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Estimates of the Potential Cost of Emerald Ash Borer (Agrilus planipennis Fairmaire) in Canadian Municipalities

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Emerald ash borer (EAB) is an invasive phloem-feeding insect causing extensive mortality to ash (Fraxinus sp.) in North America. Economic costs associated with EAB-related mortality of street and backyard trees in Canadian urban areas were estimated over a 30-year time horizon. The approach employed a simple spread model to approximate EAB arrival times at each community based on three maximum spread rates: slow (∼10 km/year), medium (∼30 km/year), and fast (∼50 km/year). Costs are estimated for four discount rates (0%, 2%, 4%, and 10%) and three treatment rates (0%, 10%, and 50% of trees treated with an insecticide). Ash density along urban roads was estimated from a variety of sources, including a recently developed survey that allows for rapid assessment of street tree compositions. Based on the 30 km/year spread rate, a 4% discount rate, and a 10% treatment rate, the present value of the costs is estimated to be approximately CAD $524 million (2010 currency rate); this value increases to roughly $890 million when costs associated with backyard trees are included. These estimates are conservative because they focus only on damage to street (and backyard) trees; nonetheless, their magnitude suggests considerable justifcation for investments to slow the spread of EAB in Canada.
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Arboriculture & Urban Forestry 38(3): May 2012
©2012 International Society of Arboriculture
81
Daniel W. McKenney, John H. Pedlar, Denys Yemshanov, D. Barry Lyons, Kathy L. Campbell,
and Kevin Lawrence
Estimates of the Potential Cost of Emerald Ash Borer (Agrilus
planipennis Fairmaire) in Canadian Municipalities
Arboriculture & Urban Forestry 2012. 38(3): 81–91
Abstract. Emerald ash borer (EAB) is an invasive phloem-feeding insect causing extensive mortality to ash (Fraxinus sp.) in North America. Eco-
nomic costs associated with EAB-related mortality of street and backyard trees in Canadian urban areas were estimated over a 30-year time horizon.
The approach employed a simple spread model to approximate EAB arrival times at each community based on three maximum spread rates: slow
(~10 km/year), medium (~30 km/year), and fast (~50 km/year). Costs are estimated for four discount rates (0%, 2%, 4%, and 10%) and three treat-
ment rates (0%, 10%, and 50% of trees treated with an insecticide). Ash density along urban roads was estimated from a variety of sources, including
a recently developed survey that allows for rapid assessment of street tree compositions. Based on the 30 km/year spread rate, a 4% discount rate, and
a 10% treatment rate, the present value of the costs is estimated to be approximately CAD $524 million (2010 currency rate); this value increases to
roughly $890 million when costs associated with backyard trees are included. These estimates are conservative because they focus only on damage
to street (and backyard) trees; nonetheless, their magnitude suggests considerable justification for investments to slow the spread of EAB in Canada.
Key Words. Agrilus planipennis; Canada; Cost-benefit Analysis; EAB Spread Model; Fraxinus; Urban Forest Management.
Emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Bu-
prestidae), is a metallic wood-boring beetle, native to Asia, that
has destroyed millions of ash trees since being accidentally in-
troduced to North America (Smith et al. 2009). During its larval
stage, EAB feeds on the inner phloem and outer xylem of ash
trees, leading to disrupted vascular flow and ultimately tree death
(Cappaert et al. 2005). Once EAB becomes established in an area,
about 30% of ash trees are killed each year (Herms et al. 2009a);
very few host trees have shown any natural resistance, though
blue ash (Fraxinus quadrangulata Michx.) and Asian ash spe-
cies may be less susceptible (Anulewicz et al. 2007; Rebek et al.
2008). A number of insecticides have proven effective in protect-
ing trees against EAB attack (Herms et al. 2009b; McKenzie et al.
2010); however, they are not likely to be widely applied because
of considerations around cost, efficacy, and safety. Furthermore,
EAB infestations are often difficult to detect until host trees show
obvious signs of stress (McCullough et al. 2009), at which point
it may be too late to reverse the damage (Herms et al. 2009b).
Since being introduced into southern Michigan in the early
1990s (Cappaert et al. 2005), EAB has spread rapidly across east-
ern and central North America, with outbreaks currently reported
from 15 U.S. states and two Canadian provinces (USDA-APHIS
2011). Though a small percentage of mated females are capable
of flying more than 20 km in 24 hours (Taylor et al. 2010), most
larvae that originate from point source introductions are found
within 100 m of adult emergence sites (Mercader et al. 2009).
Thus, human-assisted dispersal via transport of infested ash
material (Cappaert et al. 2005) and/or hitchhiking on vehicles
(Buck and Marshall 2008) is likely the main cause of the ob-
served EAB expansion (Prasad et al. 2010). Over time, EAB is
expected to continue its advance across Canada and the United
States, decimating ash in urban and rural settings along the way.
Given its rapid rate of spread and the prevalence of ash in
both natural and urban forests across much of eastern and cen-
tral North America (Burns and Honkala 1990; Woodall et al.
2009), EAB clearly has the potential to bring about significant
economic and ecological impacts. Several studies have produced
regional economic impact estimates in the U.S. (Kovacs et al.
2010; Sydnor et al. 2007; Sydnor et al. 2011). The objective
of the current study was to report on efforts to generate EAB-
related cost estimates for Canadian urban areas. The approach
employs a relatively simple spread model to coarsely simulate
EAB expansion to Canadian communities over a 30-year period.
For each community in the study area, costs related to ash
removal, replacement, and treatment are estimated and then
discounted according to the timelines projected by the spread
model. The lack of spatial data on ash distribution and abun-
dance in Canada presents a significant challenge for this type
of study. A variety of sources were used to estimate ash abun-
dance along urban streets, including early results from a sur-
vey that allows rapid assessments of street tree composition.
This research focused on street trees because they can be reli-
ably and rapidly surveyed and are almost certain to require
management action (i.e., removal/replacement or treatment)
if attacked. This is an underestimation of total EAB impact.
Regulatory efforts to prevent the introduction of alien species
to Canada and associated research are federal responsibilities,
while long term management of established pests requires strong
McKenney et al.: Cost of EAB in Canadian Municipalities
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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.
