recreational system optimization to reduce conﬂict on public … · 2016-11-10 · recreational...

Recreational System Optimization to Reduce Conflicton Public Lands

Fraser Shilling • Jennifer Boggs • Sarah Reed

Received: 30 August 2011 / Accepted: 18 June 2012 / Published online: 8 July 2012

� Springer Science+Business Media, LLC 2012

Abstract In response to federal administrative rule, the

Tahoe National Forest (TNF), California, USA engaged in

trail-route prioritization for motorized recreation (e.g., off-

highway-vehicles) and other recreation types. The priori-

tization was intended to identify routes that were suitable

and ill-suited for maintenance in a transportation system. A

recreational user survey was conducted online (n = 813)

for user preferences for trail system characteristics, recre-

ational use patterns, and demographics. Motorized trail

users and non-motorized users displayed very clear and

contrasting preferences for the same system. As has been

found by previous investigators, non-motorized users

expressed antagonism to motorized use on the same rec-

reational travel system, whereas motorized users either

supported multiple-use routes or dismissed non-motorized

recreationists’ concerns. To help the TNF plan for reduced

conflict, a geographic information system (GIS) based

modeling approach was used to identify recreational

opportunities and potential environmental impacts of all

travel routes. This GIS-based approach was based on an

expert-derived rule set. The rules addressed particular

environmental and recreation concerns in the TNF. Route

segments were identified that could be incorporated into

minimal-impact networks to support various types of

recreation. The combination of potential impacts and user-

benefits supported an optimization approach for an

appropriate recreational travel network to minimize envi-

ronmental impacts and user-conflicts in a multi-purpose

system.

Keywords Off-highway vehicles � Recreation �Multiple-use � Optimization modeling � Conflict �Public lands

The [National Forest Management Act] NFMA

requires the provision of a broad spectrum of forest

and rangeland-related outdoor recreation opportuni-

ties that respond to current and anticipated user

demands. Specifically for ‘‘off-road vehicle’’ use, the

NFMA requires that these opportunities be planned

and implemented to protect land and other resources,

promote public safety, and minimize conflicts with

other uses of the National Forest System lands.

(Tahoe National Forest 2008)

Introduction

Motorized recreation on public lands has been steadily

increasing over the past 40 years and is a major use of most

public lands in the western U.S. Between 1993 and 2003, the

number of all-terrain vehicles and off-highway motorcycles

in use in the US almost tripled, from 2.9 million to 8 million

(Cordell and others 2005). Although potential impacts of

motorized recreation have been recognized in public policy

(E.O. 11644 1972; Carter 1977) and certain specific impacts

F. Shilling (&)

Departmenrt of Evironmental Science and Policy, University

of California, One Shields Avenue, Davis, CA 95616, USA

e-mail: [email protected]

J. Boggs

The Wilderness Society, Center for Landscape Analysis,

San Francisco, CA, USA

S. Reed

Human Dimensions of Natural Resources, Colorado State

University, Fort Collins, CO, USA

123

Environmental Management (2012) 50:381–395

DOI 10.1007/s00267-012-9906-6

have been well-studied (Adams and others 1982; Bolling and

Walker 2000; Havlick 2002; Iverson and others 1981; Prose

and others 1987), understanding of the cumulative and sys-

tematic impacts of motorized recreation is limited (reviewed

in: Ouren and others 2007). In addition, there are few

examples of the use of environmental impacts analysis in

planning and management of motorized recreation.

Recreational trails on public lands in the U.S. are man-

aged under the multiple-use paradigm (Multiple-Use Sus-

tained Yield Act) and the National Forest Management Act

(NFMA; 16 U.S.C. §§ 528–31, 1600–14). These Acts

require that all land uses, even competing ones, be accom-

modated on National Forests, while at the same time

maintaining the overall integrity of forest ecosystems and

associated human benefits. When applied to recreation, the

presumption for multiple-use management is often that

motorized and non-motorized users can be accommodated

on the same trail system on a given Forest. However, con-

flicts among users are possible, especially when many users

are restricted to a limited trail system. Recreational groups

may experience ‘‘asymmetric conflict’’, where one party

(i.e., non-motorized recreationists) receives greater impacts

and is more distressed by sharing trail systems than another

(i.e., motorized recreation; Adams and McCool 2009;

Knopp and Tyger 1973; Vaske and others 2007). These

conflicts include direct disturbance of non-motorized

recreationists by motorized vehicle users, disturbance of

wildlife by motorized recreation which reduces wildlife

viewing opportunities, the perception among motorized

recreationists that others want to limit their access to trails,

and the opinion of many non-motorized recreationists that

motorized vehicles should be banned from public lands that

they use. Conflict may also occur among motorized recre-

ation groups (Albritton and Stein 2011). Conflicts like these

are common under the multiple-use paradigm, leading to

legal action to restrict activities (e.g., Colorado Off-High-

way Vehicle Coalition vs. United States Forest Service and

others 2004) and ‘‘gridlock’’ among competing interests

(Cawley and others 1997). These conflicts can be situated

within a theoretical structure of recreational conflict, where

various individual attributes, values, and activity modes

combined with physical spaces that increase the likelihood

of inter-group interaction can result in varying potentials for

inter-individual and inter-group conflict (Jacob and Schre-

yer 1980). Overall conflict may be a result of interpersonal

conflict, or of social values conflict (Vaske and others 2007).

In addition to conflict, trail-space limitations can lead to

crowding and reduced recreational goal achievement both

within and among recreational group types. There have been

attempts to bring computational modeling to bear to aid in

crowding reduction (e.g., Lawson and others 2006), but so

far no spatial modeling approach has been broadly adopted

by public lands managers for recreational trail planning.

