**3. Results**

#### *3.1. Public Green Space Inventory*

To understand current urban ES delivery rates, we first inventoried public green space in the FAN through a combination of ground survey and NDVI/ LiDAR green cover assessment methods. These revealed that lawn was the dominant green cover type (Figures 2 and 3; Tables S3 and S4), typical of low-density residential development [29]. Of the 57.4 ha of public green space, approximately 55% was covered by lawn without tree canopy, 30% by trees with unidentified understory, 9% by woodland, 4% by tall shrubs, and 3% by short shrubs (Figure 3; Table S4). All woodland and most lawn (>85%) were located in municipal parks and public schoolyards, while ~80% of all non-woodland tree canopy, short shrubs, and tall shrubs were located in right-of-way zones (Table S3).

**Figure 2.** Land cover type and distribution. (**a**) Lawn size and distribution in right-of-way zones in the Friendly Area Neighborhood, evaluated by ground measurement, and (**b**) vegetation classes and distributions on all public lands in the neighborhood identified using NDVI and LiDAR data.

**Figure 3.** Urban ecosystem services (ES) provided by existing vegetated land cover. Existing vegetated land cover distribution (**a**), detailed in Figure 2, and the corresponding provision of urban ES by vegetated land cover type: (**b**) runoff retention; (**c**) air purification; (**d**) carbon storage; (**e**) cooling fraction; and (**f**) recreation, as evaluated by supply rates compiled by Derkzen et al. [14], summarized in Table S4.

The approach combining LiDAR and NDVI was most accurate in identifying tree cover and lawn (98% and 86% accuracy, respectively), while 66% of the area classified as "tall shrub" was found to be tree canopy cover, and 33% of the area classified as "short shrub" was found to be tall shrubs, lawn, or tree canopy cover (Table S2).

Using published supply rates [14] (Table S1), we next estimated that this public green space provides nearly 2900 metric tons of carbon storage, removes over 2000 kg per year of atmospheric particulate matter (PM10), and retains over 4.7 million liters of stormwater during each 12 mm storm event (Figure 3; Table S4). Lawn covers over 50% of the total public green space and provides more than half of the runoff retention and recreation value but less than one-quarter of the air purification services and 2% of the carbon storage (Figure 3; Table S4). By comparison, trees cover less than 30% of the total public green space but supply over half of all air purification and carbon storage, as well as over 40% of cooling services; trees provide runoff retention roughly proportional to their coverage area but only one-fifth of all recreation services. Woodland covers less than one-tenth of the total public green space ye<sup>t</sup> provides over one-tenth of the recreation value and over one-quarter of the carbon storage, or more than 14× that provided by lawn. Tall and short shrubs, in comparison, cover the

least area of the total public green space but provide urban ES approximately proportional to their coverage area.

#### *3.2. Resident Surveys—Urban ES Priorities*

To understand residents' urban ES priorities for public green space, we asked a random sample (*n* = 97) to rate 17 individual urban ES on a scale from 1 ("very unimportant") to 5 ("very important"). Responses showed that outdoor recreation, stormwater quality, air quality, pollinator habitat, and native species were the top priorities (Figure 4; Table S5), showing a clear preference for supporting services; except for outdoor recreation, cultural and provisioning services were rated as relatively unimportant (Table S5).

**Figure 4.** Ratings by Friendly Area Neighborhood residents (*n* = 97), from 1 (very unimportant) to 5 (very important), of 17 urban ecosystem services (ES). Colors designate urban ES categories (green: supporting; blue: regulating; brown: provisioning; olive: cultural); bubble size designates frequency of the indicated response; outer black line indicates significance (*p* < 0.05) according to chi-square tests in which responses of 1–3 and 4–5 were binned to compare each individual urban ES to overall urban ES. Data, including Cronbach's alpha values for each urban ES domain, are tabulated in Table S5.

