Pittsburgh I-Tree Ecosystem Analysis
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Pittsburgh i-Tree Ecosystem Analysis City of Pittsburgh, Pennsylvania July 2015 Prepared for: City of Pittsburgh Department of Public Works, Forestry Division 6520 Stanton Avenue Pittsburgh, Pennsylvania 15206-2251 Pittsburgh Shade Tree Commission The Office of Mayor William Peduto 512 City County Building 414 Grant Street, Pittsburgh, Pennsylvania 15219 The Western Pennsylvania Conservancy 800 Waterfront Drive Pittsburgh, Pennsylvania 15222 Prepared by: Davey Resource Group A Division of The Davey Tree Expert Company 1500 North Mantua Street Kent, Ohio 44240 800-828-8312 Acknowledgments The City of Pittsburgh’s vision to promote and preserve the urban forest and improve the management of public trees was a fundamental inspiration for this project. Among the keystones of the Pittsburgh Urban Forest Master Plan is “Connect” and “Engage”, which outlines goals to improve access to tree benefits and for developing education and outreach strategies that increase awareness of the importance of Pittsburgh’s urban forest. Quantifying tree benefit results will help the city and its partners in the achievement of those goals. The City of Pittsburgh is thankful for the funding and expertise it received from the City of Pittsburgh Shade Tree Commission, The Pennsylvania Department of Conservation and Natural Resources, Tree Pittsburgh, and the Western Pennsylvania Conservancy. Davey Resource Group i July 2015 Pittsburgh Benefits Executive Summary This report reflects data gathered by Davey Resource Group, a division of The Davey Tree Expert Company, throughout a complete street tree inventory during summer and fall 2014. Davey Resource Group used i-Tree Eco (UFORE) and i-Tree Streets urban forest analysis tools to analyze the data and estimate the annual monetary benefits the City of Pittsburgh receives from its street tree resource (see Appendix E for more detail on i-Tree eco and i-Tree streets analysis tools). A Street Tree Management Plan was also produced in conjunction with the benefits analysis. These reports and the major tree planting efforts throughout the TreeVitalize Pittsburgh project have been led by Pittsburgh’s urban forestry partners, including: Allegheny County Parks, City of Pittsburgh Forestry Division, the City of Pittsburgh Photograph 1. This Quercus rubra (northern Shade Tree Commission, Pennsylvania Department red oak) in the North Squirrel Hill neighborhood of Conservation and Natural Resources, Tree provides shade on a sunny summer day. Pittsburgh, and the Western Pennsylvania Conservancy. This analysis is based on benefits which have been quantified by the i-Tree Eco and Streets analysis tools. It is important to note that many of the benefits provided by the urban forest and its street tree resource are not presently accounted for by these analysis tools. Urban forests have been shown to have positive effects on crime rates, hospital recovery time, community pride and cohesion, physical health, and mental and emotional well-being. For some, these intrinsic values are just as important as the tangible monetary benefits trees provide. As the i-Tree model is developed and economic values are quantified for additional benefits, the importance of Pittsburgh’s street tree resource value will continue to increase. Resource Structure For the purpose of this analysis, Pittsburgh’s street tree resource was divided into 90 neighborhoods, most of which are located in the eastern part of the city (see map in Appendix A). A thorough analysis of resource composition across Pittsburgh’s diverse mix of neighborhoods is essential to understanding the management needs and benefits of these street trees. Pittsburgh’s street tree inventory comprises 33,498 publicly-managed street trees. Looking at species diversity, age distribution, condition, canopy coverage, and replacement value, Pittsburgh’s street tree resource composition is characterized by the following findings: There are 189 distinct tree species along Pittsburgh’s street rights-of-way. Highly abundant species such as Acer platanoides (Norway maple, 10.5%) and A. rubrum (red maple, 10.0%) currently pose a threat to the biodiversity of Pittsburgh’s street tree population. Other predominant species include: Pyrus calleryana (Callery pear, 8.9%); Platanus x acerifolia (London planetree, 8.2%); and Tilia cordata (littleleaf linden, 6.7%). Norway maple and Callery pear are non-native invasive species, which is an additional concern. Davey Resource Group ii July 2015 The age structure of Pittsburgh’s street trees is nearly ideal. While there are too few trees of middle diameter classes, the high volume of young trees bodes well for the future flow of benefits. Two of Pittsburgh’s top performing species—Platanus x acerfolia (London planetree) and Quercus palustris (pin oak)—are limited when it comes to existing young replacements. That said, some young planetrees have been planted, and a variety of white oak species have been planted to replace the pin oak. Red oak is not currently being planted due to its susceptibility to oak wilt disease and the obscure scale insect pest. The majority of Pittsburgh’s street trees are in Good or Fair condition (42% and 41%, respectively). Maintaining these trees is essential to maximizing their benefits and increasing their useful lifespan. Critical and Dead trees need to be removed as soon as possible. The estimated street tree canopy covers 1,435 acres, or 4.1% of Pittsburgh’s total land area. The area covered by street tree canopy is about 26% of the total estimated street ROW area (5,461 acres) within the city. Replacing Pittsburgh’s 33,498 street trees with trees of similar size, species, and condition would cost approximately $51 million. Functional Benefits Pittsburgh’s street trees provide numerous functional benefits to the community. These cumulative benefits can be valued at an annual average of approximately $67 per tree, for a net total annual value of $2.24 million. Trees help conserve and reduce energy use, reduce local carbon dioxide levels, improve air quality, mitigate stormwater runoff, improve aesthetics, and increase property value. Pittsburgh’s street trees benefit the community in the following ways: Remove and mitigate air pollutants. The net air quality improvement provided by Pittsburgh’s street tree population is valued at approximately $417,700 per year, for an average net benefit of $12.48 per tree. Provide an annual benefit of roughly $38,335 ($1.14 per tree) in carbon storage and avoidance. Carbon storage amounts to a net 4.4 million pounds each year, which accounts for an estimated annual value of $14,400. As a result of the cooling and wind break benefits trees provide, the amount of carbon released into the environment was reduced by 7.3 million pounds, valued at $23,967. Reduce electricity and natural gas use in Pittsburgh for a total energy savings of roughly $96,501, with a citywide average of $2.88 per street tree. Intercept 15.2 million gallons of stormwater per year, for an average of 450 gallons per tree. The total annual value of this benefit is $134,848, for an average value of $4.03 per tree. Aesthetic and property values account for an estimated total annual benefit of $1,556,747, for an average of $46.47 per tree. Annual tree-related expenditures amount to a projected average of $1,488,466 over the next ten years. The net annual benefit (benefits minus costs) is approximately $755,665. The City of Pittsburgh receives roughly $1.51 in benefits for every $1 spent on its municipal forestry program. Davey Resource Group iii July 2015 Table of Contents Acknowledgments ................................................................................................................................... i Pittsburgh Benefits Executive Summary ................................................................................................ ii Resource Structure ........................................................................................................................... ii Functional Benefits ......................................................................................................................... iii The Street Tree Network ........................................................................................................................ 1 A Forest of Trees ............................................................................................................................. 1 Street Tree Numbers ........................................................................................................................ 2 Species Richness and Diversity ....................................................................................................... 4 Species Importance Value ................................................................................................................ 6 Age Distribution .............................................................................................................................. 8 Tree Condition and Relative Performance ..................................................................................... 10 The Green Umbrella ...................................................................................................................... 12 Street Tree Contribution to Pittsburgh’s Canopy ........................................................................... 13 Street Tree Benefits .............................................................................................................................