United States Department of Agriculture / Forest Service

Rocky Mountain Research Station

General Technical Report RMRS-GTR-247

October 2010

Numerical Visitor Capacity: 

A Guide to Its Use in Wilderness

David Cole and Thomas Carlson
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Cole, David; Carlson, Thomas. 2010. Numerical visitor capacity: a guide to its use in 

wilderness. Gen. Tech. Rep. RMRS-GTR-247. Fort Collins, CO: U.S. Department 

of Agriculture, Forest Service, Rocky Mountain Research Station. 20 p.

Abstract

Despite decades of academic work and practical management applications, the 

concept of visitor capacity remains controversial and inconsistently operationalized. 

Nevertheless, there are situations where development of a numerical estimate of 

capacity is important and where not doing so has resulted in land management 

agencies being successfully litigated. This report is a guide to developing estimates 

of numerical visitor capacity, with particular emphasis on wilderness. It reviews 

capacity concepts, surveys available approaches to capacity determination, and 

outlines a generic process. Appendices provide information on relevant legislation 

and policy, as well as detailed examples and templates.

Keywords: carrying capacity, indicators, recreation use, standards, visitor use 

management

Authors

David Cole is a Research Geographer at the Aldo Leopold Wilderness Research 

Institute, Rocky Mountain Research Station, Forest Service, Missoula, Montana. He 

holds a Ph.D. in geography from the University of Oregon and an A.B. in geography 

from the University of California, Berkeley.

Thomas Carlson is the Forest Service Representative at the Arthur Carhart National 

Wilderness Training Center, Missoula, Montana. He holds a B.S. degree in forestry 

from the University of Minnesota.

Cover: Hiker looks from the Mt. Baker Wilderness into the Stephen 

Mather Wilderness (inset photo by David Cole). Hikers use cables 

to ascend Half Dome in Yosemite Wilderness (photo courtesy of 

National Park Service).
Contents

Introduction................................................................................................1

Numerical Visitor Capacity in Context..................................................1

Using Numerical Visitor Capacity.........................................................1

Using This Report.................................................................................2

What is Numerical Visitor Capacity? ..........................................................3

A Procedure for Developing a Numerical Visitor Capacity.........................4

Summary of the Procedure ...................................................................5

Defining Thresholds.............................................................................5

Estimating Visitor Capacity on the Basis of Thresholds..........................6

Other Numerical Capacity Estimation Procedures......................................8

Capacity Estimation Based on ROS Coefficients ...................................8

Freezing Use at Current Levels.............................................................9

Conclusions.................................................................................................9

References ................................................................................................10

Appendix A—Relevant Legislation and Policy...........................................12

Appendix B—Examples.............................................................................14

Appendix C—An Issue-Based Numerical Visitor Capacity ........................18

USDA Forest Service RMRS-GTR-247. 2010. 1

Introduction

The concept of recreational carrying capacity has 

been around since at least the 1930s, when National 

Park Service biologist Lowell Sumner wondered “how 

large a crowd can be turned loose in a wilderness without destroying its essential qualities.” He went on to 

conclude that recreational use should be kept “within 

the carrying capacity” (Sumner 1936). The concept 

has been both the subject of academic studies (for 

example, Wagar 1964) and the basis for management 

decisions (Haas 2002). Interest in capacity has waxed 

and waned. The need to deal with capacity has been 

legislatively mandated and incorporated into policy. 

Recently, agencies have been successfully litigated because they have failed to address capacity issues (Haas 

2004, Cole and others 2005). The concept remains controversial and poorly understood and it has never been 

operationalized in any consistent way. While this has 

led some to consider the concept a failure as a recreation planning framework and a term that should be 

banished (McCool and Lime 2001, McCool and others 2007), others have extolled the concept in books 

and reports devoted to the topic (Shelby and Heberlein 

1986, Haas 2002, Manning 2007).

From the beginning, academic studies of the capacity concept have exposed its limitations. Al Wagar, the 

Forest Service scientist who first explored the concept 

systematically, noted that conceptually capacity “was a 

bad choice that has diverted attention from more promising approaches to effective management of recreation 

lands” (Wagar, 1974, p. 274) because it focused attention on limiting the number of people in an area and 

away from other management strategies. Recognizing 

these limitations and that the intent behind the capacity concept was to effectively sustain biophysical and 

experiential values threatened by recreation use, the 

notion of what carrying capacity means has often been 

enlarged to become an umbrella concept for visitor use 

management (Lime and Stankey 1971).

Numerical Visitor Capacity in Context

We share the view that capacity is more a topic and 

way of thinking (Lime 1976) than a metric and we 

strongly believe that addressing capacity is much more 

than managing the number of visitors. Therefore, before 

continuing with a guidebook on how to develop numerical visitor capacities, we must remind readers that 

deriving capacities is only one of many visitor use management tools. A large body of literature consistently 

concludes that amount of visitor use, the variable that 

capacity deals with, is often less important than such 

variables as the behavior of users or how and where 

use is distributed (Hammitt and Cole, 1998, Manning 

1999, Cole 2009, Dawson and others 2009). Since impacts are most effectively managed by mitigating the 

factors that most influence amount of impact, managing use levels by setting capacities is seldom the most 

effective way to deal with most management problems 

(Cole and others 1987). Setting a capacity should 

never be the first visitor use management approach 

to consider; rather, if used at all, it must be embedded in the context of a thorough analysis of the root 

cause of problems and a management prescription 

of diverse strategies and techniques.

That said, there are issues and impacts that are directly related to use levels—crowding, for example (Shelby 

and Heberlein 1986, Manning 1999). Addressing 

capacity is an effective means of dealing with such issues. Perhaps more common are places where a myriad 

of impact issues can be effectively dealt with through 

means other than limiting use; but the result is a complex and onerous management regime of regulations, 

site hardening, channeling visitors, closures, and so on. 

The complexity and obtrusiveness of such a regime can 

often be reduced by also setting capacities and limiting 

use (Cole 1995).

Given that developing numerical capacities is 

sometimes necessary, this report will assist managers 

interested in developing estimates of numerical visitor capacity in wilderness. We use the term numerical 

visitor capacity because we believe, as do many other 

students of capacity concepts, that numbers are not always necessary when addressing capacity (Washburne 

1982). However, the focus of this guide is on developing a numerical expression of capacity. We consider 

the concept of visitor capacity to be the same as user 

capacity or recreational carrying capacity and use the 

terms interchangeably, but we recognize that there are 

some who define these in different ways. Finally, although this guide is written for use in wilderness, with 

examples taken from wilderness, it should also be applicable on lands outside wilderness.

Using Numerical Visitor Capacity

Forest Service wilderness management regulations 

and policy do not require the establishment of a numerical visitor capacity, as long as visitor use can be 

managed in such a manner that wilderness character is not impaired by excessive recreational use (36 

CFR 293.2 and FSM 2323.1). However, we believe 
2 USDA Forest Service RMRS-GTR-247. 2010.

that going through the process necessary to arrive at 

a numerical capacity (regardless of whether a specific 

number is derived) can be a useful tool in all wildernesses and likely is required, at least in some parts of 

many wildernesses. Refer to Appendix A for a review 

of the Wilderness Act, Forest Service regulations and 

policy, and their implications for capacity.

Addressing capacity is likely to be required in many 

situations where excessive visitor use has impaired wilderness character. Policy (Appendix A) suggests that 

(1) use should be limited if necessary to avoid impairment, (2) any limits on visitor use should be based on 

estimates of visitor capacity, and (3) capacity should 

be based on concerns regarding protection of both the 

biophysical resource and social conditions. Managers 

need to think carefully before deciding to limit use 

and should not overlook other more effective means 

of dealing with impacts (Hall 2001, McCool 2001). 

But where limits are deemed appropriate, capacity estimates are important inputs to decisions regarding use 

limits.

In addition, policy requires agencies to conduct a 

needs assessment to determine if outfitters and guides 

are appropriate and if so, how many, what type, and 

where they should operate. While there are a number of 

ways to determine how much commercial use should 

be allowed, a common approach is to establish a maximum level for all use (commercial and public) and then 

to allocate a portion of this to the commercial sector. 

With this approach, a numerical visitor capacity must 

be estimated.

As will be discussed in more detail below, the process of deriving a meaningful numerical capacity is 

useful for the entirety of visitor use management. It 

involves identifying goals, objectives, desired conditions, and what we refer to as thresholds (often called 

indicators and standards). It requires monitoring, evaluating the factors that influence impacts of concern, 

and identifying the entire suite of visitor management 

actions to be taken. Consequently, working through a 

capacity estimation process, regardless of whether limiting use is an important management tool, will benefit 

any recreation management program.