This survey also investigated residents' willingness to support public green infrastructure development for urban ES improvement through contributions of time and/or money. Unexpectedly, most respondents (>85%) expressed willingness to contribute financially to urban ES projects in parks, with over one-quarter supporting direct, "out-of-pocket" payments and over 80% supporting tax measures to fund public works projects (Figure 5; Table S6). Support for such projects on right-of-way strips was lower but still substantial, with over 70% stating willingness to contribute financially; again, over one-quarter supported direct payments, but in this case, only 65% supported corresponding tax measures. Additionally, a large majority (>80%) expressed the willingness to volunteer for green infrastructure projects in the neighborhood, and over half stated interest in contributing five or more hours per year (Figure 5; Table S7).

#### **Figure 5.** (**a**) Residents' stated willingness by in-person survey (*n* = 97) to financially support green infrastructure development in parks, in the public right-of-way, and on private property that increases urban ecosystem services (ES) through tax measures alone; tax measures combined with personal contributions; personal contributions alone; or none of the above. (**b**) Residents' stated willingness by in-person survey (*n* = 97) to volunteer time toward the development of public urban ES projects from 0 to 12+ h per year. Data are provided in Tables S6 and S7.

#### *3.3. Delphi Analysis*

To understand the perspectives of stakeholders involved in the planning, implementation, and managemen<sup>t</sup> of public green space, with the potential to differ substantially from those of residents, we used a Delphi analysis to seek consensus (greater than two-thirds agreement) regarding urban ES priorities, perceived benefits of and concerns regarding lawn cover, benefits of and barriers to green infrastructure development, and strategies for overcoming these barriers. In the first-round survey, six urban ES—noise reduction, community identity, vegetable production, fruit production, improved soil health, and privacy—received sufficiently low rankings that they were excluded from the second round (Supplementary Materials Section S3). In the second-round survey, participants viewed the reduction of stormwater pollution as the top priority for both parks and for right-of-way planting strips, with over 80% agreemen<sup>t</sup> (Table 1; Figure 6; Figure S2). Improving air quality, supporting native species, increasing carbon sequestration, providing natural beauty, and reducing flooding were also consensus priorities for both parks and right-of-way planting strips. Providing shade for cooling was a strong priority for right-of-way strips but did not reach the consensus threshold in parks; instead, parks were most valued for providing habitat and educational opportunities. Outdoor recreation, plant diversity, erosion control, and physical and mental health benefits did not reach the two-thirds consensus threshold and were classified as non-priorities.


**Table 1.** Urban ecosystem services that generated consensus a among Delphi participants (*n* = 15).

a Consensus was defined as a ≥66.7% agreement. b 1 = highest; 17 = lowest. c Data are shown graphically in Figure S2. d Consensus was not reached.

**Figure 6.** Comparison of Delphi stakeholder responses in favor of each urban ecosystem service (ES; vertical axis), detailed in Figure S2, with resident priorities (horizontal axis), detailed in Figure 4 and Table S5. Delphi stakeholder priority was defined as two-thirds or greater consensus approval; residential priority was established by significance of Fisher's exact test at the *p* < 0.05 level (*n* = 97); green shaded region represents urban ES prioritized by both stakeholder groups. AQ = air quality; AT = air temperature; BH = bird habitat; CI = community identity; CS = carbon sequestration; FP = fruit production; FR = flood reduction; NB = natural beauty; NS = native species; OR = outdoor recreation; P = privacy; PD = plant diversity; PH = pollinator habitat; SH = soil health; SQ = stormwater quality; VP = vegetable production.

Participants viewed the primary benefits of public lawn in parks as providing recreational and gathering space (93% and 73% agreement, respectively) and ease of maintenance (67% agreement) (Table S8); on right-of-way strips, safety and sightlines were the only benefits that reached a consensus, with over 85% agreement. The principal concerns, in turn, both in parks and on right-of-way strips, were lawn's limited ability to provide regulating services (i.e., air and water filtration, carbon sequestration, and flood reduction), irrigation requirements, and lack of biodiversity (Table S8). Additionally, two-thirds agreed that fertilizer, pesticide, and herbicide impacts were a concern for right-of-way planting strips (Table S8).

