Abstract
The escalating impact of climate change has underscored the need to advance the understanding of sustainable design practices in landscape architecture. This study investigates the actions and priorities of landscape designers in relation to sustainable design, addressing the challenge of bridging the gap between theoretical frameworks and practical implementation. Using a nationwide survey of members of the American Society of Landscape Architects conducted in November and December 2023, the study evaluated five key themes and 23 practices related to sustainable design. The survey assessed respondents’ perceptions of the importance and frequency of application for each theme and practice while also identifying facilitators and barriers that either promote or impede implementation. To explore the sociodemographic and firm‐related factors influencing these perceptions and applications, the study employed a series of linear mixed and stepwise ordinary least squares regression models. The results revealed that employees at landscape architecture firms consistently rated the importance of sustainable practices higher than their reported frequency of application across all 23 sustainable design practices. Social justice was perceived as less important and less frequently applied, whereas stormwater management was identified as the most critical and commonly implemented application. Budget constraints and client interest were found to be the primary barriers to implementing sustainable design. This study contributes valuable insights into the landscape architecture profession and provides a foundational framework to guide future research, professional development, and strategies for advancing sustainable practices in the field.
Introduction
Rising global temperatures and intensifying extreme weather patterns present escalating challenges for urban areas as they strive to maintain a habitable environment. The consequent strain on infrastructure, services, and the population necessitates immediate adaptive strategies to manage future crises. The pandemic simultaneously revealed and exacerbated vulnerabilities in public spaces, exposing inadequacies in social services and the lack of equitable access to green spaces, both essential to physical and mental well‐being (Moraci et al., 2020; Sepe, 2021). These compounding disruptions underscore the critical importance of sustainable urban design to enhance the overall well‐being and resilience of urban populations.
However, a distinct gap exists between the theoretical knowledge of sustainable practices and their implementation, often attributable to logistical, financial, and regulatory barriers (Abd Elrahman & Asaad, 2021; Bürgi et al., 2017). Studies have argued that existing operations may discourage younger designers from diverging from conventional practices (Milburn & Brown, 2016). One study, conducted in 2013, finds that practitioners consider academic research too theoretical to apply to projects (Chen, 2013). Indeed, another study indicated that most practitioners learn from experience rather than from design (Qiu et al., 2023). This disconnect diminishes the potential impact of landscape architecture and urban design on addressing environmental and social challenges. In response, significant efforts have been undertaken by professional bodies in landscape architecture to mitigate this gap. Studies suggest generating more academic research and communicating it with practitioners (Brown & Corry, 2011). Landscape Journal recognizes the significance of connecting academia to practitioners and sets the goal of strengthening readership beyond scholarly institutions (Gobster et al., 2010). The American Society of Landscape Architects (ASLA) Climate Action Plan and the Landscape Architecture Foundation (LAF) New Landscape Declaration advocate for integrated and actionable strategies that prioritize environmental sustainability and foster social equity and community resilience (ASLA, 2019; LAF, 2017). These initiatives are grounded in academic research emphasizing the efficacy of sustainable urban design in enhancing public health and mitigating the impacts of climate change.
This commitment to environmental and social stewardship is exemplified through focused research on five critical sustainable design themes: heat reduction, CO2 sequestration, stormwater management, habitat restoration, and social justice. Effective urban cooling practices such as the use of high‐albedo materials, tree canopies, and vegetated roofs significantly filter solar radiation and reduce surface and ambient air temperatures, thereby improving the energy efficiency of buildings’ interiors (Chen & Trakas, 2020; Morini et al., 2016; Park et al., 2021). Low carbon emission strategies, including the design of nonmotorized transit systems, recycle and reuse‐based waste management practices, local sourcing of construction materials, and implementation of plant‐based infrastructure can effectively curtail urban carbon footprints (Edo et al., 2018; Hertwich et al., 2019; U.S. Green Building Council [hereafter USGBC], 2020). Managing stormwater through green infrastructure such as permeable pavements, rain gardens, and bioswales reduces urban flooding risk and enhances water quality (Sohn et al., 2017; Sohn et al., 2020). Restoring natural habitats and promoting biodiversity within urban areas provide critical ecosystem services that sustain urban life and enhance human health (Dearborn & Kark, 2010; USGBC, 2020). Addressing social disparities through equity planning, incorporating job‐creating designs, and engaging communities via participatory methods fosters more equitable and inclusive urban environments (Chapple, 2014; Zapata & Bates, 2015). The following section provides a detailed review of sustainable design practices within each of the five design themes.
Literature Review
Heat Reduction
The urban heat island (UHI) effect presents significant challenges for urban sustainability, contributing to elevated energy consumption, diminished air quality, and adverse public health outcomes (Gago et al., 2013). As cities grow, the need for effective mitigation strategies has become urgent. The efficacy of four key strategies—targeting building structures, ambient temperature, solar radiation, and surface temperature—provides a comprehensive framework for addressing urban heat.
The first strategy focuses on reducing heat transfer in building structures, which are significant contributors to UHI due to their capacity to absorb and store heat. Green infrastructure solutions, such as green roofs and planted surfaces, have been shown to lower building temperatures by providing insulation, reducing heat absorption, and creating cooler microclimates. These measures also result in energy savings by lowering the demand for artificial cooling systems, thus offering both environmental and economic benefits (Costanzo et al., 2016; Kumar & Kaushik, 2005).
