CHAPTER 2

URBAN FORESTRY: SERVICES, TOOLS, AND MANAGEMENT

SETTING GOALS AND DEVELOPING STRATEGIES IN URBAN FORESTRY
Ann Bartuska, U.S. Department of Agriculture

There has been an increased emphasis on sustainable cities. One component of a sustainable city is the inclusion of trees as part of the greater urban ecosystem. This shift toward the concept of socioecology will require a deliberate integration of social and biophysical sciences, breaking down silos in governance and management, market-based solutions, and valuing green infrastructure.

A significant challenge in urban forestry is fostering a sense of environmental stewardship. How do you engage all the needed stakeholders and provide them with useful tools and information? Environmental stewardship requires various groups to conserve, manage, monitor, advocate for, and educate their friends, neighbors, and representatives about their local environments. Everyone deserves access to green space, which ties into the idea of environmental justice.

Tools developed by the U.S. Department of Agriculture (USDA) are now focusing on an integrated ecological system, rather than simply trees, and are being developed to help foster environmental stewardship. For example, the Stewardship Mapping and Assessment Project (STEW-MAP) is a geospatial tool utilized by several cities, including New York City, to understand the intersections of green space and social space. These maps quantify stewardship networks and linkages by indicating where particular types of organizations are working together and where improvements can be made to encourage more cooperation among these organizations. These networks allow communities to share the skills that they have learned in developing green space in urban areas. STEW-MAP highlights existing stewardship gaps and overlaps to strengthen organizational capacities, enhance citizen monitoring, promote broader public engagement with on-the-ground environmental work, and build effective partnerships between stakeholders involved in urban sustainability.

This shift toward an integrated ecological system is impacting the types of R&D being conducted at USDA. For example, USDA conducts urban research in forest inventory and management, ecosystem services, health and wellbeing, urban sustainability, green infrastructure, water and watersheds, and urban long-term research. Urban agriculture challenges USDA to think about how more traditional aspects of agriculture can contribute to more sustainable urban ecosystems.

USDA is just one of several agencies that study urban issues. In the spirit of environmental stewardship, how can we bring these agencies together with the common goal of sustainable cities? The NSF Long-term Ecological Research (LTER) Program consists of 26 sites with over 1800 scientists and students studying ecological processes over extended temporal and spatial scales. This valuable effort highlights the importance of long-term observations in an interdisciplinary setting. Including urban systems into LTER networks (e.g., Baltimore and Phoenix) has been an important step forward.

The 2010 NRC report Pathways to Urban Sustainability: Research and Development on Urban Systems explores the landscape of urban sustainability research programs in the



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CHAPTER 2 URBAN FORESTRY: SERVICES, TOOLS, AND MANAGEMENT SETTING GOALS AND DEVELOPING STRATEGIES IN URBAN FORESTRY Ann Bartuska, U.S. Department of Agriculture There has been an increased emphasis on sustainable cities. One component of a sustainable city is the inclusion of trees as part of the greater urban ecosystem. This shift toward the concept of socioecology will require a deliberate integration of social and biophysical sciences, breaking down silos in governance and management, market-based solutions, and valuing green infrastructure. A significant challenge in urban forestry is fostering a sense of environmental stewardship. How do you engage all the needed stakeholders and provide them with useful tools and information? Environmental stewardship requires various groups to conserve, manage, monitor, advocate for, and educate their friends, neighbors, and representatives about their local environments. Everyone deserves access to green space, which ties into the idea of environmental justice. Tools developed by the U.S. Department of Agriculture (USDA) are now focusing on an integrated ecological system, rather than simply trees, and are being developed to help foster environmental stewardship. For example, the Stewardship Mapping and Assessment Project (STEW-MAP) is a geospatial tool utilized by several cities, including New York City, to understand the intersections of green space and social space. These maps quantify stewardship networks and linkages by indicating where particular types of organizations are working together and where improvements can be made to encourage more cooperation among these organizations. These networks allow communities to share the skills that they have learned in developing green space in urban areas. STEW-MAP highlights existing stewardship gaps and overlaps to strengthen organizational capacities, enhance citizen monitoring, promote broader public engagement with on-the-ground environmental work, and build effective partnerships between stakeholders involved in urban sustainability. This shift toward an integrated ecological system is impacting the types of R&D being conducted at USDA. For example, USDA conducts urban research in forest inventory and management, ecosystem services, health and wellbeing, urban sustainability, green infrastructure, water and watersheds, and urban long-term research. Urban agriculture challenges USDA to think about how more traditional aspects of agriculture can contribute to more sustainable urban ecosystems. USDA is just one of several agencies that study urban issues. In the spirit of environmental stewardship, how can we bring these agencies together with the common goal of sustainable cities? The NSF Long-term Ecological Research (LTER) Program consists of 26 sites with over 1800 scientists and students studying ecological processes over extended temporal and spatial scales. This valuable effort highlights the importance of long- term observations in an interdisciplinary setting. Including urban systems into LTER networks (e.g., Baltimore and Phoenix) has been an important step forward. The 2010 NRC report Pathways to Urban Sustainability: Research and Development on Urban Systems explores the landscape of urban sustainability research programs in the 7

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8 Urban Forestry: Toward an Ecosystem Services Research Agenda United States and provides useful advice that could be used by many agencies that work on urban forestry. The report explores how urban sustainability can move beyond analyses devoted to single disciplines and sectors to systems-level thinking and effective interagency and intergovernmental cooperation. It concludes that it is critical to better integrate science, technology, and research into catalyzing and supporting sustainability initiatives; find commonalities, strengths, and gaps among rating systems; and incorporate critical systems needed for sustainable development in metropolitan areas. Discussion Dr. Bartuska was asked how USDA is defining “sustainability” in the context of an increase in population, economy, and agriculture. She said there is a balance of three factors in the context of sustainability: people, planet, and profit. USDA does have a sustainability office and they must continue to be aware of what constitutes sustainability and sustainability practices. For example, USDA’s Beginning Farmers and Ranchers Program ensures that participants address water and air issues, as well as biodiversity issues and then incorporate these into practice. Dr. Bartuska also noted that the USDA Agricultural Research Service has a project in small and organic farms in urban areas. URBAN FORESTRY WITHIN THE GREATER URBAN ECOSYSTEM Moderator: Marina Alberti Urbanizing regions pose enormous challenges to ecosystem’s capacity to deliver important ecological services (Alberti, 2010). At current rates of urban growth, global urban land cover will increase by 1.2 million km2 by 2030, nearly tripling the global urban land area of 2000, with considerable loss of habitats in key biodiversity hotspots (Seto et al., 2012). Scientists have made significant progress during the last few decades in studying the role of urban forests in both mitigating urbanization’s impact and providing a variety of ecosystem services. Yet scientific understanding of key mechanisms governing ecosystem functions across multiple scales is incomplete. There are important tradeoffs across scale and between functions. There is also great variability across metropolitan areas and biophysical regions. The goals of this panel were to (1) explore the role of trees within the greater urban ecosystem and the ecosystem services they provide, and (2) review current understanding of the ecosystem services provided by urban forests, and identify research needs. Urban Ecosystems and their Potential to Provide Ecosystem Services Richard Pouyat, United States Forest Service (USFS) The environmental changes and landscape alterations typical of urban areas make it difficult to be “green.” Urban areas have highly modified environments, sealed surfaces, and species introductions that are human-caused and thus represent novel habitats made up of novel assemblages of plants and animals. From an evolutionary perspective, these assemblages are relatively new, since cities have been around for only 5,000 or so years. As a result, urban landscapes are typically thought of as artificial, harsh environments where cultivated plants grow outside their native habitats, and where animals introduced as pets (such as domesticated cats) wreak havoc on prey species such as native song birds. Despite these alterations, urban ecologists are finding high levels of biological activity and biodiversity in urban areas (Gregg et al., 2003; Ziska et al., 2004). Measurements thus far suggest there are high flux rates, large sinks for carbon and nitrogen, and high resource