Accordingly, participants agreed that replacing lawn with alternative planting regimes could increase biodiversity and improve the habitat in parks while reducing stormwater runo ff and improving aesthetics along right-of-way planting strips (Table S8). The possibility of impaired sightlines remained a safety concern, however, and emerged as the only consensus barrier to green infrastructure development on right-of-way planting strips (Table S8). While over half agreed that converting lawn to alternative planting regimes would increase maintenance time, complexity, and cost during the transition period, they did not reach a consensus regarding the importance of these barriers. Still, to address them, the consensus recommendation was to install attractive, easily maintained plantings and to implement educational and outreach e fforts to promote support. Overall, a substantial majority (>85%) of participants supported the conversion of at least some lawn to alternative planting regimes both on right-of-way planting strips and in parks.

#### **4. Integration of Stakeholder Priorities with Quantitative Urban ES Estimates**

Although the dual values of stakeholder priorities and quantitative understanding of urban ES potential in municipal decision-making have been widely discussed [2,4,16,34,37], methods to accomplish their integration have not previously been explored. To undertake this integration, we considered a series of questions planners might ask in making urban ES-motivated vegetated land cover decisions; developed a set of alternative planting regimes that responds to these questions in the context of the FAN; and evaluated them according to the local evidence collected, yielding a single integrated result.

#### *4.1. Planning Considerations*

#### 4.1.1. What Urban ES are Available from the Landscape?

Comprehensive ES assessments and contemporary literature addressing the location of interest are expected to reveal relevant urban ES for most locations; here, such resources (e.g., [3,37–41,73]) were used to identify the 17 urban ES considered in our survey (Figure 4). Since urban ES vary with climate and biome, however, analogous resources might emphasize very di fferent services for other locations, potentially including insect or disease control, provision of raw materials, production of fresh drinking water, etc. [4,37].

#### 4.1.2. What Land Cover Types Thrive in This Location?

Climate, soil, and existing land uses are expected to limit the land cover types eligible for consideration. Here, Eugene's climate and the neighborhood's existing land use and cover types (Figure 2) focused our exploration on combinations of woodlands, dispersed trees, tall shrubs, short shrubs, and grasses, including lawn.

#### 4.1.3. What are the Urban ES Priorities of Multiple Stakeholder Groups?

Stakeholder perspectives can be revealed through interviews; in-person, mail, or online surveys; focus group discussions; and/or Delphi analyses, each with their own benefits and limitations (e.g., [74–76]). Here, we chose in-person surveys to reveal resident perspectives and to ensure a su fficiently large, random distribution of responses, despite the time-intensive nature of this approach, and we chose Delphi analyses to bring coherence to the input of diverse green space managers.

#### 4.1.4. Which Urban ES can be Quantified According to Land Cover Type?

Quantitative evidence documenting the ES provided by di fferent land cover types is growing rapidly (e.g., [14,16,77–83]), and where it exists, it can be used to inform decisions among alternatives. Additionally, urban ES delivery without published land cover supply rates may be evaluated qualitatively with guidance from locally or regionally available information (e.g., [84,85]), while others (e.g., natural beauty, pollinator habitat, and native plant species) may still be factored into design decisions, particularly through species choice. Here, the priorities of stormwater quality and air quality were among those with supply rates published by land cover type (e.g., [14,58]), allowing their urban ES to be quantified. Pollinator and native species habitat urban ES had not been similarly quantified, but local guidance existed in the form of a City resolution [86] and in regional lists of recommended native tree, shrub, vine, grass, and forb species (e.g., [87,88]). Using resources such as these, new plantings designed to meet quantifiable urban ES priorities may generally be chosen to meet non-quantifiable priorities as well.

#### 4.1.5. What Barriers or Constraints Exist?

Finally, various barriers are expected to limit the resulting green infrastructure development options, particularly including lack of funds for establishment, expansion, or maintenance of green infrastructure; insu fficient social support resulting from conflicting stakeholder desires; and safety or accessibility concerns (e.g., [89]). Here, Delphi participants expressed concerns consistent with those found elsewhere, focusing on cost and safety (Table 1).