The second strategy emphasizes lowering ambient air temperatures, primarily through the use of green and blue infrastructure. Vegetation in urban areas, such as tree‐lined streets and urban greenery, promotes evapotranspiration and reduces air temperatures significantly. For instance, studies conducted in Taiwan have demonstrated that incorporating vegetation can reduce ambient air temperatures by up to 1.2°C during summer months (Sun, 2010). Similarly, blue infrastructures, including wetlands and water bodies, act as natural cooling agents, further decreasing temperatures by as much as 1.8°C in surrounding areas (Bowring & Chen, 2021). Together, these natural elements function as urban air conditioners, creating more comfortable urban environments.
Limiting solar radiation heating urban surfaces is another essential approach to mitigating UHI effects. Strategic shading through tree canopies has proven particularly effective, with research showing that 50% canopy coverage can reduce road temperatures by up to 4.1°C (Loughner et al., 2012; Ziter et al., 2019). These benefits extend to parking areas and other exposed urban surfaces, where shading structures or tree canopies significantly reduce solar heat absorption. The U.S. Green Building Council’s LEED certification guidelines highlight the importance of such measures, mandating 75% shading of parking spaces in new developments to enhance cooling (USGBC, 2020).
Finally, reducing surface temperatures through the use of high‐albedo materials offers a complementary strategy for UHI mitigation. Materials with a high albedo, such as reflective roof coatings and white concrete, reflect more solar radiation. These materials also improve energy efficiency by reducing cooling demands, making them both environmentally and economically advantageous (Bretz & Akbari, 1997). The solar reflective index serves as a critical metric for evaluating the thermal performance of these materials, further supporting their adoption in urban design (Muscio, 2018). In addition to thermal benefits, reflective materials reduce maintenance costs, providing a practical incentive for their widespread use (Sanjuán et al., 2022).
CO2 Sequestration
The United States Environmental Protection Agency identifies transportation as the largest contributor to greenhouse gas emissions in the United States by economic sector, accounting for 28.4% of total emissions (EPA, 2022). Urban planners and landscape architects play a crucial role in addressing these emissions through innovative urban design and sustainable landscape planning. Four key strategies are particularly important for CO2 sequestration: (1) promoting nonmotorized transportation, (2) minimizing construction waste, (3) utilizing locally sourced materials, and (4) sequestering carbon in soil. These strategies, supported by practical examples, demonstrate their effectiveness in tackling climate challenges and advancing environmental sustainability.
Transportation accounts for a significant share of urban carbon emissions, but thoughtful urban design can encourage nonmotorized modes of transit, such as biking and walking, to reduce dependency on personal vehicles. Enhancing bikeability, walkability, and the accessibility of public transit are essential components of this strategy. By decreasing the use of personal vehicles, commuter pollution is significantly reduced, along with the demand for extensive parking facilities, further limiting the urban carbon footprint (USGBC, 2020). For example, cities including Portland, Oregon, have invested heavily in bike‐friendly infrastructure, resulting in a measurable reduction in transportation emissions while improving public health and urban livability (Gilderbloom et al., 2016).
The construction phase of urban projects presents substantial opportunities to curtail emissions through effective waste management practices. Strategies such as recycling, reuse, and material diversion during construction and demolition have been shown to significantly reduce greenhouse gas emissions. Research indicates that minimizing construction and demolition waste can lower combustion‐related emissions, making it one of the most environmentally beneficial approaches to managing construction waste (Edo et al., 2018; Kucukvar et al., 2014). For instance, the reuse of concrete in road construction or the recycling of metals from demolition sites has proven effective in reducing the environmental impact of urban development.
Sourcing construction materials locally is another critical strategy to lower carbon emissions associated with transportation. By reducing the distance materials must travel, urban projects can achieve significant carbon savings while also cutting costs. Studies have shown that locally sourced materials not only decrease emissions but also streamline project logistics and lower overall construction costs (Hertwich et al., 2019; Oladiran, 2015). For example, using locally produced aggregates in building foundations or locally harvested timber in architectural projects reduces the reliance on long‐haul transportation, contributing to both sustainability and economic efficiency.
Green infrastructure, particularly through the process of carbon sequestration, represents a powerful tool for mitigating urban carbon emissions. This strategy involves capturing atmospheric CO2 in soil and plant biomass, providing both environmental and cost‐effective benefits in combating climate change (Lal et al., 2015). Strategic approaches such as enhancing soil health and expanding plant‐based systems, including urban forests and grasslands, significantly increase the capacity for carbon storage. These measures not only offset the carbon footprint of urban development but also contribute to long‐term environmental sustainability (Lal, 2008).
Stormwater Management
Studies have demonstrated the effectiveness of alternative stormwater management systems, suggesting their potential applicability for urban planners and designers across the United States (McFarland et al., 2019). The five key strategies to understanding and addressing stormwater management include: (1) filtering stormwater runoff through green infrastructure, (2) capturing and detaining stormwater runoff, (3) decreasing impervious surface material, (4) utilizing water‐efficient landscaping techniques, and (5) implementing erosion and sedimentation control techniques during construction.
It is imperative to control and mitigate the waste and pollution that stormwater runoff can mobilize (Barbosa et al., 2012). In this context, green infrastructure emerges as a particularly effective system. It not only enhances the social and aesthetic aspects of urban environments but also helps to improve the quality of stormwater (McFarland et al., 2019). Plants and soils within these systems act as natural filters, removing pollutants and thus mitigating health hazards (Smith et al., 2023).
Moreover, green infrastructure can significantly mitigate urban flooding by capturing and detaining stormwater runoff. Research has shown that low‐impact design elements, such as retention basins and vegetated swales, can significantly decrease runoff volumes (Kim, 2018). Full implementation of green infrastructure strategies for storms under three hours in duration can reduce the flooding area by up to 91% (Schubert et al., 2017).
