Human Ecology

, 39:641

Human Dimensions of Earthworm Invasion in the Adirondack State Park


  • Dara E. Seidl
    • Colgate University
    • Abt SRBI, Inc.
    • Colgate University

DOI: 10.1007/s10745-011-9422-y

Cite this article as:
Seidl, D.E. & Klepeis, P. Hum Ecol (2011) 39: 641. doi:10.1007/s10745-011-9422-y


The invasion of exotic earthworms in the Northern Forest of the United States alters carbon and nitrogen cycles and reduces forest litter and native plant cover. Humans are the principal agents of dispersal, spreading earthworms both inadvertently via horticulture, land disturbance, and in the tires and underbodies of vehicles, and voluntarily through composting and the improper disposal of fish bait. A study in Webb, NY—a town located within the Adirondack State Park, one of the most celebrated cultural and ecological regions in the US—exposes the human dimensions of earthworm invasion. Environmental history research, interviews with residents and bait sellers, and a mail survey of town residents show that positive attitudes towards earthworms and their ecological effects lead to casual disposal or use of them. Earthworm use is a strong cultural practice and the risk of their continued introduction in the Adirondacks is high.


EarthwormsEnvironmental knowledgeInvasive speciesLand-use changeNorthern hardwood forest, Adirondacks


The Wisconsin Glaciation eradicated native earthworms from much of the Northern Forest of the United States (James 1995). Because of subsequent invasions by exotic taxa, earthworms in the northern US today are almost all exotic species. Although earthworms may have important positive effects on ecosystems with which they have coevolved (Edwards 2004), the invasion of Asian and European earthworms into previously unoccupied areas of North America has led to changes in soil structure, nutrient availability, and habitat quality for plants and animals (Alban and Berry 1994; Gundale 2002; Bohlen et al.2004a; Hale et al.2005).

The presence of earthworms in temperate, hardwood forests may accelerate decomposition of forest litter, which potentially reduces habitat for forest-floor animals, simplifies soil structure (e.g., soil compaction, nutrient leaching, and increased soil erosion), and affects carbon and nitrogen cycles (Addison 2009; Johnston et al.2004; Suárez et al.2006). In Minnesota, for example, forests with invasive earthworms experience a decrease in forest litter, with the leading edges of invasion undergoing a rapid decline in forest litter thickness (Hale et al. 2005). Impacts include a possible reduction in plant species richness (Holdsworth et al.2007), including the endangered goblin fern, Botrychium mormo (Gundale 2002). In addition, a degraded forest litter layer potentially reduces arthropod, salamander, and small mammal populations, and may disturb communities of ground-nesting birds (Hale 2008). In central New York State, Bohlen and colleagues (2004a, b) find that invasive earthworms both reduce carbon storage in the soil by 28% and alter the nitrogen cycle through the formation of nitrogen-rich earthworm casts, which stimulate nitrification and microbial activity. The overall effects on the carbon and nitrogen cycles vary among earthworm species and habitat types, but alteration of these cycles has the potential to affect the entire ecosystem (Bohlen et al. 2004a).

Research on invasive species of all kinds, including earthworms, tends to focus on biophysical processes and conditions that affect susceptibility to invasion (landscape characteristics) and invasiveness (invading organism characteristics) (Robbins 2004a). For example, soil moisture and pH, leaf-litter quality and quantity, and level of land disturbance are key factors affecting the quality of the environment for earthworms (Hale et al.2005; Ammer et al. 2006; Tiunov et al.2006; Bernard et al.2009). Even with favorable conditions, however, earthworm invasiveness is constrained by an average dispersal rate from an initial introduction site of about 10 m per year (Tiunov et al.2006; Hale 2008; Hendrix et al.2008).

In addition to biophysical phenomena, humans directly and indirectly prepare a landscape for invasion (Maestas et al. 2003; GLP 2005). Since the origins of the earthworm invasions in North America, people have been spreading them both voluntarily (when they knowingly move a species from one area to another, regardless of whether or not they are aware that the species is invasive) and involuntarily (when people are unaware that they are transporting the species in question) (Tiunov et al.2006).

Many initial earthworm introductions stem from involuntary earthworm dispersal linked to landscape change, with the degree of success in earthworm introductions connected, in part, to past and ongoing land disturbances (Callaham et al. 2006). Kalisz and Dotson (1989) find that forested areas of the Southern Appalachians that were previously cleared for cultivation, timber production, or residences lost native earthworm species and gained exotic varieties whereas portions of the same region that have been only minimally disturbed by people apparently still support intact, native earthworm communities (see also Kalisz and Powell 2000).

Beyond playing a role in landscape change, people can act as dispersal agents, moving exotics from their native to invaded ranges. Although some earthworm invaders have effective modes of natural dispersal, recent molecular evidence supports a primary role for humans in moving them into and within new areas (Hale 2008). Understanding earthworm invasion, therefore, requires research on the human activities that facilitate it. But few such studies exist. Helping to fill this gap, we contribute to a growing body of social science research on the cultural biographies of species invasion (Robbins 2004a), a conceptualization that gives special attention to nature-society interactions and the ways that humans prepare landscapes and create invasion pathways.

