Quantifying the Value of Urban Forest Land in Macon, GA

Transcription

1 Quantifying the Value of Urban Forest Land in Macon, GA August Circle 75 Parkway Suite F-6320 Atlanta, GA (770)

2 Table of Contents Executive Summary... 3 Introduction... 5 Urban Ecological Analysis Methods... 5 Selection of Study Sites... 5 Data Collection... 7 Data Preparation... 8 Study Site Analysis... 8 Forest Health... 8 Energy Savings... 8 Air Quality... 9 Stormwater Management... 9 Urban Ecological Analysis Results Forest Health Energy Savings Air Quality Stormwater Management Macon-Bibb County Projections Conclusions Energy Savings Air Quality Stormwater Management References Appendix A Data Collection Procedures and Descriptions Appendix B CITYgreen Analysis Data Sheets Jeff De Witt, GIS Technician, Pacific Meridian Resources, 4501 Circle 75 Parkway, Suite F-6320, Atlanta, GA 30067, (770) , [email protected] Eric Fowler, Macon City Forester, Macon-Bibb County Parks and Recreation Department, P.O. Box 247, Macon, GA 31202, (912) Kass Green, President, Pacific Meridian Resources, 5915 Hollis Street, Building B, Emeryville, CA 94608, (510) Funds for this project were provided by the Urban and Community Forestry Grant Assistance Program administered through the Georgia Forestry Commission. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 2

3 Executive Summary Pacific Meridian Resources was contracted by the City of Macon to conduct an Urban Ecological Analysis that would quantify the benefits produced by the area s urban forests. The findings of this analysis are intended to provide public officials, policymakers, and city planners with a better understanding of the value of trees and their role in the urban environment. The City of Macon has seen considerable growth and development during the past decade. This growth has had a significant impact on Macon and Bibb County s urban forest lands, resulting in net loss of approximately 4000 acres of vegetation from 1985 to 1997, including almost 500 acres of forest land. The loss of urban forest lands often leads to higher summer temperatures in urban areas, poor air quality, and increased stormwater runoff and soil erosion. Trees help to alleviate these problems by lowering heating and cooling costs, decreasing air pollution, and reducing stormwater runoff and erosion. Real dollar values can be assigned to these types of urban forest benefits with a process called Urban Ecological Analysis - a way to map, measure, and calculate the value of the urban forest ecosystem. This analysis combines low-level aerial photographs, urban forest analysis software, called CITYgreen, and real-world data from several study sites throughout the region to assess the economic and environmental benefits of urban trees. Data collected at each study site included detailed information of tree, building, grass land, and impervious surface characteristics. Data from all of the study sites was entered into the CITYgreen software for analysis. Urban forest benefits analyzed include forest health, energy savings, air quality, and stormwater management. Results from this analysis for the six study sites selected include the following: Forest health average tree health rating was midway between fair and good. Trees having the best health were found in areas that had been newly developed. Trees in highly developed areas with large amounts of impervious surfaces had the lowest health rating. Energy savings existing tree canopy cover saved homeowners from $16 to $69 in summer cooling costs in residential areas, with an average of about $38 per home. The greatest savings were found in the study site with the highest tree canopy percentage, although high tree canopy percentages did not always correlate to significant energy savings. Air quality trees in all study sites produced approximately $1200 in annual pollution removal benefits. The existing trees in all the sites also store over 235 tons of carbon, sequestering about 1300 pounds of carbon per year. The estimated value of the sequestered carbon for all study areas is approximately $616 per year. Sites that had the most biomass (trees and other vegetation) had the greatest air quality benefits. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 3