In the late 1970’s, the USFS developed a system for land

managers, in part to balance sometimes competing recrea-

tional needs on limited public lands called the Recreational

Opportunity Spectrum (ROS, Clark and Stankey 1979). The

ROS defines recreational experience as being a combination

of the recreational activity and the setting. It further

decomposes the recreational experience into six activities,

with associated land classes: primitive; semi-primitive, non-

motorized; semi-primitive, motorized; roaded, natural;

rural; and urban (More and others 2003). Central to the

implementation of the ROS are two principles (1) its use of

the human experience of recreation and (2) impacts from

recreation on people and environment in rational and spa-

tially-explicit planning of activities, sometimes in restricted

locations and extents (Clark and Stankey 1979; More and

others 2003). The importance of the ROS to the USFS is

emphasized by the fact that its use is required for the

development and operation of trails (section 2353.14; For-

est Service Manual 2008), though historically, understand-

ing and acceptance of the ROS by field staff determines its

actual application (Stankey and others 1986). It is not clear

whether or not this situation has improved. In the current

project, the Tahoe National Forest used the language of the

ROS during planning of the optimization model, and we

applied ROS principles to frame our analyses of recreational

experiences and impacts to cover the spectrum of activities

in a spatially-explicit system.

Environmental effects of motorized and non-motorized

trail use are varied and include impacts to wildlife, plant

growth and succession, rates of erosion, weed invasion, and

archaeological sites (Adams and others 1982; Arp and

Simmons 2012; Brattstrom and Bondello 1983; Davidson

and Fox 1974; Iverson and others 1981; Ouren and others

2007; Wilshire 1983; Yarmoloy and others 1988). Motor-

ized vehicles include four-wheel drive automobiles (4WD),

all-terrain vehicles (ATVs or ‘‘quads’’), and motorcycles

(hereafter collectively called ‘‘off-highway vehicles’’,

OHV). These vehicles are rarely muffled and generally have

knobby tires. They produce more sound than street vehicles

and are thus thought to be a source of disturbance to wildlife

in forests and grasslands (Barton and Holmes 2007; Ouren

and others 2007). The combination of knobby tires and trail

position on steep slopes and near streams can result in

impacts to hydrologic connections to waterways, excess

compaction (Adams and others 1982), geomorphic impacts

to channels and wetlands (Arp and Simmons 2012), and

erosion (Iverson and others 1981). There are a variety of

other impacts that OHVs cause, including increased weed

invasion (Benninger-Traux and others 1992), degraded

habitat (Havlick 2002), and declines in the abundance

and survival of rodents, reptiles and birds (Brooks 1999;

Luckenbach and Bury 1983). Furthermore, OHVs allow

more visitors to travel further into the interior of public

382 Environmental Management (2012) 50:381–395

123

lands, thereby expanding the spatial extent of recreation

impacts. Non-motorized recreation also causes direct

impacts to trails and surrounding areas. For example, pro-

tected areas open to biking, hiking, and horseback riding

have fewer native carnivore species than areas closed to any

recreation (Reed and Merenlender 2008; Reed and Meren-

lender 2011). Behavioral responses (i.e., disturbance) by

wildlife to hikers and bikers can occur up to 400 m from

trails and is highly likely within 100 m of trails (Taylor and

Knight 2003). In addition, most recreation groups tend to

think that other groups are responsible for these kinds of

disturbance rather than their own group (Taylor and Knight

2003).

These environmental effects and others have led to

increased attention to and regulation of motorized recrea-

tion vehicle use on public lands, culminating in the federal

Travel Management Rule (TMR) of 2005 (36 CFR 212.55).

Prior to 2005, in most U.S. National Forests, off-trail or

‘‘cross-country’’ travel was permitted anywhere in a forest

that did not explicitly prohibit the use of motor vehicles.

The TMR requires USFS land managers to engage in a

planning process to designate an official motorized recre-

ation system in every National Forest, locating routes

suitable for motorized recreation so as to minimize envi-

ronmental impacts and conflicts among recreational users.

As pointed out in Vaske and others (2007), recreational

geographers and others have been studying conflict among

recreation group types for over 40 years, on trail systems

that have multiple uses. Recent advances in conflict

reduction have been made using GIS tools combined with

surveying of motorized recreationists in order to identify

geographic zones of conflict between groups that experi-

ence interference of their enjoyment by other motorized

groups (Albritton and Stein 2011). There have also been

suggestions that collaborative planning among stakeholders

could be used to find optimal solutions for recreational

system management (Asah and others 2012). This

approach is based on the premise that it is both necessary to

include all competing interests in policy implementation

(e.g., the TMR) and public lands management and suffi-

cient to include these interests if the goals are to reduce

conflict and improve system management. Asah and others

(2012) demonstrated that it is possible to find conceptual

agreement among competing interests within a structured

study, suggesting that conflict reduction can occur with

sufficient investment in process and careful implementa-

tion. However, when dealing with recreation across all

public lands units from a policy and analytical perspective,

it is worth considering spatial modeling of exclusive trail

systems on public lands as a strategy for conflict resolution,

during mandated route assessment and planning under the

TMR. The TMR planning process would also benefit from

evaluating and minimizing potential damage caused by

OHVs to natural systems.