Using This Report

This report is an attempt to suggest how wilderness 

planners and managers, faced with one of these situations, might go about developing a numerical visitor 

capacity. These ideas are consistent with the intent of 

The Wilderness Act of 1964 and Forest Service regulations and policy. It does not represent new agency 

policy. Currently there is no established methodology 

in agency policy for developing a numerical visitor capacity; consequently, various approaches to addressing 

capacity have been taken.

In this report, we outline a very general approach to 

developing a numerical visitor capacity. The approach 

is consistent with the many planning frameworks that 

have been developed to address visitor capacity and 

visitor use management generally. Most of these take a 

management-by-objectives approach and build on the 

original ideas of Frissell and Stankey (1972) regarding 

developing management objectives that limit degradation and impairment. Conceptually, these frameworks 

are virtually identical (McCool and Cole 1997), although they differ in implementational detail. In order of 

their development, these frameworks include Limits of 

Acceptable Change (LAC) (Stankey and others 1985), 

Management Process for Visitor Activities (VAMP) 

(Parks Canada 1985), Visitor Impact Management 

(VIM) (Graefe and others 1990), Carrying Capacity 

Assessment Process (C-CAP) (Shelby and Heberlein 

1986), Visitor Experience and Resource Protection 

(VERP) (USDI National Park Service 1993), Protected 

Areas Visitor Impact Management (PAVIM) (Farrell 

and Marion 2002), and Sustainable Visitor Capacity 

(SVC) (Queensland Environmental Protection Agency 

n.d.). Readers interested in more than numerical 

capacity—planning for visitor use management generally—would profit from reading more about these 

frameworks.

We suggest that planners and managers adopt an 

approach that meets their needs. Approaches will vary 

with available information, staff and resources and, 

particularly, with the likely consequences of prescriptive decisions based on capacity estimates. Where 

managers have little information and where the consequences of a capacity-based decision are not very 

controversial, rapid approaches may suffice. However, 

where the potential for resource degradation is significant or there is a high likelihood of the decision being 

challenged, a more involved, lengthy, collaborative, 

and precise approach is warranted. The keys to success are (1) employing the best available information; 

(2) basing an estimate on clear management objectives, 

logical thinking, sound science, and professional judgment (so it is not arbitrary); and (3) refining capacity 

estimates over time as new information becomes available. It is also important to think about implementation 

while developing capacities. There is little value to developing capacities if there is no will to implement the 

actions needed to avoid exceeding capacity.
USDA Forest Service RMRS-GTR-247. 2010. 3

What is Numerical Visitor 

Capacity?

The recommendations in this guidebook are consistent with early definitions of recreational carrying 

capacity, but not with some definitions of capacity 

that have been advanced more recently (Haas 2002, 

Whittaker and others 2010). Therefore, it is important 

to explore the capacity perspectives that are foundational to the basic assumptions of this guide. The 

original published definition of capacity was that it 

was “the maximum extent of the highest type of recreational use which a wilderness can receive, consistent 

with its long-term preservation” (Sumner 1942). Most 

definitions of capacity advanced since then are remarkably similar. For example, in their recent ruling 

on the Merced River capacity litigation, the United 

States Court of Appeals for the Ninth Circuit (Friends 

of Yosemite Valley v. Kempthorne, 520 F.3d 1024(9th

Cir.2008)) noted the “plain meaning” of the mandate 

to “address...user capacities” was to “deal with or discuss the maximum number of people...which the river 

area can sustain without impact to the ORVs [outstandingly remarkable values].”

There are three things to note about these definitions. First, capacity is a maximum number of visitors. 

Second, it is the maximum number that is consistent 

with management objectives—the maximum number 

that can be accommodated without impairment of values. For wilderness, with its emphasis on protecting 

wilderness character, capacity is the maximum amount 

and type of use that can be sustained without causing 

unacceptable impact to the wilderness’ ecological conditions or to the quality of visitor experiences.

The emphasis on sustaining values and avoiding 

unacceptable impact illustrate the importance of professional judgments and management objectives to 

identifying capacities. As McCool and others (2007) 

note, “Carrying capacity requires specific objectives” 

and because of this “each site has a whole range of 

potential capacities, each providing different consequences” (Wagar 1974, p. 275). Capacities cannot be 

identified until specific objectives or evaluative standards have been defined, leading Shelby and Heberlein 

(1986, p. 18) to define capacity as “the level of use 

beyond which impacts exceed levels specified by evaluative standards.”

The third thing to note, not apparent in the capacity definition itself, is that capacity is an attribute that 

can be estimated. Capacity is not a value-free, inherent 

property of a place (Wagar 1964). It can only be estimated once decisions have been made about management 

objectives and other management actions to be taken 

in the area. But once these decisions have been made, 

analytical processes can be used to estimate what the 

capacity actually is. Such estimates might be imprecise, uncertain, and even inaccurate, depending on the 

situation and the quality and quantity of technical and 

experiential information available, but they are an attempt to get at a theoretically discoverable attribute. 

In other words, as originally conceived, capacities are 

based on decisions about management objectives and 

they inform decisions about actions such as use limits 

but are arrived at through a process of analysis and estimation, not a decision-making process.

To illustrate the distinction between descriptive estimates and prescriptive decisions, consider the capacity 

of a football stadium. A capacity cannot even be approximated until a prescriptive decision is made about 

whether spectators will be allowed to stand or must 

be seated. But once it is decided that there will be no 

standing, capacity can be estimated with a high degree 

of precision, certainty, and accuracy. The number of 

seats can simply be counted. This estimate of stadium 

capacity should certainly inform a decision about use 

limits—how many tickets to sell. But it is also possible 

to decide to sell more or less tickets than the stadium 

capacity. Prescriptive decisions about how much use 

will be accommodated or allowed can differ from the 

analytical estimates of capacity that should inform 

such decisions.

Capacity is also considered an estimate, arrived at 

through analytical processes, in the resource management disciplines from which the recreational capacity 

concept was borrowed. Dana (1957), for example, noted its equivalence to the concept of sustained yield in 

timber management. Sustained yields are estimated 

on the basis of research, monitoring, experience, and 

logical thinking. They inform decisions about timber 

supply, but supply is not synonymous with sustained 

yield. In range management, estimates of grazing capacity are developed, again based on monitoring, 

research, and experience. These estimates, in turn, inform decisions about stocking rates (how many animals 

can be grazed). In each case, capacities are estimates 

that inform decisions—not the decisions themselves. 

This distinction between estimation and decision was 

explicitly recognized in the regulations developed 

to implement the National Forest Management Act 

(NFMA). Section 219.18(a) stated that the portion of 

forest plans providing direction for wilderness management were to “provide for limiting and distributing 
4 USDA Forest Service RMRS-GTR-247. 2010.

visitor use of specific portions in accord with periodic 

estimates of the maximum levels of use” (emphasis 

added) that do not impair wilderness values (Federal 

Register 1982).

This differs from some more recent assertions that 

visitor capacity should be a prescriptive decision, arrived at through consideration and negotiation (Haas 

2003) rather than analysis. Haas (2002), for example, 

defines visitor capacity as “the supply, or prescribed 

number, of appropriate visitor opportunities that will 

be accommodated in an area” (p. 10) and believes 

that “supply and capacity are synonymous” (p. 9). 

Traditionally, supply and capacity have not been considered to be synonymous. For example, Twiss (1971), 

in an early textbook discussion of recreational supply, 

notes that “capacity estimation” is one of the seven elements needed to make decisions about supply. This 

guide is intended to help managers make the prescriptive decisions and work through the analytical process 

that can produce descriptive estimates of numerical 

visitor capacity. These estimates should, among other 

things, inform decisions about supply or use limits.

A Procedure for Developing a 

Numerical Visitor Capacity

Given this definition, there are two major steps to 

developing a numerical capacity. First, one must establish thresholds. These thresholds represent the point at 

which impairment occurs or there is unacceptable impact to ecological conditions or the visitor experience. 

These biophysical and social thresholds are judgments, 

based on values—decisions that managers must make, 

with appropriate input from stakeholders. The implication of a threshold is that management will do whatever 

is necessary, even restrict access, to keep the threshold 

from being exceeded.

Second, one must estimate the maximum amount 

of visitor use that can be sustained without exceeding these thresholds. This is more of a science- and 

data-based step than the establishment of thresholds. 

Measures and monitoring data can be helpful, as can 

research. But, professional judgment and logical thinking will always be required and, in some cases, may 

be the primary basis for estimates. All processes for 

developing a numerical capacity have these two steps 

in common, but they vary considerably in detail.