4 Stormwater management the existing tree canopy of all the study sites reduced the volume of stormwater runoff by an average of 23 percent when compared to areas with no tree cover. Similarly, the peak flow rates (velocity) were also reduced by an average of 29 percent for all sites when compared to land with no trees. Sites having the very little vegetation and large amounts of impervious surfaces had the highest runoff volumes and peak flow rates. Projecting these results across the total area of Macon and Bibb County indicates that the existing urban forest lands in Macon save the city and its residents over $2.7 million annually, an average of $256 per acre for commercial and residential areas. Trees in the commercial and residential areas of Bibb County produce almost $7.5 million per year in savings, an average of almost $300 per acre. Based on the acres of vegetation lost from 1993 to 1997, the City of Macon lost over $9,000 in urban forest benefits during this period. The savings lost by Bibb County totaled approximately $105,000 from the loss of almost 650 acres of vegetation from 1993 to The findings for Bibb County include the total area of Macon. The results of this study indicate that the area s existing urban forest lands provide substantial energy savings, air quality benefits, and stormwater management advantages to the residents of Macon and Bibb County. The energy savings findings indicate that trees can significantly reduce a homeowner s summer cooling costs. The area s urban forests also help to improve air quality by removing and storing substantial amounts of pollutants from the atmosphere, including the green house gas carbon dioxide. The results of the stormwater analysis demonstrated that the loss of vegetation significantly increases the volume and velocity of stormwater runoff. Trees and other vegetation retain large amounts of water and decrease the rate at which stormwater travels, reducing soil erosion and minimizing the impact of flooding. The benefits quantified in this project can be used when evaluating the role urban trees should play in the area s overall urban landscape. As a result, public officials, developers, and planners will be able to better assess the economic value of trees when making decisions about their region s future growth and development. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 4

5 Introduction Like many other metropolitan areas across the country, the City of Macon is facing the problem of urban sprawl. Macon s population base has steadily grown during the past decade (U.S. Census Bureau 1999), with most of this growth occurring in areas surrounding the city. The growth and development in urban areas like Macon can have a considerable impact on a city s urban forest lands, often resulting in a significant loss of trees and other vegetation. A 1998 study found that the City of Macon and Bibb County sustained a net loss of approximately 4000 acres of vegetation from 1985 to 1997, including almost 500 acres of forest land (Pacific Meridian Resources 1998). The loss of urban forest lands can negatively impact an urban environment by creating summer temperatures that are higher in urban areas than in the surrounding countryside, concentrating air pollution problems into urban areas, and increasing stormwater runoff and soil erosion (USDA Forest Service 1990). Trees can help to alleviate these problems. Studies have shown that urban trees help to lower heating and cooling costs, decrease air pollution, conserve water, and reduce stormwater runoff and soil erosion (USDA Forest Service 1990, McPherson et al. 1994). Although the benefits of trees have been widely recognized, it has been difficult to put these benefits into real dollar figures. Without a method to quantify the benefits of urban trees, city officials and planners lack valuable information they need in order to make informed decisions about their city s urban forest resources. In response to this problem, American Forests, a non-profit forestry conservation organization, developed a way to map, measure, and calculate the value of the urban forest ecosystem with a process called Urban Ecological Analysis. This analysis combines low-level aerial photographs, urban forest analysis software, called CITYgreen, and the most up-to-date scientific research to calculate the economic and environmental benefits of urban trees. In March 2000, the City of Macon contracted Pacific Meridian Resources to conduct an analysis of Macon s urban forest lands. Pacific Meridian Resources utilized the CITYgreen software to quantify the benefits of Macon s urban forest resources. The findings of this analysis are intended to provide public officials, policymakers, and city planners with a better understanding of the value of trees and their role in the urban environment. Urban Ecological Analysis Methods Selection of Study Sites The Urban Ecological Analysis method is based on the selection of sample sites chosen to best represent the ecological and land use characteristics of a particular city (American Forests 1996). As the vegetation cover characteristics of each sample site (study site) are unique, the various study sites will provide a good representation of the differing August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 5

6 economic and ecological benefits common to the area. As in traditional forest sampling, this type of urban forest sampling allows us to make inferences about the condition of the urban forest across a larger area. Black and white low-level aerial photographs (1993 one-meter Digital Orthographic Quarter Quadrangles) were used to examine and select possible study sites. For this project, six study sites were selected throughout the City of Macon and Bibb County. Each study site chosen was approximately the size of one city block, about five acres. Table 1. - Urban Ecological Analysis Study Sites Study Site Area (acres) Land Use Approximate Age of Buildings Apartment Complex 5.13 Residential 30 years Old Neighborhood 5.62 Residential 50 years Young Neighborhood 5.23 Residential 9 years Downtown Neighborhood 4.72 Residential 80 years Office Building 5.35 Commercial 20 years Downtown Business District 6.51 Commercial 91 years As Table 1 indicates, all of the study sites were located in either residential or commercial areas. These two land use types represent over 60 percent of the total area within the City of Macon. Several attempts were made to establish a study site in an industrial land use area. Unfortunately, sites on industrial land were inaccessible. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 6

