Over the past two centuries, woody plant species have increased in density and extent throughout rangelands worldwide. Of particular concern in North America is conifer encroachment, the gradual establishment and domination of coniferous trees within a non-forest habitat type due to disruption of historic ecological processes [1
]. Species of concern vary regionally, but often are in the genus Juniperus
. Typically encroachment is viewed negatively by land managers and considered a factor in ecosystem degradation [3
]. Impacts include increased soil erosion, changes in wildfire occurrence and intensity, changes in vegetation composition, and shifts in local wildlife species [5
]. To avoid such impacts land managers often seek to remove encroaching conifers and restore historic plant communities.
Such proposals can be controversial due to concerns about environmental impacts of practices such as prescribed burning or herbicide use, as well as doubts about the severity of the problem or the motivation behind projects billed as “restoration” [7
]. Therefore land managers seek ways to predict and influence public sentiment toward removal projects, especially on federal lands where management is subject to public review as mandated by the National Environmental Policy Act (NEPA). To address existing or potential future citizen opposition, public awareness efforts often seek to emphasize the threat posed by encroaching species, thereby creating a “frame”, or rhetorical context, for the issue that may be able to influence its perception by the public [10
], and thereby increase willingness to accept intervention options.
In mountain regions of the western USA conifer encroachment has reduced the extent of native shrub-steppe communities. Much of this encroachment involves larger species, primarily Douglas-fir (Pseudotsuga menziesii) and occasionally ponderosa pine (Pinus ponderosa), along with smaller conifers such as Rocky Mountain juniper (Juniperus scopulorum). Because of the iconic nature of some of these species, rangeland managers may be wary of negative public reaction to proposed removal and thus try to influence citizen acceptance of restoration practices. In this study we sought to understand how framing the conifer encroachment issue affects acceptability of two removal practices (prescribed burning and tree felling) in the northern Rocky Mountains region.
1.1. Societal Acceptance of Management Practices
For legal and practical reasons, managers of federal lands need to predict and account for levels of public support or animosity toward their activities, i.e.
, what has become known in U.S. land management as the “social acceptability” of management practices and the conditions resulting from those practices. The social acceptability concept has been applied in various contexts including timber harvest [11
], hazardous fuels treatments [8
], and wildfire management [12
]. While acceptability is measured at the individual level, managers and social scientists assume that individual acceptability measurements can be aggregated to represent overall public opinion [13
]. Managers may use this information to alter proposed actions are implemented to better represent what the public desires, or to increase citizen awareness of issues by altering or developing educational programs.
In this study we measured levels of acceptability of two common methods for removing encroaching conifers: prescribed burning and mechanical removal using chainsaws. Previous studies in various parts of the USA have found public support for both practices [8
], but acceptance varies regionally [8
1.2. Issue Framing in Natural Resource Management
Researchers do not agree on a definition of the term “framing”, with some arguing it should be broadly defined as any effort to influence opinion or action through the shaping of message content, and others calling for a narrower conceptualization limited to the presentation of competing arguments [16
]. In this study we used a broader definition following Gamson and Modgiliani’s idea that a frame is simply the words, images, or phrases a communication source uses to reveal what is relevant to a topic at hand [17
]. The context within which an issue is presented can greatly influence the opinions people hold towards it. When the same issue is framed in different ways, preferences and attitudes for that issue can shift [18
]. Accordingly marketers, political activists and other communicators use frames to try to direct opinions along a specific path of interpretation [10
]. Environmental conflicts often become intractable due to the choice of frames used by different stakeholders [20
]. In the context of invasive species, various frames have been used to encourage changes in policy or behavior including ones that emphasize taking ownership of the problem [22
] or highlight positive restoration actions [23
], as well as more negative constructions focused on inequality of impacts [24
] or, most often, risks to people or nature [25
Battle metaphors abound in discussions of invasive species, as when Elton opened his classic work, The Ecology of Invasions by Animals and Plants
, by likening what he called “ecological explosions” to the threat of nuclear war [27
]. By comparison, actions to prevent or reverse invasions often are described in terms borrowed from medicine such as “prescription” or “treatment.” The use of military metaphor has its critics [28
] but remains standard in the field. Most scientists who study biogeography are careful to use the term “invasion” only to refer to range expansions resulting from intentional or incidental introductions by humans. Range shifts that occur without direct human agency are typically described as “encroachment” if they are undesirable, “expansion” if viewed positively or neutrally.