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
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
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.
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 Urban Human Road Estimated number of ash trees
areas (N) population length (km) Small Medium Large Total
Eastern Canada 545 17,282,389 86,477 138,363 216,193 190,250 544,806
Western Canada 96 1,510,706 11,074 96,348 223,704 364,350 684,401
Total 641 18,793,095 97,552 234,711 439,897 554,599 1,229,207
Arboriculture & Urban Forestry 38(3): May 2012
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83
m of city streets. This was done for a total of 150 randomly lo-
cated 0.5-km street segments across six Ontario cities (Table 2).
During this process, several other pieces of information were
gathered. First, to estimate impacts in residential backyards,
the number of trees in backyards were counted along the same
150 random street segments used to count street trees (Table
2). In cases where houses backed onto woodlots, making prop-
erty lines difficult to distinguish, only trees within 10 m of the
woodlot edge were counted, as these would have a higher likeli-
hood of being treated or removed in the case of an EAB attack.
The ratio of street trees to backyard trees was 1:1, suggesting
that street tree costs could be doubled to include the backyard
component. However, not all streets are fronted by dwell-
ings with backyards (i.e., some are fronted by parks, industrial
parks), thus the percentage of urban roads fronted by residen-
tial dwellings at the same 150 road segments was also estimated.
Based on these estimates, backyard tree impacts are expected
to be about 68% of those associated with street trees (Table 2).
Estimating Urban Ash Component in Western
Canada
Different data sources were available for provinces in western
Canada (e.g., Manitoba, Saskatchewan, and Alberta). The For-
estry Branch of Manitoba Conservation provided a GIS database
of an ash inventory that had been carried out for 16 urban cen-
ters in Manitoba. To make these data comparable to the street
tree data for eastern Canada, the study authors selected only trees
within a 10 m buffer of the road system in each community. Each
tree in the database had a height attribute, and so were classi-
fied into the same height classes as those outlined for eastern
Canada. The number of street ash per kilometer of road was cal-
culated for each of the 16 communities by summing the number
of street trees in each size class and then dividing each total by
the length of the urban road system in that community (Table 3).
Due to a lack of comparable data from other western provinces,
these values were applied to Saskatchewan and Alberta as well.
There were notable differences in the relative abundance of
ash in eastern and western Canada. In western Canada, there was
an average of 8.7, 20.2, and 32.9 street ash/km in the small, me-
dium, and large size classes, respectively (Table 3); comparable
numbers for eastern Canada were 1.6, 2.5, and 2.2 street ash/km
(calculated from Table 2). This approximately 8× higher inci-
Table 2. Street tree parameters used to estimate impact of EAB in eastern Canada.
City Provincez Data Trees/km % Ash % Ash % Ash % Ash Ratio of %
sourcey road <5 m 5–10 m >10 m backyard to house
tall tall tall front yard trees frontage
Bathurst NB S 84.4 4.0 0 100 0 - -
Barrie ON G 100.4 - - - - 0.95 60.3
Bracebridge ON S 185.7 0.0 - - - - -
Chatham ON S, G 115.9 - - - - 0.75 62.7
Fredericton NB S 123.0 0.0 - - - - -
Guelph ON S, G 112.7 6.3 8.1 16.2 75.7 1.21 82.7
Halifax NS P - 0.4 - - -
Huntsville ON S 164.4 1.5 0 0 100 - -
Kitchener ON G 95.7 - - - - 0.98 74.1
London ON S 97.1 3.3 - - -
Meaford ON S 120.8 8.2 12.5 25.0 62.5
Moncton NB S 72.1 0.1 - - - - -
Oakville ON P - 9.2 - - -
Ottawa - Gatineau ON G 115.5 - - - - 1.05 68.6
Oromocto NB S 149.3 0.4 - - - - -
Owen Sound ON S 106.2 6.7 23.1 46.2 30.8
Parry Sound ON S 50.5 19.8 35 25 40 - -
Sault Ste Marie ON S 91.4 2.2 5.9 28.2 65.9
St. Johns NFLD P - 7.8 - - -
South Porcupine ON S - 1.7 0 36.3 63.6
Sudbury ON S 59.0 4.9 - - -
Thunder Bay ON G 76.8 - - - - 1.08 54.4
Timmins ON S 124.0 0.4 - - - - -
Toronto ON P - 7.8 - - -
Averagex 107.6 6.0 10.4 34.6 54.8 1.0 67.5
z NB = New Brunswick; ON = Ontario; NS = Nova Scotia; NFLD = Newfoundland.
y S = street tree survey; G = Google Maps; P = published values. See text for complete details.
x Average is weighted by population size of urban areas.
Table 3. Number of small, medium, and large ash trees per
kilometer of urban road for 16 communities in western Canada.
Urban area Province Ash trees per km of urban road
<5 m tall 5–10 m tall >10 m tall
Manitou Manitoba 0.1 36.3 38.0
Treherne Manitoba 11.1 31.2 46.6
Altona Manitoba 10.6 35.6 51.2
Beausejour Manitoba 6.3 8.7 16.1
Carberry Manitoba 6.7 22.3 36.5
Carman Manitoba 21.6 19.3 49.2
Dauphin Manitoba 2.6 13.6 18.4
Deloraine Manitoba 26.4 30.7 66.8
Rivers Manitoba 8.8 4.2 16.6
Selkirk Manitoba 3.9 10.0 15.1
Souris Manitoba 11.5 27.7 44.7
Steinbach Manitoba 9.5 24.3 39.8
Stonewall Manitoba 7.6 7.7 16.3
Virden Manitoba 9.0 11.2 23.0
Winkler Manitoba 23.0 48.7 79.6
Portage La Prairie Manitoba 2.8 13.6 19.0
Averagez 8.7 20.2 32.9
z Average is weighted by population size of urban areas.
McKenney et al.: Cost of EAB in Canadian Municipalities
©2012 International Society of Arboriculture
84
dence of ash in western Canada was supported by two sources:
1) Google Maps counts of street trees at 16 random locations
in four Manitoba communities indicated that there were about
twice as many street trees in Manitoba than Ontario, and 2) street
tree composition data for the city of Saskatoon, Saskatchewan
(Geoff McLeod, pers. obs.) indicated that about 25% of street
trees were ash, approximately 4× that of eastern Canada. This
pattern is perhaps not surprising given the more limited num-
ber of tree species that can tolerate the somewhat more extreme
climate found in the prairies region (McKenney et al. 2007).