7 Figure 1. Location of Urban Ecological Study Sites Data Collection After six suitable study sites were selected, preliminary inventory themes were created using the CITYgreen software. CITYgreen is an extension of ArcView, a GIS software program. Using the digital aerial photographs as a backdrop, an inventory theme for the following features was created for each study site: trees, grass areas, buildings, and impervious surfaces. The image and corresponding inventory themes for each study site were then printed and used to ground truth and update the data for each inventory theme. Data collected at each study site included the following: Tree data - species, diameter, height class, health class, ground cover, conflicts Grass data - land use, type, height, maintenance Building data - stories, roof color, building material, overhangs, locations of air conditioners and windows Impervious surface data - land use, type, color August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 7

8 Additional data for features (trees, grass areas, buildings, etc.) not visible from the aerial photos was also collected. See Appendix A for additional descriptions of data collected. Data Preparation The next step of the project involved compiling and entering the data collected from the six study sites into the CITYgreen software for analysis. Corrections to the preliminary inventory theme data were made based on the data collected during the ground truthing process. Study Site Analysis After all of the data had been entered and verified for accuracy, the CITYgreen and ArcView analysis tools were utilized to assess the benefits of the trees in each of the study site areas. The analysis provided data about the following: Acreage of each study site Tree canopy area Average tree diameter Average tree height class Average tree health rating Total energy savings Total carbon storage and annual uptake Annual pollution removal Water runoff and peak flow reduction The following section discusses in detail the basic methodologies and techniques utilized in each of the CITYgreen analysis tools. Forest Health During the data collection phase of the project, the health of every tree was classified on a scale of one to five. A rating of one indicated that the tree was in very poor health, was damaged, or could not sustain new growth. A rating of five indicated that the tree was in excellent health, was free from major damage, and had substantial growth in the last year. Using this data, CITYgreen calculated the arithmetic mean (average) health class for the trees in each study site. Energy Savings Studies have shown that trees play an important role in reducing summer energy use in urban areas by providing shade to urban buildings and homes (Huang et al. 1992, McPherson et al. 1993). As a city that is a summer energy peaking community, Macon s urban trees can save the city considerable amounts in summer air conditioning costs. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 8

9 To calculate these savings, CITYgreen analyzes a tree s shade characteristics, height, and location to buildings. Each tree is then assigned an energy rating ranging from one to five, with five representing an optimally placed tree providing the most energy savings (American Forests 1996). These energy savings are then converted into economic values using research data from the USDA Forest Service of twelve U.S. cites. This research indicated that trees reduce air conditioner use between 5.5% and 22%, depending on the city (McPherson et al. 1993). A tree with an optimal energy rating of five is determined by applying the energy savings percent of a city with a similar climate with the annual cooling cost for a home in the city. In Macon, for example, USDA models estimate that an optimally placed tree can reduce cooling costs by 9.6%. Using an average annual cooling cost of $600, a tree with an energy rating of five can save a homeowner about $58 (9.6% of $600) during the course of a cooling season. The total energy savings for all trees are calculated by extrapolating the USDA Forest Service data to all trees in each energy rating class (American Forests 1996). Air Quality An additional benefit of trees in the urban forest and across the entire landscape is the storage and sequestration of carbon. Trees convert carbon dioxide, a green house gas, to oxygen and stored carbon. The carbon is stored in the biomass of trees and other vegetation in various levels, depending on their size, distribution, and species type. Additionally, trees absorb carbon from the atmosphere at predictable rates, known as carbon sequestration. CITYgreen calculates the amount of carbon storage and annual sequestration rates of trees based on their average diameter class distribution and canopy coverage (American Forests 1996). The annual value of carbon sequestration was then determined by multiplying the average annual costs of carbon pollution control by the amount of carbon sequestered during a year (McPherson et al. 1994). The CITYgreen software program also assesses the air pollution removal capacity of urban forests for such pollutants as Nitrogen Dioxide (NO 2 ), Sulfur Dioxide (SO 2 ), Ozone (O 3 ), Carbon Monoxide (CO), and particulate matter less than ten microns (PM10). Pollution removal estimates are based on USDA Forest Service research and models (McPherson et al. 1993). Stormwater Management As in many areas of the country, stormwater management is a major concern in the Macon - Bibb County area. The flood of 1994 clearly demonstrated the problems of managing and controlling significant amounts of stormwater produced over a short period of time. Rivers were flooded beyond their capacities, buildings were damaged, and valuable riverfront property was lost. In the vicinity of the Spring Street bridge, the heavy rainfall and large amount of impervious surfaces in the downtown and Coliseum areas contributed to the loss of over four acres of riverfront property, as well as the flooding of Interstate 16 and Interstate 75. Effectively managing stormwater runoff is August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 9