#### *4.2. Alternative Planting Regimes*

The considerations above guided the following investigation of alternative planting regimes with which to provide urban ES through the conversion of public lawn, illustrating the way in which integration of quantitative urban ES supply rates with stakeholder priorities leads to a di fferent result than that obtained by reliance on any one line of evidence alone. The status quo, to which the others were compared, represents the result of current decision-making processes that have yielded lawn-dominated public spaces, with substantial outdoor playing field area as well as several hectares of dispersed trees and one prominent woodland park. The "*Forest and Stream*" alternative planting regime maximizes the provision of quantifiable, locally relevant urban ES in the study area, named to reflect the resulting emphasis on woodlands and stormwater filtration facilities. The "*Birdland*" regime, in contrast, represents Delphi priority urban ES, showing the value placed on bird habitat and air quality; "*Flower Sports*" represents resident priority urban ES, distinguished by an emphasis on pollinator habitat and outdoor recreation; and "*Integration*" capitalizes upon the multiple urban ES provided by individual land cover types to address both Delphi and resident priority urban ES with minimal compromise to either one. Urban ES supply rates expected of each alternative planting regime were estimated as described in Methods, with the inclusion of an additional "recreational lawn" metric reflecting the local importance of soccer and other playing fields [90].

The first alternative planting regime, *Forest and Stream*, maximizes the quantifiable, locally relevant urban ES of air quality, carbon storage, cooling, and runo ff retention and purification, independent of stakeholder priorities. All park and schoolyard lawns are therefore converted to woodlands except for the 0.5 ha devoted to rain gardens, and nearly 4.6 ha of stormwater planters, as well as an additional 0.3 ha of trees, are added to right-of-way planting strips, su fficient to intercept stormwater runo ff pollution from all public and private impervious surfaces in the neighborhood (Figure 7, Tables S10 and S11). Estimated from published supply rates [14,58], this regime would increase air purification by nearly 40%, carbon sequestration by over 150%, and runo ff retention by 3.5%, as well as reduce runo ff pollutant loading by 80% (Table 2). At the same time, Delphi responses sugges<sup>t</sup> that the conversion of such a large area would encounter cost barriers as well as safety concerns associated with dense vegetation.

**Figure 7.** Land cover distributions for alternative planting regimes. Proportions of public green space (57.4 ha total) devoted to dispersed trees, woodland, tall shrubs, short shrubs, lawn or grass, and stormwater facilities, respectively. *Status Quo* describes the existing condition in the neighborhood (Section 3.1.); *Forest and Stream* maximizes locally-relevant, quantifiable urban ecosystem services (ES); *Birdland* maximizes delivery of Delphi respondents' priority urban ES; *Flower Sports* maximizes delivery of residents' priority urban ES; and *Integration* maximizes delivery of the urban ES prioritized by both Delphi respondents and residents.


**Table 2.** Urban ecosystem service delivery associated with alternative planting regimes.

a Supply rates were calculated according to Derkzen et al. [14] unless otherwise specified. b Retention by woodlands, trees, tall shrubs, short shrubs, and lawn only. c Filtration by stormwater facilities, calculated using the Simplified Approach as described in the City of Eugene Stormwater Manual [58]; accounts for stormwater pollutants from impervious surfaces removed by stormwater planters and rain gardens on both publicly—and privately—owned land (see Table S10).

The second planting regime, *Birdland*, maximizes the response to the Delphi priorities of carbon storage, bird habitat in parks, air temperature regulation (i.e., cooling), and natural beauty, as well as