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Urban Forestry: Services, Tools, and Management 9 availability (e.g., cities emit large amounts of carbon dioxide which are utilized by plants). Therefore, urban ecosystems possess the potential to provide ecosystem services. However, our ecological knowledge of these systems is lacking because ecologists in North America have only relatively recently begun to study them in a comprehensive way. Because of the novelty of urban ecosystems, urban landscapes represent a “new heterogeneity” for ecologists to quantify and understand. This term is used because, depending on the scale of observation, urban landscapes are not necessarily more complex. In fact, in some cases urban landscapes may be less heterogeneous since they have been more “homogenized” due to management activities, scales of disturbance, human preferences, and the parcelization of the landscape into management units. Since the level of heterogeneity largely depends on the scale of observation, four dimensions should be considered: longitudinal and lateral spatial dimensions, the vertical dimension (e.g., vertical air column, soil column), and the time dimension (e.g., hydro-curve for an urban stream). One of the biggest challenges for ecologists is accounting for human behavior and decision making, because humans may make irrational decisions, and human culture and value systems vary spatially. It is also difficult to quantify intrinsic and monetary values from an ecosystem services perspective. Another key point related to ecosystem services is that all life on earth is limited by available energy. Therefore, there are tradeoffs in between ecosystem services and costs. For example, there is no organism that can do everything well—allocating resources for one function takes away resources from another function. The same can be said for ecosystem services. As mentioned earlier, ecological science is a relatively young science (about 100 years) compared to the physical sciences, and urban ecological science is even younger (less than 50 years). Therefore, there is a steep learning curve. Moreover, an ecological definition of “urban” has yet to be developed (Ellis and Ramankutty, 2008). One possible definition is the threshold in human population density at which the population cannot be sustained with the resources available locally and must depend on resources brought in from outside the local area The importation of resources can cause disservices in areas at great distances from cities (Newman, 1999). Moreover, if imported resources are not used efficiently, there is a waste stream which can impact ecosystems at great distances (another potential disservice). With this definition, one may think that cities are bad; however, densely populated areas such as cities are part of the solution, since the distribution of people from cities across rural landscapes would arguably cause even greater environmental disservices than concentrating people into cities (Brown et al., 2009). Whatever the case, there are also tradeoffs of ecosystem services occurring within cities. A higher human population density will diminish ecosystem services and resources locally. For instance, cities have many polluting sources, fragmented habitats, built structures, and impervious surfaces, which lead to disrupted nutrient cycles and a loss of native biodiversity. The field of civil engineering was developed to design “gray infrastructure” to overcome some of these disservices. Civil engineers have had many more centuries of experience in developing gray infrastructure than ecologists have had with their new concept of green infrastructure. Good examples of gray infrastructure exist in ancient Rome and more modern “sanitary” cities rising from the industrial revolution such as New York City. However, there are detrimental side effects in the use of gray infrastructure that can lead to disservices. For example, gray infrastructure interrupts natural flow paths such that urban streams can become prone to flash flooding causing stream erosion downstream. Moreover, gray infrastructure degrades with time (Kaushal and Belt, 2012).

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10 Urban Forestry: Toward an Ecosystem Services Research Agenda Land use change has impacts on ecosystem services, which has been a major concern for converting natural to agricultural systems. Natural systems typically provide multiple ecosystem services, but in converting these systems to agricultural production systems, these services are greatly diminished. To address this issue, efforts are underway to design agricultural production systems so that they provide multiple services along with producing food (Foley et al, 2005; Figure 2.1). In the case of urban land use conversions, much less space (or pervious area) is available to provide ecosystem functions. Therefore, not only do we need to design urban landscapes that provide multiple functions, but those that include hyper-functioning systems as well. In urban areas, the integration of green (vegetation), brown (soils), and blue (streams) infrastructure is one way to develop a multifunctional landscape. It is best to design these infrastructures in parallel, linking one to another—for example, a green roof that is linked to a rain garden, which is then linked to a retention pond system, so that storm size events are moderated. Advantages of integrating these types of infrastructures include: avoiding side effects (e.g., high peak flows), utilizing biological processes to self-maintain, and preserving the function of pre-existing ecosystems. Unintended effects, risk, infrastructure performance, system longevity, and the possibility of disservices occurring at great distances all need to be considered when designing green infrastructures and locating those infrastructures in urban landscapes. Natural experiments can be conducted to examine the tradeoffs that occur as landscapes are urbanized. For example, when comparing forest fragments in an urban context to a rural one, roughly half the natural sink for methane, a greenhouse gas (GHG), is lost. When a forest is converted to turfgrass, the entire methane sink is lost (Pouyat et al., 2009). These kinds of unintended effects should be considered, and decision tools are needed that will optimize multiple factors simultaneously, because making a poor decision in designing or locating green infrastructures in urban landscapes may be worse than not doing anything. Pouyat summarized by stating that (1) a basic understanding of urban ecosystems should be developed, which can be accomplished by utilizing the urban mosaic to conduct “natural experiments,” conducting cross-system comparisons (local, regional, global), and developing integrated models that spatially and temporally quantify the “new heterogeneity” represented by urban landscapes; (2) urban observations should be expanded into networks (e.g., a network of urban LTER sites or existing environmental monitoring networks such as the National Atmospheric Deposition Program ); (3) decision tools need to be developed that can optimize across factors (e.g., species selection, management) while considering tradeoffs and providing a decision space (e.g., uncertainty, risk); and (4) multifunctional and hyperfunctional infrastructures need to be designed and developed. Services and Regional Tradeoffs: Resolving the Desert Forest Paradox Diane Pataki, University of Utah Urban forests in desert areas are an extreme example of novel ecosystems. Salt Lake City, Utah, for example, is naturally a shrubland, yet the city has an extensive urban tree canopy (Figure 2.2.). Virtually all of these trees are planted and irrigated, making this an extreme example of a human-created and managed forest. Given that ecosystem services is a concept intended to quantify the value of natural rather than designed ecosystems, urban ecosystems originally were assumed to have negligible monetary value on a global scale. What happens when we are designing ecosystems to have intended values? How do we cope with the costs of designing and managing novel ecosystems that require resource inputs?