Predicting EAB Spread
The Canadian Forest Service Forest Bioeconomic Model (CFS-
FBM) was used as the basic modeling framework for projecting
EAB spread over time. The model shares conceptual similarities
with the spread model described by Yemshanov et al. (2009a),
Yemshanov et al. (2009b), and Koch et al. (2009). Briefly, CFS-
FBM provides a grid-based modeling framework for simulating
a variety of processes in a spatial setting, including the spread,
establishment, and impact of alien species. For example, the
model has been used to examine potential wood supply im-
pacts from Sirex noctilio, an invasive alien wasp species (Koch
et al. 2009; Yemshanov et al. 2009a; Yemshanov et al. 2009b).
A simplified version of CFS-FBM was used to obtain a
coarse depiction of how EAB might spread across the country.
The approach required a spread probability-density function,
or ‘kernel,’ which determined the probability of EAB spread as
a function of the geographic distance to locations with known
EAB infestations. Published EAB spread rates vary by more
than two orders of magnitude, reflecting the highly variable
spread of EAB under different conditions. The smallest report-
ed value (30 m/yr) was for a new infestation starting from a
single source (a pile of infested logs) with many ash trees in
the near vicinity (Mercader et al. 2009). In contrast, Kovacs et
al. (2010) reported an average spread rate of 16 km/yr based
on spread data in Michigan, U.S., over the period 1994–2009.
Similarly, Smitley et al. (2008) reported a rate of 10.6 km/yr
for the spread rate of detectable symptoms for an outbreak
in southeastern Michigan over the period 2003–2006. These
larger estimates are based on data that include natural long
distance dispersal events that may be induced by high popula-
tion density and/or low host availability, as well as regional-
scale, human-assisted movements (such as trade and trans-
portation). Based on comparison to observed rates of spread
in southern Ontario, the spread rate reported by Smitley et al.
(2008) was adopted as a baseline value for the current study.
The spread model simulations covered an area extend-
ing from maritime Canada in the east to Alberta in west-
ern Canada with a map cell resolution of ~1 km2. The
model employed a negative exponential function to deter-
mine the probability, p that a cell would become infested as
a function of its distance, d from the nearest infested cell:
[1] p = e-0.0943d
The value of the exponent in Equation 1 (i.e., 0.0934) was
determined such that the mean distance defined by the equation
is 10.6 km (i.e., the desired average spread rate as previously
outlined). To address the wide variation in potential spread rate,
the model was run with three different maximum spread values
to represent slow, medium, and fast linear rates of spread cor-
responding to approximately 10, 30, and 50 km/year. The maxi-
mum spread value truncates the negative exponential probabili-
ty-density function, thus placing an upper limit on the extent of
annual spread – a key factor controlling overall spread rates and
patterns (Koch et al. 2009; Yemshanov et al. 2009a; Yemshanov
et al. 2009b). This approach produced a uniform spread pattern
that predicted consistent arrival times that were not influenced
by rare (and highly uncertain) long-distance dispersal events.
The model was run over a 30-year time horizon to generate
expected arrival times for EAB at each map cell in the study area.
The model was initiated from known Canadian and U.S. EAB
occurrence locations as of 2009 (USDA-APHIS 2011). An im-
plicit assumption was that any cell that fell within the study area
contained at least some ash that could be a host (and hence path-
way) for colonization. This assumption was necessary because,
as previously noted, detailed spatial data of ash abundance were
not available in Canada; furthermore, ash is considered relatively
common throughout its native Canadian range (Farrar 1995).
Unit Cost Estimates for EAB Damage
Four types of costs were explicitly incorporated into this
study: removal costs, replacement costs, treatment costs,
and what were termed as community overhead costs (Ta-
ble 4). All cost estimates are in year 2010 Canadian dol-
lars and based on a combination of published values from the
United States. (Kovacs et al. 2010) and personal communi-
cations with City Foresters in Windsor, Toronto, Oakville,
London, Ottawa, and Thunder Bay, Ontario; and Saskatoon.
It was assumed that all ash street trees, as defined in this
study, required either removal or treatment. Removal costs
vary widely according to tree size (height and diameter), lo-
cation (e.g., proximity to buildings, and power and telephone
lines), and contractor rate; the cost estimates attempted to de-
scribe an average cost for small, medium, and large trees (Ta-
ble 4). Replacement costs are also highly variable and depend
on the size and source of the planting stock; the estimate of
CAD $400 is representative of the per tree costs incurred by
municipalities when planting well established (i.e., ~ 4 cm in
diameter) saplings. It was posited that only a certain percent-
age of removed trees would actually be replaced; in lieu of
data on this subject, a 50% replacement rate was assumed.
Insecticide treatments were incorporated into the model
as an alternative to cutting large and medium sized trees.
Three plausible treatment scenarios were considered: 1) no
treatments; 2) a modest treatment rate, where 10% of large
and medium trees were treated; and 3) a high treatment rate,
where 50% of large and medium trees were treated. Cur-
rently, the main product used in Canada for protecting trees
against EAB attack is TreeAzin (McKenzie et al. 2010).
Treated trees were tracked in a separate cost stream that re-
ceived ongoing biannual treatments for the remainder of the
simulation; cost estimates were based on reported costs as-
sociated with TreeAzin for large and medium trees (Table 4).
Community overhead costs are intended to represent consider-
ations such as staff time to manage and coordinate the response,
communication costs, monitoring and surveillance costs, and dis-
posal operations for tree waste. Based on discussions with city
Arboriculture & Urban Forestry 38(3): May 2012
©2012 International Society of Arboriculture
85
foresters, it was estimated that these costs would be approximately
$0.40/household – applied in each year that an outbreak was on-
going in a given city. The number of households in each commun-
ity was obtained from Statistics Canada (Statistics Canada 2007).
