Urban tree canopy effects energy demand and carbon fluxes, a review

1. Urban tree canopy effects energy demand and carbon fluxes, a review Kaytee Duskin, Dexter Locke and David Seekell The University of Vermont

2. Urban Tree Canopy Benefits for Carbon

3. Prevention Shading Albedo Evapo-transpiration

4. Shading • Simpson, J. R., & McPherson, E. G. (1998). Simulation of tree shade impacts on residential energy use for space conditioning in Sacramento. Atmospheric Environment, 32(1), 69-74. • Developed shading coefficient • Found reduction in cooling attributable to shading • Found increase in heating demand • Calculated costs and benefits (attached $ estimates) • Results were generally consistent with other studies

5. Shading 2 • Simpson, J. R. (2002). Improved estimates of tree-shade effects on residential energy use. Energy and Buildings, 34(10), 1067-1076. • Shading reduces amount of radiant energy absorbed and stored by built surfaces (related to albedo management) • Look-up tables were developed to assist in decision making regarding expected effects of planting and building energy use

6. Shading 3 • Simpson, J. R. (1998). Urban forest impacts on regional cooling and heating energy use: Sacramento county case study. Journal of Arboriculture, 24(4), 201-209. • Uses a more regional based approach • Investigates costs and benefits from MW avoided

7. Shading 4 • Shashua-Bar, L., & Hoffman, M. E. (2004). Quantitative evaluation of passive cooling of the ucl microclimate in hot regions in summer, case study: Urban streets and courtyards with trees. Building and Environment, 39(9), 1087-1099. • Investigates geometry and density of tree planting for shading and windbreak potential • Conducted in Tel-Aviv so there is limited applicability due to climatic differences • Lots of empirical data

8. Shading 5 • Shashua-Bar, L., & Hoffman, M. E. (2000). Vegetation as a climatic component in the design of an urban street - an empirical model for predicting the cooling effect of urban green areas with trees. Energy and Buildings, 31(3), 221-235. • Cooling effect of green space is perceivable up to 100m • The cooling effect of trees in streets was found to be significant, with minimal costs relative to other plantings • This study endorses Rosenfeld et al.’s suggestion for at least one shade tree per eligible house to offset some of the cars’ parking effect in the courtyard.

9. Shading 6 • Picot, X. (2004). Thermal comfort in urban spaces: Impact of vegetation growth - case study: Piazza della scienza, milan, italy. Energy and Buildings, 36(4), 329-334. • Placed an emphasis on predicting the range of shading over time after accounting for growth • Used a planning/design approach

10. Shading 7 • Pataki, D. E., Alig, R. J., Fung, A. S., Golubiewski, N. E., Kennedy, C. A., McPherson, E. G., et al. (2006). Urban ecosystems and the north American carbon cycle. Global Change Biology, 12(11), 2092-2102. • Attempts to look at entire carbon cycle in urban areas (shading, albedo, soils, sequestration…) • There are estimates for annual CO2 reductions are given per street tree (or park tree) in 7 major U.S. cities.

11. Shading 8 • McPherson, E. G., & Simpson, J. R. (2003). Potential energy savings in buildings by an urban tree planting programme in California. Urban Forestry and Urban Greening, 2(2), 73-86. • Existing trees are projected to reduce annual air conditioning energy use by 2.5% with a wholesale value of $ 485.8 million • Looks at the difference between energy saving trees and non-energy saving trees – an important consideration • Considers the costs of urban forestry too

12. Shading 9 • Jo, H. K., & McPherson, E. G. (2001). Indirect carbon reduction by residential vegetation and planting strategies in Chicago, USA. Journal of Environmental Management, 61(2), 165-177. • Building type, materials, aspect and other variables are analyzed for the usefulness of trees for reducing CO2 emissions. Strategies are developed to maximize carbon related benefits for planting. They are: • Plant on the west to obstruct solar gain • Don’t plant on the east and/or south – although theses plantings help with solar avoidance (therefore aid cooling) the net effect is reduced because they impair winter warming. • Dense planting on N, NE, and NW is recommended because of the substantial effects on wind-reduction and evapotranspiration • Plant so as to decrease impervious surfaces. • Minimize adverse shading on adjacent properties.

