Environmental attitudes predict native plant abundance in residential yards

Highlights

• Phoenix, Arizona residents hold positive attitudes toward native plants.

• However, few native woody plants were found in Phoenix front yards.

• Knowledge about native plants was low, but did not predict native woody plant abundance.

• Residents who prioritized low water use had fewer native woody plants in their yards.

• Native plant abundance could be increased by marketing toward low water use priorities.

Abstract

Native plant landscaping can provide unique support for native wildlife in urban settings, but the drivers of native plant inclusion in private residential yards are not well characterized. As with other pro-environmental behaviors, native plant landscaping is likely driven by a combination of resident and landscape attributes. We ask, how do resident attitudes, knowledge, plant choice priorities, demographics, and parcel structure predict existing native plant abundance? To address this question, we compared resident characteristics with front yard woody vegetation in 105 parcels in Phoenix, Arizona. Although many residents had positive attitudes toward native plants, less than a third of woody plants in most yards were native. Native woody plant abundance was higher in xeric rock-covered yards where residents believed native plants belonged in the city, prioritized choosing native plants, and had higher household income. Reported knowledge about native plants was low, but did not predict native woody plant abundance. Although native plants in the arid environment of Phoenix are adapted to low water conditions, residents who prioritized low water use plant selection had fewer native plants, highlighting an opportunity for native plant marketing. These results suggest that educational campaigns to increase resident knowledge of native plant identification and care are unlikely to result in greater native plant abundance in the residential landscape. Marketing native plants to highlight qualities such as low water needs and addressing barriers such as horticultural availability and expense should be further investigated as potential methods of increasing native plant resources in urban environments.

Introduction

Residential yards are a dominant feature of cities, with 92% of new U.S. homes including some outdoor space (U.S. Census Bureau, 2019). These urban spaces can support diverse wildlife communities, depending on land management practices (Goddard, Dougill, & Benton, 2010). Landscaping with native species can support biodiversity by providing resources for wildlife that are unmatched by horticultural non-natives (Berthon et al., 2021, Burghardt et al., 2009, Narango et al., 2018, Pardee and Philpott, 2014). For example, in Phoenix, Arizona, residential yards with desert-style native landscaping provide higher quality habitat for native Sonoran bird species (Lerman, Warren, Gan, & Shochat, 2012). Native vegetation can also create locally distinct urban landscapes, reducing urban homogenization while supporting connection to the environment and local sense of place (Groffman et al., 2014, Hooper et al., 2008).

In yards, individual residents make choices about management actions, which are guided by personal motivations as well as the social and physical environment (Cook, Hall, & Larson, 2012). These choices can have important outcomes for urban biodiversity (Belaire, Westphal, & Minor, 2016). Environmental attitudes sometimes predict behavior and thus environmental outcomes, but social, financial, and other constraints often prevent direct correspondence between attitudes and behavior (Heberlein, 2012). Few studies have investigated how resident attitudes relate to native plant outcomes, despite the ecological benefits of native plants. Here, we use a case study in the arid city of Phoenix, Arizona, to ask, how do resident attitudes, priorities, and demographic characteristics together with physical yard characteristics predict native plant abundance in residential front yards?

The term “native plants” is often used in both gardening and ecology, but its definition can vary in practice (Berthon et al., 2021). Ecologically, native species are defined as organisms that have a long evolutionary history in a particular location, likely with coevolved species and adaptations suitable to local environmental conditions. However, nativity is not a trait that can be measured, so classifications of individual species are typically based on judgements of how long a species has been in a location and how it arrived (Kendle & Rose, 2000). Further, nativity classifications are regularly made following political rather than geographic boundaries, resulting in different statuses across ecologically meaningless divisions.

While ecologists use geopolitical and historical nativity classifications to describe whether a species is appropriate in a given location, non-ecologists may think of species with cultural connections to a city or with large urban populations as belonging there, regardless of ecological nativity (Head & Muir, 2006). Thus, plants seen as belonging, and sometimes colloquially considered native, could include those with a long history in the local urban environment, adaptations that make it well suited to the local environment, or historic representations in the local culture (Head & Muir, 2006). While ecologists and horticultural professionals may attach importance to native species due to their roles in healthy ecosystems, members of the general public may take a more pragmatic, functional, or cultural approach to landscaping without regard to a plant's status as native or not.