Three different positive discount rates were employed: 2%,
4%, and 10%. These rates reflect different perspectives on the
value of delaying payment for incurred costs. In addition, re-
sults are presented with no discounting (a zero discount rate),
to demonstrate the effect of discounting. Some economists
provide theoretical arguments that very low discount rates are
justifiable when significant intergenerational outcomes are at
stake; species losses could arguably be taken as one such out-
come (Weitzman 1994; Portney and Weyant 1999). For the
positive discount rates, the authors also report the cost esti-
mates in equivalent annual dollars (see Boardman et al. 2001).
Model Scenarios and Sensitivity Analysis
The model was run for 36 different combinations of spread rate
(slow, medium, and fast), treatment rate (0%, 10%, and 50%),
and discount rate (0%, 2%, 4%, and 10%). As with any model,
there was uncertainty in the input parameters; to address this, 100
Monte Carlo simulations were run for each of the 36 scenario
combinations using the @Risk software package (Pallisade Cor-
poration 2002). During each simulation, the value for each input
parameter was drawn from a user-defined distribution of possible
values. Since there were multiple estimates of the tree composi-
tion parameters for eastern and western Canada, a Gaussian dis-
tribution for each parameter was defined using mean and standard
deviation values calculated from the data (Table 4). Due to the rel-
atively small amount of empirical data behind the remaining input
parameters, they were assigned a triangular distribution for the
Monte Carlo simulations. This distribution requires knowledge of
mean, min, and max values, and assumes only a simple triangular
shape. Plots of cumulative mean cost against simulation number
indicated that 100 replications were adequate for this analysis.
The influence of each input parameter listed in Table 4 on
regional and total EAB economic impact was estimated us-
ing a regression approach (Pallisade Corporation 2002). For
this analysis, each iteration of the simulation produced an ob-
servation for a multiple regression model with cost as the de-
pendent variable and the input parameters as the independent
variables. The standardized slope coefficient associated with
each input parameter was taken as its measure of influence.
RESULTS
Overall Economic Impact
Approximately 545,000 and 684,000 ash street trees were esti-
mated in eastern and western Canada, respectively, for a total of
~1.2 million ash street trees across the 641 communities included
in the study area (Table 1). Estimated impacts for the 30-year time
horizon ranged from $265 million to $1,177 million depending
on the combination of spread, treatment, and discount rates (Ta-
ble 5). The low estimate resulted from the slow spread rate, 10%
discount rate, and 50% treatment rate; the high estimate resulted
from the fast spread rate, 0% discount rate and 50% treatment
rate. Figure 2 shows cost accumulation through time for selected
spread and treatment rates. These estimates are for street trees
only; the inclusion of expenses associated with backyard trees
can be roughly estimated by multiplying the values in Table 5 by
a factor of 1.7, bringing the range to $451 million to $2,001 mil-
lion. Total costs associated with a "middle-of-the-road" scenario
(i.e., medium spread rate, 10% treatment rate, and 4% discount
rate) were $524 million; this would increase to roughly $890.8
million if expenses related to backyard trees were included.
As would be expected, faster spread rates were associated
with higher economic impacts (Table 5). For example, total street
tree costs ranged from $265 million to $506 million (at posi-
tive discount rates) for the slow spread rate compared, to $371
million to $820 million for the fast spread rate (Table 5). These
Table 4. Model parameters and probability distributions used in the sensitivity analysis of EAB economic impacts. Currency is
expressed in 2010 Canadian dollars.
Parameter name Region Distribution Distribution
type parameters
Total trees/km Eastern Gaussian Mean = 108; S.D. = 30
% Ash Eastern Gaussian Mean = 0.06; S.D. = 0.04
% Ash - small Eastern Gaussian Mean = 0.1; S.D. = 0.1
% Ash - medium Eastern Gaussian Mean = 0.35; S.D. = 0.3
% Ash - large Eastern Gaussian Mean = 0.6; S.D. = 0.3
Small ash/km Western Gaussian Mean = 9; S.D. = 7
Medium ash/km Western Gaussian Mean = 20; S.D. = 12
Large ash/km Western Gaussian Mean = 33; S.D. = 19
Removal - small ($) Canada Triangular Mean = 150; Min = 50; Max = 250
Removal - medium ($) Canada Triangular Mean = 500; Min = 300; Max = 700
Removal - large ($) Canada Triangular Mean = 1000; Min = 700; Max = 1300
Replacement ($) Canada Triangular Mean = 400; Min = 250; Max = 550
Replacement rate (%) Canada Triangular Mean = 0.5; Min = 0.2; Max = 0.8
Treatment - large ($) Canada Triangular Mean = 165; Min = 115; Max = 215
Treatment - medium ($) Canada Triangular Mean = 110; Min = 60; Max = 160
Community cost ($ per Canada Triangular Mean = 0.4; Min = 0.2; Max = 0.6
household)
Detection lag (years) Canada Discrete Uniform (2,3,4)
uniform
McKenney et al.: Cost of EAB in Canadian Municipalities
©2012 International Society of Arboriculture
86
differences stemmed from the number of communities attacked
over the 30-year time horizon under the fast (634 communities
attacked) and slow (386 communities attacked) spread scenarios.
In fact, based on the slow spread rate, the infestation had not
reached western Canada by the end of the simulation period
(Table 5). This is evident in Figure 2, where there is an obvi-
ous rise in costs mid-to-late in the simulation under the me-
dium and fast spread rates due to the arrival of EAB at cities
in western Canada (particularly Winnipeg, Manitoba); a simi-
lar pattern does not appear under the slow dispersal rate. This
result is largely driven by the high ash abundance in western
communities. There is, of course, an inverse relationship be-
tween the present value of the cost estimates and the discount
rate. For example, a 2% discount rate resulted in costs rang-
ing from $413 million to $870 million, while a 10% discount
rate produced costs ranging from $265 million to $422 mil-
lion (Table 5). Higher discount rates effectively reduce the
present value of future costs. The influence of discount rate
was also apparent in Figure 2 where the low discount rate
was associated with higher costs, particularly under the fast
spread rate and 50% treatment rate; conversely, the high dis-
count rate resulted in considerably lower costs and relatively
little difference in cost projections between scenarios. Note
however that the equivalent annual cost estimates in Table 5
increase as the discount rate increases. While this may seem
counterintuitive, it is a standard result because present val-
ues of annuities decrease as interest rates increase and in-
crease when interest rates decline (see Boardman et al. 2001).