The reduction of post‐construction impervious surfaces is another critical measure to mitigate stormwater runoff and improve watershed health (Salerno et al., 2018). Rapid urbanization has significantly expanded impervious surface areas, disrupting the natural hydrological cycle and contributing to pollutant accumulation that degrades stream ecosystems (Haris et al., 2016). Strategies that manage stormwater by collecting and slowing runoff from impervious surfaces have demonstrated significant benefits for stream health (Ladson et al., 2006). One study highlights the effectiveness of permeable pavements and rain barrels as key solutions for reducing stormwater runoff volumes, providing scalable approaches to enhance urban water management (Kim, 2018; Sohn et al., 2017).
The use of collected rainwater for outdoor irrigation represents a dual‐purpose strategy that not only conserves potable water but also effectively manages stormwater by reducing surface runoff. Similarly, the use of greywater for irrigation offers a water‐efficient strategy, although its application requires adequate treatment to ensure safety and functionality (Gross et al., 2005). Xeriscaping, which incorporates drought‐tolerant plants to minimize irrigation needs, further enhances water efficiency while contributing to stormwater management by reducing runoff volumes and improving infiltration (Ismaeil & Sobaih, 2022). Using nonpotable water for irrigation has shown minimal short‐term impacts on soil health, although its long‐term effects remain under debate (Pinto et al., 2010).
During construction, the implementation of erosion and sedimentation control techniques mitigates the risk of off‐site water pollution (Rickson, 2014). A common concern on construction sites is dust pollution, which can render water used to suppress the dust environmentally harmful (Zuo et al., 2017). However, research highlights that the inconsistent application of control techniques is often due to a lack of knowledge and accessible data on best practices (Kaufman, 2000).
Habitat Restoration
The urbanization of previously undisturbed lands has negatively impacted surrounding ecosystems and human health (Mills et al., 2017). Addressing and mitigating this damage is crucial to sustainable design. Five strategies to consider in habitat restoration—encouraging native pollinators, providing habitats for native animal species, replacing maintenance‐heavy plants with native species, protecting undisturbed land, and restoring disturbed land—demonstrate an approachable guide to enhancing a site’s ecosystem.
Pollinators play a key role in maintaining ecosystem health and are integral to garden designs, particularly in urban settings. Thoughtfully designed urban gardens serve as vital habitats for pollinators, enhancing the ecological value of these spaces and supporting ecosystem services (YaNan et al., 2016). Incorporating native vegetation in urban gardens has been shown to significantly increase pollinator populations, fostering biodiversity and ecological resilience. This approach not only supports pollinator health but also mitigates the adverse effects of rapid urbanization by promoting ecosystem stability and connectivity (M’Gonigle et al., 2015).
Rapid urbanization has severely disrupted the survival of broader plant and animal species in surrounding areas, underscoring the critical role of wildlife‐friendly landscaping in urban environments. This set of practices extends beyond encouraging pollinators by creating habitats for a wide range of animal species, thereby preserving biodiversity (Zhiruo et al., 2023). Further research is essential to identify the most effective approaches to improving animal habitats following restoration efforts (Hale et al., 2019).
Incorporating native plants into urban landscapes reduces the stress on local ecosystem water supplies. By choosing flora that support local ecosystems, cities can drastically cut down on unnecessary water consumption and the need for fertilizers (McCarthy & Pataki, 2010). This multifaceted approach not only conserves vital resources but also supports urban biodiversity, making it a pivotal strategy for sustainable design.
The challenge of protecting undisturbed lands, which serve as vital habitats for endangered and threatened species, remains a critical yet unresolved issue in urban planning. Current efforts are hindered by inadequate policies and insufficient scientific inquiry into effective conservation strategies (Beatley, 2000). Landscape architects possess a unique ability to address this gap through the development of innovative design solutions and education initiatives that prioritize habitat protection (USGBC, 2020). Expanding research in this domain is imperative for aligning urban development with biodiversity conservation goals.
Restoration of previously developed land, such as areas dominated by nonnative turf and impervious pavement that have native, habitat‐supporting flora, offers significant ecological advantages. Such restoration not only enhances biodiversity but also improves the quality of life for various species. For instance, redesigning infrastructure to incorporate native species has been demonstrated to increase habitat quality and positively impact the livelihood of multiple species in the surrounding environment (Moore et al., 2023).
Social Justice
Previous research indicates that the design of the built environment often overlooks the needs of access for disabled, poor, and other marginalized populations (Pineo, 2022). To address such disparities, some cities have adopted equity planning, a strategy aimed at fostering racial justice by ensuring that urban development benefits all residents, not just a privileged few (Zapata & Bates, 2015). Four design practices that address the social concerns of underrepresented groups of people are: 1) promoting equitable access to public spaces, 2) incorporating public engagement, 3) preventing gentrification, and 4) fostering local job opportunities.
Design considerations that prioritize equitable access to public spaces are essential for promoting inclusivity and social cohesion in urban environments. Such approaches ensure that all individuals, regardless of their background or physical abilities, have equal opportunities to participate in public life (Miller et al., 2022). Inclusivity in design strengthens community ties, fostering a sense of belonging and shared purpose among diverse populations.
Engaging communities in the planning and design process is another critical method for amplifying the voices of underrepresented citizens. Methods such as design charettes, structured brainstorming sessions focused on tackling specific urban challenges, provide opportunities for meaningful community involvement and input (Mouly et al., 2023; Roggema, 2014). These participatory approaches help ensure that development reflects the needs and aspirations of the entire community rather than privileging a select few.