We explore the human dimensions of invasive earthworms through a case study of Webb, NY. The town is located in the Northern Forest of Upstate New York and in the western part of the Adirondack State Park, a conservation zone that represents the largest unbroken temperate forest in the world and an area of tremendous cultural and ecological significance (Wildlife Conservation Society 2009; Fig. 1). Three main elements are considered: (1) earthworm introduction, (2) dispersal mechanisms in the Adirondack mountain region (Adirondacks) since the 1800s, and (3) earthworm control motivations today.
Fig. 1

The study area—Webb, NY (Source: Adirondack Park Agency Map projection: NAD 1983 UTM Zone 18N)

Webb is the Adirondack State Park’s largest township and has an extensive history of logging and recreational fishing, two practices that make it especially vulnerable to earthworm invasion. An environmental and land disturbance history of Webb since the nineteenth century uncovers patterns of earthworm introduction and dispersal, and in particular the pathways of involuntary introduction.

Face-to-face interviews and mail surveys of current town residents and tourists build on the environmental history research. We assume that voluntary earthworm introduction—when humans are willing participants in the dispersal of earthworms—is best captured by a study of people’s values and behaviors, and the way they understand the role earthworm species play in the ecosystem. We explore these themes using the kind of mixed methods (qualitative and quantitative) uniquely suited to understanding complex nature-society relationships (see Robbins 2004a, b; Roy Chowdhury and Turner 2006).

Despite their potential negative environmental impacts, invasive earthworms receive scant attention by non-scientists compared to other invasive species (Bohlen et al.2004c). Overall, perspectives on earthworms range from those who consider them to be undesirable, requiring active control measures, to those who see them as useful, naturalized additions to the ecosystem (Hall 2003: 9). In addition to characterizing the perceptions of Webb residents, we analyze the potential for implementing control measures by testing whether increased knowledge of invasive species, in general—as well as other possible explanatory factors, such as interest in outdoor recreation and land management experience—lead to behaviors that minimize the introduction of invasive earthworms.

In addressing the human dimensions of earthworm introduction and dispersal as well as attitudes towards control measures, the Webb case study enriches understanding of nature-society relationships and raises important questions about society’s response to the invasive earthworm phenomenon.

Analytical Approach

We use environmental history, interview, and survey research to produce a coherent story of earthworm invasion in the Adirondacks and its social dimensions (see Table 1). First, environmental history analysis exposes pathways of introduction, cultural practices, and dispersal mechanisms. Second, our analysis of recent, individual behavior connected to earthworm introduction includes both a review of environmental knowledge-attitudes-behavior studies as well as interviews and preliminary surveys of Webb residents and bait sellers. These steps underpin the creation of a conceptual model connecting knowledge and attitudes to earthworm-related activity (Fig. 2). Detailed explanation of the model is described below. To test the model, in a third step, we surveyed permanent residents of Webb. In both interviews and surveys, we focus primarily on permanent residents because they represent agents of longer-term dispersal and repeated introductions, although we acknowledge that subsequent research should consider the attitudes and behaviors of seasonal residents and visitors as well.
Table 1

Analytical approaches and data sources used in the Webb, NY, case study

Focus (social dimension of earthworm invasion)

Analytical approach


Earthworm introduction

Environmental history

Secondary sources

Involuntary & Voluntary

Government documents

Interviews with 13 Webb landowners (permanent residents)

Mechanisms of human dispersal of earthworms

Literature review & content analysis

Secondary sources


Interviews with 13 Webb landowners (permanent residents)

Interviews with 3 bait sellers in Webb

Preliminary survey (28 visitors to Webb Info. Center)

Perceptions/behaviors vis a vis earthworms

Development of knowledge-attitudes-behavior conceptual model

Secondary sources


Interviews with 13 Webb landowners (permanent residents)

Preliminary survey (28 visitors to Webb Info. Center)


Statistical analysis (one-way ANOVA, t-tests, and linear regression)

Mail survey (148/400 respondents, 37% response rate)
Fig. 2

Conceptual model for voluntary earthworm dispersal behavior

Following standard mail survey methodology (as described in Dillman et al.2009, and including pre- and post-survey postcards that described the project; see Fig. 3), we mailed 400 Webb residents an eight-page survey on recreation and environmental practices. Respondent names and addresses were selected randomly from tax maps available from the Adirondack Park Agency. The survey consists of a mix of categorical and Likert-scale questions exploring the following themes: recreational activities (including a detailed exploration of fishing and gardening practices); attitudes towards and knowledge about environmental issues in general, and invasive species in particular; and respondent characteristics (e.g., income, education level, occupation, political affiliation, age, etc.). Aside from two surveys that were returned as undeliverable, the mail survey generated 148 responses (a return rate of exactly 37%), which we analyze using one-way ANOVA, t-tests, and linear regression.
Fig. 3

Preliminary postcard mailed to potential survey respondents


The detailed rationale for the hypotheses we test is provided in the next three sections. In summary, we hypothesize that age, gender, income, education, and childhood/adult environment influence environmental knowledge (i.e., understanding of basic facts) and attitudes (e.g., earthworms are “good” for the environment) through the intervening variables of political views, outdoor recreation experience, and land management experience (Fig. 2). Residents who are younger, female, have higher incomes, higher education levels, come from rural backgrounds, and who have both richer outdoor experience and more land management experience are expected to have more environmental and invasive species knowledge as well as more pro-environmental attitudes. We hypothesize that these respondents are more likely to avoid voluntary behaviors that lead to the spread of invasive earthworms.