10 extremely expensive. But if left unmanaged, the costs of damage and cleanup from uncontrolled stormwater runoff can far exceed the preventative costs. After the 1994 flood, for example, millions of dollars were spent cleaning up areas along the Ocmulgee River and its tributaries. Trees have been shown to help control stormwater flow relatively inexpensively, especially when compared to the high costs of building and maintaining stormwater control systems. A moderately sized tree s root system can absorb up to 400 gallons of water per day. A tree canopy also decreases the force at which water hits the ground, thus reducing the amount of erosion (particularly on slopes) during rainy periods (American Forests 1996). CITYgreen calculates stormwater management benefits using a hydrology model, commonly known as Technical Release 55 or TR 55, developed by the U.S. Natural Resource Conservation Service (NRCS). Using precipitation data, land cover percentages, hydrologic soil types, and slope information, TR 55 estimates runoff volume, percent change in time of concentration, and peak flow rates. Table 2 - CITYgreen Analysis Inputs Energy Savings Analysis Average Annual Study Site Cooling Costs ($$) 1 Energy Region Apartment Complex S Atl Old Neighborhood S Atl Young Neighborhood S Atl Downtown Neighborhood S Atl Office Building S Atl Downtown Business District S Atl August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 10

11 Stormwater Analysis Study Site Rainfall Type Precipitation (in.) 2 Slope (%) 3 Soil Type 4 Apartment Complex II A Old Neighborhood II A Young Neighborhood II A Downtown Neighborhood II C Office Building II B Downtown Business District II C 1 Based on estimates from the U.S. Department of Energy (Department of Energy 1994) and actual cooling costs for a home near Macon, GA. 2 Based on the average rainfall within a two-year period for a 24-hour storm event in Macon, GA. 3 Average slope of study site derived from digital elevation model (DEM) of Bibb County, GA. 4 Hydrologic Soil Type A - Very Pervious B - Somewhat Pervious C - Somewhat Impervious D - Very Impervious Urban Ecological Analysis Results The following section highlights the findings generated from the CITYgreen analysis. The detailed results for each study site are included in Appendix B. Forest Health The CITYgreen analysis of forest health indicated that the trees at each study site were rated between fair and good, with an overall average health rating of 3.6 for all study sites, about halfway between fair and good (Table 3). Not surprisingly, the study sites with the lowest health rating (Downtown Business District and Downtown Neighborhood) were located in the highly developed urban areas of the city that are covered with large amounts of impervious surfaces. The highest health rating was found in the Young Neighborhood study site. Tree age is likely the biggest factor in determining a tree s health, although additional factors likely played a role. For example, most trees in the Young Neighborhood site were relatively young and vigorous, having recently been planted after the development of the subdivision. By contrast, trees in the Downtown Neighborhood site had been established some time ago and were more mature and less vigorous. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 11