A significant challenge addressed by such equitable design practices is the issue of gentrification. Upscale developments in economically disadvantaged areas inadvertently raise living costs, displacing long‐term residents and disrupting existing communities (Finio, 2022). Designing with equity requires careful consideration of potential negative impacts on vulnerable populations, particularly those unable to afford dramatic changes in their neighborhood.
Furthermore, landscape architects and urban planners can foster local economic growth by designing projects that create employment opportunities for existing residents rather than displacing them (Chapple, 2014). This approach not only strengthens the local economy but also ensures that the benefits of development are equitably distributed, preserving the social fabric of the neighborhood and mitigating the negative impacts of urban transformation.
While the importance of integrating sustainable practices in landscape architecture has been well‐documented through the literature review, significant gaps remain in understanding how these practices are perceived and implemented by professionals. Despite substantial research emphasizing the theoretical benefits of sustainability, limited studies have explored the priorities and actions of landscape design professionals. Milburn and Brown (2016) have highlighted this disconnect, noting that even among the top five researched topics in landscape architecture, only a limited portion of this work has directly benefited practicing professionals. To address this inadequacy, this study conducted a comprehensive nationwide survey targeting landscape architecture firms and focusing on the abovementioned five key design themes and associated 23 practices derived from the literature review. This survey sought answers to critical questions regarding: 1) how perceived importance and practical applications of sustainable design varied among professionals, 2) how professional landscape architects can influence legislation, and 3) the main obstacles and enablers to implementing these practices. Understanding these factors builds on previous research and will allow for a more tailored approach to legislation on sustainability in regions with evolving climate challenges. Insights from professionals in landscape architecture regarding discrepancies between the perceived importance and the actual application of sustainable practices will highlight obstacles that impede effective practices. These insights can support efforts to procure government grants and drive regulatory enhancements. This study provides a comprehensive understanding of current practices in landscape architecture and identifies critical areas for policy and design enhancement, further research, and educational advancement.
Method
Survey Participants and Distribution
After receiving approval for distribution from the Institutional Review Board (IRB) at Michigan State University (IRB #00009813), we sent web‐based questionnaires by email to all 49 ASLA chapter leaders identified via the directory on the ASLA website (asla.org). To ensure a comprehensive and representative sample from across the United States, all chapter leaders were asked to distribute the survey to their respective membership directories, collectively comprising over 17,000 members. Thirty‐one of the 49 chapters participated in the survey distribution efforts. The participating chapters distributed the questionnaires by email, newsletter, and/or social media posts, thus ensuring a wide reach and satisfactory level of engagement. To ensure eligibility, participants were required to affirm through a consent form that they were at least 18 years of age and currently employed at a landscape architecture firm. The survey period spanned from November 13 to December 31, 2023. After filtering out incomplete surveys, we collected 225 valid responses from various locations across the nation, yielding a 5% margin of error at the 90% confidence interval (see Figure 1). To analyze the spatial effects, we grouped participants into four regions and nine divisions delineated by the U.S. Census Bureau (2024).
Spatial distribution of survey respondents across the United States. Note: The numbers depict sample size by region.
Over half of the respondents were male, and 37% were female (see Appendix). When examined next to the ASLA survey conducted in 2012 and the LABOK survey conducted in 2003, this 2023 survey shows a gradual increase in the percentage of women: they made up 21% of the profession in 2003 and 24% in 2012 (Chen et al., 2017). The demographic composition was predominantly white, with 83% of respondents identifying as such and 15% as nonwhite. The age distribution was skewed toward respondents aged 50 to 59, with few participants aged 60 years or older. Approximately 26% of participants were from the South Atlantic division, perhaps due to greater survey distribution by ASLA chapter leaders in that region or a larger population of landscape architects in the South. Of the total, 87% of participants were licensed (registered) landscape architects. Presidents/principals made up the highest percentage of participants (40%), followed by professional landscape architects (35%). Approximately 32% of respondents had over 30 years of practical experience, and 45% worked in offices with ten or fewer employees. The primary project type was the built environment.
Survey Instrument
The survey gathered information regarding: 1) the perceived importance of five sustainable design themes, 2) the perceived importance and application frequency of 23 corresponding sustainable design practices, 3) individuals’ perceived facilitators and barriers to implementing such practices, and 4) the sociodemographic characteristics of the respondents and their firms.
In the first section, survey participants were asked to use a Likert scale ranging from 0 to 10 to rate the importance of sustainable design themes (see Table 1). The results were cross‐referenced with their sociodemographic characteristics to identify personal and firm‐based differences. The second section assessed participants’ perception of both the importance and application frequency of specific practices within each sustainable design theme, using a Likert scale ranging from 0 to 10 (see Table 1). In the third section, participants were given a set of barriers and facilitators identified through a literature review (Brown, 2005; Lai et al., 2016; Oluwatayo & Amole, 2012; Sarabi et al., 2020) and asked to indicate the options that affected their ability to exercise the practices associated with each design theme. Participants could select multiple options.
Research Construct
Sociodemographic and firm characteristics were gathered in the final portion to cross‐link them with information collected in other sections. Basic personal data such as gender, age, and ethnicity were collected to assess whether personal identity and culture significantly impacted perceptions. Additionally, the survey collected data on education, career history, department/role within the firm, and overall firm demographics to draw comparisons among themes and practices.