Historical Pathways of Invasion

A review of the land use history in the Northern Forest reveals both voluntary and involuntary pathways of earthworm introduction. Nearctic (native) earthworms have not yet recolonized the Adirondacks following the Wisconsin Glaciation (Hendrix and Bohlen 2002). Exotic earthworms are present there; however, no systematic sampling has been undertaken and the distribution of earthworm species in the Adirondacks is largely unknown (Bernard et al.2009). The octagonal-tailed worm (Dendrobaena octaedra) seems to be the most common species in the region and one of only two species, the other being Dendrodrilus rubidus, of which we are aware in the region’s closed-canopy forests. Other exotic species are present in disturbed habitats, such as along roadsides or in residential yards (Bernard et al.2009). Multiple mechanisms explain the presence of these exotic earthworms in the Adirondacks.

Human Dispersal Mechanisms

European settlers arriving in North America dumped ballast, a mixture of soil and gravel used to balance ships, thereby inadvertently depositing exotic earthworms hidden within the soil. Today, recreational fishing (through improper disposal of fish bait), gardening (planting, mulching, and composting of materials transported to a new site), vermicomposting (intentional use of exotic worms in compost systems), and unintentional translocation of egg cases in the tires and underbodies of vehicles are all mechanisms by which humans may disperse exotic earthworms (Callaham et al.2006; Hale 2008; NRRI 2008). In addition, land disturbance helps to prepare the landscape for invasion.

Some researchers contest the idea that land disturbance is a necessary precursor to earthworm invasion. James and Hendrix (2004) discovered earthworms in areas without dramatic land-use change or habitat fragmentation, for example. And Tiunov et al. (2006) agree that anthropogenic land transformation is not required for earthworm colonization, although it may be conducive to the growth of larger populations. But conventional wisdom in scholarly literature is that land disturbance creates an environment suitable for earthworms by altering both the chemical composition of the soil and nutrient availability. Disturbances, such as the building of roads and homes (activities that both disturb the soil and often involve the importation of gravel and soil that may contain worms and cocoons), land clearing for oil and gas exploration, and logging are known pathways of earthworm invasion—they potentially introduce earthworms as well as improve conditions for those that are already there (Tiunov et al.2006; Cameron et al.2007; Cameron and Bayne 2008).

Forest clearing creates a suitable earthworm habitat because, although it eradicates the forest litter layer, there is often improved soil fertility and food quality in the cleared area (Kalisz and Dotson 1989; Curry 2004). Gundale et al. (2005) show that logging sites in Michigan are significantly more likely to be invaded than similar sites near roads without a history of logging. Beyond soil conditions, however, the most important mechanism by which earthworms are established in remote areas is human transport: eggs and cocoons are trapped in equipment and vehicle tires, and then carried into logging sites where there is a wealth of forest litter on which growing worms feed (Tiunov et al.2006; Hale 2008). In addition to logging sites, the older and more highly-traveled the road, the greater the earthworm biomass in the surrounding soil. Hale (2008) finds that earthworm distributions are strongly associated with roads, and Cameron and Bayne (2008) conclude that road age is a s1ignificant predictor of earthworm populations in Alberta, Canada.

The exchange and transportation of exotic soils in both rural and urban gardens contributes inadvertently to earthworm infestation (Hendrix et al.2008). During shipping, plants are often packed with soil containing earthworms, and represent a high-risk pathway for dispersal (Proulx 2003). The transplantation of exotic earthworms through horticulture is not always unintentional, however. Due to the perception that earthworms improve soil fertility and have positive effects on plant growth, some horticulturalists deliberately introduce worms into their gardens (Curry 2004).

Two other routes of intentional earthworm introduction are through vermicomposting and recreational fishing (Edwards 1998). The exotic Lumbricus rubellus is a popular compost worm in temperate regions and is often selected for use in community mulch piles. Compared to these concentrated, one-time composting introductions, however, the bait industry serves as the most important vector for widespread and scattered exotic earthworm introduction in remote areas (Hale et al.2005). Earthworm invasions often radiate outward from boat launches, campsites, and popular fishing spots, where anglers dispose of excess bait (Cameron et al.2007). There is more genetic diversity among earthworm populations at boat launches than at most other sites, suggesting multiple introductions over time from anglers dumping bait (Hale 2008).

Earthworm Introduction and Use in Webb, NY

Webb has a population of 2,000, which increases to some 3,000 in the summer months, in particular surrounding the principal tourist destination of Old Forge. European settlement began in the 1790s (Grady 1966): while the region’s acidic soils make agriculture challenging there are ample opportunities for hunting and fishing (White 1985). In 1832, the railroad reached the Fulton Chain area (now known as Thendara, see Fig. 1), which encouraged the development of private camps, hunting and fishing clubs, and a healthy tourism industry (Hochschild 1962).