The purpose of the present study was to provide a case

study for recreational system planning on public lands

combining: (1) spatial analysis of potential damage to

specific environmental values with (2) spatially optimizing

a trail system to provide reduced-conflict recreational

opportunities for both non-motorized and motorized users,

using the Tahoe National Forest (TNF), California, as a

model system. Our modeling approach was based on a

comprehensive trail-user survey, TNF staff’s collective

expertise about locations and types of recreational uses and

associated effects, and published studies of recreation

impacts on the environment. The trail-user survey provided

useful information about recreational groups’ opinions

about both the recreation system and other recreational

users, and it revealed important conflicts between motor-

ized and non-motorized recreationists. Finally, we present

an optimized system of trails designed to meet the recre-

ational needs of motorized users, while limiting both

environmental impacts and conflict with non-motorized

users. This method is a model for implementing the TMR

in a way that designates routes to minimize environmental

impact and reduce conflict among recreation types.

Methods

Study Area

The Tahoe National Forest stretches from the foothills of the

western slope of the Sierra Nevada (California, USA) to the

high desert ecosystem of the eastern slope of the range. Land

cover is primarily mixed hardwood conifer, closed-cone

conifer, alpine, and barren. Hundreds of native vertebrates

have habitat in the Forest, including many species with legal

protection. The Forest includes 522,359 Ha of land and

8,233 km of roads, of which 333,954 Ha of land and

4,249 km are public lands and roads and the remainder pri-

vate in-holdings and roads (Fig. 1). It also contains 1,223 km

of authorized and 2,253 km of unauthorized motorized rec-

reation trails. Recreational users often make use of both

unpaved roads and trails within an excursion, and hereafter

we refer to trails and roads used for recreation as ‘‘routes.’’

There are approximately 1.6 million person-visits to the

Forest each year for recreation, 35% of which are for skiing

and 8% for snowmobile riding (USDA Forest Service 2006).

Survey of Recreational Users

An online survey was used to query trail users in the TNF

about their route system preferences, experiences, and

Environmental Management (2012) 50:381–395 383

123

feedback about overall recreational route management.

They were asked which of 6 main types of activities they

engaged in: Four-wheel drive passenger vehicle (henceforth

‘‘4WD’’), four-wheel motorcycle (henceforth ‘‘quad’’), two-

wheel motorcycle (henceforth ‘‘motorcycle’’), bicycling

(primarily mountain biking), hiking, and horseback riding.

The questionnaire addressed the following concepts: where,

how often, and what type of recreation was preferred; what

physical route and environmental properties were preferred;

how they would rank their experience and what could be

done to improve their experience; and their age, gender, and

zip code. An example of a key question for developing the

‘‘trail benefits’’ analysis in GIS was: ‘‘When occupied with

your favorite recreation on the Tahoe National Forest, rank

from 1 to 4 (1 = highest) which of the following qualities of

the trail system you think are the most important?’’, which

was followed by a list of 9 factors. TNF hosted the survey for

30 days (April, 2006) using an online service and advertised

its availability to recreational users via contact lists of

people interested in Forest management, recreational inter-

est and environmental groups, and others. Because there was

no attempt to develop a random survey design and control

responses to the survey, the results should be viewed as an

opportunistic sampling of opinions about the recreation

system within recreational-user groups. The primary appli-

cation of the survey results in this study was in developing

the ‘‘route benefits’’ component of the GIS-based route

optimization model (Fig. 2b).

Environmental Impacts Knowledge Base

A knowledge base is a representation of our knowledge

about how a system works, or the interaction among ideas

that together compose a larger idea or goal. The software

Netweaver (http://rules-of-thumb.com) was used here to

generate a hierarchical knowledge base based on the con-

cept ‘‘route segments sustainably meet recreational goals

while minimizing environmental impact’’, which was

developed by the TNF-Inter Disciplinary Team (IDT,

Fig. 2) and was similar to that used by the TNF for roads

analysis (Girvetz and Shilling 2003). Netweaver is an

object- and network-based modeling system, which uses

fuzzy logic to evaluate evidence for propositions repre-

sented in its network structure. The goal statement was di-

saggregated in the knowledge base into two main concepts

– potential environmental impact and potential benefits to

recreation (Fig. 2). Each of these concepts was in turn

broken down into sub-concepts until each could be linked

to spatial data. The ‘‘environmental impacts’’ concept

(Fig. 2a) was populated with sub-concepts from the scien-

tific literature on recreational impacts. The ‘‘route benefits’’

concept (Fig. 2b) was populated with sub-concepts drawn

from the results of the trail-user survey. The knowledge

base was used to combine spatial data corresponding to

specific environmental features and potential impacts and to

balance potential environmental impacts with recreational

planning objectives.

Fig. 1 Study area map. The

Tahoe National Forest,

including highways, roads, and

trails. Inset: The position of the

Tahoe National Forest in

California


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http://rules-of-thumb.com

Fig. 2 a Knowledge base of contributions of various environmental

conditions to the concept ‘‘environmental impact’’. Rectanglesindicate concepts, circles indicate Boolean logic operators, and

rounded rectangles indicate sources of environmental data. b Knowl-

edge base of contributions of various trail conditions to the concept

‘‘trail benefits’’


123

Spatial Data and Data Processing

Spatial data representing natural and infrastructural fea-

tures were obtained from TNF and the California Depart-

ment of Forestry and Fire Protection-Forest Resource

Assessment Program (FRAP). The data types are indicated

in the knowledge base (Fig. 2). A transportation database

developed by TNF GIS staff in 2006 included the locations

of all authorized and unauthorized roads and trails

(1:24,000; hereafter, routes), descriptions of route status

(open or closed), and route width. Unauthorized routes are

also called ‘‘user-created’’ routes and are features created

by unknown users of the TNF without authorization from

the US Forest Service. TNF staff provided zone and route-

specific recreational-use information from Ranger District

recreation managers. This information was collected using

a standardized questionnaire and set of maps. Managers

were asked to indicate areas and routes that had low,

medium, or high use for each of the following types of

recreation: 4WD, quad, motorcycle, bicycle, hiking, and

horseback. Their feedback was included as route-specific

attribute information in the routes database.