Statistical Analysis
Two methods were used to analyze the collected data: a linear mixed model and ordinary least squared (OLS) regression (see Figure 2). Linear mixed models create hierarchical structures that combine fixed and random effects. Fixed effects are variables assumed constant throughout the isolated run of analysis. Random effects are parameters that capture variability between individuals and account for correlations within the same individuals’ responses. For the linear mixed model, least square means and compact letter groups were determined using the “emmeans” and “multcomp” packages in R (Hothorn et al., 2008; Searle et al., 1980). Pairwise comparisons were made via the post hoc test of the “emmeans” package in R. Multiple tests were adjusted using the Bonferroni correction, with a significance level of 0.05. Letters were assigned to group means, with the same letter indicating groups that do not differ significantly from each other.
Research design.
The first analysis involved constructing a linear mixed model to assess whether participants’ perceptions of importance differed across the five sustainable design themes. In this model, participants were treated as a random effect, while the perceived importance of the design themes was modeled as a fixed effect. The second analysis examined whether both the perceived importance and application frequency varied across specific practices for each theme. In this case, sustainable design practices were treated as a fixed effect and participants as a random effect. The final analysis compared perceived importance and application frequency for the same practice to determine whether significant differences existed. In this analysis, participants were treated as a random effect and both the perceived importance and frequency of application were modeled as a fixed effect.
OLS regression was employed to model the impact of sociodemographic and firm characteristics on design and implementation decisions. The model was specified as:
where y is the dependent variable representing the scaled importance perception and application frequency of the sustainable design themes and practices, as collected in Parts I and II of the survey; x1, x2, . . . , xn are the independent variables denoting sociodemographic and firm characteristics, gathered in Part IV of the survey; β0, β1, β2, . . . βn are the coefficients measuring the relationships among the dependent and independent variables; and ϵ is the error term. This initial model incorporated all potential independent variables collected through the survey. A stepwise regression was subsequently performed to refine the model and the configuration that yielded the lowest Akaike Information Criterion selected, thereby optimizing the model’s fit to the data.
Results
Perception of Importance of the Five Sustainable Design Themes
According to the results of the linear mixed model, the perceived importance of the themes varied significantly (F = 81.8, p < 0.001) (see Figure 3). Post hoc comparisons revealed that stormwater management was ranked the highest in perceived importance, with a mean response of 8.20 on the 10‐point Likert scale. Conversely, heat reduction and habitat restoration were perceived as comparably less important, with no statistically significant difference in their mean ratings of 6.49 and 6.32, respectively. Similarly, CO2 sequestration and social justice were rated as the least important themes, showing no significant difference between their means of 5.28 and 5.16.
Response distribution of the perceived importance of five sustainable design themes. Note: X indicates the mean. The box plot depicts the minimum, maximum, first quartile, and third quartile. For each category, the letters a through c denote similar groups.
Perception of Importance and Application Frequency for the 23 Sustainable Design Practices
Perception of importance
According to the results of the linear mixed model, significant differences were found in the perceived importance of practices designed to achieve each of the five sustainable design themes (F = 65.0, 13.6, 39.5, 27.0, and 29.0 for heat reduction, CO2 sequestration, stormwater management, habitat restoration, and social justice, respectively; p < 0.001) (see Figure 4). Post hoc pairwise comparisons identified specific groups of practices with statistically distinct means. For heat reduction, enhancing shade by planting canopy trees was rated highest (mean = 8.92), followed by reducing ambient air temperature (mean = 7.46). Other practices such as enhancing shade through structures (mean = 6.89), reducing building temperatures (mean = 6.82), and reducing surface temperatures (mean = 6.64) showed no statistically significant difference. For CO2 sequestration, nonmotorized transportation was perceived as most important (mean = 7.95), followed by locally sourced materials (mean = 7.35), sequestering carbon in soil (mean = 7.24), and minimizing construction waste (mean = 7.11), with no significant differences among the latter three. Regarding stormwater management, improving the quality of stormwater runoff (mean = 9.04), detaining stormwater runoff (mean = 8.87), and controlling erosion or sedimentation (mean = 8.73) were rated the highest. For habitat restoration, protecting native pollinators (mean = 8.61) and protecting habitable land (mean = 8.30) were rated highest, while the other three practices were rated lower, with no statistically significant differences among them. For social justice, providing equitable access to public spaces (mean = 7.94) and incorporating public engagement (mean = 7.87) were rated highest.
Perception of importance and application frequency of sustainable practices for: a) heat reduction, b) CO2 sequestration, c) stormwater management, d) habitat restoration, and e) social justice. Note: X indicates the mean. The box plot depicts the minimum, maximum, first quartile, and third quartile. For each category, the letters a through c or a’ through c’ denote similar groups.
Application frequency
There were significant differences in application frequency for each of the practices (F = 86.6, 23.3, 53.9, 58.4, and 40.4 for heat reduction, CO2 sequestration, stormwater management, habitat restoration, and social justice, respectively; p < 0.001) (see Figure 4). For heat reduction, enhancing shade by planting canopy trees had the highest application frequency (mean = 8.30). Reducing building (mean = 5.37) and surface temperature (mean = 4.82) were the least frequently applied practices and showed no statistically significant difference. For CO2 sequestration, nonmotorized transportation was the most frequently applied (mean = 5.92). Minimizing construction waste had the lowest applied frequency (mean = 4.36). For stormwater management, erosion or sedimentation control had the highest application frequency (mean = 8.02). Water‐efficient landscaping (mean = 6.08) and decreasing impervious surfaces (mean = 5.66) ranked last. In terms of habitat restoration, planting native pollinators had the highest application frequency (mean = 7.24). Restoring disturbed soil was the least applied practice (mean = 4.49). For social justice, equitable access to public spaces (mean = 5.56) and incorporating public engagement (mean = 5.42) were the most frequently applied. Fostering local job opportunities (mean = 4.20) and preventing potential gentrification (mean = 3.81) were applied less frequently, with no significant difference.