As might be expected, increased treatment rates had higher
overall costs for the 0%, 2%, and 4% discount rates; however,
this pattern was reversed under the 10% discount rate (Table 5).
This result is particularly sensitive to the time horizon of the
simulation and the spatiotemporal pattern of the spread. Many
large urban centers in eastern Canada (e.g., Toronto, Ontario;
Montreal, Quebec) were attacked very early in the simulation,
thus a large pool of trees accumulated substantial treatment costs
by the end of the 30-year period. Since treatment costs are ac-
cumulated through time, they are also strongly influenced by
the discount rate. For example, under a medium spread rate and
0% discount rate, treating 50% of trees resulted in a total cost of
$914 million; for the same spread and treatment rates, this value
dropped to $318 million under a 10% discount rate (Table 5).
Sensitivity Analysis
Table 5 also presents standard deviations of the cost distribu-
tions for each scenario based on the Monte Carlo simulations.
Standard deviation values were generally within 40% of the
mean, indicating that the impact estimates are relatively robust
to plausible changes in the input parameter values. In eastern
Canada, estimated costs were strongly affected by the proportion
of ash and the number of trees per unit of road length (Figure
3a). Costs associated with removal, replacement, and treatment
of large and/or medium trees made up most of the remaining sig-
nificant input parameters. Detection lag had a relatively minor,
negative impact on cost estimates in eastern Canada. Higher lag
values meant that EAB attacks were detected later, resulting in
lower discounted costs or, for grid cells attacked very late in the
simulation, costs being pushed outside the 30-year time horizon.
In western Canada, the most influential parameter on final
cost estimates was the number of large trees/km (Figure 3b).
Detection lag had a much stronger influence in the west; since
many western communities were attacked very late in the simu-
lation, any increase in the detection lag resulted in a significant
number of grid cells being excluded from the 30-year analysis.
Costs associated with removal, replacement, and treatment of
large and/or medium trees made up most of the remaining sig-
Figure 2. Mean economic impact of EAB over time, based on
three scenarios: a) slow spread rate and 0% of ash trees treated,
b) medium spread rate and 10% of ash trees treated, and c) fast
spread rate and 50% of ash trees treated.
Arboriculture & Urban Forestry 38(3): May 2012
©2012 International Society of Arboriculture
87
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.
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–$11 billion for
Table 5. Estimated economic impacts (mean and standard deviation) of EAB on street trees in Canada over a 30-year time
horizon. Equivalent annual values are shown in parentheses. Currency is expressed in 2010 Canadian dollars.
Max. spread rate Treatment rate Discount Eastern Canada Western Canada Total
(km/year) (% ash treated) rate (%) Mean S.D. Mean S.D. Mean S.D.
($, millions) ($, millions) ($, millions) ($, millions) ($, millions) ($, millions)
10 (slow) 0 0 468 221 0 0 468 221
2 413 (18) 195 (9) 0 0 413 (18) 195 (9)
4 372 (22) 176 (10) 0 0 372 (22) 176 (10)
10 292 (31) 138 (15) 0 0 292 (31) 138 (15)
10 0 513 251 0 0 513 251
2 440 (20) 216 (10) 0 0 440 (20) 216 (10)
4 388 (22) 190 (11) 0 0 388 (22) 190 (11)
10 292 (31) 143 (15) 0 0 292 (31) 143 (15)
50 0 642 281 0 0 642 281
2 506 (23) 220 (10) 0 0 506 (23) 220 (10)
4 414 (24) 179 (10) 0 0 414 (24) 179 (10)
10 265 (28) 114 (12) 0 0 265 (28) 114 (12)
30 (medium) 0 0 543 270 250 43 793 277
2 482 (22) 240 (11) 149 (7) 26 (1) 630 (28) 244 (11)
4 435 (25) 217 (13) 89 (5) 16 (1) 524 (30) 219 (13)
10 343 (36) 170 (18) 20 (2) 4 (0) 363 (39) 171 (18)
10 0 579 273 235 41 814 283
2 499 (22) 235 (10) 139 (6) 25 (1) 638 (29) 240 (11)
4 441 (25) 207 (12) 83 (5) 15 (1) 524 (30) 210 (12)
10 333 (36) 156 (17) 19 (2) 4 (0) 352 (37) 157 (17)
50 0 741 349 173 32 914 353
2 584 (26) 273 (12) 102 (5) 19 (1) 686 (31) 276 (12)
4 477 (28) 222 (13) 61 (4) 12 (1) 538 (31) 223 (13)
10 305 (32) 140 (15) 14 (1) 3 (0) 318 (34) 140 (15)
50 (fast) 0 0 554 269 467 77 1021 294
2 497 (22) 241 (11) 305 (14) 50 (2) 802 (36) 256 (11)
4 452 26) 218 (13) 202 (12) 34 (2) 654 (38) 228 (13)
10 358 (38) 173 (18) 65 (7) 11 (1) 422 (45) 175 (19)
10 0 602 283 455 83 1058 312
2 524 (23) 246 (11) 296 (13) 55(2) 820 (37) 264 (12)
4 465 (27) 219 (13) 196 (11) 37 (2) 661 (38) 230(13)
10 353 (37) 167 (18) 62 (7) 12 (1) 415 (44) 170 (18)
50 0 778 367 399 61 1177 367
2 615 (27) 290 (13) 255 (11) 39 (2) 870 (39) 289 (13)
4 503 (29) 236 (14) 166 (10) 26 (1) 669 (39) 236 (14)
10 321 (34) 151 (16) 50 (5) 8 (1) 371 (39) 150 (16)
McKenney et al.: Cost of EAB in Canadian Municipalities
©2012 International Society of Arboriculture
88
communities in four midwestern states, with costs increasing to
$13.4–$26 billion when the extended benefits were considered.