Four main types of geo-processing were conducted to mea-

sure environmental conditions associated with route segments:

Distance to Feature

Many of the rules developed by the TNF staff related to

distance from routes to valued cultural and environmental

features. Valued features included heritage sites (archaeo-

logical, historical, cultural), streams and riparian areas;

wetlands; bald eagle, goshawk, and California Spotted Owl

nests and activity centers; old-forest areas; Lahontan cut-

throat trout streams; roadless areas; and deer wintering and

fawning areas. Raster datasets (10 m cell size) of Euclidean

distance were calculated from each type of feature.

Landscape Attribute

Certain of the rules developed by the TNF staff related

directly to a landscape attribute (e.g., slope, or land-slide).

Digital maps composed of polygons representing different

attributes of the landscape were converted to grid maps

using ArcGIS 9.1. The attributes converted to grid maps

were weed occurrences, route density, patch density, rare

plant occurrences, adjacent vegetation, route slope posi-

tion, precipitation, and slides and mass-wasting.

Route Segmentation

The original routes database contained line segments ranging

from*0.1 m to more than 50 km in length. Because this range

was too large to effectively attribute environmental conditions

to individual segments, all route segments were divided into

smaller segments with a maximum length of 300 m.

Data Attribution

The average value of each distance or landscape attribute

grid was attributed to each route segment. The resulting

routes database included a field for each potential envi-

ronmental impact and other concern and this was used as

the basis for the Ecosystem Management Decision-Support

(EMDS) model.

Spatially-Explicit Goal Modeling

We combined geographic data using the software program

EMDS (Reynolds and others 1996; Reynolds 1999a, b;

http://www.institute.redlands.edu/emds/) to evaluate the

contribution of individual route segments to recreational

and environmental goals. The routes database containing

fields for each environmental and cultural resource concern

was used as the base data for the knowledge base. Each

data link in the knowledge base was associated with a

corresponding field in the route map attribute table. EMDS

helps resource managers make informed decisions about

landscape processes and land management (Girvetz and

Shilling 2003; Reynolds and others 2000; Shilling and

Girvetz 2007). The system is based on principles of fuzzy-

set membership, meaning that it can account for interme-

diate values relating to assertions about states and pro-

cesses in nature, thus better reflecting how natural systems

work.

EMDS interprets and synthesizes ecological attributes,

condition, risk, etc., from geographic maps using a logic

model that translates observed data into continuous mea-

sures of strength of evidence (hereafter, just evidence).

EMDS 3.1 links the GIS program ArcGIS8.3 (ESRI) with

the logic-modeling program Netweaver (Saunders and

others 1990). EMDS provides Netweaver with the neces-

sary GIS base data for combining together, based upon

user-defined logical rules to determine evidence for prop-

ositions, also called a ‘‘truth value’’ (Reynolds and others

1996; Reynolds 1999a, b). Propositions are statements to

be tested by topics in the network structure (that is, a topic

is a network object responsible for testing a proposition).

An example of a proposition is ‘‘the slope is erodible’’;

examples of topics for this proposition include slope

steepness, slope length, soil type, vegetation type, and

precipitation. Evidence for propositions and their topics are

combined using OR and AND Boolean logic operators.

The OR operator returns the evidence for its strongest

premise. Thus, for the OR operator, if only one topic within

a proposition is fully satisfied (evidence = 1.0), the entire


123

http://www.institute.redlands.edu/emds/

proposition is considered satisfied, even if all its other

premises provide no evidence (evidence = -1.0). The

AND operator is used to combine topics, when all topics

must be fully satisfied to fully support the proposition. The

AND operator combines the evidence of multiple premises

based on the formula:

AND t1; . . .; tnð Þ ¼ min t1; . . .; tnð Þ þ�average t1; . . .; tnð Þ

�min t1; . . .; tnð Þ �� ½min t1; . . .; tnð Þ þ 1�=2

where t1 to tn are the evidence of n premises being com-

bined. Thus, an AND-based proposition is completely

unsatisfied (evidence = -1) if any of its topics are com-

pletely unsatisfied and only completely satisfied (evi-

dence = 1) if all of its topics are true. A useful way to

understand the AND operator is that it treats its underlying

set of topics as limiting factors.

After the EMDS model run, truth values for environ-

mental conditions were associated with the routes database

attribute table. Each feature or landscape attribute in the

knowledge base had a corresponding truth value field, and

truth values were calculated for each route segment. These

values were used in later calculations of environmental

impact and to create optimized route networks. Truth val-

ues for environmental impact were composed of multiple

attributes, combined using the model’s logic rules.

Scenarios

Model scenarios were run for each of the 6 types of rec-

reation opportunities: 4WD, quad, motorcycle, bicycle,

horse, and hiking. Each scenario run resulted in a different

recreation opportunity truth value finding for route seg-

ments. In each scenario, the potential environmental

impacts were assumed to be similar. Within each recrea-

tional scenario, route benefits were combined with poten-

tial environmental impacts using the Boolean AND

operator. This calculation provided a direct objective

measure of the ability of each route segment to meet the

combined requirements of maximizing recreational

opportunity, while minimizing environmental impact.