13. Albedo Management 1 • Takebayashi, H., & Moriyama, M. (2007). Surface heat budget on green roof and high reflection roof for mitigation of urban heat island. Building and Environment, 42(8), 2971-2979. • Investigates different surfaces for reflectivity and emissivity. Very interesting but this article has little or no relevance to UTC in NYC and mitigating UHI with trees.

14. Albedo Management 2 • Kumar, R., & Kaushik, S. C. (2005). Performance evaluation of green roof and shading for thermal protection of buildings. Building and Environment, 40(11), 1505-1511. • About green roofs • The larger the LAI and foliage height, the larger the cooling effect

15. Albedo Management 3 • Masmoudi, S., & Mazouz, S. (2004). Relation of geometry, vegetation and thermal comfort around buildings in urban settings, the case of hot and regions. Energy and Buildings, 36(7), 710-719. • Humorous social commentary on “mans” behavior in hot urban environments. • discussion of trees and orientation relative to the sun and buildings • hard surfaces for mitigation UHI

16. Evapotranspiration • Simpson, J. R. (2002). Improved estimates of tree-shade effects on residential energy use. Energy and Buildings, 34(10), 1067-1076. • Previously mentioned • Showed how important evapotranspiration is to general cooling effects

17. Summary • A few conclusions • Trees reduce air conditioning needed but also can increase demand for heating • Carbon and Urban Forestry is complicated • Many factors can be accounted for differently • Shading from one tree may benefit one building but harm another • Net carbon depends on management and full life cycle analysis

18. Sequestration

19. Carbon Uptake • Johnson A. D. & Gerhold H. D. (2001) Carbon storage by utility-compatible trees. Journal of Arboriculture 27: 57-68. • Nowak D. J. (2006) Institutionalizing urban forestry as a "biotechnology" to improve environmental quality. Urban Forestry and Urban Greening 5: 93-100. • Nowak D. J. & Crane D. E. (2002) Carbon storage and sequestration by urban trees in the USA. Environmental Pollution 116: 381-389. • Nowak D. J., Stevens J. C., Sisinni S. M. & Luley C. (2002) Effects of urban tree management and species selection on atmospheric carbon dioxide. Journal of Arboriculture 28: 113-122.

20. Carbon Uptake • Tratalos J., Fuller R. A., Warren P. H., Davies R. G. & Gaston K. J. (2007) Urban form, biodiversity potential and ecosystem services. Landscape and Urban Planning 83: 308-317. • Pataki D. E., Alig R. J., Fung A. S., Golubiewski N. E., Kennedy C. A., McPherson E. G., Nowak D. J., Pouyat R. V. & Lankao P. R. (2006) Urban ecosystems and the North American carbon cycle. Global Change Biology 12: 2092-2102. • Lal R., Follett R. F. & Kimble J. M. (2003) Achieving soil carbon sequestration in the United States: A challenge to the policy makers. Soil Science 168: 827-845. • Brack C. L. (2002) Pollution mitigation and carbon sequestration by an urban forest. Environmental Pollution 116.Nowak D. J. & Crane D. E. (2002) Carbon storage and sequestration by urban trees in the USA. Environmental Pollution 116: 381-389. • Eatough Jones M., Paine T. D., Fenn M. E. & Poth M. A. (2004) Influence of ozone and nitrogen deposition on bark beetle activity under drought conditions. Forest Ecology and Management 200: 67-76.