Native plants have long been a subject of interest in horticulture and urban landscape design, though they are often perceived as a relatively small niche market (Hooper et al., 2008, Kauth and Pérez, 2011, Potts et al., 2002). Horticultural industry professionals have identified several motivations driving native plant sales in urban landscapes, including reduced yard maintenance requirements, limited water use, and habitat provision for wildlife (Brzuszek and Harkess, 2009, Hooper et al., 2008, Potts et al., 2002). Similarly, participants in the U.S. Master Gardener program reportedly selected native plants due to their adaptations to the local environment (Brzuszek, Harkess, & Kelly, 2010). Landscape designers in the southwestern U.S. reported increasing the use of native plants in their work, though very few considered themselves to be expert native plant users (Hooper et al., 2008). Moreover, designers perceive a lack of public support and enthusiasm for native landscaping (Crewe, 2013).

Although native plants are adapted to the local environment, they may be poorly suited to urban heat, pollution, and disturbance, and so may not always be an appropriate choice for landscaping (Kendle & Rose, 2000). Native plants can also be difficult for nurseries and landscapers to source and propagate, and only about a quarter of native vascular plant species in the U.S. are available commercially (Potts et al., 2002, White et al., 2018). Thus, finding appropriate native species at local nurseries and big box stores can be a challenge for consumers. Further, horticultural professionals suggest that consumer education is necessary for proper maintenance and to manage expectations for native plants (Brzuszek and Harkess, 2009, Brzuszek et al., 2007, Crewe, 2013, Hooper et al., 2008, Kauth and Pérez, 2011, Potts et al., 2002). While native plants can provide benefits for biodiversity and place attachment, they may present important functional challenges for residents and landscapers.

Environmental attitudes can influence pro-environmental behaviors, such as the decision to landscape with native plants (Heberlein, 2012, Kollmuss and Agyeman, 2002, Schultz, 2011). Simply defined, attitudes are positive and negative judgements about some object or phenomenon such as native plants (Heberlein, 2012, Larson, 2010). While attitudes do not always predict behavior, they can reveal motivations and constraints around actions and thus are important to promote public support and desirable behaviors (e.g., planting natives). Changing people's attitudes is rarely an effective way to increase pro-environmental behaviors, but understanding attitudes and working with existing motivations is an effective strategy to promote conservation goals (Heberlein, 2012, Schultz, 2011).

Knowledge has sometimes been linked with environmental behavior, including yard management (Frick et al., 2004, Martini and Nelson, 2015, van Heezik et al., 2012). Lack of knowledge about native plants has been specifically implicated as a major barrier to their use in residential landscaping (Brzuszek and Harkess, 2009, Hooper et al., 2008, Kauth and Pérez, 2011, Potts et al., 2002). For example, customer unfamiliarity and confusion over what native wildflowers are have been identified as two major limitations to their adoption (Kauth & Pérez, 2011). A study of Australian residents who converted their yards from typical English-style gardens to native themes identified knowledge of environmental issues as a key driver of the choice to convert yards (Uren, Dzidic, & Bishop, 2015). These results suggest that knowledge of native plants may influence choices to include native vegetation in yard landscaping.

Typically, more specific attitudes and those with greater relevance to a particular attitude object are more predictive of behavior than are more general attitudes (Kim & Hunter, 1993). In residential yards, specific attitudes toward particular plant features can drive management decisions (Kendal, Williams, & Williams, 2012). For example, we would expect specific attitudes toward low water use plants to be more predictive of succulent abundance than general environmental attitudes would be. However, more general attitudes toward the environment may also be relevant (Head & Muir, 2006). Therefore, we consider both more specific attitudes toward native plants and more general attitudes toward the regional desert environment as potential predictors of native plant landscaping.