Along with variation in the details of implementation, procedures for developing a numerical visitor 

capacity vary in the explicitness and objectiveness 

of thresholds, the accuracy of the numerical capacity 

estimates, and the time and resources required. It is 

important to understand the attributes of any capacity 

estimation process that is selected. Consequently, we 

review each of these characteristics.

Ideally, the thresholds of impairment and acceptable impact are made explicit, stated in precise and 

quantitative terms, and established through a process 

involving substantial input from an interdisciplinary 

team of agency officials, the public, and other stakeholders. This should maximize the validity of the 

thresholds and minimize subjectivity and bias in decisions about what the thresholds actually are and the 

conditions under which they might be exceeded. Less 

ideal options include establishing explicit, quantitative thresholds without much stakeholder input, using 

qualitative thresholds, and using thresholds that are implicit rather than explicit. An implicit threshold is one 

that has not been documented, leaving it unclear in the 

documentation of the process exactly what threshold 

was used. Sometimes the persons developing the capacity estimate may not even be able to articulate the 

threshold they are implicitly using. But any capacity 

estimate must be formulated with some threshold criterion in mind.

For any given threshold (or set of thresholds), there 

are many ways to estimate a numerical capacity. Some 

approaches use professional observation and experience, while others use research on the relationship 

between use and impact to arrive at an estimate; computer simulation modeling can sometimes be used as 

a way of further systematizing observation. Some approaches incorporate monitoring, while others do not. 

Some approaches are highly tailored to a specific area, 

while others rely on extrapolation and/or the use of generic coefficients. Accuracy is highest when systematic 

observation, monitoring, research, and professional 

judgment are all used and the process is tailored to a 

specific environmental, social, and managerial context, 

as opposed to being based solely on extrapolation from 

generic estimates.

Not surprisingly, time and resources are positively related to the quality of thresholds and the 

accuracy of capacity estimates. More accurate and 

defensible approaches are more costly, in time and resources. Capacity processes can generally be arrayed 

on a spectrum from (1) explicit thresholds, high accuracy approaches that require substantial time and 

resources to (2) implicit thresholds, low accuracy approaches that require little time and resources. The 

selection of a numerical estimation capacity process 
USDA Forest Service RMRS-GTR-247. 2010. 5

will largely be one of selecting an appropriate point on 

this spectrum, understanding the limitations of whatever process is undertaken, and striving to minimize 

those limitations. This is similar to the concept of a 

sliding scale described by Haas (2002, p. 29) in the following manner: “The sliding scale rule of analysis says 

that the level of analysis should be commensurate with 

the purpose or potential consequences.” The greater 

the potential consequences, impacts or risks, the more 

certainty and precision are needed, with resultant implications for the amount and quality of science and 

information that is needed.

Summary of the Procedure

In short, estimating visitor capacity involves the following steps or decision points:

1. Establish Thresholds. These should be explicit 

and quantitative, although it is possible to work 

with qualitative and even implicit (see below) 

thresholds. They should address goals or desired 

conditions for the area—values and attributes you 

are trying to protect. Appendix C is an example, 

developed by the Northern Region of the Forest 

Service, of how to base thresholds and capacities 

on issues. Assuming the wilderness has zones with 

variable objectives regarding degree of impact and 

visitor experience, thresholds are likely to vary 

among zones.

2. Define Analysis Areas. These are areas (often 

watersheds) that (1) can be analyzed and managed 

as individual units and (2) have a common set of 

thresholds (i.e., the entire analysis area is in just 

one zone).

3. Estimate Capacities for each Analysis Area.

Use professional judgment, logic, research, and/

or monitoring data to estimate the maximum use 

each analysis area can receive without exceeding 

any of the thresholds. Assuming there are multiple 

thresholds (different indicators), only one will 

be the limiting factor in any analysis area. The 

limiting factor may vary among analysis areas.

4. Convert and Aggregate Use Measures. In some 

cases a numerical estimate of capacity for the entire 

wilderness may be necessary for programmatic 

planning purposes. If so, simply sum the capacity 

estimates for each analysis area. This may require 

some conversion among different use measures 

(e.g., RVDs, PAOT, groups entering per day, and 

groups per season). This wilderness-wide capacity 

may be of little value in implementing capacity 

on the ground, however. Capacity should be 

implemented for specific places (analysis areas 

perhaps) and for particular times, to ensure that 

capacity is not exceeded in any place or at any 

time.

Defining Thresholds

As noted above, ideally thresholds should be explicit 

and quantitative. To address the most important values 

at risk, it is best to develop thresholds for multiple attributes of concern. Explicit, quantitative thresholds 

are referred to as indicators and standards in capacity 

processes such as Limits of Acceptable Change (LAC) 

(Stankey and others 1985) and Visitor Experience and 

Resource Protection (VERP) (USDI National Park 

Service 1993), as well as in some more general planning processes and in Forest Service regulations and 

policy. In this document, we will at times use the terms 

“threshold” and “standard” interchangeably, although 

we use the generic term “threshold” most often. We 

recognize that the term “standard” is sometimes used 

in ways that differ from our use of the terms. As noted 

earlier, thresholds are not to be exceeded. They are requirements, not a suggestion.

Thresholds (or indicators and standards) can sometimes be found in existing plans, but in many cases 

they will need to be developed. Even thresholds in existing plans may need to be adapted or supplemented, 

because existing plans may not have identified some 

of the specific issues that are important in wilderness. 

Although the general issues which thresholds should 

address, such as preserving natural conditions, are similar across all wilderness areas, specific indicators will 

vary among areas. For example, in one wilderness the 

concern might be grizzly bears; in another it might be 

trampling of a rare plant.

To establish thresholds, first identify the wilderness 

values that are both most important and most likely to 

be at risk from high levels of visitor use; these are the 

indicators that are most relevant to capacity. Consider 

attributes of wilderness character and outstandingly remarkable values on rivers. Attributes that are unrelated 

to visitor use or that can be protected without limiting 

use are not needed for capacity estimates. However, 

these other indicators may be equally or more important to visitor use management generally; they should 

not be ignored. Decisions about indicators are best 

made on the basis of the experience of professionals and stakeholders. Lists of potential indicators that 

might be considered can be found in Manning (1999), 
6 USDA Forest Service RMRS-GTR-247. 2010.

Manning and Lime (2000), Lime and others (2004), 

National Park Service (n.d.) and on Wilderness.net 

(n.d.).

Once indicators have been developed, decisions will 

need to be made about the maximum level of impact to 

each of these attributes and values that will be tolerated; these are the standards or quantitative thresholds. 

Thresholds represent managers’ decisions regarding the 

dividing line between impaired and unimpaired values, 

and between acceptable and unacceptable conditions. 

Thresholds may trigger management actions. There 

is no magic and little science in the establishment of 

quantitative thresholds, although it is helpful, when defining them, to have information on current conditions. 

Thresholds should be thought of as a balance between 

preserving desired conditions and avoiding excessive 

regulation and restriction on access. Thresholds should 

be set at the point where it would be generally acceptable to limit use in order to avoid exceeding that 

threshold. Visitor opinions captured in surveys, often 

referred to as norms (Vaske and others 1986, Manning 

2007), provide one useful source of input, although 

some have questioned the sufficiency of such data for 

making prescriptive decisions (Stewart and Cole 2003).

Most wilderness areas are diverse in terms of how 

pristine they are and the wilderness experience they offer. This diversity should be maintained by providing 

several different wilderness zones (similar conceptually to ROS classes), each of which has different 

quantitative thresholds. For this purpose, managers 

will need to decide how many different zones to have 

(usually 2-4) and what the thresholds for each zone are. 

There may be some smaller wilderness areas that only 

have one zone, but this is likely the exception rather 

than the rule.

Then managers must allocate the zones to specific 

geographic areas. The entire wilderness must be zoned, 

with every specific place in the wilderness being assigned to only one zone. A typical wilderness will have 

multiple geographic areas assigned to the same zone, 

separated from each other by geographic areas assigned to different zones.

As an example, consider Inspiration Wilderness, a 

wilderness with four zones from most to least pristine. 

Managers there are most concerned about avoiding 

excessive crowding on trails, too many highly impacted campsites, and adverse effects of visitor use on 

populations of black bears. They decide to have three 

indicators, one for each of these concerns: a maximum 

number of encounters with other groups on trails per 

day, a maximum number of campsites per square mile 

with a condition class of 3 or more, and a maximum 

reduction in the population of black bears attributable 

to recreation use. For the maximum number of encounters per day, thresholds are 1, 2, 5, and 15 groups per 

day in the four zones. For campsites, thresholds are 

none, none, 2, and 5. For black bears, thresholds are 

none, none, 10%, and 10%.