The model output consisted of normally-distributed

values for the higher order primary knowledge base con-

cept: ‘‘Route segments sustainably meet recreational goals

while minimizing environmental impact’’. This concept

was the product of an AND relationship between the sub-

concepts: ‘‘Environmental impact’’; and ‘‘Trail benefits’’

(Fig. 2). The high values in all cases corresponded to a low

environmental impact and high-value recreational route,

the low values corresponded to a high environmental

impact and low-value recreational route. ‘‘High value’’

recreational routes are defined as meeting user preferences

as found in the recreational use survey and from TNF

staff’s expert opinion. The higher order concepts contain

multiple sub-concepts and can guide larger decisions about

route systems. Because each higher order concept is an

aggregate of lower order concepts (Fig. 2), the recreation

planner or land manager can use the knowledge base to

‘‘drill down’’ in the model output attribute table to find out

why a particular segment received a relatively high or low

score. The combination of mapped potential environmental

impacts and trail user preferences for each recreation

activity type was then used to develop guidelines for

overall system planning and to make recommendations to

TNF route designation staff.

Route System Optimization

There is no software currently available to automate the

selection of recreation routes on a landscape in order to

optimize recreational experience opportunities, while

minimizing environmental impact. In particular, the desire

expressed by motorized and non-motorized visitors for

looping paths makes automated optimization difficult for

multiple starting and end points. Here, we demonstrate two

methods for approximating an optimized route system that

maximize recreation opportunity and minimize potential

environmental impact. In both cases, the goal was to derive

an optimized route system that met recreational demand for

motorized recreation, while minimizing conflict with

impacts on the environment and potential for conflict with

non-motorized recreationists.

Data collected for the USFS National Visitor Use

Monitoring program (NVUM) indicates that between 3.7

and 7.3 % of visitors to the TNF were engaged in ‘‘OHV

Use’’ as a primary activity or ‘‘Motorized Trail Activity’’

as a general activity, respectively (USDA Forest Service

2006). The NVUM also describes 26.9 % of visitors using

routes in non-motorized recreation as a primary activity

and 50.3 % of visitors engaged in hiking, biking, fishing,

wildlife viewing, backpacking, camping, and other non-

motorized recreation in general. Because, at most, 7% of

recreationists in the TNF use wheeled, motor-powered

vehicles (e.g., 4WD, quads, motorcycles; USDA Forest

Service 2006), we constructed each motorized recreation

route system on a corresponding proportion of the TNF

transportation system: specifically, 7% of the existing trail

and dirt road network. We chose this approach because it

was the most parsimonious way to determine a threshold

for sharing a system where there is conflict among groups,

although we acknowledge that other factors could be

considered (e.g., average distance of trail traveled by a

visitor in each recreational user group).

Manual Selection: Because there was no suitable auto-

mated alternative available to optimize a route network


123

with multiple loops, routes were selected by hand within

the GIS—‘‘manual selection’’. The output from the mod-

eling of potential environmental impact was used as the

basis for manually selecting routes that had the lowest

environmental impact in contained, looping networks

around six motorized recreation trail-head facilities in the

TNF: China Wall/Parker Flats, Big Trees, Prosser, Sterling

Lake, Washington Overlook, and Eureka Diggins. By

selecting motorized recreation trail-heads as the core of the

optimized system, we made the assumption that concen-

trating motorized recreation use in certain areas that were

familiar to users and that were not near non-motorized

recreational areas, conflict could be minimized.

For each trail-head area, route segments were manually-

selected on-screen at 1:24,000 from the TNF route network

that had the lowest potential environmental impact. The

segments were selected so that they avoided environmental

harm and provided for looping routes and routes that

accessed more remote areas. The final systems were ana-

lyzed for minimization of environmental harm relative to

the entire set of roads and trails.

Cost-Distance Modeling: This consisted of automated

calculation for each route segment of the combined dis-

tance from the same six motorized recreation trailheads and

environmental impact of all route segments. These values

were used to illustrate routes that could meet combined

needs of trailhead access and minimized environmental

impact. We used Path Distance analysis in ArcGIS Spatial

Analyst and converted the path distance value back to the

poly-line route network file. Path Distance calculates the

least accumulative cost to the nearest point from a given

source taking into account surface distance, and the cost of

traveling across that point, modeled as the environmental

impact value (range 0.5–1.5) multiplied by the travel

distance.

Results

Survey of Recreational Users

During the one month the online survey was available, 813

recreational trail users responded. Of these, 49 were from

outside California and 40 did not provide zip codes. The

respondents were asked to describe their recreational

preferences and other uses of the route system. Not all

respondents answered all questions. Based on their indi-

cation of their ‘‘favorite type of recreation’’, respondents

were roughly split between motorized (n = 444) and non-

motorized (n = 325) recreation types, with the largest

groups being 4WD vehicle drivers (n = 294) and hikers

(n = 209).

Recreation frequency varied slightly by type of recrea-

tional activity, and among all respondents, monthly recre-

ation was the highest (54 % of respondents), with weekly

(21 %), annually (19 %), and daily (6 %) frequencies

ranking lower. Age distributions were different among

recreation types, with a greater representation of older age

classes for hikers and horseback riders and a greater rep-

resentation of younger and middle age classes for motor-

ized recreation. Similarly, gender distributions varied by

recreation groups, with horseback riders and hikers having

greater proportions female respondents than motorized

recreation.

Conflict Among User Groups

None of the survey questions asked explicitly whether or

not the respondents were opposed to multiple recreation

types using the same route system. However, two open-

ended questions in the survey provided an opportunity for

respondents to indicate ways that the TNF could improve

the route system. Seventy six percent of non-motorized and

79% of motorized recreationists responded with text com-

ments. Of those respondents including text comments, 63%

of non-motorized recreationists reported conflict with

motorized recreationists, and 4% of motorized recreation-

ists reported conflict. Hikers and horseback riders reported

conflict at higher rates than all other recreation types.

Conflict statements from non-motorized recreation respon-

dents often included sentiments like: ‘‘No motorized vehi-

cles allowed period’’. Conflict statements from motorized

recreation respondents were similar, but rarely suggested

banning non-motorized recreation: ‘‘Seperate [sic] the

hikers from the off highway adventures’’.