12 Table 3 - Tree Health Ratings Study Site Tree Canopy (%) Average Health Rating 1 Apartment Complex Old Neighborhood Young Neighborhood Downtown Neighborhood Office Building Downtown Business District Average Health Class Rating 1 - Dead/Dying 2 - Poor 3 - Fair 4 - Good 5 - Excellent Energy Savings In the City of Macon, air conditioning costs represent a considerable expense to most residents, costing them about $600 a year to cool their homes. Analysis of data from the four residential study sites suggests that the existing tree canopy can save homeowners $16 to $69 in summer cooling costs. At this point, U.S. Forest Service research of energy savings from urban trees has only modeled the benefits provided to residential homes and not to commercial buildings. As a result, the energy savings for the two commercial study sites (Downtown Business District and Office Building) are estimations and are presented only to provide an approximation of the energy savings afforded to commercial buildings. Not surprisingly, Table 4 indicates that the homes located in the study site having the greatest tree canopy cover (Old Neighborhood) had the highest energy and kilowatt hour (kwh) savings. However, significant tree canopy cover did not always correlate to large energy savings. For example, existing trees in the Young Neighborhood site are saving each homeowner about $39 a year. This site had the lowest canopy cover, seven percent, but had 16 percent of the existing trees in an energy rating class of three or better. By contrast, only ten percent the Downtown Neighborhood study site s trees, with a canopy cover of 21 percent, were assigned to the three highest energy ratings. As a result, the greater canopy cover in the Downtown Neighborhood site produced lower energy and kwh savings than the Young Neighborhood site, largely because the existing trees in the Young Neighborhood site were planted in a way that afforded a greater energy savings. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 12

13 Table 4 - Energy Savings Killowat Hour Savings Number of Tree Total kwh Study Site Buildings Canopy (%) kwh Savings 1 Savings / Home 1 Apartment Complex Old Neighborhood Young Neighborhood Downtown Neighborhood Office Building Downtown Business District Average Dollar Savings Number of Tree Total Energy Study Site Buildings Canopy (%) Energy Savings ($$) Savings / Home ($$) Apartment Complex Old Neighborhood Young Neighborhood Downtown Neighborhood Office Building Downtown Business District Average Based on $0.08 per kilowatt hour (kwh) (Southern Company 2000). 2 As USDA Forest Service research has thus far only modeled savings to residential buildings, the energy savings represented are estimates and are presented only to provide an approximation of the energy savings afforded to commercial buildings. Air Quality As in most expanding metropolitan areas, air pollution is an unwelcome and unhealthy byproduct of urban growth and development. In addition to reducing air pollution through energy conservation, trees also help to remove and store several major air pollutants. The CITYgreen air pollutant and carbon sequestration models estimated the amount of several major air pollutants that trees remove. Table 5 indicates the pollution removal benefits from each of the study sites. State Public Service Commissions (PSCs), the appointed bodies that regulate utilities, estimate the costs of externalities, or social costs, associated with energy production. An example of these costs is the health costs associated with treating the disease that pollutants would cause. The dollar value savings shown represent the savings of these externality costs derived from the trees storage of pollutants. The Old Neighborhood study site provided the greatest amount of savings, about $455 per year, due to its high canopy cover. With a smaller canopy cover, the August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 13

14 Young Neighborhood site produced approximately $83 per year in air pollution removal benefits. Table 5 - Annual Pollution Removal Benefits 1 Study Site Ozone ($$) SO 2 ($$) NO 2 ($$) PM 10 ($$) CO ($$) Total Apartment Complex Old Neighborhood Young Neighborhood Downtown Neighborhood Office Building Downtown Business District Total , Average CITYgreen results based on 1994 dollars. In addition to the air pollutant benefit analysis, CITYgreen estimates the amount of carbon that is sequestered and stored in trees. Carbon accounts for about half of the dry weight of most trees. Trees help to control the amount of carbon in two important ways storage and sequestration. Carbon storage is the amount of carbon currently stored in a tree s biomass while carbon sequestration is the rate at which trees absorb carbon (American Forests 1996). The CITYgreen carbon models estimate that the existing trees in all study sites store over 235 tons of carbon each year, an average of about 39 tons per site. The varying storage levels correspond to the different amounts of tree biomass at each site. A tree s biomass can roughly be measured by analyzing the number of trees, the size of the trees, and the canopy percentage for each study site (American Forests 1996). For the rate of carbon sequestration, the CITYgreen software calculated an annual rate of carbon absorption of 0.67 tons for all study sites, an average of 0.11 tons per study site. The differing levels of sequestration also correspond to the wide range of vegetation biomass found at each site. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 14

