Healthy Trees Healthy People Consortium 2019-01-29T09:18:02-05:00

Healthy Trees Healthy People Consortium

Photo: Paul Krueger, CC BY 2.0, Wikimedia Commons.

Trees and other plants cool urban spaces and reduce pollutant concentrations, but only if they are abundant and healthy. Unfortunately, heat and pollution can decrease the ecosystem services provided by urban trees due to physiological stress and pests.

Around the world, urban populations of people are increasing but urban tree cover is decreasing. Our goal was to initiate multidisciplinary interactions that focus on sustaining human and environmental health in cities and generate a proposal for a formal working group at SESYNC or similar organization.

Healthy Trees Healthy People Consortium 2018

May 22, 2018 – NCSU JC Raulston Arboretum


Steven Frank – Professor, Department of Entomology and Plant Pathology, NCSU
Nora Lahr – Postdoc, Department of Entomology and Plant Pathology, NCSU
Robert Dunn – Professor, Department of Applied Ecology, NCSU

Consortium Summary

This informal meeting consisted of discussion based on topic questions presented by the organizers. Comments and discussion were recorded in long-form minutes and on white boards. This is a summary of key points discussed in relation to each topic. Our goal is to identify key teams and directions that will lead to grants and solutions that connect the health of trees and green infrastructure with the health of people.

MichaelJustPostdoctoral ResearcherDepartment of Entomology & Plant Pathology, NCSU
WillWilsonProfessorDepartment of Biology, Duke
AdamTerandoEcologistUSGS Southeast Climate Science Center
Melissa MarselleResearch AssociateGerman Center for Integrative Biodiversity Research (iDiv)
MichaelReiskindProfessorDepartment of Entomology & Plant Pathology, NCSU
AlexJohnsonUrban Forestry ManagerCity of Durham General Services Department
Laurie DukesAssistant City ArboristCity of Charlotte
KelbyFiteVice President/DirectorBartlett Trees, Bartlett Tree Research Labs
ChadRigsbyEntomologistBartlett Trees, Bartlett Tree Research Labs
AaronHippAssociate ProfessorCenter for Human Health and the Environment, NCSU
BarbFairAssociate ProfessorHorticultural Science, NCSU
CarenCooperAssociate ProfessorDepartment of Forestry & Environmental Resources, NCSU
LeslieMoormanExecutive DirectorNorth Carolina Urban Forest Council
ZachManorUrban ForesterCity of Raleigh Dept of Parks, Recreation & Cultural Resources Management
KristiBackeGraduate StudentDepartment of Entomology & Plant Pathology, NCSU
Participants expressed interest and concerns about large scale issues such as declining tree cover, gentrification, and environmental justice. People participated to learn more about urban factors that influence tree health such as pollution and the urban heat island effect. Others wanted to learn more about health services trees provide including psychological benefits, pollution reduction, and relation of trees to particulate pollution and noise pollution. Participants expressed interest in meeting other people with new perspectives or knowledge and developing collaborations. Participants were interested in funding for this work.

Important topics that came up of particular interest and reasons for attending included: studying mechanisms for health benefits since many studies are correlative; address tension between conservation and urban planning goals. For example, exotic trees like crape myrtles may provide human services but not ecological, conservation benefits; differences in perspectives of open space to ecologists, conservationists, urban planners, urban residents, and other stakeholders; most trees are not owned by the city but are on private land subject to minimal regulations; attitudes about trees held by different stakeholders; managing biodiversity for conservation and for health. Synergy due to the diverse participation between scientists, managers, tree care people, and others; need more collaboration and communication between people in different roles; cities are great opportunities for citizen science and to focus efforts on reducing extinction of experience since most people live there.

Lack of understanding by residents and decision makers of tree benefits was identified as an important missing link. Tools to monetize value of trees are too general and do not account for health of trees, pests, etc. Discussion focused a lot on why trees and tree canopy cover are disappearing. These mechanisms for tree loss include in-fill development, subdividing already small lots, building larger houses that require removal of trees and don’t leave space for trees.

Another missing link is interdisciplinary collaboration in research and planning. Missing connections with medical practitioners and researchers, and public health officials for perspective on common, costly, issues. Need civil engineers, landscape architects, developers, elected officials, and HOA representatives.

Preservation of trees and greenspace comes down to different things for different groups. For developers it is economics. For home owners could be liability, cost, benefit, but often an emotional issue. There was discussion about how to link the interests of these and other disparate groups, such as politicians, home owners associations, conservationists, to increase tree conservation and benefits.

There is a disconnect in funding opportunities that tend to be system or discipline specific.