Respondents also used the open-ended questions to

voluntarily report their positive or negative feelings about

multiple-uses of recreational route systems. Almost half of

hikers and almost two-thirds of horseback riders were

opposed to multiple uses of the route system by motorized

and non-motorized recreation (Fig. 3). In contrast, very

few motorized recreationists opposed multiple-uses of the

route system. For the 9 % of all respondents who supported

multiple-uses, motorized recreation respondents were twice

as likely to support multiple-uses as non-motorized

(Fig. 3). Older recreationists were more likely to report

conflict and oppose multiple uses of the route system than

younger respondents.

There were several ‘‘cut-and-paste’’ comments in the

survey, exclusively from respondents who identified them-

selves as motorized users. This indicates that the online

survey URL was likely passed along among groups with

access to a common set of responses. The following are the

more prevalent among the survey responses, quoted verba-

tim: ‘‘Develop new OHV and 4x4 trails’’ (n = 21);


123

‘‘Increase dispersed camping opportunities’’ (n = 29);

‘‘Provide additional structure parking for OHV [and/or]

equestrian support vehicles’’ (n = 45); and ‘‘Balance use by

trail miles, not just by acreage. A healthy forest acre has huge

opportunity for campers, hikers, bird watchers’’ (n = 17).

Model Outputs

The EMDS model provided 3 main findings that can be

applied to design an optimal recreation system for TNF. The

first was an estimate of the potential recreational opportunity

for each of the 6 recreation types. The second was an esti-

mate of the potential environmental impact of each segment

in the route network, including dirt roads, authorized trails,

and unauthorized trails. The third provided an estimate of

management sustainability from the combined potential

environmental impacts and recreation benefits. This com-

bined cost-benefit output (where cost = environmental

impact) would allow a recreation planner to design a route

system that meets the combined social and statutory

requirements of accommodating forest users’ needs while

minimizing environmental impacts. Because one of these

outputs was developed for each recreation type, recreational

planners could develop an overall system that also mini-

mized conflict among user groups through sub-sets of trails

for recreation groups. In each case of modeling environ-

mental impacts or recreational benefits, the values provided

in this section are relative to each other. In other words

‘‘high impact’’ of a trail segment means high relative impact

compared to potential impacts of other segments of the trail

system. Because of the wide range of benefits and impacts in

the system, we suggest that low and high relative model-

values are similar to actual values.

Benefits for recreational use were modeled based on 8

spatial data sources for all 6 non-winter recreational user

types and results are shown separately for motorized and

non-motorized uses (Fig. 4a, b). The values are normally

distributed across the range from 0 (low use) to 1.0 (high

use). However, there was a strong spatial concentration of

high recreation benefit values on the eastern side of the

Forest, where route systems and facilities have been more

developed for motorized recreational use.

Based on the 22 datasets of environmental conditions

and the knowledge base defining their contributions to

environmental impact (Fig. 2a), the potential environ-

mental impact of each dirt road and trail segment was

modeled (Fig. 4c). The distribution of values was normal

across the range from 0 (high impact) to 0.87 (low impact),

and the low and high values were relatively evenly dis-

tributed across different parts of the Forest.

The outputs of the models for potential environmental

impacts and recreational benefits were combined to iden-

tify routes that had low potential environmental impact and

high recreational benefits and were thus more sustainable

and preferable in the long-term. Results are shown for the

top quartile of routes for all motorized recreation combined

(Fig. 4d). The truth values for the combined output were

normally distributed across the range from 0 to 0.90. There

was some spatial concentration of preferable routes across

the Forest, with higher values—indicating a lower envi-

ronmental impact and greater recreation opportunity—

more concentrated in the eastern side of the Forest.

Optimizing Route Systems to Minimize Impact

and Maximize Recreation

Manual Selection

Six optimal networks were delineated for the TNF, one for

each OHV staging area (Fig. 5a). Each proposed network

Fig. 3 Proportions of

participants engaged in different

recreation types reporting

conflict and support or

opposition to multiple-use of

trails


123

was analyzed for the potential environmental impact of its

component route segments. On a per-segment basis, the

recommended routes had overall lower environmental

impact than the existing system (Fig. 5b). In addition,

because the recommended route network had only 7 % of

the total distance of the existing transportation system—

603 km of routes compared to 8,713 km of authorized and

unauthorized roads and trails available for recreation—the

net environmental impact of the combined recommended

route systems was much lower than that of the existing

system (Fig. 5c).

Cost-Distance Modeling

An alternative approach that can further assist in the

manual selection of looped networks to meet route

Fig. 4 a Trail benefits of routes for mixed non-motorized recreation and b mixed motorized recreation. c Environmental impact of routes

according to the EMDS model. d Management sustainability of routes for motorized recreation according to the EMDS model


123

optimization goals is the use of ‘‘cost-distance’’ modeling,

where cost is the product of travel distance and potential

environmental impact (Fig. 6). Using an OHV staging area

as a starting point, the combined cost-distance was calcu-

lated for each route segment around each of 7 trail-heads

and staging areas in the TNF. This allows a manual selec-

tion of routes based on the efficiency of the system through

a combination of travel distance from the trail-head (indi-

cated with a circle) and potential environmental impact.

