CHAPTER 3

NEXT STEPS FOR THE FUTURE

Time was set aside during the workshop to allow for interactive discussion among all of the participants in breakout groups. For each of the four main themes discussed in the plenary sessions, the breakout groups were asked to suggest what they see as key remaining challenges to advancing our understanding of urban forestry ecosystem services and to identify the steps needed to address these challenges.

The following are some of the general themes that emerged in the groups’ discussions about the key remaining challenges-both in terms of expanding our scientific understanding and advancing the reach and effectiveness of current urban forestry programs. (For a more detailed list of the specific questions, challenges, and suggestions raised, see Appendix A.)

• Quantifying both the large- and small-scale ecosystem services and benefits of urban forests
• Conducting economic evaluations of urban forest ecosystem services
• Effectively communicating to the public and decision-makers about the benefits of urban trees
• Encouraging private landowners to plant and maintain trees on their land but also acknowledging that urban trees require public acceptance
• Identifying effective management and maintenance of urban trees to increase their lifespan and maximize the return on investments in urban forestry programs
• Making informed choices about tree species selection and planting location strategies to optimize ecosystem services and tree health
• Promoting collaboration and partnerships among stakeholders (e.g., industry; local, state, and federal government; public; and academia)
• Building the scientific foundation to allow cities and regions to receive official regulatory credit (in air and water pollution programs) for benefits of urban forests
• Improving the tools, models, and methodologies to better meet users’ needs
• Balancing competing objectives and values among stakeholders
• Using urban trees as a stepping stone to designing sustainable, resilient cities
• Identifying indicators of a healthy, functioning, sustainable urban ecosystem
• Identifying and quantifying the costs and tradeoffs of urban forests (e.g., water demands, allergy concerns, costs to maintain, etc.)

The groups were then asked to discuss what steps would be needed to make progress in addressing the types of challenges identified above. Some of the general areas of effort that were suggested are listed below. (More detailed lists of suggested steps for each of these general areas are shown in Appendix A.)

• Improving tools to inform decision-makers
• Collecting more detailed, comprehensive, and standardized data
• Improving communication and collaboration among stakeholder groups
• Improving public outreach and education
• Conducting research in key areas:

ο to better characterize the biophysical effects of trees

ο to identify innovative approaches to incorporating green space into cites (e.g., “green walls”)

ο to create and sustain a culture of environmental stewardship (through research of social scientists, psychologists, and marketing specialists)

ο to provide the scientific quantification that is needed to integrate urban trees into regulatory management frameworks

ο to better understand interactions between natural and human systems in the urban setting

• Promoting regulatory and urban growth policy changes that are more “tree friendly”
• Optimizing the investment of urban trees by planting trees in appropriate locations and emphasizing the importance of maintaining the health of existing trees
• Advancing interdisciplinary high-resolution ecosystem service models
• Developing indicators of tree health and performance
• Developing criteria for setting appropriate tree canopy goals
• Standardizing remote sensing technologies (LANDSAT, National Agriculture Imagery Program [NAIP], LIDAR) to support urban ecosystem assessment
• Securing adequate resources to support urban forestry efforts

In the final stage of the breakout group discussions, participants were asked to focus squarely on the workshop goal of advancing the research agenda for understanding ecosystem services of urban forestry by answering the following question: “If I were a Program Manager (at a federal agency, private foundation, etc), I would place a priority on supporting research efforts related to: …” The following is a sample collection of the many answers received in response to that question.

Social/economic based research

• Understanding how individuals relate to trees and forest where they live; public attitudes towards trees (Why do some people not want more trees?)
• Understanding the factors that drive change in behavior and attitudes on managing privately-owned trees. (What motivates citizens to stewardship?)
• Conducting anthropologic and economic analysis of different types of urban forestry programs. (Why do some programs work more effectively than others?)
• Exploring the benefits of “horticulture therapy”
• Evaluating the distribution of urban forestry benefits across socioeconomic divides (environmental justice)
• Quantifying the different types of economic benefits of planting a tree (in order to identify and pursue the highest value benefits first)
• Identifying how urban forests support human and social capital (i.e., cultural ecosystem services)

Regulatory/policy issues

• Improving quantification of urban forest benefits at the level that they can meet regulatory requirements for air and water pollution mitigation efforts
• Developing interagency (and public-private) collaborative pilot projects that lead to development of integrated assessment tools to aid the inclusion of urban forests in State Implementation Plans
• Determining how to use urban tree planting to gain credits for TMDL (Total Maximum Daily Load) water quality