Even after accounting for population size differences, their re-
moval and replacement estimates are about three times higher than
those reported here. Again, this is partly explained by the inclusion
of all street, private, and park trees in their estimates. Another ma-
jor difference is that Sydnor et al. (2007; 2011) did not incorporate
spread dynamics, and hence economic discounting considerations,
into their estimates. As demonstrated here, discounting can have
a major impact on cost estimates. This variation demonstrates the
wide range in projected costs that can result from (sometimes subtle)
methodological differences between impact studies and underlines
the importance of exploring multiple approaches to such work.
The estimates provided here are conservative in a number of
ways, focusing on direct financial costs associated with street (and
backyard) tree management. While this represents an important and
more readily quantifiable portion of EAB impacts, there are a number
of other direct financial considerations that warrant mention. These
estimates do not include costs related to trees in parks and urban
woodlands. Though the number of ash in these land use categories
can be substantial (Nowak et al. 2010), there is significant difficulty
finding reliable estimates of ash density for them. Furthermore, it
is not clear what percentage of ash trees in the park\woodland set-
ting would pose safety risks and thus require management action.
These estimates also ignore costs associated with ash trees in smaller
towns and rural residential settings—again, due to data availability.
Finally, it should be recognized that ash trees do exist in urban cen-
ters outside the native range of ash, which could significantly add
to the cost of EAB in Canada [e.g., 5.3% of municipal trees in Van-
couver, British Columbia, are ash (McManus, pers. comm.)]. How-
ever, pathways and spread rates into these areas are highly uncertain.
Many other benefits have been attributed to urban trees, including
home value premiums, energy savings, pollution and runoff reduc-
tion, and human health benefits (Dwyer et al. 1992). These benefits
have been quantified for various locations, allowing approximate
economic values to be attached to urban trees (e.g., McPherson et
al. 2007). Including the loss of these benefits would clearly increase
the economic impact attributed to EAB. In fact, EAB cost estimates
provided by Sydnor et al. (2007) and Sydnor et al. (2011) approxi-
mately doubled when these “landscape values” were included in
their calculations. These benefits were not incorporated here because
widely accepted values do not exist for Canada and published values
are situation dependent (McPherson et al. 2007). Nevertheless, the
incorporation of such values could be the subject of future efforts.
Losses in timber sales would also be expected as a result of an
EAB invasion (Schwan and Elliott 2010). However, detailed spatial
data on ash volumes are not available for much of Canada, making
it very challenging to estimate potential harvest losses in the natural
forest setting. Ash also plays an important ecological role in many
southern Canadian ecosystems. For instance, ash is a common ripari-
an species and its loss will likely effect water quality for both wildlife
and humans (Kreutzweiser 2010). Furthermore, the loss of ash could
have a major impact on biodiversity in agricultural landscapes of
southern Ontario, where it is often a key component of remnant for-
est woodlots (Schwan and Elliott 2010). While these ecosystem ser-
vices are extremely challenging to include in an economic analysis,
they are mentioned here to emphasize the extent to which this assess-
ment underestimates the full impact of this invasive alien species.
For the three lower discount rates, costs increased as treatment
rate increased; this pattern was reversed at the 10% discount rate.
This finding suggests, for example, municipalities/homeowners
that have high borrowing costs should consider treating a portion
of their trees because this results in a series of smaller, delayed
payments compared to large scale removal and replacement ef-
forts (McKenney and Pedlar 2012). Even at lower discount rates,
the opportunity to spread removal costs over time through the use
of treatments may be appealing to some municipalities. These re-
sults provide a simple approximation of how overall costs may
vary under different treatment rates. However, it is important to
note that decisions to treat versus remove trees can be complex
and involve not only relatively straightforward considerations such
as treatment, removal, and replacement costs, but also more subtle
factors like the influence of tree cover on property values, energy
budgets, and pollution control. Recent studies have examined this
topic from the perspective of both individual homeowners (McK-
enney and Pedlar 2012) and municipalities (Sadof et al. 2011).
Additionally, these results may be roughly interpreted to sup-
port slow-the-spread efforts against EAB. If the medium or fast
spread rate models are deemed to be more indicative of likely
outcomes, then the cost differences between the slow versus me-
Figure 3. Sensitivity of EAB economic impact estimates to model
parameter values for: a) eastern Canada, b) western Canada, and
c) the entire study area. The sensitivity coefcients were gener-
ated using a regression approach; larger values indicate more
inuence on the impact estimates.
Arboriculture & Urban Forestry 38(3): May 2012
©2012 International Society of Arboriculture
89
dium and fast spread models are suggestive of potential benefits
for slowing the spread of EAB. The difference in annual costs
between the slow and medium spread rate models are between
$6 million/year and $10 million/year (derived from the differ-
ences in the annuity values shown in Table 5). Cost differences
are of course higher for the slow versus fast rate models ($11–
$18 million/year). Notably in slow rate models, western Canada
has not been affected in the 30-year simulation period. Clearly
the arbitrary cut-off of a 30-year time horizon does affect these
results but with higher discount rates (e.g., 10%), this effect is
lessened simply because of the strong effect of discounting over
that length of time. At the 10% discount rate, the differences
between the fast and slow spread rate models range from about
$11 to $14 million/year ($3 to $7 million/year for the medium
versus slow spread rate). Annual expenditures up to these lev-
els to slow the spread of EAB would be justified on economic
efficiency grounds if indeed they were judged to be effective.
CONCLUSION
EAB-related street tree damage was estimated in the study area
over a 30-year time horizon to range from $265 million to $1,177
million depending on the combination of spread, treatment, and
discount rates (~$451 million to $2,001 million with backyard
trees included). Based on a medium spread rate, 10% treatment
rate, and 4% discount rate, estimated costs were $524 million;
this value increased to $891 million when costs were extended
to include backyard trees. Cast in equivalent annual values,
these estimates range from $18 million/year (2% discount rate,
Table 6. Canadian cities projected to show the greatest economic impact from EAB invasion over the next 30 years; ten cities
are listed for each of three spread rates and two discount rates. Currency is expressed in Canadian dollars.