Discussion

Spatial Optimization

According to Executive Order, designated routes under the

TMR must meet the following requirements: ‘‘the

responsible official shall consider effects on National

Forest System natural and cultural resources, public

safety, provision of recreational opportunities, access

Fig. 5 a Selected route networks around motorized recreation access

points in the TNF. The background is the TNF administrative lands in

gray, with private in-holdings shown in white. b Proportion of all

routes and selected routes in each environmental impact category

from high impact (0.00) to low impact (1.00). c Combined lengths of

all routes and selected routes in each environmental impact category

from high impact (0.00) to low impact (1.00)


123

needs, conflicts among uses of National Forest System

lands, the need for maintenance and administration of

roads, trails, and areas that would arise if the uses under

consideration are designated; and the availability of

resources for that maintenance and administration.’’

(TMR, § 212.55(a)) The main finding from the present

study was that collaborative modeling with a USFS Rec-

reation Inter-Disciplinary Team could provide a National

Forest with the tools to develop a potential environmental

impacts analysis for the entire route network, a recrea-

tional benefits analysis, and an optimized recreational

route system that could reduce conflict. We were also able

to combine the impacts and benefits into a whole recrea-

tion system analysis that was effectively a cost-benefit

accounting, consistent with requirements of both the

federal Travel Management Rule (TMR) and the National

Environmental Policy Act. This approach also allowed

for estimation of cumulative effects and through optimi-

zation of the network, a demonstration of cumulative

effects minimization and minimization of user-conflict.

Previous studies have used the least-cost path analysis

approach for forest road system optimization (Girvetz

and Shilling 2003) and for single motorized recreation

route optimization (Snyder and others 2008). An impor-

tant advance in this area would be the development of a

recreational route-network optimization approach in GIS

that minimized environmental impact and user conflict,

while providing some reasonable level of recreation

opportunities.

The important contribution that this analysis makes is that

it is possible to minimize environmental impact and provide

mixed recreational opportunities within the same overall

system. If the recommended motorized route networks were

implemented, the net result should be an efficient system in a

compact area to limit impacts to surrounding natural systems

and non-motorized recreation. The recommended, opti-

mized system is also more manageable from a maintenance,

administrative, and law enforcement point of view because it

is limited to * 600 km of trails and dirt roads, which seems

appropriate, based on the dollar values for cost per mile of

trails and dirt roads ($1,500-$5,770/mile) and the amounts of

funding available for at least roads maintenance described in

the TNF-DEIS (Vol. 3, 2008). The TNF estimated that

motorized recreation costs approximately $23–$28 million

annually in terms of road and trail maintenance, whereas the

roads-maintenance budget for 2007 fiscal year was $1.2

million,*5 % of the amount needed. Management action to

resolve conflict has not been forthcoming in the TNF and

other Forests, possibly because, federal agency officials

reported that they ‘‘cannot sustainably manage their OHV

route systems’’ (GAO 2009). A reduced motorized routes

system would be more sustainably managed and reduce

conflict between motorized and non-motorized user groups.

User Conflict

Conflict among out-door recreational groups can take many

forms; Jacob and Schreyer (1980) posited that there are 4

Fig. 6 Least-cost paths

originating from motorized

recreation trail-head and staging

area (‘‘Parker Flat’’), where cost

is a combination of

environmental impact and

distance


123

main classes of factors that could produce conflict: activity

style, recreational resource specificity, mode of recrea-

tional experience, and lifestyle tolerance. The potential for

these factors to result in conflict increases as the rate of

encounter among recreation group type increases (Jacob

and Schreyer 1980). The recognition that conflict among

uses be considered and presumably kept to a minimum

through spatial separation of activities has a long history in

recreational management by the US Forest Service (Clark

and Stankey 1979). This philosophy derives from the

highly varied patterns of recreational behavior and recre-

ationist demographics in National Forests (Chavez 2001).

One assumption of the public and land managers is that

these varied patterns and activities can co-occur under a

multiple-use model. This may be true, but if conflict occurs

or is perceived, then land managers have a responsibility to

minimize it through system and activity management.

As demonstrated here, conflict among users of the Tahoe

National Forest is perceived to be high by non-motorized

route users, but not by motorized users. Approximately

one-quarter to half of all hikers and horseback riders

reported significant conflict with motorized recreation and

about half opposed multiple-use of route systems. In con-

trast, very few motorized recreationists reported conflict or

opposed multiple-use. Although users were not asked the

reason for the perception of conflict, it seems likely that

interactions between motorized and non-motorized users

on the same route will have a greater effect on the non-

motorized users. These findings are critical for 3 reasons:

(1) According to the National Vehicle Use Monitoring

study conducted by the US Forest Service (USDA Forest

Service 2006), the vast majority of TNF recreationists are

not motorized recreationists, but instead are hikers, walk-

ers, bird-watchers, campers, anglers, and equestrians. (2)

People engaging in non-motorized recreation are signifi-

cantly impacted by motorized recreation because of sound

and safety issues, whereas motorized recreationists repor-

ted no impacts and may suffer few disadvantages from a

mixed use system. (3) Multiple-use at the route-scale (as

opposed to whole Forest scale) is a management option that

conflicts with the needs of the majority of users of the

Forest. If this option is failing, then other options should be

explored to meet the requirements of the National Forest

Management Act, the Travel Management Rule, and the

National Environmental Policy Act. One such option is the

establishment of defined ‘‘Motorized Recreation Areas’’

that can be managed to reduce conflict with non-motorized

recreation, allow multiple-use of the Forest, but not each

route, allow effective law enforcement, be affordable with

current maintenance allocations, and reduce overall envi-

ronmental impact. The proposed networks in the present

study would be one way to effectively reduce conflict,

while also providing sufficient motorized recreational

opportunities and minimizing environmental harm. By

decreasing the likelihood of encounters among recreation

groups, Jacob and Schreyer’s (1980) conflict factors are

less likely to result in actual conflict.