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Urban For restry: Service Tools, and Management es, d t 11 FIGURE 2.1 Conceptual fr 1 ramework for comparing land use and tradeo of ecosystem services. The natural ecosys c offs m e stems (left) are ab to support many ecosystem services at hig levels, excep for food prod ble m m gh pt duction. The int tensively managed cropland (m middle) is able to produce food in abundance (at least in the short term), b ut loses other e t d e e ecosystem services. However, a cropland that is explicitly ma anaged to main ntain other ecossystem services may be able to support a bro s o oader portfolio of ecosystem serv f vices (right). Th framework could be applie to urban land use conversio his c ed d ons, albeit on a smaller sca since there is less land avai ale ilable in the urb landscape. SOURCE: Fole et al., 2005. ban ey Novel and non-native ecosystem often have significant mo ms onetary and e environmental cessarily a bad thing. For ex costs, but this is not nec d xample, urban forests in arid and semi- n arid cities use a lot of water. These designed ecosy w ystems will of ften have significant costs, which ma be acceptab if benefits outweigh the costs. Howev our resear increasing ay ble e ver rch gly shows tha the most imp at portant benefits of novel ur rban forests ar cultural and thus are very re d difficult to quantify with existing tool We need a new set of to o h ls. ools that exten beyond the nds standard ecosystem serv e vices framewo to capture the complex relationship between urba ork e x an residents and the novel urban enviro a onment. One tool we can bring to an exp t panded toolbo for plannin g and managi urban ox ing forests is urban metabolism (Kennedy et al., 2012) This concep has been us by several u y ). pt sed l different disciplines for decades and has been vari d iously defined but it generally involves d, quantifyin the total res ng source inputs, outputs, and transformatio in cities. A ons Although there e are some data constrain in quantify d nts ying urban meetabolism, this concept is cr s ritical for quantifyin the role of urban forests in the function ng u i ning of the cit as a whole. ty . Urban metabolism can be used as a tool to he us charact n a elp terize the bene efits of trees in n a larger co ontext. Urban forests are of ften thought of as a tool for mitigating cliimate change; ; however, carbon seque estration by urrban trees doe not have a s es significant impact in offsetting fossil fuel emi f issions (Pataki et al., 2006; 2011). Trees do, however, have a i , significant cooling effec (through evapotranspirati and shade which may impact GHG t ct ion e), y G emissions indirectly (Fra anco and San nstad, 2008). For example, a city can sav on energy F ve costs by reequiring less air conditionin It is impor a ng. rtant to undersstand these m mechanisms because urban forests designed for carbon sequest u d tration may lo quite diffe ook erent than fore est canopy de esigned to ma aximize coolin ng.

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12 Urban Forestry: Tow n oward an Ecosy system Service Research Ag es Agenda FIGURE 2.2 The left imag is a picture of Salt Lake City UT. Notice th natural shrubland in the for 2: ge o y, he reground and th he nted) trees in the city. The right image shows what Salt Lake City would like in its natural state. SOURCE novel (plan e t e E: Barry Howe/Corbis (left immage); Diane Pa ataki (right image). here are other useful tools fo designing a planning urban tree po Th or and opulations thatt origina in enginee ate ering. There is currently a g reat deal of discussion abo substituting out g green infrastructure for “gray” infrastructure. HHowever, utiliz zing trees as u urban infrastru ucture require monitoring and validatio to ensure th urban fore meet desig targets. For es on hat ests gn examp to conside pollution re ple, er emoval by tree as urban in es nfrastructure, w need we measurements and monitoring of the specific a local impacts of trees o pollutant m f and on concen ntrations. This regularly occ s curs in gray in nfrastructure pprojects; sewa treatment age plants, for example, are routinely monitored to ensure that e y o effluent meets water quality s y standards. It is not necessary to quantify the ec n cosystem servi ices provided by sewage treatment plants—th are engine hey eered to meet specific regu t ulatory requireements. The scientific methodolo necessary to make simi measurem ogy y ilar ments for green infrastructur n re, such as urban trees, currently exists as shown b the other w by workshop spea akers, and nee to eds be more commonly implemented along with tr planting p d ree programs. Ot ther tools for designing and planning urb forests are available fro the disciplines d d ban e om of arch hitecture, plan nning, and dessign. Existing tools can also be used for s o stakeholder engageement, which can help dete ermine local v values. “Envission Utah”2” w a well-known was program that used a participatory process to de y evelop a set o common, sh of hared scenario for os future urban growth It is possible and necessa ry to develop similar plann h. e ning and visioning processses for urban trees and gree space. The beginnings o such progra are under en e of ams rway; “Envisi Tomorrow is a plann ion w+” ning tool being developed t include env g to vironmental outcom and some initial estima of ecosyst mes e ates tem services. In conclusion, tools for charaacterizing the net services o urban trees should be pla of ace- specific and spatially explicit, hav visualizatio componen include co ve on nts, ommunity valu ues and vis sioning, incor rporate urban metabolism s stock and flow and captur measurable ws, re e perform mance-based metrics. Thes tools can al so be utilized by people fro different se d om disciplines. This appproach extend the tools an vision for u ds nd urban forests b beyond the ecosys stem services concept, to ca c apture the larg role of urb forests in the functionin of ger ban ng cities. 2 http:// //www.envision nutah.org/

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Urban Forestry: Services, Tools, and Management 13 Challenges for Green Infrastructure at the Interface of Science, Practice, and Policy Thomas Whitlow, Cornell University There are many challenges in reaping ecosystem services within a city, including competing agendas (e.g., many goals, many languages, and many metrics), immature science and technology, need for hyperfunctional design, and unanticipated findings in case studies in air pollution. As one example of failing to meet expectations, Bernhardt et al. (2005) found that many stream restoration projects did not accomplish their goals. Several as-yet-unpublished air quality case studies from the New York City area found that air quality was poorer downwind of trees. In Case Study 1, it was hypothesized that greener surroundings (e.g., trees, shrubs, etc.) in an urban environment leads to cleaner air because leaves filter out pollution. The study found that particulate matter (PM2.5) concentrations were higher ten meters from the curb and downwind of two rows of mature trees than at five meters, suggesting that trees impede dispersion, creating zones of increased pollution. Fifty meters of separation were needed to disconnect a location in the landscape from events occurring on the street (Figure 2.3). In Case Study 2, researchers monitored two transects downwind of Van Wyck Parkway in New York City and found that PM2.5 concentration decayed more rapidly along an open transect than a vegetated transect. In Case Study 3, measurements were taken at a rural site to test the influence of tree canopy on background concentration. Researchers discovered that air quality was worse more than 90 percent of the time in a stand of either spruce or deciduous trees compared to an open field. In Case Study 4, the extinction of particle plumes was monitored in a wind tunnel containing varying amounts of leaf surface. Leaf area had no effect on the decay rate of the plumes. In Case Study 5, human health implications were studied using cytokines3 as biomarkers for inflammation. Cell cultures challenged with airborne particulates collected from parks showed higher cytokine induction than samples near streets or rooftops. In all of these cases, findings ran counter to expectation, indicating that we need a more sophisticated understanding of the mechanisms influencing particulate behavior if we hope to design effective pollution mitigation using green infrastructure. Another challenge for green infrastructure is to move from multi-functionality to intentional hyperfunctionality. That is, if cities can only afford to allocate limited space to green infrastructure, each unit of green needs to be hyperefficient if we intend to achieve meaningful reductions in pollution, runoff and temperature; green space needs to be deliberately designed to enhance its benefits. In conclusion, we should move beyond the simple notion that “more green is better.” Designing hyperfunctional green infrastructure requires an adaptive management approach involving experiments, modeling, ground truthing, and comparative studies in order to promulgate useful policy and effective practices. Urban Nature: an Artifact of the Industrial City4 Stephanie Pincetl, University of California, Los Angeles We are living in a new age: the Anthropocene5. Humans are now an urban species and shape many of Earth processes. This raises questions about what it is to be human in an 3 Substances that are secreted by specific cells of the immune system and are used extensively in cellular communication. 4 Dr. Pincetl was unable to attend the workshop, but provided her PowerPoint presentation to all workshop participants.