As noted above, ideally thresholds should be carefully developed through a process of public and 

stakeholder involvement. Although often time-consuming and costly, this enhances the credibility of 

decisions. But a time-consuming public involvement 

process is not always necessary and may be wasteful 

of scarce resources in situations where important wilderness values are not substantially at risk and there is 

little controversy. In such a situation, a small interdisciplinary team or even a single individual could make 

these decisions in a single meeting.

Qualitative thresholds and even implicit thresholds 

are less desirable options. They should be avoided unless it is not possible to quantify critical attributes. In 

the example above, perhaps it is not possible to quantify impacts on black bears. Developing a qualitative 

threshold is better than ignoring an important issue. An 

example of a qualitative threshold for the issue of black 

bear impact might be “there will be negligible impact 

to populations in the more pristine zones and no more 

than moderate impact in the other zones.” A team of 

bear experts might be convened to evaluate whether 

or not likely levels of impact exceed these thresholds. 

Implicit thresholds will be discussed more below.

Estimating Visitor Capacity on the 

Basis of Thresholds

The second step in arriving at a numerical visitor capacity is to estimate the maximum amount of use that 

can be sustained without exceeding any of the thresholds. As first noted by Frissell and Stankey (1972), this 

will involve deciding which threshold is the factor that 

ultimately limits capacity. The limiting factor is not 

the most important factor; all thresholds are important. 

The limiting factor is the one most sensitive to use, the 

threshold that is compromised at the lowest use level. 

But the limiting factor is likely to vary from place to 

place—between one trail and the next, between drainages, or between one bay and the next. Consequently, 

separate estimates will need to be developed for each 

of a number of individual analysis areas in the wilderness. There also may need to be coordination among 

adjacent wilderness units.
USDA Forest Service RMRS-GTR-247. 2010. 7

There is no simple rule to follow regarding how to 

divide a wilderness into analysis areas. Generally, an 

entire analysis area should be accessible from one or 

a few access points and it should be possible to manage it as a single unit. In mountainous wilderness, a 

watershed accessed by one main trail often makes a 

good analysis unit. But, an entire analysis area must 

be allocated to just one zone. If a watershed is long, 

with a popular section accessed by day users as well as 

a remote lake basin, it will usually be best to use more 

than one analysis area. Separate fjords or bays in an 

Alaskan wilderness, for example, should probably be 

separate analysis units and the popular shoreline locations should probably not be lumped with large tracts 

of unvisited interior lands for analysis purposes.

Estimates of capacity must be made for each individual analysis unit. Then these separate estimates 

can be summed to arrive at the capacity of the entire 

wilderness. Although a single overall capacity for the 

entire wilderness can be derived, capacities will usually need to be implemented at the scale of the individual 

analysis area, to avoid having over- and under-utilized 

management areas. For example, the entire wilderness 

might have a capacity of 10,000 groups, but this assumes that use will be distributed such that none of the 

analysis units exceeds capacity. If half the groups want 

to go to one place, either overall capacity will have to 

be reduced substantially or some system (e.g., a placespecific permit system) will have to be developed to 

ensure that use is more equitably distributed.

Professional judgment, logic, research, monitoring, and even tools like computer simulation modeling 

can all contribute to estimates of how much use can 

be accommodated without exceeding thresholds. The 

accuracy of estimates can be increased by using varied 

sources of information and tools and by periodically 

refining estimates on the basis of new and better information. Monitoring is not absolutely necessary to 

estimate capacity but, if done well, it always increases 

the accuracy of estimates. The importance of monitoring increases as the risk to valued resources increases 

and as the uncertainty associated with predictions based 

on professional judgment, logic, experience or research 

increases.

For example, consider the threshold of no more than 

one encounter with other groups per day in the most 

pristine zone of Inspiration Wilderness. For Analysis 

Area 1 in the Pristine zone, an estimate based on professional judgment could be that three groups per day 

could enter that area without exceeding the threshold of one encounter per day. Moreover, logic might 

suggest that with only three groups per day entering, 

there should be no campsites with a condition class of 

3 or more and that impacts to black bears should be 

negligible. Thus the capacity estimate based on trail 

encounters appears to be the limiting factor. Similar 

analyses could be done for all analysis areas. These 

could be aggregated to provide an estimate of how 

many groups per day could enter the entire wilderness, 

assuming it was possible to distribute use in such a way 

that every analysis area is managed to capacity without 

exceeding capacity.

Note that estimates of maximum use, for a given 

analysis area, must be based on consideration of all other management actions being taken (or planned) in that 

area. This is critically important. Capacities can only 

be estimated in the context of the complete management prescription for each analysis area. Management 

actions, such as making trails more durable, teaching 

visitors Leave-No-Trace techniques, and designating 

campsites, will increase capacity if they are effective 

in reducing the per capita effects of use. All aspects of 

a management prescription affect capacity.

Monitoring data can be used to provide more accurate initial estimates of capacity. Assume monitoring 

data for Analysis Area 1 (from the example above) indicates that the threshold of one encounter per day is 

seldom exceeded until more than four groups per day 

enter. This monitoring-based estimate of four groups 

per day should be a more accurate estimate of capacity 

than the estimate of three groups based on logic and 

professional judgment. If there is a 100 day use season, 

total capacity would be about 400 groups per year. Or 

perhaps data show that encounters average about 0.5 

encounter per day and total use is about 200 groups per 

year. This would suggest, as a starting estimate, that capacity might be about 400 groups per year. Computer 

simulation modeling, if available, can be a useful tool 

for estimating how much use can be sustained without 

exceeding established thresholds (Cole 2005, Lawson 

2006). As noted earlier, although monitoring data and 

tools such as computer simulation increase the accuracy of estimates, they are not necessary. Estimates can 

be based on logic and professional judgment.

Once initial numerical capacity estimates are made, 

monitoring provides a means for adjusting estimates, 

resulting in increased accuracy over time. For example, it was assumed that number of encounters was the 

limiting factor. But if 400 groups per year are allowed 

into the area and bear populations seem to be adversely 

affected, this estimate might have to be lowered. Or 

perhaps, once use increases from 200 groups per year to 

400 groups per year, data suggest encounter levels are 

still well below the threshold and that bear populations 
8 USDA Forest Service RMRS-GTR-247. 2010.

are not adversely affected. This would mean that capacity estimates were too low and use levels could 

be increased without exceeding any thresholds. Note 

that the numerical capacities are estimates not decisions. These estimates are likely to change over time, 

as conditions change and better information becomes 

available. In contrast, the thresholds should be stable at 

least through planning cycles.

As noted before, even if there is no monitoring data 

and uncertainty is high, capacities can still be estimated. It is not necessary to wait until research and 

monitoring data are available or to avoid making an 

estimate because there are insufficient resources for 

research and monitoring. However, as the likely level 

of controversy associated with a capacity estimate increases, so does the desirability of more information, 

research, and monitoring. This is the sliding scale principle (Haas 2002). As was done in the example above 

(three groups per day in Analysis Area 1), consider the 

threshold and make a professional judgment about the 

maximum use that would not exceed the threshold.

This is the approach to use with qualitative thresholds as well. In the absence of data, it is probably 

preferable to convene a group of knowledgeable people and/or stakeholders to make estimates. Moreover, 

in wilderness particularly, when uncertainty is high, it 

is important to use the precautionary principle to make 

conservative capacity estimates until monitoring data 

are available and more accurate predictions can be 

made. In wilderness, the provision of recreational opportunities is a management objective but one that is 

constrained by the need to protect wilderness character. 

So, where there is high uncertainty, lower the estimate 

somewhat to be precautionary. In addition, it is always 

easier politically and economically to increase capacity 

estimates than to lower them once use levels and patterns become established. This illustrates that one of 

the costs of not allocating sufficient resources to monitoring and research will be capacity estimates that are 

somewhat lower than perhaps they would need to be.

For some thresholds, estimating capacity is straightforward. For example, if there is a threshold for a use 

density measure like PAOT (persons at one time), such 

as no more than 200 PAOT, the capacity estimate would 

obviously be 200 PAOT. However, we do not advocate 

writing thresholds for use density itself because there 

is nothing good or bad about any particular use density. 

It is the effect of use density on the environment or the 

visitor experience that is a more legitimate concern.

Another example of a capacity that is easily estimated is a threshold such as no more than one campsite 

per square mile in a wilderness where camping is only 

allowed on designated campsites. In this case, the capacity estimate, in groups, would be the number of 

designated campsites (or more realistically some proportion of this number, if groups are not assigned to 

specific sites) plus an unlimited amount of day use. 

This latter example illustrates how capacities sometimes apply to only one recreational activity, in this 

case camping. It is quite common, for example, for 

there to be limits on river users but not other users. 