Overall, while the rankings of perceived importance and application frequency demonstrated similarity, the linear mixed model, with both responses treated as fixed effects, consistently revealed a significant disparity between application frequency and perceived importance. For all 23 practices, actual application frequencies were lower than perceived importance (p < 0.001). The largest discrepancies were identified in disturbed soil restoration and gentrification prevention, whereas the smallest gap was observed for canopy tree enhancement.
Facilitators and Barriers of Sustainable Design Themes
Based on the participants’ responses, client interest/demand and environmental stewardship were the two biggest facilitators (see Table 2). Environmental stewardship served as a particularly important facilitator for stormwater management and habitat restoration practices. Client interest/demand was regarded as influential by over half of the participants for four out of the five practices, with stormwater management showing the highest percentage. Government incentives and long‐term cost savings were also important factors for stormwater management, with 66.7% and 72.0% of participants marking them as influential, respectively.
Facilitators for Practicing Sustainable Design Themes
In contrast, budget constraints and client interest/demand were the biggest barriers to practicing the five themes (see Table 3). Over half of the participants marked client interest/demand as an influential barrier to practicing all of the themes, and a similar proportion marked budget constraints as a barrier in relation to four of the five. The uncertainty of cost savings served as a particularly important barrier to practicing heat reduction, with 83.6% of participants marking it as a significant barrier. Additionally, lack of public awareness was an important barrier in the case of several themes, and the need for maintenance was a barrier for stormwater management and habitat restoration in particular.
Barriers to Practicing Sustainable Design Themes
Impacts of Sociodemographic and Firm Characteristics on Sustainable Design
Perceived importance of the five design themes
The OLS regression analysis revealed that sociodemographic factors significantly influenced perception of the five themes across all model iterations (see Figure 5). All themes were consistently rated as less important at a statistically significant level (p < 0.05) by male participants relative to female respondents. Geographically, participants from the South and West regions perceived heat reduction as significantly more important than their counterparts in the Midwest (p < 0.05). Individuals from the Northeast and West perceived CO2 sequestration as more significant than did those from the Midwest, but apart from this, no other significant regional effects were found. Regarding professional credentials, registered (licensed) landscape architects placed a greater emphasis on stormwater management than did their unlicensed peers (p < 0.01). Additionally, this group perceived habitat restoration as significantly more important (p < 0.05). However, the model did not indicate any other significant differences in the remaining design themes between licensed and unlicensed professionals. Finally, individuals from firms in operation for over 30 years perceived heat reduction practices as less important than did participants from firms in operation for less than five years (p < 0.05). Individuals from firms operating for more than 40 years valued habitat restoration less than did those from younger firms (p < 0.05).
The results of the OLS models predicting the perceived importance of the five sustainable design themes, based on sociodemographic and firm characteristics. Note: The scale represents the nonstandardized coefficients. The degrees of freedom range from 180 to 200. ∙p < 0.1; *p < 0.05; **p < 0.01; ***p < 0.001.
Perception and application frequency of the 23 sustainable design practices
A series of OLS regression analyses indicated that geographical differences significantly influenced both the perception and application frequency of the practices (see Figure 6). Participants from the South applied heat reduction practices more frequently than those from the Midwest, especially through measures such as enhancing shade through canopy trees and structures (p < 0.01). In contrast, Northeastern participants showed a significantly higher application frequency for providing nonmotorized transportation and minimizing construction waste (p < 0.1). Participants from the West prioritized social justice practices, including public engagement and fostering local job opportunities (p < 0.05). In comparison, participants from the Midwest applied stormwater detention practices more frequently than those from the West (p < 0.5).
The results of the OLS models predicting the perceived importance and application frequency of the sustainable design practices of (a) heat reduction, (b) CO2 sequestration, (c) stormwater management, (d) habitat restoration, and (e) social justice, based on sociodemographic and firm characteristics. Note: The scale represents the nonstandardized coefficients. The degrees of freedom range from 170 to 210. ∙p < 0.1; *p < 0.05; **p < 0.01; ***p < 0.001.
Professional roles and licensure levels emerged as significant determinants of design practices. Principals and presidents assigned significantly higher ratings to most practices related to heat reduction, stormwater management, habitat restoration, and social justice practices compared to landscape architects (p < 0.1), and they also applied those practices more frequently. Licensed landscape architects also applied habitat restoration practices more frequently and valued them more highly than their unlicensed counterparts (p < 0.1). In the realm of social justice, they rated providing equitable access to public spaces and incorporating public engagement as more important (p < 0.5). Additionally, licensed professionals applied stormwater‐related practices more often than their unlicensed peers (p < 0.5).
Finally, age, gender, and firm size had significant effects on the application of sustainable practices. Participants in their 30s applied stormwater runoff detention practices significantly less often than those under 30 (p < 0.05), and respondents under 30 were more likely to apply wildlife‐friendly landscaping practices (p < 0.1). The gender effect was most profound in social justice: male participants applied these practices far less often than female participants (p < 0.1). Additionally, those employed in mid‐sized offices (11 to 50 employees) attached more importance to and more often applied practices of enhancing shade from structures when compared to respondents from smaller offices (p < 0.1).