Colonial era logging in the Adirondacks began in the eighteenth century when the French and British cut timber for ship construction (Henshaw Knott 1998). By 1850, New York State became the nation’s top producer of timber and most logging enterprises in the region established small railway lines (Welsh 1995; Kudish 2005), the construction and use of which, presumably, facilitated earthworm establishment. As one book on Webb’s history notes, “almost every Adirondack clearing has a lumber camp in its past” (Beetle 1948: 6). Thendara, in particular, became a boom town for lumbering in the mid-1800s, with peak production from 1900 to 1922, a time when there was work for over 300 lumberjacks (Beetle 1948). In addition to creating habitat suitable for earthworms, this peak production period witnessed increasing mechanization (Welsh 1995) and the influx of truck tires and equipment that had the potential to transport earthworm eggs.

Logging activity in the region has not proceeded unchecked, however. The Forest Preserve of the Adirondacks was established in 1895 and by 1983 consisted of 2,476,000 acres or about 41.8% of the Adirondack Park’s 5,927,600 acres (Brown 1985). Under the “forever wild” clause of the state constitution (adopted in 1894), logging or any other type of forest extraction process is prohibited on state-managed land (Henshaw Knott 1998). Today, the lumber industry in Webb is in decline, with many companies clear-cutting before selling their lands to the state (Henshaw Knott 1998).

In addition to logging, through the years, visitors of all kinds potentially introduce earthworms (e.g., by bringing firewood into the region) (Keller et al.2007). The Adirondacks contain innumerable trails, roads, and cabins, which result in many possible “edges of earthworm invasion” (Hale 2008). A crucial pathway for earthworm introduction in Webb is recreational fishing. A 1920 article on the Adirondacks advises tourists to dig for earthworms around human settlements because finding them in the deep woods is unlikely (Billow 1920). The article goes on to advise visitors who do not wish to search for earthworms to bring them from home, packed in moss. Webb residents recall using earthworms for bait in the 1930s at Big Moose Lake in the town’s northern confines. One angler remembers finding an earthworm hotspot at a campsite with buried garbage (Barlow 2004). These accounts speak to the ease with which earthworms were located for fishing over 80 years ago. They also invoke earthworm use as a fond childhood memory and strong cultural practice. A noteworthy aside is that Old Forge is the birthplace of a type of artificial bait called the “devil bug,” which became popular in the 1920s (Buck 1975). Through the course of the twentieth century, artificial bait came to be viewed as standard for expert anglers, and the use of earthworms amateurish (White 1985). In addition to these cultural considerations, environmental information campaigns could explain a decline in earthworm use.

Increasingly, people in the Adirondack region are informed about invasive species through programs such as the Adirondack Park Invasive Plant Program (started in 1998) and the annual Adirondack Park Invasive Species Awareness Week (which began in 2005 and is held during the second week of July). Unlike places such as Minnesota, however—which has an aggressive earthworm awareness program and laws against introducing invasive earthworms into the environment—New York State has focused on other invasive species (NYS 2005). It is unclear whether this difference in focus is due to differences in the environmental threats posed by earthworms in these regions or simply differences in awareness of the threats.

Natural Resource Use and Human Behavior

Multidisciplinary research on natural resource use and human behavior presents a clear consensus that a web of biophysical and socioeconomic factors, operating across multiple scales of analysis, influences peoples’ decisions and actions (see Blaikie and Brookfield 1987; Lambin et al.2001; Robbins 2004b; Roy Chowdhury and Turner 2006). Despite this consensus, however, environmental policy often centers on information campaigns, drawing on the assumption that people will adopt behavior that mitigates the environmental problem in question if presented with more facts about it (MacNaghten and Urry 1998: 212). Exemplifying this kind of approach is the University of Minnesota’s “Great Lakes Worm Watch” program, which is designed to promote the effective management of invasive earthworms, in large part, through education and increasing awareness (NRRI 2010).

While knowledge about an environmental issue plays an important role, the perceived efficacy of the environmental policy, a person’s values (e.g., ecocentric, technocentric), her degree of civic engagement, and her access to the necessary resources (e.g., non-live fish bait, money), as well as many other possible factors, may affect whether or not behavior and actions to mitigate the problem are taken (Eden 1993; Guagnano et al.1995; O’Riordan 1995; MacNaghten and Jacobs 1997; Burgess et al.1998; Kasperson et al.1999; Corraliza and Berenguer 2000; Barr 2003). For example, Robbins (2007: xvii) finds that despite an understanding of the danger of lawn chemicals to public health and the environment, “monocultural lawn cultivation imposes a set of economic relationships between grasses, weeds, chemicals, companies, and people,” which causes landowners to use lawn chemicals even when they are well informed about their toxicity. In another example, new information about how to minimize one’s exposure to wildfire may be ignored if it does not fit into preconceived notions or if the purveyor of the information is not trusted (McCaffrey 2004). And a person is less likely to buy “green” products or use public transportation if it is not affordable or convenient even if he supports those principles (Guagnano et al.1995).

But while knowledge about an environmental issue may not be the only factor influencing behavior, it is a reasonable assumption that if individuals perceive earthworms, in this case, as having a positive or benign ecological impact then, all things being equal, they will not change behavior that leads to their spread. Giving credence to this assumption, Keller et al. (2007) assess the impact of angler behavior on earthworm introduction in the Great Lakes and conclude that the prevention of future invasions will require educating people to avoid disposing of earthworms on land. And García-Llorente et al. (2008) find that people in Spain who demonstrate a better understanding of invasive species of many kinds are more likely to contribute funds to support their eradication.

