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  • City of Mississauga Urban Forest Study

    Technical Report

    July 2011

  • City of Mississauga Urban Forest Study

    Ju ly 20 11

    Toronto and Region Conservation Authority i

    Acknowledgements

    The City of Mississauga Urban Forest Study was prepared by the Toronto and Region Conservation

    Authority. We wish to thank the many people that contributed to this project for their input and

    support. Appreciation and thanks are extended to the following members of the Technical Working

    Group:

    Gavin Longmuir, City of Mississauga

    Samantha Chung, City of Mississauga

    Gary Linton, City of Brampton

    Brian Baird, Town of Caledon

    Mark Head, Region of Peel

    Janet Wong, Region of Peel

    Simone Banz, Region of Peel

    Aviva Patel, Credit Valley Conservation

    Paul Tripodo, Credit Valley Conservation

    Dr. Andy Kenney, University of Toronto, Faculty of Forestry

    Lionel Normand (Project Manager), Toronto and Region Conservation Authority

    Meaghan Eastwood (Author), Toronto and Region Conservation Authority

    Ziya He, Toronto and Region Conservation Authority

    Leilani Lee-Yates, Toronto and Region Conservation Authority

    Thank you to the staff of the USDA Forest Service, Northern Research Station, as well as the University

    of Vermont, Spatial Analysis Laboratory, for their technical services, guidance and expertise:

    Dr. David J. Nowak, USDA Forest Service

    Robert E. Hoehn, USDA Forest Service

    Jarlath O'Neil-Dunne, University of Vermont

    Keith Pelletier, University of Vermont

    Funding for this project has been generously provided by:

    The Region of Peel

    The City of Mississauga

    The City of Brampton

    The Town of Caledon

    Credit Valley Conservation

    Toronto and Region Conservation Authority

  • Technical Report

    Ju ly 20 11

    ii Toronto and Region Conservation Authority

    Executive Summary

    The City of Mississauga Urban Forest Study – Technical Report has been prepared by the Toronto and

    Region Conservation Authority, in partnership with the Region of Peel, Credit Valley Conservation (CVC),

    the City of Mississauga, the City of Brampton, and the Town of Caledon. The purpose of the study was to

    assess the distribution, structure and function of the urban forest, and to provide management

    recommendations for enhancing the sustainability of both the urban forest resource and the community

    as a whole. The study serves as a baseline for future research and monitoring, and will equip managers

    with the knowledge necessary to direct forest structure to deliver desired ecosystem services, including

    climate change mitigation and adaption, air pollution removal, stormwater management, residential

    energy savings, wildlife habitat, and community aesthetics.

    Summary of Results

    A suite of tools of analysis created by the United States Department of Agriculture (USDA) Forest

    Service, Northern Research Station and the University of Vermont, Spatial Analysis Laboratory were

    used to quantify the distribution, structure and function of the urban forest in the City of Mississauga.

    Tree Cover and Leaf Area:

    The City of Mississauga’s 2.1 million trees cover 15 percent of the total land area, providing 224 km2 of

    total leaf area. By ownership type, homeowners and tenants (renters) control the largest percentage of

    the City’s urban forest; more than half of the existing tree cover is located within the residential land

    use. The greatest opportunity to increase total leaf area and canopy cover is also found within the

    residential land use.

    Tree Cover by Land Use:

    • Agriculture: 13 %

    • Commercial: 6 % • Industrial: 5 %

    • Institutional: 14 %

    • Natural Cover: 44 %

    • Open Space: 32 % • Other: 24 %

    • Residential Low Density: 20 %

    • Residential Medium / High Density: 19 %

    • Utilities and Transportation: 5 %

    Tree Size:

    As urban trees increase in size, their environmental, social and economic benefits increase as well. In

    Mississauga a tree that is 65 cm in diameter at breast height (dbh) stores 65 times more carbon and 11

    times more pollution than a tree that is 11 cm dbh. Approximately 33 percent of all trees in Mississauga

    fall within the smallest diameter class and 63 percent of all trees are less than 15.3 cm dbh. The

  • City of Mississauga Urban Forest Study

    Ju ly 20 11

    Toronto and Region Conservation Authority iii

    proportion of large trees is low; less than 7 percent of the tree population has a dbh of 38.2 cm or

    greater.

