have been experimentally applied:(1) global positioning system (GPS) surveysof the location and extent of visitor-createdtrails, (2) trail condition class assessmentsbased on vegetation and soil loss, (3) photo-graphic monitoring from permanent GPS-mapped photopoints, and (4) a point sam-pling method with a systematic sampling



interval of 300 ft following a randomizedstart. LMI is a very small, pristine islandlocated off the Schoodic Peninsula and isonly accessible to hikers during low tide.

The GPS and condition class surveysrevealed a surprisingly large network of vis-itor-created trails, totaling 15,618 ft (2.96mi) (Figure 3 & Table 1). While 8,552 ft

(54.8% of the total) were classified as hav-ing impacts that were barely distinguishableor being in a lightly impacted condition(Class 0 or 1), 2,864 ft (18.3%) wereassessed as being heavily impacted witheroded treads (Class 5) (Table 1). Theseprocedures and data illustrate the most effi-cient methods for tracking the proliferation



Figure 3. Trails on Little Moose Island.

and degradation of undesignated trails.Park staff analyzed and employed these datato define a limited subset of 1.09 mi of des-ignated trails, a 63% reduction, that retainaccess to the island’s principal destinationsites. These trails received subtle mainte-nance work to facilitate their use, while 1.86mi of trail were closed to use with brush andsmall trail closure/revegetation signs. Atrailhead sign with a Leave No Trace mes-sage was installed asking visitors to protectsensitive vegetation by staying on the maintrails or rock ledges.

Photopoint monitoring can be easilyadded to GPS surveys to provide a visualdocumentation of changing trail conditions.Park staff purposely identified and tookphotos at 24 photopoints in 2001 and2003, including points along the newly des-ignated trail system and along the trailsidentified for closure. Few changes in vege-tation cover were detectable along the des-ignated trails but photos revealed substan-tial recovery beginning along the closedtrails. Finally, the point sampling surveyprovided additional quantitative transectdata on indicators such as tread width, soilloss, and tread substrates (e.g., percent

cover of vegetation, organic litter, exposedsoil, rock, and roots). This type of data ispresented for illustration purposes in thenext section on IAH.

On IAH two trail condition assessmentmethodologies, the point sampling andproblem census methods, were integratedto provide quantitative data describing con-ditions for several impact indicators. Apoint sampling method with a systematicsampling interval of 500 ft, following a ran-domized start, was the primary method(Leung and Marion 1999b; Marion andLeung 2001). Data assessed for a subset ofthe indicators are reported here, includingtread width, maximum tread incision, and anew, more efficient variable interval methodfor determining cross-sectional area (CSA)of soil loss (see Figure 4). While more time-consuming than maximum incision, CSAprovides an accurate measure of trail soilerosion that can be extrapolated to providean estimate of total soil loss from each trail.

A problem census method integratedinto the monitoring procedures providedcensus information on three specific trailimpact problems: excessive erosion (>5 in),excessive muddiness, and number of infor-



Table 1. Condition class and length of visitor-created trails on Little Moose Island in 1996.

mal trails branching from the formal trailsince the last sample point (Leung andMarion 1999a). As they hiked, field stafflooked for and recorded the beginning andending distances from the starting point forall occurrences of these problems. In con-trast to point sampling, this method pro-vides census data on the extent and locationof specific pre-defined problems, facilitat-ing management efforts to rectify suchimpacts. Both methods can be applied con-currently at an assessment rate of approxi-mately one mile/hour by two surveyors.

All 12 NPS trails on IAH wereassessed; trail length ranged from 0.16 to3.99 mi, with a mean of 1.56 mi and a totalof 20.1 mi. Use data were developed foreach trail based on trail use monitoring anddevelopment of a simulation model of visi-tor use (Manning et al. 2004). Based on nat-ural breaks in the use data, IAH trails wereclassified as low-use (0.3–1.0 encoun-ters/mi), moderate-use (4.0–6.0 encoun-ters/mi), and high use (10.0–11.0 encoun-ters/mi).

