Objective:

To investigate the association between year-to-year increases in urban tree canopy and mortality rates in Chicago neighborhoods.

Approach:

• Study Design: An 11-year longitudinal study analyzing annual data from 801 Chicago census tracts between 2011 and 2021.
• Data Sources: Integrated US Department of Agriculture tree canopy estimates, summer maximum temperatures, mortality records, nitrogen dioxide concentrations, and neighborhood demographic characteristics.
• Population: Included 220,711 deaths and adjusted for population size, income, neighborhood characteristics, air pollution, and regional differences.
• Statistical Analysis: Examined associations between tree canopy and mortality, interactions with heat exposure, and used K-means clustering for neighborhood patterns.

Key Findings:

• Year-to-year increases in tree canopy were associated with approximately 10% lower all-cause mortality for each 1% increase.
• Similar associations were found for cardiovascular, respiratory, mental health, and selected musculoskeletal causes of death.
• Existing tree canopy levels were not significantly associated with all-cause mortality.
• Greater canopy losses in hotter neighborhoods correlated with higher predicted mortality.
• A hypothetical annual 0.03% citywide increase in tree canopy could correspond to about 105 fewer deaths per year.

Interpretation:

Limitations:

• The study could not establish causality.
• Lacked information on how long decedents lived at their recorded addresses.
• 30-m resolution canopy data may have missed smaller or newly planted trees.
• Residual area-level confounding could not be excluded.

Conclusion:

The findings indicate an association between increasing urban tree canopy and lower mortality rates, particularly in areas with higher temperatures.

Sources:

• GeoHealth