Managers often struggle to calculate the ecological and economic costs associated with invasive species. Yet, knowing these impacts can boost support and understanding for invasive species management.
In a new book chapter, NWRC economist Dr. Stephanie Shwiff and colleagues describe how economists determine costs of both primary and secondary impacts from invasive species and how these translate into jobs and revenue in regional economies.
Primary impacts are relatively simple to calculate. They include costs associated with destruction, depredation, and disease transmission. Most invasive species cause damage to one or two of the categories. Some, such as European starlings, can impact all three [1) destruction by roosting on buildings and bridges, 2) depredation by eating crops, and 3) disease by contaminating livestock feed]. Costs are estimated using market, loss, repair, and restoration values of the impacted resource.
Estimating secondary impacts requires the use of regional economic models that look at both upstream and downstream effects of the primary impacts. For instance, when starlings eat crops it results in lower yields for farmers. This, in turn, means less product is delivered to the processor and retail outlets. These are downstream impacts. Additionally, farmers may buy less fuel or equipment because there are fewer acres to harvest. These are upstream impacts. The regional economic models take these linkages into account to estimate impacts to revenue, income and jobs.
The authors note the need for more comprehensive national estimates of invasive species damage, as well as species population estimates and rates of expansion. If nationwide data were available, models could be used to determine invasive species damage on a national scale.
For more information, please contact NWRC@usda.gov.