15 Table 6 - Carbon Storage, Sequestration, and Sequestration Value Current Annual Annual Study Site Storage (tons) Sequestration (tons) Sequestration Value ($$) 1 Apartment Complex Old Neighborhood Young Neighborhood Downtown Neighborhood Office Building Downtown Business District Total Average Annual sequestration rate multiplied by costs of pollution control, $920/ton. (McPherson et al. 1994, American Forests 1996) Annual carbon sequestration values can be calculated by multiplying the costs of pollution control by annual sequestration rates (McPherson et al. 1994). Using this method, the annual value of carbon sequestration ranges from almost $37 for the Downtown sample site to a high of about $250 for the Young Neighborhood site. The average value of carbon sequestered for all study sites is approximately $103 per year. As these estimates are based on the cost of controlling emissions, it is likely that they overestimate the value of reducing the pollution. These estimates do not take into consideration the adverse effects that pollution causes on human health, structures, and visibility before the pollutants are removed by trees (McPherson et al. 1994). Stormwater Management Reducing volume and velocity of stormwater runoff is a significant part of stormwater management. CITYgreen stormwater analysis provided important insight into how trees can help to control stormwater runoff volume and velocity (peak flow rate). According to the analysis of the Macon-Bibb County study sites, existing trees reduce the volume of stormwater runoff by an average of 23 percent when compared to areas with no tree cover. The estimated volume of stormwater runoff ranges from 0.35 to a high of 3.25 inches per square inch. Not surprisingly, study sites having very little vegetation and large amounts of impervious surfaces (Office Building and Downtown commercial study sites) had the highest runoff volumes and peak flow rates. By contrast, study sites with high vegetation cover and low to medium impervious cover (Apartment Complex and Old Neighborhood sites) had the lowest runoff volumes and peak flow rates. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 15

16 Table 7 - Stormwater Runoff Benefits Tree Impervious Runoff Peak Flow Runoff Canopy Grass and Building Peak Flow Volume Reduction Reduction Study Site Cover 1 Cover 1 Cover 1 (cu.ft./sec.) (in. / sq.in.) (percent) 2 (percent) 2 Apartment Complex L H M Old Neighborhood M H L Young Neighborhood L H H Downtown Neighborhood M M H Office Building L M C Downtown Business District L V C Average Cover Classes V - Very light (0-5%) L - Light (6-20%) M - Medium (21-40%) H - Heavy (41-60%) C - Covered (>60%) 2 Benefits of existing tree canopy compared with benefits derived from no tree canopy with 3.75 inches of precipitation. Macon-Bibb County Projections The results from the six study sites were combined with the findings of the Macon-Bibb County vegetation change detection study (Pacific Meridian Resources 1998) and land use maps of Bibb County to make projections of the overall benefits provided by the area s existing urban forest lands. To estimate these annual savings, an average savings per acre from the six study sites was calculated for each land use type. The study site savings per acre for each benefit was then multiplied by the total number of acres in each land use, resulting in an annual benefit for each type of savings. These totals were then summed to obtain the total annual benefit. Table 8 - Annual Macon-Bibb County Urban Forest Benefits by Land Use City of Macon Land Total Air Total Carbon Total Land Use Use (acres) Pollution Benefit Sequestration Value Energy Savings Commercial 4040 $69,313 $22,837 $249,065 Residential $790,804 $252,539 $1,386,495 Total $860,117 $275,377 $1,635,560 Total Annual Benefits = $2,771,054 August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 16