In this situation, capacities need only be estimated for 

river users—for the purpose of making decisions about 

maximum levels of river use.

Sometimes it will be necessary to translate between 

different measures of use. For example, estimates of 

groups per day or PAOT may need to be converted into 

recreation visitor days (RVDs) per year. Some procedures for converting use measures are included in the 

user’s guide to the Recreational Opportunity Spectrum 

(USDA Forest Service 1982).

Other Numerical Capacity 

Estimation Procedures

As noted above, some capacity estimation processes 

rely on implicit thresholds. Two processes that have 

frequently been used, in which the thresholds are implicit, are (1) capacity estimates based on procedures 

described in the Recreation Opportunity Spectrum 

(ROS) handbook (USDA Forest Service 1982) and 

(2) capacity estimates based on a freeze on current use.

Capacity Estimation Based on 

ROS Coefficients

The process included in the handbook for implementing the Recreation Opportunity Spectrum (ROS) 

is as follows (USDA Forest Service 1982):

1. Map ROS classes in the wilderness.

2. Multiply the number of acres in each ROS class 

by capacity coefficients unique to each ROS 

class. Coefficients are maximum persons at one 

time (PAOT) per acre. These are most often 

taken from the table of coefficients in the ROS 

handbook, although that table has a footnote 

stating that coefficients should be developed 

specifically for local conditions. These coefficients 

are simply estimates of maximum use levels that 

will not exceed thresholds. The difference is that 
USDA Forest Service RMRS-GTR-247. 2010. 9

these coefficients are someone else’s estimates, 

developed for some place other than where you are, 

using thresholds that are implicit and not defined. 

Consequently, it is unclear what was assumed to be 

relevant or important.

3. Adjust capacities down to account for such 

variables as the proportion of acres that are useable, 

environmental screening, and so on. For example, 

if only 10% of acres are usable for recreation, 

capacity should be reduced 90%. If there is lots 

of screening by vegetation and local topographic 

variability, capacity might be higher because the 

environment can “absorb” more people. Again, it 

is up to local planners to decide which factors to 

consider and how to make adjustments.

4. Convert these adjusted PAOT/acre estimates to 

recreation visitor days (RVDs) using the formula in 

the guide (USDA Forest Service 1982).

There is an infinite number of ways that local managers can adjust their estimates to reflect local factors 

that managers feel should influence capacity levels. 

This is suggestive of the subjectivity inherent to this 

approach. Independent planners are likely to derive 

substantially different capacity estimates depending 

on the factors they judge to be important. The capacity coefficients published in the ROS handbook 

(USDA Forest Service 1982) were developed in the 

early 1980s by a small group of Forest Service planners in the Rocky Mountain Region, based on their 

best professional judgment. Coefficients were based 

on concern about impacts both to the environment and 

visitor experience, but exactly what thresholds these 

planners had in mind is not stated. The thresholds they 

used are implicit.

The low level of accuracy inherent to this process 

is reflected in the fact that the coefficients published in 

the handbook have wide ranges: from 0.002 to 0.025 

PAOT/acre in the primitive zone and from 0.008 to 

0.083 PAOT/acre in the semi-primitive non-motorized 

zone. Although selecting a coefficient at the high end of 

the range would result in a capacity estimate 10 times 

higher than selecting the low end coefficient, there is 

no guidance about how to select a precise coefficient 

within this range. Moreover, as noted above, there is a 

footnote on the table of coefficients noting that “specific ranges must be developed to meet regional or forest 

conditions.”

This process is most commonly used in situations 

where capacity is much higher than current use, so there 

is no immediate need to limit use. Given the lack of explicit thresholds, high subjectivity and low accuracy, 

this approach is best suited to situations where only 

rough estimates of capacity are needed and where the 

“cost” of relatively inaccurate estimates is low. The 

primary advantage to this approach is that costs are 

relatively low. However, this approach still requires 

considerable field information, such as ROS zoning 

and information about the environment, facilities, and 

use that enable the coefficients to be adjusted. It also 

involves a large number of subjective judgments, many 

of which may not be apparent if one attempts to apply 

the ROS handbook in a routine manner.

Freezing Use at Current Levels

Another common approach to setting capacity in 

places where use limits are needed now is to set the 

capacity at the current level of use—to freeze use at 

current levels. This approach was taken on many rivers and in many national parks and wilderness areas, 

mostly in the 1970s and 1980s. With this approach, the 

implicit thresholds are the conditions that exist today. 

The current condition of resources is deemed acceptable because if they were not acceptable, capacity 

would have to be lower. But further deterioration would 

be deemed unacceptable; hence the need to limit use. 

Estimating capacity using this approach is extremely 

easy. It is simply the amount of use that exists today.

Although this is an inexpensive way to estimate numerical capacity and perhaps is politically expedient, it 

can be costly in terms of either allowing excessive use 

or not allowing as much use as might sustainably be 

accommodated. This follows from the fact that current 

conditions are unlikely to represent optimal thresholds. 

Indeed, many of the places that froze use in the 1970s 

and 1980s have tweaked their estimates as more information became available.

Conclusions

We want to close by rearticulating points made in 

the introduction to this guide. These suggestions are 

as applicable outside wilderness as they are inside 

wilderness. Although developing a numerical visitor 

capacity is worthwhile, addressing capacity is not primarily about managing the number of people. Many of 

the benefits of addressing capacity come from gathering information, monitoring, making decisions about 

thresholds, and prescribing the entire suite of management actions that are necessary to meet management 

objectives.
10 USDA Forest Service RMRS-GTR-247. 2010.

It is also important to remember that capacities can 

only be estimated in the context of all the other management actions that have been or will be taken in the 

area. Because these actions influence the relationship 

between amount of use and resource and social conditions, they affect capacity. Capacity will often change 

when new management actions are taken.

Consider the sliding scale principle and adjust the 

time and resources allocated to estimating capacity in 

relation to the resources at risk and the consequences 

of decisions. Think about implementation while developing capacities. There is little value to developing 

capacities if there is no will to implement the actions 

needed to avoid exceeding capacity. Similarly, it is important to implement capacities at appropriate spatial 

scales. Capacities are likely to be exceeded in local areas if a wilderness-wide capacity is employed without 

sufficient means for distributing use appropriately.

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cfm?fuse=toolboxes&sec=vum, under VII. Resources.
12 USDA Forest Service RMRS-GTR-247. 2010.

The Wilderness Act

The Wilderness Act does not direct wilderness managers to address visitor capacity. However, it does direct 

them to preserve wilderness character, protect natural 

conditions, and ensure that the benefits of wilderness 

(including outstanding opportunities for quality wilderness experiences) are available in an unimpaired 

condition for future generations. Since there are places 

where wilderness must be protected from excessive impacts of visitor use, the Wilderness Act implies a need 

to address capacity at least in some places. The following paragraphs highlight relevant excerpts from the 

Wilderness Act.

The Wilderness Act of 1964, in Section 2(a), established 

the National Wilderness Preservation System to provide 

“... the benefits of an enduring resource of wilderness.” It 

requires that wilderness areas are to be “... administered 

for the use and enjoyment of the American people in such 

a manner as will leave them unimpaired for future use and 

enjoyment as wilderness ...” while ensuring the “... preservation of their wilderness character ...” The definition 

of wilderness, in Section 2(c), includes a mandate to “... 

preserve its natural conditions ...” while providing “... 

outstanding opportunities for solitude or a primitive and 

unconfined type of recreation ...”

In Section 4b of the Wilderness Act, visitor use (recreation) is included in a mandate that “Except as otherwise 

provided in this Act, wilderness areas shall be devoted 

to the public purposes of recreational, scenic, scientific, 

educational, conservation, and historical use.” This 

means that visitor use is a public purpose of wilderness and opportunities should be provided as part of the 

benefits of wilderness. But note the phrase “Except as 

otherwise provided in this Act ...” which constrains the 

public purposes, in part, by reference to other mandates 

of the law including the primary responsibility of managers to preserve wilderness character. The definition of 

wilderness character is derived from the four statutory 

qualities of: undeveloped, natural, untrammeled, and 

outstanding opportunities for solitude or a primitive and 

unconfined type of recreation found in Section 2c. All 

four qualities of wilderness character influence visitor 

experiences and are useful in setting thresholds for estimating visitor capacity.

