APPENDICES - Laserfiche WebLink

Page 25 Appendix IV. General Recommendations for Air Quality Improvement Urban vegetation can directly and indirectly affect local and regional air quality by altering the urban atmosphere environment. Four main ways that urban trees affect air quality are (Nowak 1995): •Temperature reduction and other microclimate effects •Removal of air pollutants •Emission of volatile organic compounds (VOC) and tree maintenance emissions •Energy effects on buildings The cumulative and interactive effects of trees on climate, pollution removal, and VOC and power plant emissions determine the impact of trees on air pollution. Cumulative studies involving urban tree impacts on ozone have revealed that increased urban canopy cover, particularly with low VOC emitting species, leads to reduced ozone concentrations in cities (Nowak 2000). Local urban management decisions also can help improve air quality. Urban forest management strategies to help improve air quality include (Nowak 2000): Strategy Result Increase the number of healthy trees Increase pollution removal Sustain existing tree cover Maintain pollution removal levels Maximize use of low VOC-emitting trees Reduces ozone and carbon monoxide formation Sustain large, healthy trees Large trees have greatest per-tree effects Use long-lived trees Reduce long-term pollutant emissions from planting and removal Use low maintenance trees Reduce pollutants emissions from maintenance activities Reduce fossil fuel use in maintaining vegetation Reduce pollutant emissions Plant trees in energy conserving locations Reduce pollutant emissions from power plants Plant trees to shade parked cars Reduce vehicular VOC emissions Supply ample water to vegetation Enhance pollution removal and temperature reduction Plant trees in polluted or heavily populated areas Maximizes tree air quality benefits Avoid pollutant-sensitive species Improve tree health Utilize evergreen trees for particulate matter Year-round removal of particles