Arboriculture & Urban Forestry 38(2): March 2012 honeylocust. Roughness of bark, depth of foliage, twig surface area, and leaf surface area are among the plant related factors influencing stormwater interception. Note that most of these factors would be expected to be greater for the larger plant. Thus I suggest that the paper’s conclusion that stormwater re- tention for larger plants is greater than for smaller trees is true. Aesthetic Values. Aesthetic values reported were not property (asset) values although they do have an origin in what is com- monly called the trunk formula method. Essentially, what is being reported as aesthetic benefits is the value of the tree in the year reported less the value of the tree in the previous year. This value is called aesthetic value and is a surrogate for a host of benefits such as reduced police calls in the community, increased sales in a commercial district, ,annual increase in property value, reduced use of pain killers in a hospital, reduced domestic violence, reduced deaths during a drought and heat wave, and increased community pride. I am sure that everyone can think of additional benefits that have been reported in the literature and are lumped in i-Tree Streets as aesthetic benefits. Aesthetic value may be a poor choice as a term for what was represented. The problem is that property values is the first thing that comes to mind in a ten-second sound bite. Perhaps someone else has a better term. What the aesthetic values as reported in i-Tree Streets is not, is an attempt to do what CTLA has been working on for more than a decade. Defining a meaningful value to an asset such as a tree is com- plex, site specific, and confounded by the issues Mr. Brady noted. Summary. Thanks for the opportunity to clear up misconcep- tions and further explain what we did. We think that when you consider that the cross-sectional area of each honeylocust is more than two-times that of a hawthorn and that i-Tree Streets is using canopy volume which is a cubic measure of size, that eight-times the benefits is expected. We also feel that we did show that in the 46th year following planting, that ten honeylocusts produced 7.5 times the annual benefits of ten hawthorns planted in similar cir- cumstances. We further hope we showed how this might be used to market what we do in dollars to a public who profess to be inter- ested in economic returns on their investment in time or resources. T. Davis Sydnor Professor Urban Forestry The Ohio State University School of Environment and Nat Resources 210 Kottman Hall 2021 Coffey Road Columbus, Ohio 43210-1085, U.S. 77 The following letter was submitted as feedback to: Peterson and Straka. 2011. Specialized discounted cash flow analysis formu- las for valuation of benefits and costs of urban trees and forests. Arboriculture & Urban Forestry 37(5):200–206. The author re- sponse follows the letter submission. To whom it may concern: Peterson and Straka (2011) use the following data on white oaks (Quercus alba) to “standardize” their models: * white oaks live 120 years * white oaks are structurally sound for the first 90 years * white oaks provide significant canopy coverage around 10 years of age * white oaks can be bought and planted for USD $70.00 * white oaks 60.96 cm in diameter can be removed for $406.00 Theoretically, any of these items are possible. Taken as a whole, however, the probability that the data is representa- tive of any white oak is small. The variables are too great. The authors state that showed that in ares of land with Atlanta, Georgia, U.S., 0.4 hect- tree ral gas usage by $13.67 (I assume the data is cited). The minimum size for coverage would white oaks to provide “shade” in this study is achieved at year 10. What is not stat- ed is the number of 10-year-old and older white oaks re- quired to produce coverage similar to the 0.4 ha in Atlanta. Table 3 has the annual savings for a white oak aged 10 to 90 years at $13.67. The American Forests study, however, attributes $13.67 to the value of 0.4 ha of tree coverage—not a single tree. If I’m correct, Establishing the this would future be value a of significant trees and error. for- ests is, in my opinion, next to impossible. But there appears to be no dearth in those willing to try. I wish them luck. Regards, Norm Brady St. Michaels, Maryland, U.S. Author Response Mr. Brady is correct about the white oak data. We used actual cost and benefit data to illustrate the use of the specialized formulas. The resulting examples were meant to be independent and cumu- lative valuations could be impracticable. He is also correct that the energy savings in Table 3 would be for more than the single tree. However, all of the examples were designed to illustrate the application of a specific formula and costs or revenues were merely intended to be part of that illustration. The savings in Ta- ble 3 do correctly illustrate that use, even if they overstated as part of an example. Mr. Brady is also correct in closing to note these types of calculations are difficult in practice, but, hopefully, the specialized formulas make the application easier for those who use discounted cash flow analysis to value trees and urban forests. Thomas J. Straka Professor Division of Forestry and Natural Resources Clemson University Box 340310 Clemson, South Carolina 29634-0310, U.S. ©2012 International Society of Arboriculture natu- American Forests (2011) reduce
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