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14 Urban Forestry: Toward an Ecosystem Services Research Agenda urban age, how cities are built and grow, as well as our “need for nature.” Cities are nature—inert minerals transformed by humans into infrastructure. However, where does living nature fit in? Until the industrial revolution, cities were essentially devoid of living nature, except for elite gardens. There was a hierarchical order of civilization out toward the wilderness— cities were surrounded by agriculture and the countryside, which were surrounded by wilderness. In fact, nature was feared and powerful. The wilderness had wolves, bears, and other predators. Agriculture was a struggle against weather, weeds, animals, soils, water supply, and trees. The harnessing of fossil energy enabled industrialization and changed humans’ relationship with the planet. This led to a dramatic transformation of nature, enormous increases in manufacturing productivity, and the concentration of humans in urban centers as never before. The Industrial City was polluted, crowded, and insalubrious. During the early years of the industrial revolution, living conditions in cities were abysmal. Tree-lined streets and parks were seen as agents of change to make cities more livable. Frederick Law Olmsted’s Central Park was seen as the lungs of the city for the working class: “A park is a work of art, designed to produce certain effects on the mind of men (Olmsted, 1868).” This led to the rise of landscape architecture and interest in the exotic, including plants that were non-native. This interest reflected the new cosmopolitanism, reaching far beyond the local. Human views of trees began to change. George Perkins Marsh6 showed the importance of trees for watershed function, which led to preservation of forests that were still in the public domain. This coincided with the rise of the preservation movement and the idealization of nature. Eventually there was a tree-planting movement in cities. The urban expansion across the American west into the treeless plains provoked deliberate urban tree planting, starting in the 1870s in Nebraska with the founding of Arbor Day, as lands west of the 100th Meridian were arid and treeless. Citizen-based urban tree planting spread in mostly affluent areas. Tree planting became a civic obsession; there was an association of virtue with trees. In the United States, emphasis was placed on neighborhood trees (planted by individuals along streets). Gifford Pinchot, the first director of the USFS, actively promoted tree planting in cities. In the 20th century, parks and open space became normalized as part of urban planning and design. Urban trees were seen as part of the health of residents and a sign of a well-tended neighborhood. Postwar prosperity led to urban expansion. In the mid-20th century, concerns were raised about the preservation of nature and the environment. Rachel Carson (1962) sounded the alarm on chemical impacts, which led to the modern environmental movement. In the 1970s there was formal federal Forest Service assistance for urban tree planting. Eventually Tree City USA was initiated by the National Arbor Day Foundation in cooperation with the U.S. Conference of Mayors, the National League of Cities, the National Association of State Foresters, and the USFS7. 5 An informal geologic chronological term for the present geological epoch (from the time of the Industrial Revolution onwards), during which humanity has begun to have a significant impact on the environment. 6 For more information on George Perkins Marsh, see http://www.clarku.edu/departments/marsh/about/ 7 http://www.arborday.org/programs/treeCityUSA/about.cfm

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Urban For restry: Service Tools, and Management es, d t 15 FIGURE 2.3 PM2.5 conce 3: entration taken from various distances from a curb and dow d wnwind of 2 row of mature tre ws ees plotted aga ainst time. Unex xpectedly, the air 10m from th mature trees is dirtier than t air 5m from the mature tre a he the m ees. SOURCE: Thomas Whitlow. T Urban sustainability has been pa of the public focus since the 1980s. C n y art e Cities are now w seen as sit of their ow pollution and impacts re tes wn emediation. A n instrumenta urban natur al re can be developed to he in this end elp deavor, as it ca provide pro an ovisioning, re egulating, cultural, and possibly supporting serv a vices. Trees have become e emblematic o urban of ecosystem services in cities across th country, and million tree planting prog m c he e grams have become popular. p But what is sustaina w able for whom and where? Do alleged se m ervices add up? Some parts s of the couuntry are naturrally treeless and water-rest a tricted; yet pla anting trees re equires water resources. Maintaining trees also requires long-term funding an d specialized knowledge. . This is pro oblematic if re esidents have neither. It also should be ac o cknowledged that not all d people lik trees. Some ecosystem se ke e ervice structur such as bio res oswales, wate infiltration, er and trench are also co hes ostly and requ fundamen changes i urban morp uire ntal in phology. How do we implem ment the right urban ecosys stem services f each place This will for e? require ne forms of pu ew ublic administ tration and different rules to create new agendas, o sharing of budgets, and co-managem f ment of new in nfrastructure (e e.g., water and sanitation with street services). Ne sources of funding are also needed, a well as new skills to t ew a as w maintain “living infrastr “ ructure.” Each region will have different climatic toler h h rances, and ecosystem services will have to be ap m ppropriate to the condition Success will depend on ns. public accceptance of a different-look king city, and willingness to lend their in o ndividual private prooperty to the effort. This will require a de shift invol e eep lving public s stewardship,

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16 Urban Forestry: Toward an Ecosystem Services Research Agenda and new ideas of property rights and obligations. Finally, the sanitary city8 of the 20th century needs to be retrofitted so natural processes can work to help mitigate urban impacts and to develop the sustainable city of the twenty-first century. Urban ecosystems have costs and benefits, and quantifying the benefits is difficult. Trees perform differently across different ecosystems and in different urban locations. Does their performance translate to the benefits claimed such as reducing the use of air conditioning or sequestering GHG emission? Trees that are brutally pruned will see their ecosystem services severely curtailed. These kinds of factors should be taken into account. What is the value of ecosystem services? This is still largely unknown and represents the instrumentalization of nature. Humans have transitioned from fear of and vulnerability to nature’s impacts and processes, to domination and pricing of its functions, with meager quantification compared to the complexity of what is being proposed. There has been minimal effort to address the public administration and land management changes that are necessary to implement the changes proposed. The issues of beauty and wellbeing are also unaddressed. Yet humans are now urban dwellers and our relationship to nature has changed. Do we need nature to feel happy? Discussion Some points raised in the open discussion that followed this panel’s presentations:  An important goal for improving urban forestry models is to link hyperfunctional ecosystem services to regulatory requirements.  Optimizing hyperfunctionality across many outcomes while focusing on the factors that the local community most values, would take into account people’s widely differing values and priorities.  The urban environment brings together many different types of plant and animal species that have no history of co-evolving. The mechanisms of how these unique ecosystems function is therefore largely unknown.  National-level support could help capture knowledge and foster collaborative learning across cities. BIOPHYSICAL SERVICES OF THE URBAN FOREST Moderators: Kenneth Potter, University of Wisconsin; ST Rao, North Carolina State University As discussed in the previous session, urban forests provide a variety of functions including climate mitigation, carbon sequestration, mitigation of stormwater runoff, and regulation of nutrient cycling, as well as habitats for many species of wildlife. This session was a continuation of the previous session and focused on the biophysical services of trees with respect to air, water, climate, wildlife, and health. Panelists were asked to discuss the current state of the science in their respective disciplines on the biophysical services provided by urban forests. They were also asked to discuss the remaining challenges and open questions surrounding the science and the additional research, data, and observations that are needed to resolve these questions. 8 An urban form developed to correct the ills and hazards of the industrial city.