• Developing realistic regional tree-growth models for predicting future canopy coverage
• Exploring how parcel-level land stewardship decisions aggregate at the landscape scale to affect tree canopy goals

Designing urban forestry practices to maximize benefits

• Identifying the optimal ratio for the amount of intact forest required to offset x area of impervious surface; apply this in planning tools and regulatory guidelines for development
• Conducting research on bird-urban forest interactions to identify the resources necessary to sustain bird populations
• Assessing how birds and other wildlife are benefiting from urban forests and which tree species are best at supporting food webs and biodiversity
• Identifying tree species that are best for planting under utility lines
• Identifying thresholds or tipping points in ecosystem services (e.g., What is the minimum tree exposure time needed to maintain a positive mental condition? Will these benefits be realized only after the trees have reached a certain size)?

Urban tree health and maintenance

• Conducting statistical analyses of the factors that lead to large “successful” trees
• Assessing how regular management and maintenance efforts can help reduce risks of tree loss, and how to incentivize such efforts
• Evaluating how to make urban forests resilient in a changing climate
• Assessing urban tree growth and morality rates
• Assessing costs and benefits of protecting trees already in place versus planting more trees (relative value for air quality? storm management? water quality?)
• Determining best practices for mature tree restoration in an urban area

Assessments, tools, data

• Assessing tree canopy on a regional scale with an integrated benefits matrix
• Systematically identifying knowledge gaps in health benefits or costs of urban forests, community-based participatory research in local areas to fill these gaps, integrating health into the larger discussion of urban forestry and ecosystem sources
• Creating a centralized, open-access database to collect and share all of the relevant data being collected through different research efforts
• Developing national standards for urban forestry and metrics for ecosystem services
• Collecting national tree inventory data at the municipality level
• Further developing i-Tree, including coverage of natural areas and interactive mapping capabilities

Collaboration and partnerships

• Supporting collaboration between science and regulatory agencies on effective use of urban forestry tools
• Exploring efficiencies to be gained in regional-scale cooperation and collaboration

Outreach, education, and communication

• Determining how to reach the public with best science on tree benefits, and how to deliver relevant scientific findings to users in a way that is useful and applicable (what messages best resonate for municipalities? what messages motivate tree planting activities?) (note: New York City’s million trees initiative is evaluating how well their messages reached people)
• Identifying best practices in community engagement, outreach, and “targeted marketing” (what information will work best with specific audiences?)
• Public education covering not just the planting of trees, but also, pruning, tending, etc.

Risk assessment

• Exploring how the risk of falling trees relates to an increase in intensity of storms, aging infrastructure, and lack of good management practices
• Exploring how trees also help reduce risks of some impacts of extreme weather
• Identifying best practices in “proactive” removal of trees that may pose large risks (e.g., during wind and ice storms), and viewing trees as we do other forms of infrastructure that are regularly replaced and maintained.

CONCLUSION

Many participants noted that the workshop provided a valuable opportunity to reflect on the state of science regarding the role of trees in urban ecosystems, and that it identified knowledge gaps and challenges in translating science into practice. These discussions drew on the expertise of scientists from multiple disciplinary perspectives and of stakeholders from a wide variety of public agencies and non-governmental organizations. At the same time however, participants signaled that there is a larger research community that can contribute to this conversation in order to fully understand the potential synergies and tradeoffs of services and disservices provided by trees in the urban ecosystem. Current researchers have made significant progress in studying how trees can mitigate some of the detrimental impacts of urbanization through a variety of ecosystem services. However, a number of workshop participants noted that scientific understanding of key mechanisms governing ecosystem functions across multiple scales is incomplete, and most benefits of urban trees require further investigation. In many specific cases, the existing base of studies is too limited to allow one to make generalizations.

Some participants pointed out the need to ask fundamental questions about the assumptions that guide most urban forestry research. Some emphasized the challenges of informing decision making in the context of this evolving science and noted the potential pitfalls of translating premature conclusions into practice. Others pointed to the need for a shared definition of an “urban forest” and the need to examine the ecological, historical, cultural, and institutional dimensions that shape urban forestry research. Several highlighted how inconsistencies in existing methodological approaches and measurement methods can affect progress of the science. Overall, the workshop discussions indicated that to advance the study of urban trees and their role in providing ecosystem services, it is necessary to continue to raise new questions and to develop new paradigms and new tools that can fully address the complexity of urban ecosystems as human habitats.