We wondered whether such meticulous care in language might be counter-productive from a public influence standpoint. While social scientists have given considerable attention to public attitudes toward invasive species [30
], few have focused on conifer encroachment. Given that encroachment is viewed as having ecological and economic consequences comparable to non-native species invasions [31
], use of the milder term might tend to diminish those consequences in the public eye. Alternatively, would attitudes toward conifer removal—an action directed against “encroaching” rather than “invading” species—be different if harsher militaristic terminology were used?
Social scientists have shown that changing the label of an issue in an opinion survey changes its symbolic meaning, which in turn can dramatically affect responses and support [32
]. Therefore we assessed the effect of issue frame on public opinion by means of a survey about the social acceptability of practices used to reduce conifer density and cover. To do so, we surveyed citizens using a questionnaire in which the frame differed across recipients. Framing reflected how managers and scientists typically describe the problem, distinguishing between non-native plants described using battle metaphors and native species described in more benign terms. We hypothesized that the acceptability of prescribed burning and felling would be enhanced if conifer increase were framed as invasion rather than as encroachment or expansion.
The study area consisted of 75 counties in the Northern Rocky Mountain region of the USA where encroachment by large conifers into sagebrush-dominated rangeland was likely to occur. County selection was made using land-cover data from a recently completed regional gap analysis [33
], downloaded into the spatial analysis program ArcGIS 9.2. Study counties were those where cover classes dominated by large conifers adjoined land cover zones designated as sagebrush steppe: 33 in Montana, 21 in Idaho, 16 in Wyoming and 5 in South Dakota.
To gather data representative of beliefs among the public we obtained a list of 2,000 households within the 72 study counties from a private research firm, Survey Sampling International (SSI) of Fairfield, Connecticut, USA. SSI draws its random samples from telephone directories, which offer a comprehensive, frequently updated source for obtaining addresses but do present some drawbacks. Phone directories can contain incomplete addresses, making survey delivery difficult in small rural communities where all mail delivery is to post office boxes. Directories do not include names of households whose telephone number is unlisted, nor those of households whose members rely solely on mobile phones. This may tend to skew the sample toward older respondents as persons who choose to forgo a “land line” are more likely to be under 35 years old, unmarried, Hispanic, and students [34
Survey administration followed a modified version of the procedures recommended by Dillman [35
]. A survey was mailed in September 2008 to each of the 2,000 households along with a cover letter explaining the objectives of the research. This was followed 10 days later by a reminder and thank-you postcard. Two weeks later a second survey was sent to those households who had not responded to the initial mailing. Recipients who did not respond to either mailing were assumed to be unwilling or unable to participate, and no further efforts were made to recruit them.
An eight-page questionnaire, titled “Western Conifer Survey”, was used that included items about demographic information, assessments of the condition of and threats to natural landscapes in the region, beliefs about rangeland management, and acceptability judgments for selected practices used to change rangeland vegetation as well as conditions that may result from use of those practices. The cover letter accompanying the survey included a summary of problems associated with increased growth of unwanted vegetation: “The scenic landscapes of the West are constantly changing due to both natural processes and human activities. One change that is of growing concern in many parts of the West is an increase in the amount of land covered by conifer trees such as pines, firs, and junipers. When this change occurs in landscapes previously covered by grasses, shrubs, and other smaller plants, it’s called ‘conifer’. In some cases, conifer can negatively affect rural areas by increasing wildfire hazard, restricting forage for livestock, and reducing biological diversity.” The words used in the blank space above (encroachment, expansion, invasion) were randomly assigned to each survey. The survey and cover letter were reviewed and approved by Utah State University’s Institutional Review Board.
