82 involvement of provincial ministries and municipalities. The Ca- nadian Food Inspection Agency has regulatory authority over any new species entering the country, including the development of quarantine measures. The Canadian Forest Service is the federal government’s lead in forest research with a strong capacity in forest insects and diseases. Provincial and territorial governments manage most of the forestlands in the country and therefore have a strong interest in alien species threats. Because of this the Ca- nadian Forest Service is often engaged in monitoring and survey- ing efforts. Municipalities (and homeowners) manage removal, replacement, and treatment efforts in the urban setting—often bearing the financial burden of these frontline activities. All of these stakeholders have expressed the desire for more quan- titative damage estimates to help justify mitigation activities. METHODS Study Area and Associated Data This study was carried out for Canadian urban centers that fall within the natural geographic range of native ash (Fraxinus sp.) as defined by Little (1971) (Figure 1). Urban centers were identified using a digital version of Canada’s urban areas cartographic boundary file (Statistics Canada 2007). For this coverage, an urban area is defined as having a population of at least 1,000 persons and a density of not fewer than 400 persons per square kilometer. There are 895 urban areas across Canada in this database; 641 of these fall within the native range of ash (Figure 1). The study is road based, so a digital version of the national road network was intersected with the urban areas boundary file to provide an estimate of the kilometers of road in each of these communities. A summary of the human popula- tion and road network in these communities is provided in Table 1. McKenney et al.: Cost of EAB in Canadian Municipalities Estimating Urban Ash Component in Eastern Canada For estimating EAB impacts, the primary focus of the study authors was ash trees within 10 m of urban roadways (“street trees”) as these trees would almost certainly require action (i.e., removal/replacement or treatment) if attacked. The cost for these actions would be borne by the municipality, utility com- pany, or property owner depending on the specific location and/ or ownership of a given tree. The number of ash street trees were estimated using a variety of methods and data sources for both eastern and western Canada. Potential impacts to back- yard trees were also included as an additional focus. There are other trees in the urban setting, such as those in parks and ri- parian areas, which could also have direct financial costs if at- tacked. Reliable data on these urban forest components are difficult to find, hence, not further considered at this stage. The primary data source on ash abundance in eastern Canada is a survey that was developed to help rapidly assess the compo- sition of street trees. Data currently exists for 16 urban centers in Ontario and New Brunswick, Canada (Table 2). Briefly, the survey protocol involves participants walking or driving routes (0.5 km in length) randomly located throughout an urban center. Trees within 10 m of the road edge are identified and placed in coarse height classes (small = 1.5 to 5.0 m; medium = 5.0 to 10.0 m; large = >10 m). In total, the routes covered approximately 10% of the total length of roads in each urban center. While de- veloping the survey, this level of coverage yielded reasonably ac- curate estimates of percent cover for major street tree species. From this data, the total number of trees per km of road was calculated, the percentage of those trees that were ash, and the percentage of ash in each size class (Table 2). The survey was web-based and random survey routes were generated for all 895 urban areas in Canada (contact the authors for further details). Surveys are ongoing that will enable further refinements to the re- sults presented here and support other alien species risk analyses. These tree survey data were augmented with information Figure 1. Geographical range of Fraxinus spp. (shaded) and lo- cations of urban centers (dots) in Canada; urban centers falling within the shaded area were included in the current study. from existing tree inventories for Canadian urban centers, for example, information for three cities in eastern Canada (Table 2) from the Urban Forest Effects model (Nowak et al. 2010). This program was designed to collect forest composition data from urban areas in the U.S., but has been applied to several Canadian communities as well. Information for the city of St. Johns, Newfoundland, Canada (Table 2) (Environmental De- sign and Management, Ltd. 2006) was also obtained. All of these surveys were carried out to estimate tree species composi- tion for the entire urban landscape. For this analysis it was as- sumed that the relative composition values were representative of trees within 10 m of city streets (i.e., definition of street trees). A final source of information came from high resolution sat- ellite imagery available through Google Maps. It was not pos- sible to identify trees to the species level with this approach, but it was possible to count the total number of trees within 10 Table 1. The number of urban areas, the human population, road length, and estimated number of street ash found within the Canadian range of Fraxinus spp. Region Eastern Canada Western Canada Total Urban areas (N) 545 96 641 Human population 17,282,389 1,510,706 18,793,095 ©2012 International Society of Arboriculture Road length (km) 86,477 11,074 97,552 Small 138,363 96,348 234,711 Estimated number of ash trees Medium 216,193 Large 223,704 439,897 190,250 364,350 554,599 Total 544,806 684,401 1,229,207
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