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Urban For restry: Service Tools, and Management es, d t 17 FIGURE 2.4 A schematic of a subsurface gravel wetland. SOURCE: U niversity of New Hampshire S 4: e w Stormwater Cen nter. Trees Incorporated into Urban Stormwater M anagement s d S Tom Ballester University of New Hamp T ro, y mpshire Sewag treatment utilizes very so ge u ophisticated systems, where stormwate manageme s eas er ent is relativel low tech. Many types of processes are utilized in sto ly M e ormwater ma anagement, including hydraulic con ntrol, storage, sedimentation, filtration, in nfiltration, sor rption, biodegrad dation (microbbial, rhizospheeric, plant), an chemical. S nd Systems that p perform filtration yield higher water quality effluent than other systems. Common filtr y w ration systems s can includ constructed systems (e.g permeable pavements an sand filters and biologic de d g., nd s) cal systems (e e.g., subsurface gravel wetla and, tree filter and bioreten r, ntion systems) ). Green infrastructure can be desig n e gned to perform better at st tormwater maanagement tha an pre-develo opment ecosy ystems. Often, aside from filtration, these designs incorporate e infiltration as part of the stormwater management. n e m A tree box filter is a mini-biorete e ention system. A bioretentio system con on nsists of a high h permeabillity, manufactured organic soil bed plant with suitab preferably native ted ble, vegetation Vegetation in the soil pla n. anting bed assists in removi ng pollutants from stormwate runoff. er Subsu urface gravel wetlands, an example of a biological me w e b echanism for ffiltration, are a an innovative variation on the traditiona stormwater wetland (Figu 2.4). Subsurface gravel e al ure wetlands have high efficiencies for re h emoving sedim ments, nutrien and other pollutants nts, commonly found in run y noff. The storm mwater is filtered as it flows underground horizontally s d, y through th wetland. Be he ecause the priimary flowpat is subsurfac the system runs th ce, m anaerobiccally, which suupports denitrrification. How wever, an aero obic zone nee to be eds placed in front of the su ubsurface grav wetland to convert mos of the dissol vel o st lved nitrogen forms to nitrate. As stormwater move from the aerobic zone th rough the sub n es bsurface grave el, it become denitrified. This type of sy es T ystem requires a significant amount of la t and, but it doe es allow for more diversity in the types of vegetation that can be p m y planted over it (e.g., native t wetland grasses, reeds, herbaceous plants, and shr p rubs). There are various metrics that ca be used to measure the s m an social benefits of the use of s f astructure for stormwater management. One example is cost. Conv green infra m O ventional technolog (e.g. gray infrastructure) are typically the cheapest initially, how gies ) y t wever, more advanced methods (e.g., low impact development have the low maintena t) west ance costs overall. A normalizing method of comparing costs considers do s ollars per poun of pollutan nd nt

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26 Urban Forestry: Toward an Ecosystem Services Research Agenda The air quality component of i-Tree is broad scale and estimates pollution removal by trees and VOC emissions. Some current challenges related to air pollution include linking i- Tree with a more integrated modeling framework, developing fine-scale modeling, integrating secondary effects (energy and temperature effects), improving particulate matter (PM) modeling, estimating pollen loads, and linking to regulations. There are many water quality models including HSPF (Hydrological Simulation Program—Fortran), BASINS (Better Assessment Science Integrating point and Nonpoint Sources), SWMM (Storm Water Management Model), RHESSes, and i-Tree Hydro. Challenges related to urban hydrologic modeling include: making the models more user friendly for local and program managers, capturing water quality measures and procedures, obtaining water quality data for calibrating and verification, linking to pollution reduction credits, and developing more fully distributed models. Models capture the storage and sequestration of GHGs, particularly carbon dioxide, via biomass equations and growth rates. They also estimate energy impacts on carbon emissions. Future goals are to expand outputs beyond carbon dioxide, gain a better understanding of urban equations for biomass and growth, improve the modeling of tree effects on energy use, and capture tree species influences on albedo and atmospheric conditions (e.g., moisture). A module is currently being built to estimate tree effects on exposure to ultraviolet radiation. It will be based on simulating shadows and sky view. Current challenges include utilizing Light Detection and Ranging (LIDAR) data, linking to human health, and capturing diverse atmospheric conditions. Modeling biodiversity, nutrient cycling, and urban soil conditions is limited at this time. Models can estimate tree species diversity, leaf area and biomass, and some soils information. The challenge is to incorporate even more soils data, link structural data to nutrient cycles, and link to forest nutrient and soils models (e.g., BIOME-BCG, CENTURY). The modeling of wildlife impacts is still in development. Currently nine bird species will be represented in the model, which is small relative to the total number of bird species. Eventually, modelers would like to capture many more species, develop regional equations, and integrate existing wildlife models with urban data. Various studies on noise exist, but i-Tree does not currently address this topic. Researchers are currently investigating conversion factors for urban tree biomass to products and fuel production. It is a challenge to capture mortality rates, pruning debris, storm debris, and market data. For example, urban areas tend to discard substantial amounts of wood. How do we encourage this resource to be more fully utilized? Incorporating monetary values into the model is fairly straightforward. For example, the value of carbon comes from the Interagency Working Group on the Social Cost of Carbon. Users are free to add or adjust for their own values if they do not like i-Tree values. Monetary values are straight multipliers. Water effects are one of the most difficult services to assign a dollar value. In conclusion, many areas of modeling can be and are being improved. The framework exists to integrate science and models, which will ultimately lead to a more robust integrated systems approach.