Previous research in the U.S. has identified consistent key priorities for residential yard management, including low maintenance requirements, neat and orderly appearances, and aesthetic beauty (Cook et al., 2012, Larson et al., 2009, Nassauer et al., 2009). In accordance with these priorities, choices to purchase and install native plants in landscaping may be linked to plant traits (Kendal et al., 2012). In the arid southwestern U.S., residents reported positive attitudes toward desert plants, including natives, mostly agreeing that they look attractive and provide sufficient variety (Spinti et al., 2004, St. Hilaire et al., 2010). Additionally, residents reported that they would use native plants if they conserved water and were attractive (Lockett, Montague, McKenney, & Auld, 2002). However, residents have also expressed concerns about the presence of thorns on plants in yards where pets and children may play (Larson et al., 2009). Although informative, these studies have not tested whether prioritizing particular traits align with actual native plant cultivation in residential yards.

A recent survey of U.S. residents found a positive relationship between attitudes toward native plants and intentions to use them in yard landscaping (Gillis & Swim, 2020). In this study, attitudes about the aesthetic appeal of native plants and their importance to local ecosystems predicted intentions to plant native species and reported yard native plant composition, while attitudes toward maintenance requirements were weakly predictive. However, the accuracy of reported behavior depends on the assumption that respondents are able to correctly classify the nativity of their yard landscaping, and comparison with actual yard plant composition is needed to fully align attitudes with ecological outcomes.

Attitudes alone cannot predict behavior, and the gap between attitudes and behavior can sometimes be explained by social characteristics and urban structure (Kollmuss & Agyeman, 2002). For residential yards, studies have shown more abundant and diverse vegetation in higher income neighborhoods (Avolio et al., 2018, Cook et al., 2012, Hope et al., 2003). One proposed mechanism for this so-called “luxury effect” is financial resources (Hope et al., 2003), which can impact native plants because they are often more expensive than non-natives (Avolio et al., 2018, Brzuszek et al., 2007). Education level can also predict yard vegetation outcomes, such as tree planting rates and cultivated plant composition (Padullés Cubino et al., 2018, Roman et al., 2014). The local specificity of native plants suggests that acculturation to a particular region might affect attitudes toward native plants, and thus related behaviors. For example, in Phoenix, Arizona, newer residents tend to prefer naturalistic xeric landscaping while long-term residents prefer grass (Martin et al., 2003, Wheeler et al., 2020). By extension, newcomers may also embrace native plants relative to long-term residents.

Urban structure, or parcel and neighborhood characteristics, also affects yard outcomes. Lot and garden size constrain the area available for planting and amount of vegetation present (Bigsby et al., 2014, Ossola et al., 2019). Vegetation management may also be driven by a desire to match home and yard aesthetics, such as an adobe-style house with a desert-like yard and desert species, or a brick colonial house with a manicured English-style garden (Ossola et al., 2019, Peterson et al., 2012, Uren et al., 2015). Native species may be perceived as not fitting in with a manicured yard aesthetic (e.g., turfgrass lawns), or may be seen as the most appropriate choice for a yard with a naturalistic design (e.g., gravel groundcover in desert regions).

In this research, we evaluate how resident attitudes and priorities, demographic characteristics, and parcel structure are associated with the abundance of native plants in residential yards. Using a paired social and vegetation survey of residential yards in Phoenix, Arizona, we tested four hypotheses:

H1) Plant nativity is a recognizable and important trait for residents.

H2) Plant selection priorities will best predict native plant abundance, followed by attitudes toward native plants, more general attitudes toward the desert, and resident knowledge of native plants.

H3) Native plants are selected when residents prioritize low water use, low maintenance needs, and providing habitat for wildlife, but are avoided due to negative aesthetic perceptions, potential hazards (e.g., cactus spines), and lack of availability or expense of purchasing.

H4) Resident characteristics and parcel structure have more influence on native plant abundance than do resident attitudes and priorities.

To address these hypotheses, we explored variation in front yard native plant abundance using resident knowledge of native plants, attitudes toward native plants, attitudes toward the desert, plant selection priorities, resident characteristics, and parcel structure as predictors to determine their relative importance.