Success of Application of the Travel Management Rule

In an exhaustive review of the social and legal aspects of

TMR implementation, Adams and McCool (2009) suggest

that ‘‘the agencies need to do their best to imagine the best

possible arrangement of ORV routes, rather than simply

tinkering around the edges of the current allocations.’’ The

Tahoe National Forest has been preparing a management

response to the federal TMR since 2006 by designating

routes and preparing a ‘‘Motor Vehicle Use Map’’. It was

once one of the leading forests in California in this effort,

but was the last to complete its Final EIS (http://www.fs.fed.

us/r5/routedesignation/statusreport/report042010.html), partially

in response to receiving [3,000 scoping comments and

[7,000 comments on the draft EIS. A possible cause for the

delays and comments is that, contrary to the goals and

requirements of the TMR, the plan for motorized recreation

management available for public input (Tahoe National

Forest 2008) failed fundamentally to deliver a low-impact

motorized route alternative. One reason for this is that under

the proposal analyzed in the DEIS, the existing route system

remains substantially un-modified, motorized recreation

routes were added in almost all alternatives, and the DEIS did

not consider the individual and cumulative effects of routes

used for motorized recreational and other vehicular travel.

For example, under DEIS preferred alternative B, routes pass

through streams, wildlife nesting and foraging areas, and

meadow areas. In addition, despite impacts to wildlife being

one of the primary concerns about motorized recreation

management, only two routes were identified as needing any

mitigation activity from the use of OHVs (Tahoe National

Forest, Vol. 2, 2008) and no significant analysis of noise

impacts were conducted, despite motorized-recreation noise

being one of the most obvious impacts to wildlife. This is in

contrast to the optimized system proposed in the current

study, based upon TNF staff rules, the literature on impacts

of motorized recreation, the results of the user survey, and the

principles of the Recreation Opportunity Spectrum (ROS).

There is no reason to think that the Tahoe National

Forest is any different from many other Forests in its

designation and environmental analysis of routes under the

TMR. For example, the neighboring Eldorado National

Forest (http://www.fs.fed.us/r5/eldorado/projects/route/index.

shtml) and the more distant Six Rivers National Forest

(http://fs.usda.gov/srnf) also maintained or increased the

available length of routes for motorized recreation and did

not base route designation decisions on minimizing envi-

ronmental impacts. This conclusion is based on the fact


123

http://www.fs.fed.us/r5/routedesignation/statusreport/report042010.html

http://www.fs.fed.us/r5/routedesignation/statusreport/report042010.html

http://www.fs.fed.us/r5/eldorado/projects/route/index.shtml

http://www.fs.fed.us/r5/eldorado/projects/route/index.shtml

http://fs.usda.gov/srnf

that, although the Forests comprehensively describe

potential impacts, these impacts were not explicitly used as

part of decision-support for designation of individual or

networks of routes, or what was the ultimate selection of

the most environmentally-harmful alternative (Eldorado

National Forest 2008; Six Rivers National Forest 2010). In

addition, neither Forest developed a system to minimize

conflict among user groups, despite a requirement under

the TMR to minimize conflict (TMR, § 212.55(a)).

Although evidence of conflict is provided by the present

study and close reading of responses from the public to

National Forest environmental analyses, the Forests largely

ignored conflict in their route designation process. Essen-

tially, all 3 Forests ‘‘tinkered around the edges of current

allocations’’ (Adams and McCool 2009) and failed to

design an effective and manageable recreational system

based on requirements under the TMR.

Optimization and Resolution

We present here one way to resolve possible conflicts that

arise among recreational user groups and address trade-offs

between recreation opportunities and environmental val-

ues. This approach is consistent with current recommen-

dations for policy and management directions that the US

government and its constituent agencies, the US Forest

Service and Bureau of Land Management should take to

minimize conflict and environmental impacts from

motorized uses (Adams and McCool 2009). At the same

time we recognize that the land management agencies may

not have the ability or desire to resolve conflict in this way,

by segmenting competing uses in a way that limits

motorized recreation (Wilson 2008).

By selecting environmentally optimized roads and trails

for motorized recreation around existing staging areas, both

environmental harm and potential conflict between

motorized recreationists and non-motorized can be mini-

mized. One important step in the proposed approach is to

estimate potential environmental impact for the recrea-

tional routes, as required by the TMR and NEPA. This

estimate of harm can be combined with recreation prefer-

ences to develop an environmentally-optimized road and

trail system that provides motorized recreation while

minimizing environmental harm. We chose the approach of

selecting route system length for a group (i.e., motorized

users) based on proportion of total number of users,

because it was the most parsimonious way to determine a

threshold for sharing a system where there is conflict

among groups. This approach also does not favor one

group over another in that each group is allocated a pro-

portion of the system according to the group’s size. Finally,

this approach has the secondary benefit of limiting the

degree and spatial extent of cumulative environmental

impacts from motorized recreation. The approach descri-

bed could be used to implement the ROS approach in a way

that has not previously been available. Specifically,

developing a recreational system that deals with conflict,

environmental impacts, and system limits is more likely to

be sustainable and manageable on public lands. We pro-

pose this approach as a way forward for public lands

managers attempting to resolve differences over transpor-

tation system management.

Acknowledgments Funding for this work was provided by the US

Forest Service, Tahoe National Forest (TAH-OHV-02-05) and the

Recreation Planning Program of The Wilderness Society. Particular

thanks are given to Carol Kennedy and other members of the Tahoe

National Forest-Inter-Disciplinary Team for recreational routes

analysis and planning and for helping to develop the optimization

model. Thanks also to Mark Lubell, UC Davis, for advice on

designing the survey instrument and analyzing survey data. The

article benefited from the insightful comments of the editor and 3

anonymous reviewers.

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