Ecological scientists and natural resource managers typically maintain a strict vocabulary for describing changes in plant and animal distribution that distinguishes between invading, encroaching, and expanding species. These distinctions may not be ecologically necessary, as native and non-native plants tend to respond similarly when they can exploit previously untapped biotic resources [43
] but they do reflect the social desirability of outcomes for the ecosystem being colonized [44
] and in the type and perceived urgency of management response that is recommended [45
]. Because scientists and land managers generally perceive that the need for a response is most urgent when the spreading species is not native, the use of military metaphors has become common in the discipline of invasion biology as well as in applied fields such as weed management. As Larson notes, “Invasion biologists and conservation managers presumably (and perhaps unconsciously) rely on the rhetorical power of this language to generate action against these species, which are invisible to most people” ([29
], p. 495).
In this study we found little evidence that such language leads to increased support for control actions. The vegetation change process of interest in our study is appropriately called “encroachment” [1
], a word with a mildly pejorative meaning. Yet when we substituted the militaristic term “invasion” or the benign term “expansion”, there was no statistically significant difference in respondents’ estimations of the threat posed by increasing woody plant populations, nor did we see a difference in levels of acceptance for vegetation removal practices or the landscape conditions created by varying levels of woody plant cover. We did find that respondents who received the “invasion” frame held higher acceptance levels for the general idea of removing trees from rangelands than did those who received the “expansion” frame. Yet even though the acceptability score for the “invasion” group was twice as large as that for the “expansion” group (1.54 vs.
0.72), the means for all three groups were within a range describing mild acceptance for tree removal.
We chose scientific terms as our issue frame. These are not necessarily the same words that resonate most with the general public. For example, Metz and Weigel tested the terms “controlled burn”, “managed burn”, “proactive burn”, and “prescribed burn” using focus groups to determine how much each term resonated with public sentiment [46
]. The term “controlled burn” resonated most strongly with the general public. Study participants preferred the term “burn” versus
“fire” because burns were perceived as smaller, less “wild”, and better able to be controlled. Managers, conversely, prefer the term “prescribed fire” over “controlled burn”. It is important to understand that the terminology and language that resonate most with the public may not be the same as is used by scientists or natural resource managers.
Further, people with no previous experience with an issue are likely to answer survey questions even though they essentially have no formed opinion about the issue [47
]. When asked to self-assess their knowledge “about the management and condition of natural environments in your region,” 80% rated themselves as moderately to very knowledgeable. However, when asked to rate how various landscape processes might affect healthy landscapes, conifer expansion/encroachment/invasion was the least likely to be identified as a threat, suggesting knowledge of that particular process is low. We found no relationship between education level and perceived threat. Describing an earlier public survey about rangeland management, Brunson and Steel suggested that when people are presented with new ideas concerning the scientific world they are likely to apply an already established lens or filter to judge the new item [48
]. Similarly, respondents to the present survey may have judged the issue of conifer encroachment using knowledge and attitudes formed for more familiar and basic landscape health issues.
Our results not only are contrary to the expectations of ecologists and land managers concerned about invasion and encroachment effects, but they also seem to contradict those of social marketing researchers who argue that using message framing in combination with a specific target audience can enhance the success of an environmental action campaign [17
]. Typically pro-environmental social marketing is a multi-step programmatic activity and not a one-time exposure to an issue frame in a survey instrument [10
], so perhaps the effect would be enhanced by multiple exposure to the frame. Smith did measure an effect through use of a survey [32
], but the issue in that study was social welfare programs, which likely are more salient to a wide array of citizens as compared to removal of undesirable trees. It is also worth noting that the terms used in the study were chosen for their scientific correctness, not the likelihood that they would resonate differently in a social marketing campaign. Therefore while we cannot assert from this study that using a militaristic scientific metaphor would enhance the social acceptability of burning and/or felling encroaching conifers in rangelands, neither can we dismiss the notion that framing could be an effective tool in a broader marketing campaign.