    Most Common Tree Species by Land Use (expressed as a percent of the total leaf area):

    Open Space + Natural Cover + Agriculture

    • Sugar maple: 43 %

    • Manitoba maple: 10 %

    • Willow spp.: 10 %

    Residential (Low, medium and high density)

    • Norway maple: 12 % • White ash: 9 %

    • Green ash: 9 %

    Commercial + Industrial

    • Blue spruce: 29 % • Red pine: 18 %

    • Austrian pine: 16 %

    Institutional + Utilities and Transportation

    • Sugar maple: 28 %

    • Norway maple: 16 %

    • Red oak: 12 %

    Other

    • Sugar maple: 22 % • Green ash: 16 %

    • Elm spp.: 11 %

    Structural Value of Trees in Mississauga:

    The estimated structural value of all trees in Mississauga in 2008 is approximately $1.4 billion. This value

    does not include the ecological or societal value of the forest, but rather it represents an estimate of

    tree replacement costs and/or compensation due to tree owner’s for tree loss.

    Carbon Storage and Sequestration:

    As a tree grows, it removes, or sequesters, carbon dioxide from the atmosphere. This carbon is stored in

    the woody biomass of the tree. When a tree dies, much of the stored carbon is released back to the

    atmosphere through decomposition. Annually, trees in Mississauga sequester approximately 7,400

    tonnes of carbon, with an associated annual value of $220,000. Trees in Mississauga store 203,000

    tonnes of carbon, with an associated value of $5.8 million.

    Air Pollution Removal:

    The urban forest can improve local air quality by absorbing and intercepting air born pollutants.

    Mississauga’s urban forest removes 292 metric tonnes of air pollution annually; this ecosystem service is

    valued at $4.8 million annually.

    • Ozone: 237 metric tonnes

    • Particulate matter (10 microns) : 88 metric tonnes • Nitrogen dioxide: 87 metric tonnes

    • Sulfur dioxide: 12 metric tonnes

    • Carbon monoxide: 4 metric tonnes

  • Technical Report

    Ju ly 20 11

    iv Toronto and Region Conservation Authority

    Residential Energy Savings:

    Trees reduce local air temperature due to shading effects, wind speed reductions, and the release of

    water vapor through evapotranspiration. In Mississauga the urban forest reduces the annual energy

    consumption by approximately 79,000 MBTUS and 7,300 MWH, with an associated annual financial

    savings of approximately $1.2 million. As a result of this reduced demand for heating and cooling the

    production of over 2,100 tonnes of carbon emissions is avoided annually (associated annual savings of

    $61,800).

    Hydrologic Effects of the Urban Forest:

    The i-Tree Hydro model simulated the effects of tree and impervious cover on stream flow in the Spring

    Creek and Fletcher’s Creek subwatersheds. Based on model estimates, the loss of existing tree cover (14

    percent) in the Spring Creek subwatershed would increase total stream flow by approximately 1.2

    percent. Increasing tree cover from 14 percent to 30 percent would reduce overall flow by 1.8 percent

    (149,000 m3) during the 8 month period in 2008 and by 1.9 percent (128,000 m3) in the 8 month period

    in 2006 (see Figure 26 for the 2008 simulation period). In the Fletcher’s Creek subwatershed a loss of

    existing tree cover (10.6 percent) would increase total flow by approximately 0.9 percent during the

    2007 simulation period and by 1.1 percent. Increasing canopy cover from 10.6 percent to 20 percent

    would reduce overall flow by 1.0 percent (15,300 m3) during the 2007 simulation period, and by 1.2

    percent (49,100 m3) during the 2008 simulation period.

    Summary of Recommendations

    The recommendations provide here reflect the actions needed in order to progress towards many of the

    short and long term objectives associated with the criteria and performance indicators for sustainable

    urban forest management presented by Kenney et al. (2011). To evaluate the City’s performance for

    each of the 25 criteria is beyond the scope of this report. Such an extensive exercise should be

    conducted through the development of the City of Mississauga’s Urban Forest Management Plan. It

    follows that the development of a Management Plan that will more fully expl

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