Health Impact Assessment of Targeted Tree Planting in Ann Arbor Michigan and Identification of Neighborhoods Vulnerable to Climate Change

BACKGROUND:  The City of Ann Arbor is developing its first Urban and Community Forest Management Plan with a goal of planting 1,000 trees in 2013, while addressing uneven tree canopy cover in neighborhoods potentially vulnerable to extreme heat events and other climate change impacts. A Health Impact Assessment (HIA) was conducted to assess health and psychosocial outcomes associated with urban tree planting and identify vulnerable neighborhoods whose populations would most likely benefit from increasing tree canopy.

METHODS:  Methodology developed by the North American HIA Practice Standards Working Group was used to assess the proposed policy of targeted tree planting, and included: screening for value and feasibility; scoping to determine health issues for analysis and research methods to be employed; assessment of vulnerabilities and key health impacts in affected communities; reporting the assessment findings; and communicating the results. Scoping and assessment employed both qualitative and quantitative methods based on literature reviews and available health and demographic statistics.  A Vulnerability Index was created using 13 Census demographic measures at the block level to identify and map neighborhoods that are likely vulnerable to adverse effects of heat events; this was overlayed with current tree canopy cover to identify high priority areas for tree planting.  Scoping meetings with the communities and HIA planning team, combined with a thorough review of the literature linking tree canopy with health or psychosocial outcomes, identified priority outcomes for the assessment phase of the HIA, which were measured using existing prevalence data including Behavioral Risk Factor Survey and Washtenaw County Health Improvement Plan Survey, hospital discharge data, and Michigan Uniform Incident Crime Reporting statistics.

RESULTS:  The HIA identified neighborhoods with low tree canopy whose inhabitants were more likely to be exposed to air pollution and crime, and less likely to participate in physical activity, compared to neighborhoods with more trees.  These vulnerable neighborhoods were at risk for higher rates of heat related illness, asthma, COPD, diabetes, obesity, hypertension, and mental illness than neighborhoods with greater tree canopy.  Vulnerable neighborhoods had a preponderance of individuals who were female, multiracial or black, aged 18-24 years and 5 to 9 years old, non-high school graduates, or those earning less than $15,000.

CONCLUSIONS:  The Ann Arbor HIA documented the value of targeting tree planting in vulnerable neighborhoods, and identified specific outcomes likely to be impacted by targeted tree planting.  Monitoring will be needed to reveal any measurable benefits to the neighborhoods or City.