In addition to the Great Lakes Worm Watch program, there are many examples of knowledge-building campaigns regarding invasive species. Indeed, New York State’s Partnership for Regional Invasive Species Management (PRISM) consists of public-private partnerships, which have as an integral element the education and engagement of the public. Given the state’s commitment to knowledge building and the critical importance of knowledge and community-building approaches to the effective management of invasive species in other contexts (e.g., Andreu et al.2009; Klepeis et al.2009), evaluating the importance of residents’ knowledge of invasive earthworms is a key variable in the Webb case study.

Interviews and Preliminary Survey

The first phase of primary data collection involved a preliminary two-page survey distributed at the Webb Visitor Information Center (28 respondents) as well as 13 interviews conducted face-to-face in Old Forge. The survey explores reasons for visiting Webb (for non-residents), types of recreational and outdoor activities, fishing practices, knowledge of environmental issues and the source of this knowledge, and basic demographic information. Seventeen respondents fish in Webb, 88% of whom use earthworms for bait (usually nightcrawlers), which they normally purchase at a convenience store: 39% of earthworm users dispose of them in lakes or rivers, 21% save them for future use, 14% dispose of them on shore, and two respondents put unused earthworms in their gardens.

In general, the disposal of earthworm bait in forests, lakes and gardens corresponds with less familiarity with invasive earthworms and more positive perceptions of these species. But 21% of respondents “somewhat agree” that they are familiar with the concept of invasive earthworms. One possible explanation for this level of awareness is a 2003 Adirondack Life magazine article that features invasive earthworms and recommends that people avoid dumping bait in the woods and check the roots of newly purchased plants for worms (Stager 2003).

The interview results reinforce those from the exploratory survey: earthworm users tend to dump unused worms in the forest, gardens, and the trash. Those who purchase bait worms tend to save them for the next fishing trip, while those who dig for earthworms return them to the ground. One respondent notes, “I only use worms when I fish with my kids. Otherwise, I use artificial lures.” Earthworms are considered an easier form of bait to use, but artificial bait is perceived as more effective.

While almost all residents are familiar with the concept of invasive species, over half have trouble identifying more than two individual species. The regional environmental issues most commonly identified by participants are acid deposition (a significant problem in the Adirondacks), water mercury content, and tourists who are assumed to “trash the place” and “leave their garbage everywhere.” While residents acknowledge that invasive species are a problem, many are not optimistic that the issue can be resolved. One woman says that “people should be doing something about invasive species, but they’re almost unstoppable. You can’t solve it. There are too many ways things can get here.” The perception that the spread of invasive species is inevitable and that individual action is, perhaps, wasted effort may be a barrier to implementing effective management programs; however, McIntosh et al. (2009) find that the average American is willing to make a one-time payment of $48 to delay the encroachment of invasive species, even when told that the invasion is inevitable.

Conceptual Model Specified

The Webb environmental history, interviews, and preliminary survey, combined with a scholarly literature review (below), underpin the creation of a conceptual model and survey instrument. We focus on three voluntary dispersal behaviors: the disposal of earthworm bait on land; the deliberate introduction of earthworms into gardens; and the use of earthworms for composting. We assume that environmental knowledge and values influence these behaviors (Fig. 2). Drawing on environmental knowledge-attitudes-behavior studies (e.g., Bloom 1956; Meinhold and Malkus 2005; Steele et al.2006; Barr 2007; Fischer and van der Wal 2007; Persson et al.2009,), the conceptual model includes both background and intervening variables as predictors of environmental knowledge and attitudes and includes demographic characteristics expected to contribute to these outcome variables. “Environmental knowledge” is defined here as the degree of understanding about biophysical phenomena (i.e., ecosystem structure and function), a subset of which includes invasive species and invasive earthworm ecology. “Environmental attitudes” are conceptualized as both the level of concern regarding environmental issues and sentiments held regarding nature. We acknowledge that there are other explanatory frameworks that are important in understanding the human dimensions of invasive species. For example, a political ecology perspective would consider the social context and external political economic constraints on an individual’s range of choice and behavior (Robbins 2004b). But here we focus primarily on a person’s individual characteristics and a narrow subset of possible explanatory factors.

In general, those who are more highly educated are more likely to have greater environmental knowledge and embrace ecocentric values (Cottrell 2003; Fischer and van de Wal 2007). Olli et al. (2001) find a significant positive relationship between age and environmental behavior in the form of sustainable or “green” lifestyle choices. For older people (e.g., those who experienced the Great Depression), pro-environmental behaviors, such as recycling and reuse, may be associated with experiences of scarcity and, therefore, are actions to be avoided. Younger generations may perceive these actions as socially responsible behaviors. The type of environmental issue also makes a difference. García-Llorente et al. (2008) find that younger people have greater awareness of invasive alien species.

Similar to the influence of age, evidence regarding the role of gender in environmental behavior is mixed. Olli et al. (2001) find little evidence that proves that women are more environmentally concerned than men, however, Schahn and Holzer (1990), reflecting arguments made in ecofeminist literature, conclude that male and female environmental attitudes and behavior are significantly different.