Max. spread rate 0% Discount rate 4% Discount rate
(km/year) City Impact City Impact
($, millions) ($, millions)
10 (slow) Toronto 96 Toronto 85
Montréal 95 Montréal 76
Ottawa - Gatineau 27 Ottawa - Gatineau 24
Québec 23 Hamilton 18
Hamilton 20 St. Catherines - Niagara 13
St. Catherines - Niagara 15 Kitchener 9
Kitchener 13 Windsor 9
Windsor 10 London 9
London 10 Québec 8
Oshawa 8 Oshawa 7
30 (medium) Winnipeg 161 Toronto 85
Toronto 97 Montréal 78
Montréal 93 Winnipeg 58
Ottawa - Gatineau 27 Ottawa - Gatineau 24
Québec 25 Hamilton 18
Hamilton 20 Québec 15
Brandon 16 St. Catherines - Niagara 13
St. Catherines - Niagara 15 Kitchener 10
Kitchener 13 Windsor 9
Windsor 10 London 9
50 (fast) Winnipeg 172 Toronto 85
Toronto 96 Winnipeg 84
Montréal 92 Montréal 78
Regina 53 Ottawa - Gatineau 24
Ottawa - Gatineau 27 Regina 19
Québec 25 Hamilton 18
Moose Jaw 23 Québec 17
Brandon 22 St. Catherines - Niagara 13
Hamilton 20 Brandon 10
St. Catherines - Niagara 15 Kitchener 10
slow spread, and no treatments) to $45 million/year (10% dis-
count rate, fast spread, and no treatments). Including backyard
trees would increase these annual equivalents to ~$31 million
and $77 million per year. Though conservative, these estimates
are comparable to a similar study carried out in the U.S. (Ko-
vacs et al. 2010), once differences in population size and study
scope are taken into account. Community-specific cost esti-
mates can be obtained by contacting the corresponding author.
These findings can provide some justification for slow-the-
spread initiatives, such as early detection surveys and wood
movement laws. However, the net value of a slow-the-spread
program depends on two major considerations: 1) the ex-
tent to which it delays EAB arrival at a given urban centre,
and 2) the perceived time value of expenditures as influenced
by the discount rate. Nevertheless, even just the simple no-
tion of preserving ash in communities for future generations
may be an important consideration for some decisionmak-
ers, especially if EAB proves to be as devastating as some be-
lieve. Given the magnitude of the damage estimates provided
here, there is also considerable economic justification for on-
going research efforts to better understand and manage EAB.
Acknowledgements. We thank: Irene Pines, Robert McMahon, and oth-
ers at Manitoba Conservation for generously sharing their ash survey data;
the Ontario Stewardship Rangers and all other volunteers who have helped
to collect street tree data in eastern Canada; and Geoff McLeod, Bill Roe-
sel, Jason Pollard, John McNeil, and Richard Ubbens for feedback on tree
removal and replacement costs. We also thank two anonymous reviewers
for their comments. Any errors remain the responsibility of the authors.
McKenney et al.: Cost of EAB in Canadian Municipalities
©2012 International Society of Arboriculture
90
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Dan.McKenney@NRCan-RNCan.gc.ca
John H. Pedlar
Natural Resources Canada, Canadian Forest Service
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Denys Yemshanov
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D. Barry Lyons
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Kathy L. Campbell
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Sault Ste. Marie, ON, P6A 2E5, Canada
Kevin Lawrence
Natural Resources Canada, Canadian Forest Service
Great Lakes Forestry Centre
1219 Queen Street East
Sault Ste. Marie, ON, P6A 2E5, Canada
Résumé. L’agrile du frêne est un insecte perceur invasif qui cause
la mortalité à grande échelle des frênes (Fraxinus spp.) en Amérique du
Nord. La présente étude présente une estimation des coûts économiques
associés à la mortalité par l’agrile des frênes le long des rues et dans les
cours arrières privées en milieu urbain au Canada sur une période de 30 ans.
L’approche a fait appel un simple modèle de dispersion pour estimer le mo-
ment d’arrivée de l’agrile du frêne au sein de chaque ville en se basant sur
trois vitesse maximales de propagation: lente (~10 km/an), moyenne (~30
km/an) et rapide (~50 km/an). Les coûts sont estimés en fonction de quatre
taux d’escompte (0%, 2%, 4% et 10%) et trois niveaux de traitement (0%,
10% et 50% des arbres traités avec un insecticide). La densité en frêne le
long des rues urbaines a été estimée à partir de sources variées, incluant une
méthode d’évaluation récemment développée qui permet une évaluation
rapide de la composition en arbres des rues. En se basant sur une vitesse de
propagation de 30 km/an, un taux d’escompte de 4% et un taux de traite-
ment de 10%, les coûts sont estimés à environ 524 millions de dollars CAN
(en dollars de 2010); cette valeur s’accroît de manière brute d’environ 890
millions de dollars si on y ajoute les coûts associés aux arbres dans les cours
arrières privées. Ces estimations sont conservatrices parce qu’elles mettent
en évidence seulement les dommages associés aux arbres de rues (et dans
les cours arrières privées); quoiqu’il en soit, leur magnitude constitue une
justification majeure pour investir dans les moyens qui permettront de ral-
entir la progression de l’agrile du frêne au Canada.
Zusammenfassung. Der Asiatische Eschenprachtkäfer (EAB) ist ein
invasives, Phloem-schädigendes Insekt, welches zu flächendeckendem
Absterben von Eschen in Nordamerika führt. Die gegenwärtige Studie
bewertet die ökonomischen Kosten, die mit dem massenhaften Absterben
von Eschen als Strassenbäume durch den EAB in Kanadas besiedelten
Räumen über einen Zeitraum von 30 Jahren. Der Ansatz verwendet ein
einfaches Streumodel zur Abschätzung des Eintreffens des Käfers in der
jeweiligen Kommune, basierend auf drei maximalen Streuraten: langsam
(~10 km/ Jahr), mittel (~30 km/ Jahr), und schnell (~50 km/Jahr). Die
Kosten wurden für vier Abschlagsraten (0%, 2%, 4%, und 10%) und drei
Behandlungsraten (0%, 10%, und 50% der Bäume, die mit einem Insekti-
zid behandelt wurden). Die Eschendichte entlang der Strassen wurde an-
hand von verschiedenen Quellen geschätzt, einschließlich einer kürzlich
entwickelten Erhebung, die eine schnelle Erfassung der Baumartenzusam-
mensetzung erlaubt. Basierend auf der 30 km/Jahr-Ausbreitungsrate, einer
4 % Abschlagsrate und einer 10 % Behandlungsrate wird der gegenwärtige
Wert der Kosten mit schätzungsweise CAD$ 524 Millionen(Wechselkurs-
Stand 2010) angenommen. Dieser Wert steigt grob geschätzt auf $ 890
Millionen, wenn die Kosten der Bäume in den Hinterhöfen hinzuaddiert
werden. Die Schätzungen sind konservativ, weil sie nur auf den Schaden an
Strassen- (und Hinterhof-)bäumen fokussieren, nichtsdestotrotz gibt ihre
Höhe doch eine ernstzunehmenden Faktor bei der Berechnung von Inves-
titionen zur Eindämmung des Prachtkäfers in Kanada.