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Urban For restry: Service Tools, and Management es, d t 27 Mapping the Urban For from Abo ve t rest Jarlath O’Nei il-Dunne, Uni iversity of Ver rmont The use of aerial monitoring to study tree cano was moti vated by two questions from m opy local fores managers: (1) How much tree canopy do we have n st h now? (2) How much room w do we hav to plant trees? ve Accurrate estimates of tree canop are importa especially when the soc context is py ant, y cial s considered Within any given city, th land is man d. y he naged by thou usands of indiv vidual land owners. Quantifying an modeling tr cover at th scale of the land owners Q nd ree he e ship parcels could help motivate res p sidents to maintain or incre ease their tree canopy. It is difficu to map tree in urban are Shadows from tall buil ult es eas. ldings can hid trees. The de use of LID DAR data can help address this problem. Mapping tree canopy at hi resolution t e igh allows for studies to be conducted on multiple sca n ales, from parc or jurisdic cel ction to watershed For example studies can begin with in d. e, ndividual hous seholds and aaggregate up t to neighborh hood level and city level. Or studies can assess larger metropolitan areas and loo d O ok across sev veral jurisdictions, up to ent watershed tire ds. FIGURE 2.7 Crime and Tree Canopy in Pittsburgh, PA. This map show per capita cr 7: ws rime and the pe ercent of existin tree ng canopy at the neighborhood level. There is an inverse relationship bet t e tween crime pe capita and the percent of ex er xisting tree canopy For example, in Highland Park, with its 49 percent tree ca y. , P 9 anopy, there w were three crime per capita in 2010, es as compare to 13 crimes per capita in Larimer, where the tree canopy is 22 percent . ed s L y Dunne. http://dx SOURCE: Jarlath O’Neil-D dx.doi.org/10.60 084/m9.figshare e.716318.

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28 Urban Forestry: Toward an Ecosystem Services Research Agenda Maps need to be affordable, have a high degree of accuracy, and have excellent cartographic representation to be useful to decision makers. It is important to note that mapping does not replace fieldwork. Field inventories provide unique information (e.g., tree species and condition, etc.), that cannot be effectively acquired through overhead mapping. However, unlike field inventories, remotely sensed data can provide a complete census of the tree canopy. High-resolution land cover maps can help resource managers prioritize areas for tree canopy preservation, maintenance, restoration, and plantings. That being said, they will never replace on-the-ground site surveys, as numerous factors go into planting a tree. These maps do show what areas in the city have a high vs. low percentage of tree canopy and how tree canopy overlays with other variables of interest. For example, tree canopy and crime are closely associated (Figure 2.7). Mapping larger areas can help address watershed issues across county boundaries. Tree canopy maps can also help city managers and their staff understand ownership patterns, which is important because residents are the primary owners of land where trees can be planted. Many city managers want to increase their cities’ tree canopy by planting street trees, but residential areas (not just streetscapes) as a whole provide the most opportunity for increasing tree canopy. Mapping of tree canopy can also be used in outreach and communication efforts. Mapping different demographic groups and their geographic spread can help city managers develop tactics to reach out to different groups in different places. Researchers can do a change detection analysis which helps city managers understand where changes in tree canopy are occurring and what the drivers may be. Maps can also be used for pest management, but it is very expensive. Finally, although there is not a mandate to share the data, it is important to move toward a policy of openly shared local and regional data. The Role of Urban Forestry in Public Health Laura Jackson, EPA EPA recently developed EnviroAtlas, a mapping application that allows users to view and analyze multiple ecosystem services nationally and in specific communities. The beta- release of EnviroAtlas is planned for late Spring of 2013, with the first public version available in Fall of 2013. A key purpose of EnviroAtlas is to communicate how ecosystem services have an impact on human health and well-being. The following science questions were considered in developing EnviroAtlas:  How can we effectively quantify and communicate the production of the goods and services we receive from ecosystems?  What is the supply of those services in relationship to the demand and future demand? How do drivers of ecosystem services such as land use change (e.g., road development), climate change, and pollutant loads impact the delivery of ecosystem services?  At the screening level, where does it make sense to invest or prioritize land and water restoration, conservation, or use?  If we invest in green space, can we reduce the costs of gray infrastructure while also gaining other co-benefits?  How can we promote the incorporation of this type of information into decision making?

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Urban Forestry: Services, Tools, and Management 29  How can we demonstrate how these services explicitly relate to human health and well-being? The utility of ecosystem services and green infrastructure to buffer impacts from climate change and extreme events is a key message for the public health community. Furthermore, the loss of ecosystem services is frequently disproportionate in low-income neighborhoods, contributes to cumulative community burdens, and is aligned with the public health concept of social stressors in weakening resiliency and increasing vulnerabilities. The community component of EnviroAtlas is a high-resolution analysis of 50 cities and towns along gradients of interest (e.g., location, population size, demographics, and health and environmental ranking). Mapped metrics calculated for EnviroAtlas by the Forest Service include ambient air pollutants removed, water runoff reduction and filtration, ambient temperature reduction, carbon storage and dollar valuation, and health benefits of urban air filtration. EPA is developing additional metrics and qualitative information about the following topics: near-road tree buffers and adjacent residential population, vulnerability to heat stress and other localized climate-related hazards, homes and schools with limited green window views, and physical and mental health benefits of access to natural amenities.16 Where possible, EnviroAtlas estimates environmental value in units of public health and well-being (e.g., senior longevity, chronic illness, hospitalizations, days missed from school or work, self-reported happiness) which can all be converted to dollar amounts. However, research on the role of the natural environment in human well-being has not been uniform; variability in study designs and in the selection of specific dependent and explanatory metrics makes it difficult to conduct a metadata analysis for many of these issues. At a minimum, EnviroAtlas provides fact sheets that qualitatively describe the current state of knowledge. EPA will continue to move toward quantitative analyses where possible. BenMAP is the EPA Office of Air’s model for estimating the human-health benefits of criteria air pollutant rules. It uses data from air quality models and estimates the change in population exposure to certain ambient air pollutants. Based on this information, the model estimates changes in the incidence of a variety of health outcomes. Finally, it places a dollar value on changes in the incidence of health outcomes. Forest Service calculations for EnviroAtlas-Communities include BenMAP estimates at the Census block-group scale. One significant environmental health issue is the effects of living near roads. Elevated pollutant concentrations (e.g., carbon monoxide, nitrogen oxides, particulate matter mass, benzene, and metals) have been measured near roads. Living, working, or going to school near major roadways has been associated with numerous adverse health effects. These include respiratory and cardiovascular effects, adverse birth outcomes, premature mortality, and cancer. A significantly large portion of the U.S. population lives near large roads, and of those who do not, many work or go to school near large roads. Can near-road vegetation buffer air pollution? Models and fieldwork suggest that tall, dense vegetation has the potential to improve near-road air quality. However, results vary depending on wind speed, direction, seasonality, road design, and traffic conditions. Barrier type, depth, gaps, and edge effects are also important. Wind tunnel studies and computational fluid dynamics models have respectively shown that roadside vegetation can obstruct ultrafine particles and dilute pollutant concentrations. Field studies show there can be significant buffering of pollution, but the results depend on many variables (including tree type, height, wind conditions). EnviroAtlas is mapping near-road tree buffers, but it is 16 Please refer to EPA’s Eco-Health Relationship Browser at http://www.epa.gov/research/healthscience/ browser/introduction.html.