Another important background variable present in environmental behavior literature is political ideology: liberalism that supports a strong role for the government is an indicator of ecological concern, pro-environmental behaviors, and support for environmental policies (Olli et al.2001; Cottrell 2003).

Relative wealth and experience in nature are additional factors in perceptions of the environment. People tend to place increasing value on political participation and the environment as they become more financially secure (de Poorter 2001; Olli et al.2001). And increased time spent in nature, such as direct environmental experience of children growing up in a rural context or regular participation in outdoor recreation, can lead to place attachment (a sense of connectedness to a place) and heightened environmental concern and levels of environmental advocacy (Staples 2001; Ryan 2005).

Time spent in nature is represented in the conceptual model as both a background variable (“childhood/adult environment”) as well as an intervening variable because access to nature in childhood may influence the amount of outdoor recreation experience people have. Another intervening variable in the conceptual model is land management experience. If people are employed in land management they tend to spend more time in the outdoors and have greater environmental knowledge. Finally, while earthworms are generally not as appealing to the public as more charismatic species, their perceived benefits to society (i.e., they are good for the soil and garden) make them likeable (Brown et al.2003; Fischer and van de Wal 2007). Our study considers perceptions of earthworms to be a subset of environmental attitudes.

Key Survey Results

Mail survey respondent age follows a normal distribution, ranging from 15 to 85 (mean of 57.7, which is indicative of Webb’s popularity as a retirement destination): 62.2% are male. Of the 88 people who fish, 78.8% are male, suggesting that fishing is a gendered practice in Webb, although more males returned the survey than females. Six of the 148 respondents (4.1%) are seasonal residents. In general, the respondents are conservative politically, and 95.9% participate regularly in at least one outdoor activity: 79.1% of respondents hike, 48.0% fish regularly, 59.5% have gone fishing at least once, and 49.3% actively garden. Close to 90% of respondents strongly or moderately agree that they are familiar with the concept of invasive species. Seventy respondents (47.3%) include invasive species in their top three natural resource concerns and 44.9% spend time or money towards the eradication of invasive species.

Analysis of the survey data yields mixed results: only the background variables of age, gender, and education influence the intervening variables of outdoor recreation and land management experience in Webb (Fig. 4). A greater number of outdoor experiences increase environmental knowledge and, especially, familiarity with invasive species. Land management experience also increases invasive species knowledge. Political views influence environmental attitudes about climate change, but are not significantly correlated with attitudes towards invasive species. While respondents are active in the outdoors, and familiarity with invasive species and other environmental issues is high, recognition of earthworms as invasive species is low (17% of respondents).
Fig. 4

Updated conceptual model displaying only significant relationships (results at the 95% confidence interval—the effect of gender on land management experience uses a t-test; otherwise, the model shows the results of one-way ANOVA tests as represented by the F statistic)

The frequency of both participation in fishing activities and the use of earthworms for fish bait are deciding factors in whether earthworms are saved for the next trip or dumped on land. Anglers tend to save their earthworms and are less likely than non-anglers to contribute to earthworm invasion by dumping bait. As with other respondents, however, most anglers are unaware of the negative ecological impacts of earthworms and believe that earthworms have a positive impact on soil and plant life. Indeed, anglers who donate time or money towards the eradication of invasive species are less likely to save their earthworm fish bait for future use than those who do not. Of the 21 anglers who report disposing of earthworms in the forest (certainly, there is a convenience in getting rid of unused worms by dumping them) only two are aware that earthworms are invasive. The Webb study’s main qualitative and quantitative findings are summarized in Table 2.
Table 2

Summary of key results

Research Focus


Key Results

Historical pathways of land disturbance, and involuntary and voluntary introductions of earthworms

Environmental History

Extensive history of logging and land clearing dating to the colonial era

Earthworms abundant in soils near settlement areas as early as the 1920s

For centuries loggers, settlers, and tourists have created pathways for involuntary introduction

Use of earthworms in fishing and gardening a strong cultural practice

Mechanisms of voluntary earthworm dispersal

Preliminary Surveys and Interviews

Primary mechanisms:

 - improper bait disposal

 - introduction of earthworms in gardens

 - use of earthworms in composting

Most earthworms for fishing from convenience stores, although widely accessed in the ground as well

Knowledge, attitudes and behaviors (K-A-B) related to voluntary earthworm dispersal

Mail Survey

K-A-B model applies to general invasive species behaviors (see Fig. 4)

Those with richer outdoor recreation and land management experience are more likely to have greater environmental knowledge

Those who believe invasive species are inevitable are less likely to donate to eradication or general environmental causes

Those with greater environmental knowledge more likely to participate in general eradication efforts

44.9% of respondents spend time or money towards eradicating invasive species of many kinds

Only 17% of respondents know that earthworms are invasive exotic species

Non-anglers are more likely than anglers to dump unused earthworm bait

Frequent participation in fishing or gardening is most correlated with disposal of earthworms in forests and gardens

Detailed Survey Analysis

Age is a statistically significant predictor of one of the intervening variables: it affects the number of recreational activities in which Webb residents participate (a one-way ANOVA produces an F-statistic of 1.713 and a p-value of .013). Older residents tend to participate in a greater number of outdoor recreation activities, likely because their retirement affords them increased leisure time.