Discussion
Perception of Importance of the Five Sustainable Design Themes
Stormwater management’s importance in the results can be attributed to its critical role in landscape architecture education and practice. Academically, this theme’s prominence is underscored by licensure examinations administered by the Landscape Architectural Accreditation Board. Furthermore, it is deeply entrenched in regulatory frameworks within the United States, such as the Environmental Protection Agency’s National Pollutant Discharge Elimination System permit program, which mandates that practitioners mitigate post‐development runoff discharge (40 CFR Part 122). This regulatory framework highlights the profession’s commitment to integrating stormwater management practices into sustainable land use and ecosystem preservation efforts. In contrast, CO2 sequestration and social justice’s lowest perceived importance is conceivably associated with the political polarization of climate change mitigation and diversity, equity, and inclusion (DEI) initiatives throughout the nation. While there is growing recognition of the urgency of climate action, substantial ideological divides persist regarding the regulation of carbon emissions. This ideological rift fragments public and policy responses to climate change (Fisher et al., 2013). Such polarization not only limits broad‐based support for carbon sequestration practices but also complicates efforts to integrate social justice principles into sustainability frameworks. Evidence suggests that ideological resistance to DEI initiatives, especially in the context of environmental planning, often reflects deeper sociopolitical divides, making it challenging to prioritize equity alongside environmental goals. This divisiveness hinders cohesive, collective action, presenting obstacles for designers in advocating for and implementing carbon sequestration measures. The resulting challenges highlight the need for context‐specific approaches that foster inclusive dialogue and develop effective strategies to advance both carbon emission reduction and social equity within sustainable design frameworks.
Perception of Importance and Application Frequency of the 23 Sustainable Design Practices
The survey results revealed distinguishable differences among the 23 sustainable design practices. While practicing landscape architects consistently rated each practice highly in terms of perceived importance, there was a relative shortfall in the actual application frequency. This divergence highlights a critical gap between the profession’s aspirations to take the lead in transformative environmental design and practical implementation of this goal. Despite a shared desire to drive meaningful environmental change, a range of obstacles were found to impede the translation of this ambition into practice.
Heat reduction
Among the five design practices for heat reduction, the use of canopy trees to enhance shade emerged as the practice with the highest perceived importance and application frequency. Beyond the ecological benefits, the aesthetic appeal and functional utility of trees likely contributed to this heightened emphasis. Conversely, the practice of reducing surface temperature, such as reflective coatings or cool pavements, showed the largest disparity between perceived importance and actual application. This gap suggests that while surface cooling is recognized as beneficial, implementation is often hindered by practical constraints. As shown in Table 3, more than 60% of survey respondents identified uncertain cost savings and budget constraints as substantial barriers to the applications of heat reduction practices. This financial hesitancy may stem from limited data on long‐term cost benefits and a lack of awareness regarding the economic advantages of advanced materials. Without clear evidence of cost‐effectiveness, decision‐makers prioritize projects with more immediate or demonstrable financial returns.
Firm characteristics also play a significant role in the adoption of heat reduction practices. The regression analysis revealed that firm age influenced prioritization, with younger firms placing greater emphasis on heat reduction practices compared to their more established counterparts. This trend reflects a discernible shift in the field’s focus, driven by growing concerns about global warming and a stronger inclination among newer firms to align with contemporary sustainability goals. Moreover, larger firms were found to be more likely to implement heat reduction practices than smaller firms, likely due to their greater access to resources and personnel, a factor in overcoming the financial and logistical barriers to adopting advanced materials.
These findings emphasize the need for targeted policy interventions and research efforts to address the barriers limiting the adoption of heat reduction practices. Policymakers could focus on developing incentive programs or subsidies to alleviate cost‐related concerns, particularly for smaller and younger firms that may lack the financial resources of larger organizations. Similarly, further research is needed to provide robust evidence of the long‐term economic and environmental benefits of surface cooling technologies. This would not only reduce financial hesitancy but also equip firms of all sizes with the data necessary to advocate for and prioritize these practices in the face of growing climate challenges.
CO2 sequestration
Minimizing construction waste is a critical yet underimplemented strategy for CO2 sequestration. Survey results revealed that 73% of respondents identified a lack of client demand as the primary barrier, highlighting a misalignment between professional sustainability goals and client priorities (see Table 3). This challenge is further compounded by logistical issues, such as coordinating construction schedules, managing on‐site material segregation, and ensuring proper recycling or disposal. The absence of standardized waste management protocols across projects complicates implementation, leading to inconsistent adoption. These findings align with prior research, which emphasizes that clients’ limited awareness of the economic and environmental benefits of sustainable practices often hinders their prioritization (Osmani & Villoria‐Sáez, 2019).
At the same time, the survey identified key facilitators for advancing CO2 sequestration efforts, with 64% of respondents citing environmental stewardship as the primary motivator (see Table 2). Strengthening this commitment could involve integrating sustainability‐focused education into professional development programs, showcasing successful case studies of CO2 sequestration in landscape architecture, and fostering industry recognition for firms that prioritize environmentally responsible practices.
Regional disparities further underscore the importance of localized approaches. Respondents from the Northeastern United States reported less frequent application of nonmotorized transportation and construction waste minimization practices. This discrepancy may stem from the older urban infrastructure and higher density of northeastern cities, where retrofitting for sustainability often involves greater logistical and financial challenges. For instance, densely built environments limit opportunities for waste segregation and reuse, and higher project costs may discourage investment in sustainable alternatives. These findings suggest that regionally tailored interventions, such as locally adapted incentives or infrastructure‐specific guidelines, are necessary to address these challenges effectively.