21. Carbon Storage • Jo H. K. & McPherson E. G. (1995) Carbon storage and flux in urban residential greenspace. Journal of Environmental Management 45: 109-133. • Johnson A. D. & Gerhold H. D. (2001) Carbon storage by utility-compatible trees. Journal of Arboriculture 27: 57-68. • Myeong S., Nowak D. J. & Duggin M. J. (2006) A temporal analysis of urban forest carbon storage using remote sensing. Remote Sensing of Environment 101: 277-282. • Nowak D. J. (2006) Institutionalizing urban forestry as a "biotechnology" to improve environmental quality. Urban Forestry and Urban Greening 5: 93-100. • Nowak D. J. (1993) Atmospheric carbon reduction by urban trees. Journal of Environmental Management 37: 207-217 • Nowak D. J. & Crane D. E. (2002) Carbon storage and sequestration by urban trees in the USA. Environmental Pollution 116: 381-389.

22. Carbon Storage • Nowak D. J., Stevens J. C., Sisinni S. M. & Luley C. (2002) Effects of urban tree management and species selection on atmospheric carbon dioxide. Journal of Arboriculture 28: 113-122. • McPherson E. G. (1998) Atmospheric carbon dioxide reduction by Sacramento's urban forest. Journal of Arboriculture 24: 215-223. • Pouyat R. V., Yesilonis I. D. & Nowak D. J. (2006) Carbon storage by urban soils in the United States. Journal of Environmental Quality 35: 1566-1575. • McPherson E. G. (1994) Using urban forests for energy efficiency and carbon storage. Journal of Forestry 92: 36-41. • Rowntree R. A. & Nowak D. J. (1991) Quantifying the role of urban forests in removing atmospheric carbon dioxide. Journal of Arboriculture 17: 269-275. • Pataki D. E., Alig R. J., Fung A. S., Golubiewski N. E., Kennedy C. A., McPherson E. G., Nowak D. J., Pouyat R. V. & Lankao P. R. (2006) Urban ecosystems and the North American carbon cycle. Global Change Biology 12: 2092-2102. • Pouyat R., Groffman P., Yesilonis I. & Hernandez L. (2002) Soil carbon pools and fluxes in urban ecosystems. Environmental Pollution 116.

23. Emissions - Maintenance Nowak et al (2002.) found that depending on species, whether fossil fuels are used or not, and the maintenance scheme tree may be net sources of C Maintenance emissions vary considerbly (0.18 x 10-9 kg yr-1 to 4.27 kg yr-1 per tree depending on the city (McPherson et al. 2005).

24. Emissions - Maintenance Maintenance causes net C emissions unless it increases the trees lifespan (Nowak et al. 2002)‏ Management decisions will determine whether or not tree planting will be effective in reducing carbon emissions (Pataki 2006)‏

25. Decomposition If disposesd of in landfill minimal decomposition occurs (Nowak et al. 2002)‏ If composted, the tree becomes a net source of carbon (Nowak et al. 2002)‏ If burned without reduction in heating emissions then it is a net source of carbon (Nowak et al. 2002)‏

26. References • Pataki, D.E., R.J. Alig, A.S. Fung, N.E. Golubiewski, C.A. Kennedy, E.G. Mcpherson, D.J. Nowak, R.V. Pouyat and P. Romero Lankao. 2006. Urban ecosystems and the North American carbon cycle. Global Change Biology 12:2092-2102. • McPherson, E.G., J.R. Simpson, P.F. Peper, et al. 2005. City of Boulder, Colorado Municipal Tree Resource Analysis. USDA Forest Service, Pacific Southwest Research Station. • McPherson, E.G., J.R. Simpson, P.F. Peper, et al. 2005. City of Minneapolis, Minnesota Municipal Tree Resource Analysis. USDA Forest Service, Pacific Southwest Research Station. • McPherson, E.G., J.J. Simpson, P.F. Peper, et al. 2005. Municipal forest benefits and costs in five US cities. Journal of Forestry 103:411-416. • Nowak, D.J., J.C. Stevens, S.M. Sisinni, et al. 2002. Effects of urban tree management and species selection on atmospheric carbon dioxide. Journal of Arboriculture 28:113-122.

27. Questions? • Thank you