Men are significantly more likely to have land management experience than women (Table 3). Likewise, education is significantly and positively correlated with land management experience (Table 3). Income has no significant impact on any of the intervening variables, and the null hypothesis cannot not be rejected for the effect of residents’ childhood rural, suburban, and urban environments. But respondents who grew up in rural settings tend to participate in more recreational activities and have more land management experience than those who grew up in urban contexts. Contrary to what might be expected, they are also slightly less conservative than people who grew up in urban settings.
Table 3

Factors affecting land management experience


Mean for Men

Mean for Women



Gender (t-test)






Mean High School

Mean Some College

Mean Bachelor’s

Mean Master’s

Mean PhD



Education (one-way ANOVA)








All statistical results are reported at the 95% confidence interval

Each of the primary intervening variables has important effects on the secondary intervening variables of environmental knowledge and attitudes. While political views are not significantly correlated with environmental knowledge, they correlate significantly with the belief that the effects of climate change will be experienced in this lifetime (Table 4).
Table 4

Results of a one-way ANOVA for the effect of political ideology on environmental attitudes


Mean Strongly Conservative

Mean Moderately Conservative

Mean Neutral

Mean Moderately Liberal

Mean Strongly Liberal



Belief that climate change will have a noticeable impact in this lifetime








All statistical results are reported at the 95% confidence interval

Outdoor recreation experience is significantly positively correlated with environmental knowledge in the form of both the number of sources a person consults for environmental information and the respondent’s familiarity with the topic of invasive species (Table 5). In particular, respondents who actively participate in hiking are significantly more likely than those who do not to be familiar with the concept of invasive species (Table 6). Frequent hiking may allow participants to become more familiar with the landscape and more likely to notice changes in plant communities. In addition, a one-way ANOVA finds that the number of years of recreation experience is significantly positively correlated with invasive species familiarity (F = 2.751, p = .009).
Table 5

One-way ANOVA for impact of number of outdoor recreation activities on environmental knowledge

Environmental knowledge indicator



Number of environmental information sources



Familiarity with concept of invasive species



All statistical results are reported at the 95% confidence interval

Table 6

T-test for impact of hiking on invasive species familiarity


Mean non-active hikers

Mean active hikers



Familiar with concept of invasive species





All statistical results are reported at the 95% confidence interval

Land management experience has a significant relationship with environmental knowledge, but not with environmental attitudes. Land management experience is significantly positively correlated with professed knowledge of environmental issues and familiarity with specific invasive species (Table 7). While education level is not significantly correlated with knowledge of invasive species, it affects how environmentally knowledgeable respondents consider themselves as well as the number of sources they consult for information on environmental issues (Table 8).
Table 7

One-way ANOVA for effect of land management experience on environmental knowledge

Environmental knowledge indicator

Strongly Disagree

Moderately Disagree

Not Sure

Moderately Agree

Strongly Agree



Considers self well-educated on environmental issues








Knowledge of listed invasive species








All statistical results are reported at the 95% confidence interval

Table 8

One-way ANOVA for impact of education level on environmental knowledge


Mean High School

Mean Some College

Mean Bachelor’s

Mean Master’s

Mean PhD



Considers self well-educated on environmental issues








Number of environmental sources consulted








All statistical results are reported at the 95% confidence interval

The survey confirms a relationship between environmental knowledge, attitudes, and donor behavior regarding invasive species. The belief that invasive species are inevitable makes residents significantly less likely to donate their time or money towards their eradication and towards environmental causes in general (Table 9). Perceptions of inevitability regarding invasive species lead to apathetic attitudes and little motivation to eradicate them. In contrast, however, recognition of individual invasive species is positively correlated with donations to both invasive species eradication and general environmental causes (p = .031 and .010 respectively). These results suggest that while knowledge of invasive species increases preventative behavior, apathetic attitudes may negatively affect efforts to manage them.
Table 9

ANOVA for the effect of belief that invasive species are inevitable on environmental donations

Donation type

Strongly Disagree

Moderately Disagree

Not Sure

Moderately Agree

Strongly Agree



Invasive species eradication








General environmental causes








All statistical results are reported at the 95% confidence interval

Earthworm-Related Behavior

A major pathway of earthworm introduction is the disposal of fish bait on the forest floor. Of the 59.5% of residents who have ever gone fishing, the vast majority (87.5%) have used earthworms bait at least once. Roughly half of anglers (47.7%) report earthworms as their preferred bait. Confirming testimony from the exploratory research, the nightcrawler is by far the most popular species of fish bait worm. Anglers obtain earthworms from one of three sources: bait shops (27.3%); convenience stores (67.5%), where they are cheapest; or from the ground (46.8%). The percentage of purchased earthworms underscores the regularity with which they are introduced from outside the region. And the number of respondents and apparent ease with which they obtain earthworms from the ground suggests widespread invasion in areas proximate to human settlements and recreation areas. Saving earthworms for future use is the most common method of handling surplus earthworms (36.4% of respondents who fish), while 29.9% of anglers deposit unused earthworms in their gardens, and 27.3% dispose of them on the forest floor, which facilitates the invasion of remote regions.

Gardening and composting are important secondary pathways of earthworm invasion in Webb. Twenty-three respondents (15.5%) maintain a personal compost pile, and almost half of respondents actively garden. Close to 85% of residents “strongly agree” or “moderately agree” with the statement: “earthworms have a positive impact on plant life.” And most anglers (57%) feel that the use of earthworms for bait is an important cultural tradition in Webb.