Section 4d (6) contains a special provision that allows 

for commercial services (outfitters and guides) if they are 

Appendix A—Relevant Legislation and Policy

needed to support recreation and other wilderness purposes. “Commercial services may be performed within 

the wilderness areas designated by this Act to the extent 

necessary for activities which are proper for realizing 

the recreational or other wilderness purposes of the areas.” The language of the law uses the term “may be 

performed” and “to the extent necessary” to both allow 

and constrain these activities to match the wilderness 

purposes or to help provide the benefits of the wilderness resource. As with all other activities the primary 

mandate for administration (preservation of wilderness 

character) provides the guide for determining how much 

commercial visitor use is needed (the extent necessary) 

within the overall wilderness visitor capacity and the desired social, biological, and physical conditions.

Forest Service Regulations and 

Policy

Forest Service Wilderness Management Regulations 

and Policy do not define what is meant by visitor capacity or prescribe a specific method for estimating a 

numerical capacity. However, policy makes it clear that 

wilderness character must be protected from excessive 

use and that this may require limiting and distributing visitor use based on periodic estimates of capacity. 

Policy also makes it clear that any estimate of visitor 

capacity must be based on the capabilities of the social, 

biological, and physical components of the wilderness 

resource to accommodate use without impairment of 

wilderness character. Finally, policy requires a needs 

assessment for outfitter and guide operations that may 

include an estimate of visitor capacity. Listed below are 

the sections of federal regulations and Forest Service 

wilderness management policy most relevant to visitor capacity. Visitor capacity must always be done in 

compliance with NEPA analysis and forest planning 

regulations and policy, which are not shown here.

Regulations

36 CFR 293.2 Objectives:

(b) Wilderness shall be made available for human 

use to the optimum extent consistent with the 

maintenance of primitive conditions.
USDA Forest Service RMRS-GTR-247. 2010. 13

Forest Service Policy

FSM 2320.3: Policy

• Where there are alternatives among management 

decisions, wilderness values shall dominate over 

all other considerations except where limited by 

the Wilderness Act, subsequent legislation, or 

regulations.

FSM 2323.11 Management of Recreation Use in 

Wilderness:

• Provide, consistent with management of the 

area as wilderness, opportunities for public use, 

enjoyment, and understanding of the wilderness, 

through experiences that depend upon a wilderness 

setting.

• Provide outstanding opportunities for solitude or a 

primitive and unconfined type of recreation.

FSM 2323.14 Visitor Management:

• Plan and manage public use of wilderness in such 

a manner that preserves the wilderness character of 

the area.

• Provide for the limiting and distribution of visitor 

use according to periodic estimates of capacity in 

the forest plan.

FSM 2323.13g Outfitter and Guide Operations:

• Address the need for and role of outfitters in the 

forest plan.

• The plan must address the type, number, and 

amount of recreation use that is to be allocated to 

outfitters.

• Ensure that outfitters provide their service to the 

public in a manner that is compatible with use by 

other wilderness visitors and that maintains the 

wilderness resource.

FSH 2709.11 part 41.53e Needs Assessment, Resource 

Capacity Analysis, and Allocation of Use

• Allocate outfitting and guiding use in a project 

decision pursuant to 36 CFR Part 215 or in a 

programmatic decision pursuant to a wilderness 

plan, wild and scenic river plan, or plan for another 

type of congressionally designated area.

• Conduct a needs assessment to determine the 

public or agency need for authorized outfitting and 

guiding activities.

• When conducting a needs assessment for outfitting 

and guiding activities in a wilderness area, assess 

whether these activities are necessary for realizing 

the recreational or other wilderness purposes of 

the area and the extent to which the activities may 

be authorized consistent with maintaining the 

wilderness character of the area.

Review previous needs assessments when 

reauthorizing use to ensure that they remain 

relevant to current and projected use trends, 

and update them if necessary.

• When monitoring demonstrates that impacts 

associated with use may exceed desired conditions, 

conduct a resource capacity analysis to assess the 

amount of use and types of activities that may be 

conducted without detrimental environmental and 

associated impacts. The resource capacity analysis 

may be conducted at a programmatic level or at 

a project level to address specific activities or 

geographical areas. In analyzing resource capacity, 

consider:

a. The applicable land management plan and 

other applicable programmatic and project 

decisions.

b. Inventoried conditions.

c. Current visitor use and visitor use trends 

(amount, type, length of stay, and group 

size).

d. Correlation of visitor use to plan guidance 

and inventoried conditions.

e. The results of management actions, such as 

vegetation treatments, watershed rehabilitation, and findings from monitoring.

Wilderness Planning

Where there is no estimate of visitor capacity in the 

units’ comprehensive plan, a subsequent wilderness 

planning process, supplemental to the comprehensive 

plan, may be necessary. Examples of situations that 

could trigger such additional planning could include 

deteriorating conditions that will exceed thresholds 

(standards) or a level of crowding that detracts from 

the wilderness experience, or as part of a needs assessment and allocation of use for commercial services. 

In these situations, if changes in management actions 

are anticipated, a NEPA-compliant planning process 

may be needed. In other situations, where no significant change in management actions are anticipated, or 

where it is simply desirable to identify current conditions or establish a baseline, an estimation of capacity 

may be determined without a lengthy planning process.
14 USDA Forest Service RMRS-GTR-247. 2010.

A Complete Example from 

the Hypothetical Imagination 

Wilderness

Consider the Imagination Wilderness, which consists of nine major drainages that vary substantially in 

recreation use and resultant impacts. Consequently, the 

wilderness has been divided into three distinct zones 

(using ROS or some similar framework): pristine, 

primitive, and semi-primitive. Three of the nine drainages are zoned pristine, three are zoned primitive, and 

three are zoned semi-primitive.

Step 1. Establish Thresholds. Some thresholds 

were available in the forest plan that has indicators and 

standards for each of the three zones. Two thresholds 

from the plan were considered applicable to capacity 

determination because too much use is likely to violate standards. Those indicators were the maximum 

number of other groups encountered per day and a 

reduction in the population of black bears attributable 

to recreation use. But wilderness managers were also 

concerned about campsite impacts. Consequently, they 

decided to also develop thresholds for both the density 

and condition of campsites. The thresholds applicable 

for each zone are shown in Table 1.

As noted before, the time, resources, and process of 

developing thresholds needs to be matched to the level 

of significance and potential controversy associated 

with capacity decisions. Where controversy is low, decisions can be made quickly without substantial input 

from diverse stakeholders, the public, and technical experts. At one extreme, thresholds might be defined in a 

few minutes, by a single individual, simply on the basis 

of professional judgment. At the other extreme, where 

the potential for controversy and the consequences 

of capacity decisions are high, it might be necessary 

to invest substantial periods of time in incorporating the input from diverse stakeholders in decisions. 

Regardless of process, the output is the same.

Step 2. Define Analysis Areas. Each of the 

drainages was considered a separate analysis area for 

analysis purposes. Our example is simplified by the 

fact that entire drainages are in the same zone. If a single drainage had been divided into more than one zone, 

it would have been necessary to divide the drainage 

into different analysis areas to reflect the zones.

Step 3. Estimate Capacities for Each Analysis 

Area. The outcome of this step is the maximum 

amount of use per unit of time that can be accommodated in each analysis area. In our example, it will be 

the maximum number of groups per day that can be allowed into each analysis area. Separate tables might be 

created for the analysis areas in each zone (as illustrated in tables 2-4). This maximum will be determined by 

the most limiting of the thresholds. Separate estimates 

must be made for each threshold. If it is suspected that 

one threshold is likely to be limiting, start with this one. 

For other thresholds, all that is needed is to conclude 

that capacity would be higher than would be allowed 

by the most limiting threshold.

In our example, assume that there are no monitoring 

data. Managers must use logic and their professional 

Appendix B—Examples

Table 1. Thresholds (indicators and standards) for each zone.

Indicator Pristine Zone Primitive Zone Semi-primitive Zone

Maximum number of groups 0 groups on 5 groups on 90% 15 groups on 90% of days in

encountered per day 90% of days in of days in use use season

use season season

Maximum number of 2 5 10

campsites per square mile

Maximum number of 0 1 5

campsites per square mile 

with condition class greater 

than 3

Effect of recreation on black No adverse No adverse No more than 10% 

bear populations effect effect reduction
USDA Forest Service RMRS-GTR-247. 2010. 15

judgment to estimate how many groups per day could 

enter the analysis area without violating any of the 

thresholds. In the pristine analysis areas (table 2), in 

Analysis Area 1, managers estimate that only two 

groups/day can enter without it being likely that groups 

would encounter each other. Considering their efforts 

to get groups in this area to camp on previously undisturbed sites and to leave no trace of their camp, 

they estimate that campsite thresholds are unlikely to 

be violated even if use was greater than two groups/

day. In a similar manner, biologists conclude that black 

bears would also not be adversely impacted at these 

low levels of use. Consequently, managers conclude 

that capacity in these areas will be limited by number 

of encounters. Analysis Area 3 is twice as big as the 

other areas, so capacity estimates were twice as high.

