Arboriculture & Urban Forestry 41(6): November 2015 Costs of not planting The costs of not planting trees have been explic- itly quantified in only a few studies. McPherson (2001) quantified “benefits forgone” (e.g., air- conditioning savings, stormwater management) to express the difference between the current level of shading benefits provided by trees on parking lots in Sacramento, California, U.S., and the ben- efits to be expected if all parking lots conformed to the 50% shaded area required by ordinance. This “benefits forgone” metric can be interpret- ed as the cost of not planting trees, equal to USD $1.9–3.4 million annually as calculated in this study ($1.4–2.5 million in 2000$; McPherson 2001). However, McPherson (2001) notes that this figure is strictly benefits forgone, rather than net benefits forgone, and does not include the full costs associated with planting and maintaining the greater number of trees to provide benefits (e.g., repair to pavements due to tree damage). Miller and Morano (1984) also provided data that enables calculating the costs of not plant- ing trees (see sidebar The Costs of Not Planting). 305 Removal Tree removal is a tree maintenance activity necessitated by a variety of circumstances in urban areas: failure to establish in the land- scape; old age; pest or disease attack; construc- tion of roads or buildings; ice, wind, or other storm damage; risk that exceeds what managers are willing to accept; and more (Nowak 1990). Tree removal is often the second-most costly expense for municipal tree program operations after pruning (Kielbaso et al. 1982; Kielbaso 1990; Tschantz and Sacamano 1994). Kielbaso and colleagues reported that tree and stump removal accounted for 28% of the municipal tree budgets on average in 1980 (Kielbaso et al. 1982) and 1986 (Kielbaso 1990). Tschantz and Saca- mano (1994) reported an average of 20.1% of the tree care budget was allocated solely for tree and stump removal. In a benefit-cost analysis by McPherson (2003), removal costs ranged from 26% of total tree costs for ginkgo (mostly due to high mortality rates during establishment) to 2% for Modesto ash and sweetgum trees. The Costs of Not Planting In a 1984 article in Journal of Arboriculture, Miller and Morano presented a computerized urban forest management simulation or game designed to model changes in a street tree population over time as a result of maintenance activities. The program, entitled URFOR/SIMULATION, used actual street tree data from a city in Wisconsin, U.S., and allowed a user to select management plans to set planting, pruning, and remov- al rates (Miller and Morano 1984). The simulation ran on an annual basis for the number of years specified by the user, and the program output described the impact of management plans on the street tree popula- tion, calculated the value of the trees, and summarized management costs. The simulation also included the ability to introduce any of six random events: wind storm, ice storm, new disease, drought, budget increases, and budget cuts. Data from an example simulation presented in Miller and Morano (1984) illus- trated the impact of planting on the net value of trees in the urban forest. While a fully-stocked urban for- est was initially the most costly management scenario, over the 40-year run of the simulation, it resulted in the greatest net benefits (see Figure 7). The difference between the fully-stocked or repacement scenarios and the no-planting scenario can be interpreted as the costs (benefits forgone) of not planting trees. The URFOR/SIMULATION program was a DOS-based program. CityTrees! Lite v1.0 is an updated version that operated under Microsoſt Windows 3.1 (Miller 1997). The program has not been updated since 1996. Figure 7. ©2015 International Society of Arboriculture
November 2015
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