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
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City of Macon
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Land
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Total Air
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Total Carbon
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Total
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Land Use
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Use (acres)
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Pollution Benefit
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Sequestration Value
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Energy Savings
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Commercial
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4040
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$69,313
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$22,837
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$249,065
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Residential
|
14155
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$790,804
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$252,539
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$1,386,495
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Total
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18195
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$860,117
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$275,377
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$1,635,560
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Total Annual Benefits =
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$2,771,054
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Bibb County
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Land
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Total Air
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Total Carbon
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Total
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Land Use
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Use (acres)
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Pollution Benefit
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Sequestration Value
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Energy Savings
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Commercial
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6430
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$153,642
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$49,879
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$555,897
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Residential
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37405
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$1,711,288
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$947,593
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$4,000,058
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Total
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43835
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$1,864,930
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$997,472
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$4,555,955
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Total Annual Benefits =
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$7,418,357
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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 1997. 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 1997.
Table 9 - Total Loss of Urban Forest Benefits from 1993 - 1997
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City of Macon
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Land
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Total Annual
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Total Net Vegetation Loss
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Total Loss of
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Land Use
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Use (acres)
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Benefits Per Acre
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from 1993-1997 (acres)
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Benefits from 1993-1997
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Commercial
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4040
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$84
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28.53
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$2,410
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Residential
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14155
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$172
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39.21
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$6,731
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Total
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18195
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$256
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67.74
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$9,140
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|
|
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Bibb County
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Land
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Total Annual
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Total Net Vegetation Loss
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Total Loss of
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Land Use
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Use (acres)
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Benefits Per Acre
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from 1993-1997 (acres)
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Benefits from 1993-1997
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Commercial
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6430
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$118
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151.14
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$17,850
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Residential
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37405
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$178
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491.43
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$87,486
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Total
|
43835
|
$296
|
642.57
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$105,336
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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.
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.
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