the priorities held in common with residents (i.e., air quality, stormwater quality, and native species throughout the neighborhood, as well as pollinator habitat in parks). Clear sightlines for safety and moderate cost were prominent Delphi concerns, expressed in part as a desire to retain some existing lawn, and *Birdland*, therefore, converts only about one-quarter as much existing park lawn to woodland as *Forest and Stream*, or ~8 ha, envisioned as patches of native oak woodland and restoring native willow and ash woodland for bird habitat in the area designated as Westmoreland wetlands [91]. To address air quality and cooling priorities while maintaining ground-level openness, *Birdland* adds ~8 ha of dispersed trees to parks and schoolyards, capitalizing on the superior air pollutant removal rates of trees near roadways [14]. Like *Forest and Stream*, this regime adds 0.5 ha of rain gardens and ~5 ha of short and tall shrubs to parks, again removing all recreational lawn (i.e., softball fields) but leaving ~6 ha of other lawn intact, responding to Delphi safety concerns. On right-of-way planting strips, *Birdland* reduces the ~5 ha of stormwater planters proposed by *Forest and Stream* to ~2 ha, su fficient to manage the publicly-owned impervious area in the neighborhood (Table S10) and responding to Delphi participants' cost concerns. The remaining ~3 ha of right-of-way lawn are then replaced with dispersed trees for air quality (Table 2). This conversion, involving ~5 fewer ha than *Forest and Stream* (Table S11), is estimated to increase existing air purification by over 40%, carbon storage by ~100%, and runo ff retention by ~2%, as well as to provide pollutant filtration for about one-third of the neighborhood's total stormwater runo ff (Table 2).

The substantial conversion of playing-field lawn found in *Forest and Stream* and *Birdland* is reversed in the third planting regime, *Flower Sports*, which maximizes responses to resident priorities of outdoor recreation and pollinator habitat throughout the neighborhood, while accommodating the priorities of air and water quality held in common with Delphi respondents. A recent survey of Eugene residents showed that outdoor playing fields (i.e., recreational lawn areas) were in especially short supply compared to resident desires, providing specific, local evidence that superseded the outdoor recreation supply rates compiled by Derkzen et al. [14]. In parks and schoolyards, *Flower Sports*, therefore, converts only half as much lawn to native oak and ash woodland around the Westmoreland wetlands (4 ha) and ~15% less lawn (~7 ha) to dispersed trees as *Birdland*, while preserving the full 4 ha of existing sports fields (Table S11). Like *Birdland*, this regime adds 0.5 ha of rain gardens and ~5 ha of tall and short shrubs to parks, as well as ~2 ha of stormwater planters to the right-of-way, for stormwater purification; in contrast, however, it adds 2 ha of flowering shrubs to right-of-way plantings for additional pollinator habitat in place of dispersed trees. This regime converts ~5 fewer ha of lawn than *Birdland* but still increases air purification over the existing condition by about one-third and carbon storage by 70% while adding the ability to remove about one-third of the neighborhood's stormwater runo ff pollution.

The fourth planting regime, *Integration*, prioritizes the urban ES held in common by both resident and Delphi stakeholders (i.e., stormwater quality, air quality, park pollinator habitat, and native species), using quantitative supply rates to indicate the most e ffective land cover types for each priority and allowing other priorities to be addressed through species selection. *Integration*, therefore, converts an area of existing park lawn to woodland between those of *Birdland* and *Flower Sports* (6 ha), representing a significant compromise that diminishes the outdoor playing field area by one-quarter in the interest of greater air quality, cooling, bird habitat, carbon storage, and native species urban ES. *Integration* also includes less dispersed tree area in parks (~6 ha) than either stakeholder-driven scheme, accommodating both the outdoor playing field area prioritized by residents and woodland urban ES prioritized by Delphi participants. Like *Birdland* and *Flower Sports*, this scheme converts 0.5 ha of park lawn to rain gardens and ~5 ha to flowering shrubs. To compensate for tree loss in parks, *Integration* increases tree cover and diminishes flowering shrubs relative to *Flower Sports* on right-of-way strips; stormwater planters are maintained at the level of both stakeholder-driven schemes. Compared to *Forest and Stream*, which maximizes quantifiable urban ES, *Integration* converts ~30% less land area but provides 95% of its air quality improvement and over one-third of its stormwater pollutant filtration, while retaining over 3 ha of outdoor playing field area (Table 2). *Integration* also provides clear but unquantified increases in pollinator habitat and native species diversity through the inclusion of flowering shrubs and woodland, and it addresses concerns of cost and safety raised in the Delphi analysis by converting less total lawn and maintaining greater openness at ground level than *Forest and Stream* or even *Birdland* (Table S11).