Stormwater management
For stormwater management, decreasing impervious surface area emerged as the most underapplied practice, conceivably due to cost considerations. Survey responses indicated that 59% of participants identified budget constraints as the major obstacle, reflecting the substantial up‐front costs associated with retrofitting or removing impervious surfaces (see Table 3). These financial barriers are particularly pronounced in high‐density urban areas, where space limitations and the complexity of established infrastructure amplify logistical challenges. Water‐efficient landscaping also demonstrated a notable gap between perceived importance and application frequency, underscoring challenges related to client demand. Fifty percent of survey respondents highlighted a lack of client interest or demand as a significant limitation, revealing a disconnect between design priorities and client preferences. The implementation of water‐efficient landscaping often requires the use of specific plants that can survive with minimal water and maintenance, potentially limiting design options and constraining creativity. As a result, sustainability goals are sometimes in tension with client expectations.
Professional roles and qualifications further influence the prioritization and application of stormwater management practices (see Figure 6). Principals and firm presidents consistently rated the importance of several practices higher and reported greater application frequency compared to landscape architects. This indicates that leadership within firms plays a critical role in driving sustainability initiatives. Moreover, licensed professionals demonstrated a stronger emphasis on stormwater management, highlighting the value of expertise and certification in advancing sustainable solutions. These findings suggest that leadership advocacy and professional training are key leverage points for embedding stormwater management practices into organizational priorities.
Habitat restoration
Habitat restoration presented distinct challenges, with significant gaps between perceived importance and application frequency across various restoration practices. Among these, the restoration of disturbed soils particularly showed the most significant disparity, indicating both high recognition of its ecological value and difficulty in practical implementation. Survey data revealed that a primary barrier to implementing habitat restoration practices was a lack of client demand and interest, a factor identified by 66% of respondents (see Table 3). This lack of demand suggests that while professionals acknowledge the importance of habitat restoration, its adoption is often contingent on client priorities and preferences, which may not always align with sustainable design goals. Nonetheless, client engagement emerged not only as a barrier but also as a critical facilitator for implementing these practices (see Table 2). This dual role underscores the complexity of client influence in habitat restoration, where active client interest can accelerate adoption, while a lack of engagement can hinder progress.
Moreover, the regression results indicate that higher‐level professionals and licensed individuals possess greater influence in advocating for and implementing these practices (see Figures 5 and 6). Leveraging this influence could play a vital role in bridging the gap between perceived importance and actual implementation. Targeted outreach and educational efforts led by senior professionals, designed to communicate the long‐term ecological and economic value of habitat restoration, could help align client interests with ecological design principles.
Social justice
Among all five design themes, social justice showed the most significant gap between the high perception of importance and lower frequency of application. Survey results indicated that client interest and demand emerged as the primary facilitators for implementing social justice practices (see Table 2), suggesting that, while professionals recognize the value of equitable design, actual implementation often relies on external drivers. Social justice, particularly the provision of equitable access to public spaces, represents a foundational value for all landscape architects. However, the survey highlighted a concerning gap in prioritizing this value, especially among male practitioners, who showed a lower recognition of its importance despite increased funding for scholarships designed to enhance access to education in the field.
The survey results underscore an urgent need for sustained advocacy for DEI within the landscape architecture profession. To address these challenges, professional organizations must continue to lead by example, establishing and promoting actionable strategies to mitigate social justice disparities. Noteworthy initiatives include the ASLA Climate Action Plan and the Landscape Architecture Foundation’s (LAF) New Landscape Declaration, both of which outline frameworks for advancing DEI across the discipline (ASLA, 2019; LAF, 2017). By maintaining focus on these strategic objectives, it is anticipated that DEI awareness and implementation of social justice practices will become more integral to the profession, fostering a cultural shift that aligns with both the ecological and social imperatives of sustainable design.
Conclusion
This study examined perceptions and implementation gaps around sustainable design practices in landscape architecture, focusing on five key themes: heat reduction, CO2 sequestration, stormwater management, habitat restoration, and social justice. The findings revealed significant disparities between the perceived importance of these themes and their associated practices and practical application. These disparities were driven by barriers such as budget constraints, insufficient client demand, and logistical challenges. Regional variations further highlighted the need for localized strategies tailored to specific contextual challenges. Leadership roles, professional licensure, and targeted education emerged as pivotal facilitators for advancing sustainable practices, while the underutilization of social justice principles emphasized the critical need to integrate DEI values more systematically into professional practice.
Despite providing valuable insights, this study’s methodology presents certain limitations. Potential sampling bias may have arisen from inconsistent survey distribution methods across ASLA chapters, potentially influencing outreach and response rates. In addition, the reliance on self‐reported data introduces the risk of response bias, including the overreporting of sustainable practices or socially desirable responses. Future research should address these limitations by implementing systematic and standardized sampling methodologies, ensuring consistent distribution across regions and enhancing the representativeness of findings. Collaboration with professional organizations to establish uniform outreach protocols could further strengthen response quality and quantity. Future studies should also explore regional determinants of sustainable practice adoption, employing advanced modeling techniques to quantify the effectiveness and scalability of interventions across diverse contexts. These efforts would contribute to a more robust evidence base, enabling the development of targeted policies, enhanced professional training, and strategic advocacy to foster a more sustainable, inclusive, and impactful landscape architecture profession.
Peer Review
Landscape Journal uses a double‐blind peer review process for research manuscripts, systematic literature reviews, and other article types.
Acknowledgments
The authors gratefully acknowledge the support of the ASLA chapter leaders for their assistance in distributing the survey and extend sincere thanks to the ASLA members whose participation made this study possible.
Appendix
Sociodemographic and Firm Characteristics of the Sample of US Landscape Design Firms
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