In the primitive analysis areas (table 3), managers 

conclude that the limiting factor is a combination of 

two thresholds. They decide that to make certain that 

there will be no more than one highly impacted campsite per square mile, they will only allow camping on 

designated sites, will establish one designated site per 

square mile, and will manage for a 50% occupancy 

rate. Because Analysis Areas 4 and 5 have 10 designated campsites, they can accommodate no more than five 

overnight groups per night. Analysis Area 6, which is 

twice as large, can accommodate 10 overnight groups 

per night. This establishes a capacity for overnight users. Day use capacity is limited by encounters. In our 

example, managers estimate that another 10 day-use 

groups could enter each day (in addition to the five 

overnight groups in Analysis Areas 4 and 5 and the 10 

overnight groups in Analysis Area 6) before the encounter threshold would likely be violated.

In the semi-primitive analysis areas (table 4), it was 

decided to limit the number of campsites by requiring 

people to camp in designated campsites. This makes it 

possible to accommodate large numbers of overnight 

groups and not exceed campsite thresholds. The encounter standards were also lax enough to allow many 

groups. Wildlife biologists estimated that the levels of 

use that would still not exceed the encounter and campsite thresholds would probably have unacceptable 

impacts on black bear populations. Consequently, capacity is limited by the black bear threshold. Their best 

estimate of the maximum number of groups that could 

Table 3. Capacity estimates (maximum number of groups/day that can enter without 

exceeding thresholds) for the primitive analysis areas.

Primitive Analysis Area

Threshold 4 5 6

≤ 5 groups/day on 90% of days 15 15 20

≤ 5 campsites/square mile Not the limiting factor

≤ 1 campsite/square mile with condition class > 3 5a 5a 10a

No adverse effect on bear populations Not the limiting factor

Capacity (entering overnight groups/day) 5 5 10

Capacity (entering day groups/day) 10 10 10

a

Maximum number of overnight groups.

Table 2. Capacity estimates (maximum number of groups/day that can enter 

without exceeding thresholds) for the pristine analysis areas.

Pristine Analysis Area

Threshold 1 2 3

0 groups/day on 90% of days 2 2 4

≤ 2 campsites/square mile Not the limiting factor

0 campsites with condition class > 3 Not the limiting factor

No adverse effect on bear populations Not the limiting factor

Capacity (entering groups/day) 2 2 4
16 USDA Forest Service RMRS-GTR-247. 2010.

enter per day, without reducing bear populations by 

more than 10%, are 40, 40, and 60 in the three analysis 

areas. Obviously there is a high degree of uncertainty 

to such a professional judgment. Hopefully, such an 

estimate is conservative and can be refined over time 

with more information and data.

Step 4. Convert and Aggregate Use Measures.

The total number of groups that can be allowed to enter 

per day is simply the sum of the capacities of the nine 

individual analysis areas—198 groups per day. To display this as an annual capacity, this number could be 

multiplied by the number of days in the use season. For 

a three-month use season, capacity could theoretically 

be as high as about 2000 entering groups. But the only 

way to accommodate the full capacity of 2000 groups 

per year, without exceeding thresholds, is to ensure 

that 198 groups enter each and every day. If it is likely 

that there are days when capacities will not be reached, 

capacity estimates must be reduced to account for this. 

This is similar to the approach described in the ROS 

handbook to reduce estimates by a factor (PU) related 

to the ratio between weekday and weekend use.

Capacities, expressed in terms of groups, can be 

converted to people by multiplying by mean group size 

(2.7 is typical of many wildernesses). This would suggest that the capacity of Inspiration Wilderness could be 

as high as 5400 people per year (if use was distributed 

evenly by day). This could be converted to recreation 

visitor days (RVDs) by multiplying capacity in people 

by average length of stay (in hours) and dividing by 

12 hours. Average length of stay varies substantially 

among wildernesses, particularly with variation in the 

proportion of use that is day use. Recent data from the 

National Visitor Use Monitoring program suggest that 

mean length of stay in designated wilderness is about 

15 hours. Using this figure, capacity of Inspiration 

Wilderness could be as high as 6750 RVDs. Again, this 

assumes that use can be distributed spatially such that 

use never exceeds capacity in any of the analysis areas.

Variations on Step 3, 

Estimating Capacities

There are many variations on Step 3 depending on 

the nature of the thresholds that have been established 

and the information (common sense, monitoring, 

research, and so on) that can be used to develop estimates. This makes it impossible to outline a standard 

method for making such estimates. The example above 

relied on logic and judgment. Below we outline other 

examples. If these do not work for your situation, use 

other estimation procedures. The critical point we are 

trying to make is that you must take the best available 

information and use that information in a logical manner to arrive at the best possible estimate of capacity, 

given available information. The keys are (1) to use 

whatever information is available and (2) to use it in 

a logical rather than arbitrary estimation process that 

draws on professional experience and judgment.

If monitoring data are available, either to develop or 

refine initial estimates, the process outlined above does 

not change. But there is a richer source of information 

available for making estimates. For example, consider 

the threshold of no more than five encounters per day 

in the primitive zone. If you have data on use levels 

and encounter levels and the monitoring data show that 

encounter levels currently average about 2.5 groups per 

day (half of the threshold), it would be reasonable to 

estimate that capacities could be approximately double 

the current use levels. This estimate may be misleading, however. To double use and stay within capacity, 

use would have to be distributed evenly across the days 

Table 4. Capacity estimates (maximum number of groups/day that can enter without 

exceeding thresholds) for the semi-primitive analysis areas.

Semi-primitive Analysis Area

Threshold 7 8 9

≤ 15 groups/day on 90% of days Not the limiting factor

≤ 10 campsites/square mile Not the limiting factor

≤ 5 campsites/square mile with condition class > 3 25a 25a 40a

≤ 10% reduction in bear populations 40 40 60

Capacity (entering groups/day) 40 40 60

a

Maximum number of overnight groups; there can be an unlimited number of day groups.
USDA Forest Service RMRS-GTR-247. 2010. 17

and across the trailheads. It is likely that this would 

require implementation of a permit system. If unwilling to do this, capacity would be lower and would have 

to be estimated using a more detailed analysis of individual analysis areas and daily use and encounter data. 

This is an illustration of how capacity is dependent on 

all the management actions that have been or will be 

taken.

As an example of a more detailed analysis, consider 

data that show that encounters are five or less per day 

on only 80% of days in the 100-day use season (violating the threshold of 90% of days). This suggests that 

current use exceeds capacity, but by how much? If 

daily use is arrayed from lowest to highest, unacceptable numbers of encounters typically occur when use 

exceeds the 80th percentile. For example, suppose that 

7000 groups per season enter and that daily use levels 

range from 0 groups/day to a high of 150 groups/day. 

Assume that the 80th percentile use level is 100 groups/

day (i.e., 80% of days have 100 groups or less). This 

suggests that there are currently 20 days when use exceeds 100 groups but that, to avoid exceeding capacity, 

use should exceed 100 groups on only10 days. That is, 

on 10 of the days when somewhere between 100 and 

150 groups enter, only 100 should be allowed to enter. 

This suggests it might be reasonable to reduce current 

use by perhaps 25 groups on each of those 10 days. So 

capacity would be about 6750 (250 groups less than 

the current use level of 7000). Note, capacity could be 

maintained at 7000 or even increased if use was simply 

shifted from high-use days to low-use days.

In contrast, estimates are quite straightforward if 

thresholds are written in terms of allowable use per 

unit area. Perhaps black bear researchers estimate that 

the effect of recreation on bears is likely to be negligible if use density is no more than five persons at 

one time for every one thousand acres. For a 100,000 

acre wilderness, capacity would be 500 people at one 

time. To derive an annual capacity, this could be multiplied by the length of the use season. If the season is 

100 days, capacity would be 50,000 people per year. 

But this capacity would have to be reduced if use was 

unevenly distributed among days. For example, if 

there was four times as much use on weekends as on 

weekdays, capacity would be 22,500 people per year 

(50,000 x 0.45).

It is important to remember that this estimate of capacity can only be realized if use is fairly uniformly 

distributed among the analysis areas in the wilderness. 

Capacities need to be implemented on an analysis 

area basis to ensure that no analysis area exceeds the 

five persons at one time for every one thousand acres 

threshold.
18 USDA Forest Service RMRS-GTR-247. 2010.

