Arboriculture & Urban Forestry 38(3): May 2012 87 Table 5. Estimated economic impacts (mean and standard deviation) of EAB on street trees in Canada over a 30-year time horizon. Equivalent annual values are shown in parentheses. Currency is expressed in 2010 Canadian dollars. Max. spread rate (km/year) 10 (slow) Treatment rate (% ash treated) 0 10 50 30 (medium) 0 10 50 50 (fast) 0 10 50 Discount rate (%) 0 2 4 10 0 2 4 10 0 2 4 10 0 2 4 10 0 2 4 10 0 2 4 10 0 2 4 10 0 2 4 10 0 2 4 10 Mean Eastern Canada S.D. ($, millions) 468 413 (18) 372 (22) 292 (31) 513 440 (20) 388 (22) 292 (31) 642 506 (23) 414 (24) 265 (28) 543 482 (22) 435 (25) 343 (36) 579 499 (22) 441 (25) 333 (36) 741 584 (26) 477 (28) 305 (32) 554 497 (22) 452 26) 358 (38) 602 524 (23) 465 (27) 353 (37) 778 615 (27) 503 (29) 321 (34) ($, millions) 221 195 (9) 176 (10) 138 (15) 251 216 (10) 190 (11) 143 (15) 281 220 (10) 179 (10) 114 (12) 270 240 (11) 217 (13) 170 (18) 273 235 (10) 207 (12) 156 (17) 349 273 (12) 222 (13) 140 (15) 269 241 (11) 218 (13) 173 (18) 283 246 (11) 219 (13) 167 (18) 367 290 (13) 236 (14) 151 (16) nificant input parameters. For all of Canada, the percentage of ash street trees and the number of street trees per kilometer of road were the most influential input parameters (Figure 3c). Impacts on Specific Urban Areas The 10 cities showing the greatest EAB-related impacts differed depending on the spread and discount rates (Table 6). Toronto, Ontario; Montreal, Ottawa-Gatineau, and Quebec City, Quebec; and Hamilton, Ontario, were consistently among the most heavily affected cities with losses of roughly $100 million predicted for Toronto and Montreal under each of the scenarios shown in Table 6. As noted, under the slow spread rate, no western communities were attacked within the simulation timeframe. However, under the faster spread rates, Winnipeg, Manitoba, was projected to ex- perience some of the heaviest EAB-related losses – nearly $200 million in undiscounted cashflow equivalent. Other cities in west- ern Canada, such as Brandon, Manitoba, and Regina and Moose Jaw, Saskatchewan, also make the list when costs are not discount- ed. These western communities are much smaller than some of the eastern communities that appear in Table 6, but involve comparable costs due to the considerably higher abundance of ash along urban streets. The impact of discounting is large in western communities because they are generally attacked late in the simulation period. Mean 0 0 0 0 0 0 0 0 0 0 0 250 149 (7) 89 (5) 20 (2) 235 139 (6) 83 (5) 19 (2) 173 102 (5) 61 (4) 14 (1) 467 305 (14) 202 (12) 65 (7) 455 296 (13) 196 (11) 62 (7) 399 255 (11) 166 (10) 50 (5) Western Canada S.D. ($, millions) 0 ($, millions) 0 0 0 0 0 0 0 0 0 0 0 0 43 26 (1) 16 (1) 4 (0) 41 25 (1) 15 (1) 4 (0) 32 19 (1) 12 (1) 3 (0) 77 50 (2) 34 (2) 11 (1) 83 55(2) 37 (2) 12 (1) 61 39 (2) 26 (1) 8 (1) Total Mean ($, millions) 468 413 (18) 372 (22) 292 (31) 513 440 (20) 388 (22) 292 (31) 642 506 (23) 414 (24) 265 (28) 793 630 (28) 524 (30) 363 (39) 814 638 (29) 524 (30) 352 (37) 914 686 (31) 538 (31) 318 (34) 1021 802 (36) 654 (38) 422 (45) 1058 820 (37) 661 (38) 415 (44) 1177 870 (39) 669 (39) 371 (39) DISCUSSION It was estimated that, over a 30-year time horizon, the discount- ed financial costs of EAB on urban street trees in Canada may range from about $0.3 to $0.9 billion; when backyard trees are included, the range of projected impacts increases to approxi- mately $0.5 to $1.5 billion. Kovacs et al. (2010) estimated an economic impact of $10.7 billion (using a 2% discount rate) for EAB in urban areas of 25 eastern U.S. states. There are a number of differences between the studies that help explain the disparity in the magnitude of these estimates. The population base cov- ered by the Kovacs et al. (2010) study is about 8× that of the current study; and since urban costs are closely related to popu- lation size, this explains much of the difference. Furthermore, Kovacs et al. (2010) estimated the economic impacts associat- ed with all ash trees in communities, as opposed to only street (and backyard) trees in the current study. When these factors are taken into consideration, the estimates are very comparable. Using a different approach, Sydnor et al. (2007) estimat- ed removal and replacement costs of $1 to $4.2 billion for the state of Ohio alone, with costs increasing to $1.8–$7.6 billion when tree-related benefits such as shading, stormwater mitiga- tion, pollution abatement, and property values were included in the calculation. In a related study, Sydnor et al. (2011) esti- mated removal and replacement costs of $5.7–$11 billion for ©2012 International Society of Arboriculture S.D. ($, millions) 221 195 (9) 176 (10) 138 (15) 251 216 (10) 190 (11) 143 (15) 281 220 (10) 179 (10) 114 (12) 277 244 (11) 219 (13) 171 (18) 283 240 (11) 210 (12) 157 (17) 353 276 (12) 223 (13) 140 (15) 294 256 (11) 228 (13) 175 (19) 312 264 (12) 230(13) 170 (18) 367 289 (13) 236 (14) 150 (16)
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