Resumen. El barrenador esmeralda del fresno (EAB) es un insecto
invasivo del floema que causa mortalidad extensiva del fresno (Fraxinus
sp) en Norte América. Este estudio estimó los costos económicos asocia-
dos con EAB-mortalidad relacionada de árboles de calles y patios en áreas
urbanas de Canadá en un periodo de 30 años. Esta aproximación empleó
un modelo simple de propagación para los tiempos de arribo de EAB a
cada comunidad con base en tres tasas máximas: lenta (~10 km/año), me-
dia (~30 km/año), y rápida (~50 km/año). Los costos son estimados para
cuatro tasas de descuento (0%, 2%, 4%, y 10%) y tres tasas de tratamiento
(0%, 10%, y 50%) de árboles tratados con un insecticida. Se estimó la den-
sidad del fresno a lo largo de las vías urbanas de una variedad de fuentes,
incluyendo una encuesta reciente que permite una evaluación rápida de la
composición de árboles. Con base en una tasa de propagación de 30 km/
año, una tasa de descuento del 4%, y una tasa de tratamiento del 10%, el
valor presente de los costos es estimado aproximadamente en CAD $524
millones (valores del 2010); este valor incrementa a $890 millones cuando
se incluyen los costos asociados con árboles de los patios. Estas estimacio-
nes son conservadoras debido a que se enfocan solamente al daño a árboles
de las calles (y patios); no obstante, su magnitud sugiere justificación con-
siderable de inversiones para reducir la propagación de EAB en Canadá.
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Technical Report
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Technical Report
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A model is presented to assist in deciding the fate of ash trees (Fraxinus spp.) threatened by the arrival of emerald ash borer (Agrilus planipennis Fairmaire) in North America. The model tracks ongoing treatment costs versus one-time costs associated with removal and replacement. All future values are discounted following standard economic practice. For each year over a period of interest, the net treatment gain/ loss is calculated, indicating the period of time over which a homeowner would be financially ahead/behind by treating the existing ash tree. The model was populated, with values that may be expected in Canadian conditions, where treatment options are more limited than in the United States. Optional model features include property value premiums, energy savings, runoff and pollution benefits, and ongoing maintenance costs. When these extended benefits and costs are included, positive treatment gains for a medium-sized ash persist for about 17 years. Negative values can be interpreted as a "break-even existence value," an amount a homeowner would be required to pay in order to protect their ash if various other benefit flows fail to compensate the costs. An interactive version of the model is available online (http://gmaps.nrcan.gc.ca/apm/index.php.
Article
Emerald ash borer (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae), a phloem-feeding insect native to Asia, was identified in 2002 as the cause of widespread ash (Fraxinus) mortality in southeast Michigan, U.S. and Windsor, Ontario, Canada. Little information about A. planipennis is available from its native range and it was not known whether this invasive pest would exhibit a preference for a particular North American ash species. We monitored A. planipennis density and canopy condition on green ash (F. pennsylvanica) and white ash (F. americana) street trees in four neighborhoods and on white and blue ash (F. quadrangulata) trees in two woodlots in southdast Michigan. Green ash street trees had significantly more canopy dieback and higher A. planipennis densities than white ash trees growing in the same neighborhood. Density increased by two- to fourfold in both species over a 3-year period. Canopy dieback increased linearly from 2002 to 2005 as A. planipennis density increased (R2 = 0.70). In each of the woodlots, A. planipennis densities were significantly higher on white ash trees than blue ash trees. Woodpecker predation occurred in all sites and accounted for 35% of the A. planipennis that developed on trees we surveyed. Results indicate that surveys for A. planipennis detection in areas with multiple ash species should focus on the relatively preferred species.
Article
The agriculturally dominated Counties of Huron and Perth in southwestern Ontario regulate forest harvesting on private land through diameter-limit-based tree conservation by-laws. The rates of harvesting, along with the volume and value of timber sales and the type and quantity of tree marking were examined for the years 1997 to 1999. Although these harvests may form an important part of periodic farm income, at only 13% forest cover, these landscapes may be further degraded by unsustainable forest harvesting practices. Based on the three study years, the mean annual area of forest harvested was found to be 4.4% of the total private forest landbase. The mean volume harvested from upland and lowland deciduous forest was 4666 and 6148 fbm/ha, respectively. Over-harvesting under a diameter-limit or hybrid method occurred in 8% of woodlot area with removal rates in excess of 10 000 fbm/ha. The most severe over-harvesting disproportionately targeted lowland woodlots, possibly compromising the ecological health of these often sensitive areas. Sugar maple, red/silver maple and ash were most commonly harvested at 33%, 31% and 21% of total species volume, respectively.On average, for standing timber, landowners received $680/Mfbm in the upland hardwood forests and $281/Mfbm in the lowland hardwood forests. On an area basis, mean price paid was $3680/ha and $1956/ha respectively on upland and lowland forests. Only 8% of the private land was harvested using single-tree selection or stand improvement (92% harvest was diameter-limit or a hybrid of same). Using a simple model, we found that woodlot owners comprising at least 74% of private woodland area would need to participate in forest harvesting in order to maintain the 1997 to 1999 partial harvest area rate of 2349 ha/yr. This rate may not be sustainable, given poor forest conditions in some areas, past management practices and a reduction in landowners interested in forest harvesting. Improvements are needed to bring the level of good forestry practice up by 62% to meet the rates that were being performed under pre-1994, free, provincial government private land forestry programs.