None of the background variables of age, gender, income, education and child/adult environment have any significant correlation with earthworm dispersal behavior. Four linear regressions test the predictive power of the independent variables on the outcome variables of saving earthworms for future fishing excursions, forest-floor disposal, disposal in gardens, and composting. A linear regression for predicting the retention of earthworms for future fishing trips finds three significant predictors: donation towards invasive species eradication, frequency of earthworm use when fishing, and frequency of participation in fishing (Table 10). Those who go fishing more often and use worms more frequently are significantly more likely to save their worms for future use. Anglers who donate their time or money towards the eradication of invasive species are less likely (p = .005) to save their worms, indicating that they use at least one of the other disposal techniques—placing earthworms on land or in the water.
Table 10

Results of linear regressions predicting voluntary earthworm-related behaviors


Linear regression results

Retention of earthworms for future fishing excursions

Independent variables




Donates time or money to eradicate invasive species




Frequent use of earthworms when fishing




Frequent participation in fishing




Model statistics

Adjusted R²







Disposal in forests

Independent variables




Frequent participation in fishing




Donates time or money to eradicate invasive species




Model statistics

Adjusted R²







Disposal in gardens

Independent variables




Active participation in gardening








Model statistics

Adjusted R²







Use of a personal compost pile

Independent variables




Belief that earthworms have a positive impact on plant life




Donates time or money to eradicate invasive species




Self-reported knowledge of environmental issues




Training in natural resource management




Model statistics

Adjusted R²







All statistical results are reported at the 95% confidence interval

For forest-floor disposal, frequent participation in fishing is negatively correlated with earthworm disposal in forests (Table 10); quite simply, anglers want to save them for later use. The donation of time or money to eradicate invasive species is positively correlated with forest-floor disposal, and is close to achieving significance (p = .080). Both age and active participation in gardening are significant positive predictors of earthworm disposal in gardens (Table 10). Older anglers who enjoy gardening are more likely to bring worms home to their gardens.

The belief that earthworms have a positive impact on plant life, donations towards the eradication of invasive species, and training in natural resource management are all positively correlated with composting; however, only the first variable achieves significance (Table 10). Self-reported knowledge of environmental issues is negatively correlated (p = .043) with participation in composting. The divergent directions between natural resource management and knowledge of environmental issues for the outcome variable of composting are surprising because natural resource management generally enhances environmental knowledge. This suggests that self-reported environmental awareness is not an accurate indicator of environmental knowledge. Overall, the belief in a positive impact on plant life is the strongest driver of composting.


The Webb case study makes two important contributions to understanding the human dimensions of invasive species and nature-society relationships. First, it provides a concise overview of human dispersal mechanisms of invasive earthworms and represents the first study to systematically document attitudes towards earthworm invasion. While general knowledge of invasive species is high among Webb residents, only 17% of respondents are aware that earthworms in the Adirondacks are not native to North America. The use of earthworms for fish bait and their presence in gardening and composting are perceived as beneficial to ecosystem services and an important part of the region’s cultural fabric.

Presently, earthworms are not a key factor in regional debates about invasive species. The study’s results help pave the way for more active discourse in the Northern Forest region about the presence of earthworms and what the appropriate societal response might be. Even in locations already containing earthworms, repeated introductions exacerbate negative ecological effects (Cameron et al.2007; Hale 2008). Given its popularity in Webb and the positive correlation between gardening and the disposal of earthworm fish bait in gardens, garden clubs might be an important venue for disseminating invasive earthworm information. And because one-time users of earthworm bait are more likely to discard earthworms in the forest than more regular anglers, information campaigns should focus on tourists and residents who are more likely to fish during peak season; the convenience stores where most anglers obtain their worms would be good locations to distribute information.

Knowledge building exercises, while key components to the evolution of environmental policy, do not necessarily translate to changes in behavior, however. Risk communication and education psychology research suggests that, in addition to basic information, the public needs to be empowered to implement behavior that helps mitigate the introduction of earthworms. For example, anglers might be provided with increased access to non-live bait and proper disposal methods (e.g., labeled trashcans at docks)1.

The second main contribution the Webb case study makes is in testing statistically the impact of environmental knowledge on behavior. While our results are mixed, we show that the knowledge-attitudes-behavior model is applicable to invasive species management, although it seems best suited for predicting more general environmental behaviors rather than specialized ones corresponding with a single plant or animal species. People who have greater knowledge of invasive species are more likely to donate their time or money to invasive species eradication whereas those who share the attitude that invasive species are inevitable are less likely to do so. The most important factors predicting the outcome behaviors of saving earthworms for future use, forest-floor disposal and garden disposal, are more closely tied to fishing characteristics, such as frequency of earthworm use and the number of fishing trips in a given year.


We thank Emily Oilver for the idea about labeling trashcans.



The authors thank Tim McCay, Jacob Brenner, Ellen Kraly, Emily Oliver, Sam Walker, the Colgate Department of Geography’s fall 2009 senior seminar class, Bruce Condie, Linda Rauscher, the editor, and the anonymous reviewers.

Copyright information

© Springer Science+Business Media, LLC 2011