17 Bibb County Land Total Air Total Carbon Total Land Use Use (acres) Pollution Benefit Sequestration Value Energy Savings Commercial 6430 $153,642 $49,879 $555,897 Residential $1,711,288 $947,593 $4,000,058 Total $1,864,930 $997,472 $4,555,955 Total Annual Benefits = $7,418,357 Projecting these findings to Macon and Bibb County, Macon s urban forests save the city and its residents over $2.7 million annually, an average of $256 per acre for commercial and residential areas. Furthermore, trees in the commercial and residential areas of Bibb County produce almost $7.5 million per year in savings, an average of almost $300 per acre. The findings for Bibb County include the total area of Macon. The total annual benefits were then combined with the losses in vegetation determined in the Macon-Bibb County change detection study to estimate the amount of benefits that were lost during 1993 to The results suggest that the City of Macon lost over $9,000 in urban forest benefits during this period. The savings lost by Bibb County totaled approximately $105,000 from the net loss of almost 650 acres of vegetation from 1993 to Table 9 - Total Loss of Urban Forest Benefits from City of Macon Land Total Annual Total Net Vegetation Loss Total Loss of Land Use Use (acres) Benefits Per Acre from (acres) Benefits from Commercial 4040 $ $2,410 Residential $ $6,731 Total $ $9,140 Bibb County Land Total Annual Total Net Vegetation Loss Total Loss of Land Use Use (acres) Benefits Per Acre from (acres) Benefits from Commercial 6430 $ $17,850 Residential $ $87,486 Total $ $105,336 August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 17

18 Conclusions The results of this study indicate that the area s existing urban forest lands provide substantial energy savings, air quality benefits, and stormwater management advantages to the residents of Macon and Bibb County. Energy Savings The energy savings findings indicate that trees can significantly reduce a homeowner s summer cooling costs. These findings also show that the amount of energy savings is not dependent on the percentage of tree cover, but is the result of tree location and size. Previous studies substantiate this conclusion by indicating that a tree s height and relative location to a home directly influence summer energy use (American Forests 1996, USDA Forest Service 1990). Therefore, even a limited number of trees, placed in locations to shade windows, walls, or air conditioners and allowed to grow to a substantial height (around 35 feet), will provide homeowners with significant energy savings. With this information, local tree planting projects could be targeted to areas with high-energy consumption to help reduce energy costs in the area. Air Quality Urban forests also help to improve air quality throughout the area. The results of the air quality analysis show that urban trees remove and store substantial amounts of pollutants from the atmosphere, including the green house gas carbon dioxide. The removal of harmful pollutants also generates considerable dollar savings to the region by helping to reduce the cost of pollution controls. Furthermore, by improving the air that we breathe, municipalities can reduce the expensive health care costs associated with respiratory diseases and complications. Stormwater Management As in many growing communities, impervious building and pavement surfaces have replaced large amounts of vegetation. The results of this study demonstrated that this loss of vegetation significantly increases the volume and velocity of stormwater runoff. Trees and other vegetation retain large amounts of water and decrease the rate at which stormwater travels. Consequently, soil erosion, particularly on slopes and riverbanks, is reduced and flooding damage is minimized. The stormwater analysis findings also indicate that trees can reduce the amount of storage volume needed to hold stormwater runoff. As a result, trees can economically supplement expensive stormwater control infrastructures by helping to decrease the stormwater storage capacity needed to retain stormwater runoff. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 18

19 The results of this Urban Ecosystem Analysis of Macon and Bibb County clearly indicate that the area s existing urban trees provide substantial dollar savings by reducing energy costs, cleaning the air, and controlling stormwater runoff. These benefits can be used when evaluating the role urban trees should play in the area s overall urban landscape. As a result, public officials, developers, and planners will be able to better assess the economic value of trees when making decisions about their region s future growth and development. References American Forests Urban Ecological Analysis for Atlanta, Georgia. American Forests. Washington, D.C. Energy Information Administration Reducing Home Heating and Cooling Costs. SR/EMEU/ Department of Energy. Washington, D.C. Huang, Joe, Ronald Ritschard, Neil Sampson, Haider Taha Cooling Our Communities: A Guidebook on Tree Planting and Light-Colored Surfacing. U.S. Environmental Protection Agency, Office of Policy Analysis. Washington, D.C. McPherson, E. Gregory, Paul Sacamano, Steve Wensman Modeling Benefits and Costs of Community Tree-Planting in 12 U.S. Cities. U.S. Department of Agriculture, Forest Service. Washington, D.C. McPherson, E. Gregory, David J. Nowak, Rowan A. Rowntree, eds Chicago s Urban Forest Ecosystem: Results of the Chicago Urban Forest Climate Project. General Technical Report NE-186. U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. Radnor, PA. Pacific Meridian Resources Macon-Bibb County Tree Canopy Change Detection Study. Pacific Meridian Resources. Atlanta, GA. Southern Company Georgia Power Residential Service Schedule: R-13. Southern Company. Atlanta, GA. U.S. Census Bureau Metropolitan Area Population Estimates for July 1, 1998 and Population Change for April 1, 1990 to July 1, Report MA Population Estimates Program, Population Division, U.S. Census Bureau, Washington, DC. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 19