The following guidelines were developed by recreation managers on the Lolo National Forest and staff 

from the Northern Region office during a workshop on 

April 6-7, 2010. The purpose of the workshop was to 

test the method described in an early version of this 

General Technical Report to assist managers in establishing capacities using available information. The 

group ran through several existing recreation management challenges on the Lolo NF using the outlined 

method. The method in the report was found to be 

useful, but participants suggested a few adjustments 

to make the process more applicable to specific placebased issues, both in wilderness and non-wilderness 

areas. The steps include:

• Identify the issue or management question

• Define the analysis area and existing condition

• Review existing guidance for the area and refine 

the desired condition

• Determine thresholds and the limiting factor

• Determine estimated capacity

• Identify management actions affecting capacity

• Identify additional information needs

Step 1. Identify the issue or management question that can be informed by developing visitor 

capacity. What is the issue or management question 

prompting staff to look at the amount or types of uses 

in an area? There are numerous and diverse issues that 

may force planners and managers to assess visitor use 

impacts in an area. Examples include perceived crowding, user conflicts, decline in the quality of hunting, 

receiving proposals for more or new commercial use, 

increase in number and/or size of dispersed campsites, 

overflowing parking lots, and pollution (human waste, 

litter, water pollution). In all of these cases, an understanding of visitor use in the area will be valuable.

Before jumping into the capacity analysis, it is useful to determine the extent to which a capacity will be 

helpful to decision-makers. In some cases, information 

provided by a capacity may not help decision-making, 

as the issue is not clearly tied to the amount of visitor 

use in an area. The important question to ask is: will 

a capacity help resolve the issue or provide useful 

information for a decision? A few examples where a 

capacity may not be very informative include: exceeding capacity to administer permits to standard, outfitter 

camps out of compliance, and illegal ATV use. Clearly 

identifying the issue or question will ensure that the 

analysis is focused. See Cole and others (1987) for 

common problems associated with recreational use.

Step 2. Define analysis areas and the existing condition. What area is impacted by the issue? This is 

the analysis area. Managers can also begin a capacity 

study by defining an analysis area, then identifying issues within that area. In other words, steps 1 and 2 can 

be switched depending on the reasons for developing 

a capacity. The boundaries of the analysis area can be 

based on terrain, access, or where certain activities are 

found. An analysis area should be possible to manage 

as a single unit and be allocated to one type of management area. For example, in one case study the group 

divided a large hunting area into drainages. In another 

example, hydrologic units were used as analysis area 

boundaries.

Once the analysis area(s) have been defined, provide 

a thorough description of what is occurring in that area. 

This should include a description of the types and timing of activities, amount of current commercial use, 

any signs of resource degradation, user conflicts and 

perceptions, and possible trends in use. The more accurate the description, the more accurate a capacity study 

can be. Use as many sources of information as possible 

to paint a picture of visitor behavior and use levels. 

Observations, database reports, resource conditions, 

information on the internet, applicable landscape-level 

assessments, volunteer registration at trailheads, visitor 

encounters, and any monitoring data are all excellent 

resources.

In some cases, once a clearer picture of the existing condition is developed, the issues identified for that 

area may change. If this is the case, make sure the issue 

or management question (step 1) is clearly understood 

before proceeding, as the rest of the process revolves 

around the issue(s).

Appendix C—An Issue-Based Numerical 

Visitor Capacity
USDA Forest Service RMRS-GTR-247. 2010. 19

Step 3. Review existing guidance for the area 

and refine the desired condition. Forest plans provide the most important guidance for management 

actions. In addition, Forest Service manuals and handbooks, forest-wide standards, and landscape-specific 

standards and guidelines may direct how an area, or 

a type of use, is to be managed. Other planning products such as travel plans, landscape assessments, and 

river management plans can also provide place-based 

recreation guidance to help describe the area’s desired 

condition. In some plans, the Recreation Opportunity 

Spectrum (ROS) (USDA Forest Service 1982) for a 

given management area provides direction on the types 

of recreation opportunities the unit wants to provide.

In the capacity study, you are quantifying use in 

terms of the desired condition. Thus, there needs to be 

a clear picture as to what the desired condition for recreation is in that area. In plans, however, the desired 

condition is often very general and broad to allow for 

flexibility in implementing the plan. Take this opportunity to refine the desired condition for recreation in 

the area being analyzed. If the desired condition is left 

vague, it will be more difficult to complete the capacity 

and the unit will have a harder time selecting appropriate management actions.

Step 4. Develop threshholds and identify the limiting factor for use in each analysis area. Thresholds, 

for this process, are the point at which social or biophysical conditions will be unacceptably impacted by 

visitor use and serve as triggers for action. These are 

identified through indicators and standards. Indicators

are the most important attributes of an area most likely 

to be at risk from high levels of visitor use. Attributes 

that are unrelated to visitor use or that can be protected 

without limiting use are not needed for capacity estimates. Standards are the maximum acceptable level of 

impact to the indicator. If these standards are exceeded 

(the threshold is crossed), different management actions may be necessary to prevent further resource 

degradation. Along with being directly linked to visitor use impacts, the best thresholds for determining 

numerical capacities are also quantitative, reliable, 

sensitive to change, and administratively feasible (see 

McCool and others 2007). Indicators and standards can 

be established for social or biophysical resources. For 

example, the indicator for a hunting area may be an opportunity for solitude for the visitor as described in the 

ROS class for that area. The standard might be that the 

visitor encounters no more than three other hunters in 

one day. Thus, the threshold is encountering three other hunters in one day. Other thresholds may deal with 

impacts to wildlife, vegetation, campsite occupancy, 

parking, space at a destination, or other attributes.

The limiting factor is the threshold that allows for 

the least amount of use. In one example, thresholds 

were established for encounters, parking spaces, and 

space for viewing a waterfall. Because visitors expect 

to see a lot of other people and can spread out along the 

trail to avoid congestion at the waterfall, the relatively 

small parking lot was the limiting factor. See the interagency strategy for wilderness monitoring (Landres 

and others 2008) for examples of indicators designed 

for wilderness, many of which can be applied to nonwilderness settings as well.

Step 5. Determine estimated capacity for the 

analysis area. Use the limiting factor to estimate 

the amount of use an analysis area can sustain. Along 

with the amount and location of visitor use, capacities 

should also be based on the type of use and the time 

when these uses occur. Capacities can be established 

for all types of use in an area at a given time, or for a 

single type of use; this should be determined by the issue, the desired condition, and the limiting factor. For 

instance, if the limiting factor for use in an area is parking lot size, then the capacity would be for all types 

of uses occuring at the same time, assuming that all 

visitors use that site for parking. On the other hand, if 

the limiting factor is number of campsites, then there 

may be a capacity for camping each night, but day use 

hiking might be unlimited.

Different capacities may also be established for different types of uses in an analysis area. If there is a 

need to establish a capacity for an area that includes 

more than one analysis area (district- or forest-wide), 

the estimates for each analysis area can be added together, according to the type and season of use. Large 

scale capacities can help inform programmatic planning efforts.

Step 6. Identify other management actions to 

manage visitor use impacts. The estimated capacity 

should be refined based on the potential influence of 

other planned projects or other management actions in 

the analysis area, since we are looking at impacts to the 

resource and not merely the number of people in the 

analysis area to achieve a defined desired condition. 

Also, an understanding of capacity can help determine 

appropriate management actions that need to be implemented. For example, a district is finding degraded 

conditions at a number of campsites in a backcountry 

area. They are planning to establish designated campsites along a popular trail to reduce this impact. This 

may result in a higher or lower estimated capacity for 
20 USDA Forest Service RMRS-GTR-247. 2010.

overnight use, depending on how many campsites are 

designated. Other actions such as increasing trail durability, educational outreach about LNT principles 

and techniques, increasing parking lots, or restricting 

certain uses may also have an impact. Cole and others 

(1987) provide a number of actions to help mitigate 

common problems associated with recreation use.

Step 7. Identify additional information needs.

While developing an estimated capacity, managers may 

find significant gaps in their understanding of recreational use and impacts in an area. First, clearly define 

the questions that need to be answered or studied and 

the types of information that will be useful. How can 

this information be gathered efficiently? Most likely, 

other districts or forests have dealt with this same issue 

and can provide suggestions for actions that worked for 

them. Receiving input from outfitters and guides, other 

interested groups, and other individuals is extremely 

valuable and will help increase awareness and transparency in the capacity analysis process. If use levels 

are high and there is evidence of user conflicts, public 

participation is highly recommended, even if the unit 

is not planning to immediately develop a specific proposed action based on the estimated capacity.

Once actions are implemented regarding visitor use, 

monitoring is essential to allow the unit to refine the 

estimated capacity. Evaluate whether the action has 

resolved the issue or if other issues have arisen in the 

area. If there are still issues, reassess the estimated capacity and management actions being used. Thus, this 

process is intended to be cyclical, with each iteration 

offering a more refined capacity.
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