From their analysis, Roy and Olson concluded that there are times when the best route is to allow some entry of pests: when damages are low, the pests' growth rate is low and the discount rate the relative weight placed on present costs and benefits compared to those in the future is high enough.
Also, trade policy doesn't have to be too restrictive if the cost of controlling established pest populations is low enough. On the other hand, managing trade to prevent further entry may be warranted when the current established population of the species is below a stage where the growth rate of the invasion is likely to increase sharply. The same is likely to be true if the future cost of controlling an established invasion is likely to be high.
"What we're suggesting is a more sophisticated approach to learning the cost to an economy for various scenarios, such as allowing pests to come in and then controlling them over time," Roy says. "Different strategies would have different costs. If you can establish how the damage grows and the cost of controlling it, then we can tell you the best strategy, whether it should be controlled, eradicated completely, whether there should be some trade restrictions or prohibition of trade."
Their study also can be seen as relevant to the control and prevention of invading diseases, such as HIV and various strains of influenza, Roy says.
|Contact: Margaret Allen|
Southern Methodist University