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30 Urban Forestry: Toward an Ecosystem Services Research Agenda still too soon to do simple predictive calculations. Qualitatively, it appears that having no tree cover is worse for near-road ambient air quality than having a buffer. In the future, Dr. Jackson would like to replicate published findings on eco-health associations, refine metrics and thresholds for eco exposures,17 conduct meta -analyses (which requires more replicable studies), and conduct more studies to determine causation (i.e., animal studies) and mechanistic pathways (e.g., of how green space alleviates stress). There are key data needs for studying the effects of urban forests on public health: public health data at sub-country scales, morbidity data (e.g., chronic disease, mental health), school performance, and prescription drug sales. Collaborations among the Department of Health and Human Services, the Department of Education, local health departments, local school districts, regional pharmacies, and schools of public health could help address some of these data and analysis needs. Discussion Some points raised in the open discussion that followed this panel’s presentations:  Currently United States Geological Survey (USGS) is attempting to do nationwide LIDAR data collections; it is important that forest-appropriate data is captured.  Improving public health studies would help quantify the benefits of urban forests.  Better models could assess the negative outcomes of trees in a larger context, such as allergy impacts.  i-Tree can quantify the influence trees have on stormwater runoff, which is important for both regulatory credit design and regulatory project review.  Some regulators recommend using i-Tree-type data over a 20- or 40-year time span because tree benefits will change over time. However, these calculations are difficult to do because tree mortality data are scarce. MANAGING THE URBAN FOREST Moderator: Gary G. Allen, Center for Chesapeake Communities Given that urban forests are increasingly being viewed as critical to sustaining environmental quality and human well-being, there has been significant growth in the number of urban areas across the United States declaring ambitious goals for expanding their tree canopy. Some cities are going one step further and are attempting to include large-scale tree planting as an official measure in air and water quality control plans. Governance issues of the urban forests is further complicated by the different (and sometimes competing) interests and priorities of the federal, state, and local organizations and private individuals who own and manage the land in cities. Panelists were asked to discuss: (1) the challenges of planning and managing urban forests in a manner that optimizes multiple ecosystem services simultaneously (e.g., synergies, tradeoffs in selecting tree species, determining planting locations) and (2) opportunities for enhancing collaboration and coordination among federal agencies, academic researchers, and other stakeholders. 17The amount of exposure to ecosystems a person needs to receive various services (and disservices). For example, how long does a person need to sit in a park to relieve stress?

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Urban Forestry: Services, Tools, and Management 31 Air Quality and Urban Forestry Janet McCabe, EPA Sustaining urban forestry programs is a significant challenge, and it is becoming especially challenging for some states, given budget constraints. Therefore, it is important to explore how urban forestry programs could provide the added benefit of helping cities and states comply with Clean Air Act regulations. Some benefits of trees are well known (e.g. reducing local temperatures). But some less direct benefits are underappreciated. For instance, a yard that has more trees will need less mowing, thus reducing emissions from that activity. Cars parked under shading trees will be much cooler and have less evaporative emissions. Planting programs can also be designed for reducing emissions by, for example, focusing on large trees that absorb more pollution or on low-maintenance trees (given that the maintenance efforts themselves lead to emissions). EPA recently launched “Ozone advance/PM advance” for areas that are already meeting current clean air standards, but are close to non-compliance or are expecting growth that will jeopardize future compliance. So far, 31 communities have signed up. Through this program, EPA offers partnerships, information resources, and tools, without any formal expectations or mandates for improvement. Communities can use these resources to help expand community engagement, identify new activities to improve air quality, and expand urban forestry programs. EPA also provides support for areas that are not meeting current air quality standards. EPA just revised the national standards for PM, and state governments are now in the process of identifying which areas will not meet the new standards. EPA will formally designate areas not in compliance. States with areas that are not in compliance must begin the State Implementation Plan (SIP) process, which is a lengthy process of state planning and EPA approval with the end goal of complying with the Clean Air Act. Under this process, national mandates may drive some actions, but there are opportunities for states and cities to identify their own measures. The question therefore is, can urban forests be part of a SIP? Perhaps, but it would be challenging. In order to be counted in a SIP, a measure has to be quantifiable, enforceable, permanent, and surplus (i.e., not already required for other reasons). Several cities, including Houston, Baltimore, Sacramento, and New York, have proposed using urban forests in their SIPs. But none have yet been approved by EPA. Houston came close, but the quantification requirement has proven to be a challenge. Cities like the idea of including urban forests in SIPs, but EPA needs to find ways to use these nontraditional programs in the SIP. It would be valuable to have this additional air pollution mitigation measure in the tool box since numerous cities have already undertaken many of the reasonable measures that are available. Climate change is another major issue that EPA considers in the context of urban forestry. EPA does calculate the impact of trees in their annual GHG inventory. They estimated that in 2011, urban trees stored 69 million metric tons of carbon (EPA, 2013). EPA also acknowledges that the local cooling effect of trees leads to less energy demand for air conditioning, resulting in lower emissions. The role of trees in mitigating UHIs is also of great interest to EPA18. In conclusion, there are some significant challenges in the regulatory structure, but EPA is committed to encouraging innovative, multi-benefit programs so that in the future, cities can receive regulatory credit for their expansion of the urban forest. 18 http://www.epa.gov/hiri/

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32 Urban Forestry: Toward an Ecosystem Services Research Agenda From Street Trees to Sustainability: Science, Practice, Tools Morgan Grove, USFS Up until now, most urban forestry research on benefits and services has focused on improving science and tools for general planning measures. But research is needed in quantifying the ecosystem services of urban forests so they can be used in a regulatory context. The quantification of urban tree benefits has led to interest and demand for tree planting goals. There have been a number of cities declaring ambitious planting goals (typically a symbolic number like 1 million trees). However, does a city have enough plantable space for 1 million trees? How does a city prioritize available sites? Assessments are needed to quantify existing and available plantable space at the decision-making scale. Three questions should be asked when prioritizing where to plant trees in any given city: Where is it biophysically feasible to plant trees? Where is it socially desirable to plant trees? Where is it economically likely to plant trees? City leaders often ask if they can reach their tree-planting goal exclusively by planting public street trees. This is not possible. The opportunities for increased tree planting are largely in residential areas, which is an extremely distributed set of individually owned land parcels. How do city leaders work with the new “forest landowner” (i.e., the private urban homeowner) to produce a public benefit? What happens when private landowners ask to be paid for the benefits they are providing? Any particular organization usually has insufficient funds to achieve and maintain a significant urban tree canopy goal. Tools are needed to identify opportunities for coordination and collaboration among the various organizations that have an interest in urban forestry. Coordination and collaboration requires an understanding of the types of organizations, their preferences, categories, and areas of interest, and how the organizations are linked. Stakeholders and local agencies should work together to develop priority areas for tree planting based on the benefits the organizations would like to attain. Every city department with potential relevance should answer the following three questions: Do you have any regulatory requirements that might involve planting trees? What variables would you use to decide where to plant? How do you share that information? Many city agencies and non- governmental organizations (NGOs) have overlapping missions related to tree planting. Analyzing and mapping the data from the different agencies based on areas of interest (e.g., a watershed, a neighborhood, etc.) allows scientists to provide individual maps tailored to the different stakeholders. Areas of overlapping interest can be identified when the individual maps are compared. Such an analysis was conducted in Baltimore. Among the various departments, the highest priority that emerged was reducing impervious surfaces, followed by mitigating the UHI and identifying opportunities for stewardship. Most groups were focused on street trees, with very few groups focused on utilizing residential lands to increase the number of trees. There were numerous affinities among the groups, based on metrics such as where they work, what they work on, or areas of interest. Understanding stewardship networks is key to addressing the question of which groups are most likely to want to work together. Stewardship mapping illustrates how organizations are working together, or how they may need to. In Baltimore, most groups were neighborhood-focused, and only a few were city-wide. There was a lot of redundancy among different groups’ goals which encouraged them to