Education disconnect with tree care professionals who need training in tree benefits, environmental justice, and other topics in addition to tree care. They are on the front lines and interact with the public daily.

Scientific knowledge gaps include tree physiology, tree diversity, biodiversity generally, mechanisms of tree benefits (e.g. particulate capture, cooling, biodiversity), soil health, planting and maintenance techniques, landscape planning, effects of tree density, relationship of tree density/diversity and health benefits (e.g. is it linear), sociology, human behavior. Missing link is that we do not have good micro climate data for urban spaces to tell what people are experiencing. It is all coarse land cover data. This plays into physical activity and use of public spaces like play grounds that may be too hot in summer without trees.

Trees are important but we also need knowledge about other aspects of green infrastructure such as green roofs, public gardens, parks, bioretention cells, and others.

There’s a conception that healthy trees or more trees will make healthier people; if we take that to be a general concept there are many details and mechanisms that affect this relationship. This includes technical details about trees, how they function, and the biodiversity and services they provide, and about people and their values of trees, and who benefits and when. A lot of psychological research has been conducted but all correlative and it is hard to identify or hypothesize a mechanism.

One mechanism for many health benefits is increased physical activity when more trees and greenspace are present. Trees and people represent a coupled human semi natural system that needs to be studied that way. Because tree care and management matters but also management; community organizers; private homeowner engagement in that system. Cultural and personal differences in how people perceive green space as either natural and relaxing or as chaotic and frightening.

Increasingly mechanisms related to biodiversity are being recognized. This includes health benefits provided by multiple tree species, by the microbes they support, and by the experience provided by living with diverse plant and animal life. Mechanisms for the benefits of biodiversity are difficult to identify in many cases but this is a field of active study and an area where funding is likely available.

In addition to biodiversity in a general sense tree diversity is expected to provide many benefits to people and the environment. Thus the type of trees, number of tree species, specific combinations, and those with different origins or traits could all interact to affect health outcomes. For example, natives may have more diversity and benefits for human experience and microbes but exotic trees may have less pests, grow better, catch more water, or have other benefits. Physiological functions of trees related to emissions, volatile compounds, pollen, differ so tree may provide different benefits or harm at different times of year or under different weather or abiotic conditions. For example, some oaks provide great benefits for biodiversity, carbon sequestration, pollution capture but in spring release abundant pollen. Spatial patterns and density of trees is also important for example forests and forest fragments may be more valuable than many street trees due to concentration of trees that can’t be replaced. Mechanisms the group identified with benefits also include noise reduction by planting trees strategically, capture of PM2.5, atmospheric cooling, energy reduction.

Practitioners include tree care professionals, urban planners, landscape architects, homeowners, and other involved in planting and maintaining trees and creating urban greenspace. More training on basic things like tree care, planting, soil properties, sites selection, species selection, diversity, spatial arrangement. Also, practitioners need training in the benefits and potential harm from trees to inform decisions and to help them talk to policy makers, the public, donors, and other stake holders.

Training could take the form of workshops and discussions conducted by extension, International Society or Arboriculture, NC Urban Forest Council (or other organizations), in schools, colleges. Articles in organization newsletters and professional publications could translate scientific papers into an accessible format. Monetized concrete examples of benefits are needed when dealing with decision-makers and trying to obtain funding to support trees and green infrastructure. Partnerships with Universities, citizen science projects, and other interactions are helpful.

The expertise of the participants was focused largely on trees, ecology, sociology, urban forests, and climate change. Based on this research questions related to tree diversity/density/type, biodiversity, and conservation are quite tractable and underway in some labs already. However, these projects would benefit from interdisciplinary collaborators. Citizen science was mentioned frequently as a good way to address urban tree and health questions. Many citizen science projects are underway by Cooper lab, Frank lab, Dunn lab, and others. It is possible to deploy sensors to measure noise, light, temperature, PM2.5, trees, microbes, and other things by citizen scientists that will help describe urban conditions and serve as explanatory variables.

Considerable public data are available on socioeconomic factors and health at coarse scales (i.e. zip code) that could be used to test initial hypotheses albeit in correlative ways.

Tree databases are available from many cities provide free data that can be used to test hypotheses related to tree diversity, density, change over time.

Cities sometimes have mobile apps to collect data that may be useful on trees, pests, or other issues.

It was generally agreed that another workshop with other participants with other areas of knowledge would be useful. Expertise to include in future meetings could include medical professionals, epidemiologists, elected officials, landscape architects, psychologists, planners. Informal meetings, such as this one, or formal workshops focused on a particular goal or end product (e.g. peer reviewed publication) would be valuable. A workshop focused on stakeholder training was also identified as a priority.