http://www.rff.org/Publications/Pages/PublicationDetails.aspx?PublicationID=22562
Abstract:
Quantifying economic damages caused by invasive species is crucial for cost-benefit analyses of control measures. Most studies focus on short-term damage estimates, but evaluating exclusion or prevention measures requires estimates of total anticipated damages from the time of establishment onward. The magnitude of such damages critically depends on the timing of damages relative to a species’ arrival because costs are discounted back to the time of establishment. Using theoretical simulations, we illustrate how (ceteris paribus) total long-term damages, and hence the benefits of prevention efforts, are greater for species that a) have short lags between introduction and spread or between arrival at a location and initiation of damages, b) cause larger, short-lived damages (as opposed to smaller, persistent damages), and c) spread faster or earlier. We empirically estimate total long-term discounted impacts for three forest pests currently invading North America - gypsy moth (Lymantria dispar), hemlock woolly adelgid (Adelges tsugae), and emerald ash borer (Agrilus planipennis) - and discuss how damage persistence, lags between introduction and spread, and spread rates affect damages. Many temporal characteristics can be predicted for new invaders and should be considered in species risk analyses and economic evaluations of quarantine and eradication programs.
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As the table below shows the total present value of residential damages from the gypsy moth ranges from $32 million with a discount rate of 5% to $6.415 billion at a discount rate of 1%, and $0.7 million to $20 million for the hemlock wooily adegid and from $9.2 billion to 26.4 billion for the emerald ash borer invasion
Table 1. Estimated total present value (millions 2011 USD) of residential damages from gypsy moth and hemlock woolly adelgid and of ash tree removal and replacement costs from emerald ash borer invasion. Present values are calculated from the time of both introduction and initiation of damages (1869 and 1880 for gypsy moth, 1911 and 1971 for hemlock woolly adelgid, and 1990 and 2002 for emerald ash borer).
Fig. 1. Panels show the (a) radial extent, (b) invaded area, (c,e) nondiscounted annual damages, and (d,f) present value of annual damages for the first 100 years of invasion for spread models A, B, and C (lines) with the baseline parameterizations. The second row (c,d) shows damages when persistence P is 1 year, and the third row (e,f) shows damages when persistence P is 100 years.
Quantification of gypsy moth spread and damages.
[The authors] used historical invasion records to characterize past invasion spread from the time of its initial introduction in Medford, Massachusetts, in 1868 through 2012. Past spread of gypsy moth from 1868 to 1912 is summarized in Liebhold et al. and Liebhold and Tobin from a variety of historical records. Spread from 1912 to the present is recorded in county-level quarantine records published by the US Department of Agriculture (US Code of Federal Regulations, Title 7, Chapter III, Section 301.45). Future spread of the gypsy moth was projected based on an assumption of constant radial spread, using a rate of 5 km/yr (the average spread rate estimated for 1999–2012 along the expanding population front in the United States; ... Year of establishment was predicted for each county in 39 eastern states . [They] excluded spread into counties whose climates are unsuitable for gypsy moth development.