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Urban Forestry: Services, Tools, and Management 33 focus on more cooperation and collaboration. These kinds of relational databases can help city leaders determine how to achieve that 1 million tree goal (or whether it is feasible). The next big step is to think about goods that will ultimately come out of the benefits and services. For instance, a lot of the wood biomass coming out of cities is going to landfills. The “Baltimore wood project19” is focused on assessing optimal uses for all that wood. In conclusion, the next major phase in urban forestry will be a shift in focus from street- tree planting to sustainability in a broader sense by including goals that are social, economic, and environmental. Management Challenges and Opportunities: City of Trees Mark Buscaino, Casey Trees A recent tree canopy study by Nowak and Greenfeld (2012) showed tree canopy decline in many U.S. cities over the past 10 years with equal increases in impervious surface cover. Following this national trend, Washington DC’s canopy declined 2 percent from 2006 through 2011; historically, aerial photos show that DC’s canopy was 50 percent in 1950 compared to 36 percent today. In short, arboricultural and urban forestry professionals are failing at keeping our cities green, and development pressures will only make our task more difficult. How can this be reversed? There are several steps that need to be taken to increase urban tree canopy in cities across the United States. First an inventory of the extent and condition of the urban forest is needed so realistic canopy goals can be determined. While these assessments are becoming more common, many jurisdictions lack resources to conduct them. Another challenge is the lack of national standards for monitoring tree canopy—technology changes so rapidly that jurisdictions often receive conflicting data. A national inventory clearinghouse would greatly facilitate efforts and raise local success, and 10-year interval urban canopy change data at the 1-meter level for all major U.S. cities should be the standard provided by the USFS Forest Inventory and Analysis National Program.20 Once inventory data are available, canopy goals should be set and clearly communicated to the public in easily understandable terms. Until better guidance is available, goals will be set based on what is attainable, but this will do nothing to reverse the national trend of canopy decline. We must answer the question of what is optimal to truly make a difference. More research is needed to help jurisdictions nationwide determine appropriate canopy goals that are based on the multiple benefits of trees—environmental, economic, social, human health, etc., as well as climate constraints of the various regions. When known, this information could change the face of urban areas from coast to coast, and perhaps globally as well. Achieving these goals requires devising strategies by city leaders, agency heads, nonprofits, interest groups, and others (Figure 2.8). Tree protection laws and regulations form the foundation for canopy goal attainment and shift our culture’s understanding of what is and is not acceptable behavior. From these laws flow other initiatives, but without them it is doubtful that canopy goal achievement will be successful or, even if attained, long-lasting. 19 http://www.fs.fed.us/research/urban/baltimore-wood-project.php 20 http://www.fia.fs.fed.us/

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34 Urban Forestry: Tow n oward an Ecosy system Service Research Ag es Agenda FIGURE 2.8 Washington, DC is a good example to high 8 e hlight the many organizations involved in ach y hieving tree cannopy goals, and the land types impacted. DC is complicated due to the fact that a large portion of land (about 30 percen is t i i nt) owned by the federal gove t ernment, with that too divided up to several agencies. DDO (District Dep t d OT partment of Transportattion); UFA (Urb Forestry Administration); DGS (Departme of General S ban D ent Services); DCO (Department of OP t Human Res sources); DDOE (District Depa artment of Environment); NGO (Non-governmental Organiz O zation); GSA (General Se ervices Adminis stration); NPS (National Park Service). SOUR Mark Busca S RCE aino, Casey Treees. ogress on goa attainment needs to be co Pro al n onveyed clear and consis rly stently. Accommplishing this communication function h been made easier in rec has e cent years with e- h media and similar outlets, but rep o porting is also controversial and nationa reporting lac l, al cks consist tency to be usseful. A nation registry sh ould be publi nal ished of urban area canopy and n y impervvious surface levels, as well as progress ttoward meetin urban cano goals. A ng opy national tree report card based on easily verifia n able metrics is another opti for reporti s ion ing. Withou such report ut ting, most goa once achie als, eved, will hav no staying power. ve Comm munication is critical to long c g-term success s. Fin nally, goal atta ainment requires periodic d data collectio and informa on ation review t to ensure progress is be e eing made an the process stays on track. A feedback loop should be nd s k incorporated into th broad strate to ensure success. he egy

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Urban Forestry: Services, Tools, and Management 35 Discussion Some points raised in the open discussion that followed this panel’s presentations:  Mr. Buscaino indicated that tree mortality is not a major factor when setting canopy goals. The key is to design an effective maintenance plan.  Models of air quality impacts of trees are not yet sufficient to be used as a basis for regulatory decision making. States are asking EPA to allow the usage of new and alternative tools.  National standards for assessing urban tree canopy goals would be useful, but one could argue that guidelines for local-level efforts would be even more helpful.  Giving high priority to addressing research needs in a regulatory context could help pave the way for cities to receive regulatory credit for expansion of their urban forests. CLOSING REMARKS In closing the plenary session, Mr. Allen said that the most significant threat to urban forests is not the longhorn beetle or the emerald ash bore, but rather the changing demographics of our communities. More and more people are moving to urban areas. Local governments are trying to accommodate this growing urban population, which often leads to incompatible objectives. As an example, Mr. Allen cited his local jurisdiction in Maryland, which recently adopted an urban canopy goal of planting 20,000 trees in the next decade, partly in response to a Chesapeake Bay program that advocates for local governments in the watershed to set canopy goals. But at the same time, this community also adopted an electrical reliability standard in response to residents’ concerns about power outages due to storms, especially from falling trees. To address these concerns, in less than 18 months the local utilities cut down 30,000 trees—more than the total number of trees slated to be planted in the next 10 years. It is a significant challenge to encourage local stewardship to replace the trees that were cut down for valid electric service reliability reasons (or other local social goods). This example illustrates how the numerous services provided by local governments can be incompatible, and at times, a threat to urban trees. Mr. Allen urged the workshop participants to take a look at service objectives in their local area and determine whether or not they are compatible with preservation, protection, and enhancement of urban forests. Finally, Mr. Allen noted that the frontier of ecology can be found in urban areas where daily decisions are made about how we live, learn, move, and play. The workshop participants are among the pioneers in this young field. Their work will help focus new research and determine the next steps toward our growing knowledge base. Although much was learned at the workshop, many issues remain, and ultimately it is clear that a broad and challenging agenda lies ahead for urban forestry.

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