Table 2 presents point sampling datafor each trail with summaries by level of trailuse and for the entire island. Results revealincreasing degradation with use level,though conditions on even the high-usetrails are good—which we attribute to rela-tively low use, good design, and durablesubstrates. However, even with a mean max-imum incision value of 1.4 in, estimated soilloss for the entire trail system totals 553 yd3,

which equates to a loss of about 55 truck-loads of soil. Problem assessment data(Table 3) also reveal very few occurrences ofexcessive soil erosion and muddiness, witha lineal extent of only 368 and 292 ft/mi,respectively. These data illustrate the capa-bility of more measurement-based trailassessment protocols that provide quantita-tive data for tracking degradation.Preliminary standards of quality have beenselected for tread width and maximum inci-sion, and monitoring will be replicated toevaluate these approximately every fiveyears.

An associated program of social sci-ence research was also conducted on trail-related impacts at IAH. Trail widening anderosion, visitor-created trails, and vegeta-tion loss affect park resources, but theseimpacts can also degrade the quality of thevisitor experience. At what point do suchimpacts become unacceptable from anexperiential perspective? To help answerthis question, two series of photographswere prepared illustrating a range of recre-ation-related trail impacts on IAH, includ-ing trail erosion and proliferation of visitor-created trails (Manning et al. 2004).Preparation of these photographs was guid-ed by the assessment of trail conditionsdescribed above. The photographs for visi-tor-created trails are shown in Figure 5. Aswith the photographs of visitor use on thecarriage roads described earlier, these pho-tographs of resource impacts were incorpo-



Figure 4. Diagram of the cross-sectional area method (variable intervals) for assessing soil erosion on trails.

rated into a survey of visitors to IAH. Theresulting social norm curve for visitor-creat-ed trails is shown in Figure 6. These andrelated data are also being used to help for-mulate standards for recreation-causedresource impacts.

ConclusionRecreation monitoring is an expand-

ing, evolving, and increasingly importantelement of park management at Acadia.This monitoring program is conductedwithin the context of the NPS VERP frame-work, which requires identification of indi-cators and formulation of associated stan-

dards. Indicators provide a focus for themonitoring program and standards providereference points that inform interpretationof resulting monitoring data and ultimatelyguide management action. Identification ofindicators and formulation of standards isinformed by a continuing program of natu-ral and social science research.

Monitoring of recreation at Acadiaincludes both resource and experientialvariables. The monitoring program, and theresearch upon which it is based, explicitlyrecognize the interrelationships that cancharacterize the resource and social dimen-sions of park and recreation management.



Table 2. Point sampling data for tread width and soil loss.

For example, natural science research helpsdocument the ecological impacts of recre-ation and how these impacts progress overtime, while social science research helpsunderstand the degree to which theseimpacts degrade the quality of the visitorexperience. An integrated program of natu-ral and social science research can helpdevelop a more comprehensive and coordi-nated suite of recreation-related indicatorsand standards.

Recreation monitoring at Acadia isconducted through a combination of field-based measurements (e.g., measures of trailwidth and erosion, direct observation ofPPV levels, visitor surveys), remote sensing(trail counters), and computer simulationmodeling. This combination of methods is

designed to maximize efficiency and pro-vide measures of cross-validation wherepossible.

Recreation monitoring began at Acadianearly 10 years ago, but was relatively nar-rowly focused on the quality of the visitorexperience on the carriage roads.Monitoring has since been extended toother areas of the park and to both experi-ential and resource-related visitor impacts.Ultimately, a suite of resource and experien-tial indicators and standards will be formu-lated for all major areas of the park, andmanagement of recreation use and relatedimpacts will be guided by data derived fromthe park’s program of recreation monitor-ing.



Table 3. Problem assessment data for number of occurrences and lineal distance of excessive soil erosion and muddi-ness.

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