20 Appendix A Data Collection Procedures and Descriptions Data collected during the ground-truthing phase was based on the following criteria: Tree Inventory Windows/Air Conditioners: Windows at least 2 x 3 feet in size and air conditioners were located and marked on the inventory maps by a W and AC correspondingly. Public / Private: Each tree inventoried was recorded as either located on public or private property and was assigned a B for public trees or V for private trees. Species Identification: Trees were identified by genus and/or species. Columnar species were noted. If all species in the genus had similar leaf area and tree characteristics, therefore not affecting light or water-filtration rates, just the genus was recorded. If the tree characteristics were significantly different among species, each species was recorded separately. Each tree species was recorded using the abbreviations as established by American Forests. Diameter Class: Tree diameters were measured at 4.5 feet above the ground and were recorded within 2 inches. Diameter measurements were also entered according to 10- inch classes as follows: 1 = <10 inches 2 = inches 3 = >20 inches Height Class: Tree heights were estimated and recorded to the nearest height class: 1 = <15 feet 2 = feet 3 = >35 feet Reduced Height: Trees that had been topped were recorded Y, those not topped were recorded as N. Overall Health Condition: Each tree s overall health was evaluated by examining its twig growth, presence of epicormic sprouting, crown, trunk, and roots. The tree s health was then rated according the following guidelines: 1 = Very poor, no new twig growth, heavy sprouting Crown more than 50% dead or dying Trunk large cavities, girdled Roots evidence of trenching or cutting within 5 feet of trunk base 3 = Fair, moderate twig growth, some sprouting Crown some evidence of damage, poor pruning, insect/disease problems Trunk some evidence of damage, cambial layer penetrated, not girdled Roots space confined by physical structures August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 20

21 5 = Excellent, substantial twig growth, no sprouting Crown full, uniform, no evidence of damage or insect/disease problems Trunk no evidence of damage Roots no evidence of damage, not confined by physical structures Conflicts: Conflicts with trees were listed according to the following guidelines: 1 = Potential problem with overhead utilities 2 = Existing problem with overhead utilities 3 = Building, other structure 4 = Sidewalk, curb 5 = Other tree Groundcover: Groundcover underneath the tree s dripline was listed according to the following criteria: 1 = Shrub 2 = Grass 3 = Pavement 4 = Exposed soil 5 = Mulch Building Inventory Land Use: Each building inventoried was recorded as a residence, business, commercial facility, industrial complex, garage, or shed. Building Age: Approximate age for each building was recorded using maps from the city planning/zoning maps. Building Material: recorded. The major building construction material was identified and Building Floors: The number of floors in each building was identified and recorded. Overhangs: The length of building s roofs were estimated and recorded to the nearest inch. Roof Color: The color of the roof on each building was identified and recorded. Wall Color: The color of the walls on each building was identified and recorded. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 21

22 Impervious Surface Inventory Land Use: Each impervious surface inventoried was recorded as a roadway, sidewalk, driveway, tennis court, or parking lot. Impervious Surface Type: The surface material of each impervious surface, either concrete or asphalt, was identified and recorded. Impervious Surface Color: The color of each impervious surface was identified and recorded. Grasslands Inventory Land Use: Each grassland area was inventoried and its use was recorded as a lawn, park, cemetery, or golf course. Grassland Type: The type of each grassland area, either Bermuda, Centipede, or Zoysia, was identified and recorded. Grass Height: The height of each grassland area was estimated and recorded to the nearest inch. Maintenance: The maintenance of each grassland area was identified as either Y for being mowed or N for not being mowed. Erosion Problems: Erosion problems for each grassland area were identified as either Y for being having some erosion or N for not having any erosion problems. August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 22

23 Appendix B CITYgreen Analysis Data Sheets August 8, 2000 Macon-Bibb County Urban Ecological Analysis Final Report 23

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