Optimal Surveillance for
Eradication of Invasive Species
Becky Epanchin-Niell (Resources for the Future)
Robert Haight (USDA Forest Service)
Andrew Liebhold (USDA Forest Service)
Ludek Berec (Institute of Entomology)
John Kean (AgResearch)
RFF First Wednesday Panel, March 7, 2012
Three Universal Phases
of Biological Invasions
Arrival
Establishment
Spread
Permanent Range
Three Universal Phases
of Biological Invasions
Arrival
Methods for Managing
Biological Invasions
Quarantine, inspection
Eradication
Establishment
Barrier Zones,
domestic quarantines
Spread
Permanent Range
Biological & other control,
Adaptation
Bioeconomics of Eradicating New Populations
of Biological Invaders
Economic Tradeoffs
Surveillance (detection)
Eradication (e.g., spraying)
Management objective:
• Determine the optimal level of surveillance to
minimize the total expected costs of invasion
management, where management costs include:
• costs of surveillance
• eradication costs
• invasion damages
Invasion process:
- Populations arrive and establish randomly
- Population area grows
- Number and size of populations not known
Focal management region
Establishment rate
(b)
(g)
populations
Growth
rate
(g)
(g)
How much surveillance effort should be deployed?
Surveillance effort = sample density (e.g., field surveys, pheromone traps)
Probability of detecting a population depends on:
-Size of population, sample density, and sample sensitivity
samples
populations
Bioeconomic model
• Determine the optimal long-term sampling density
to minimize:
Total expected management costs =
Surveillance
costs
+
Eradication + Damage
costs
costs
Optimal Surveillance Effort
• Greater effort warranted when:
– Establishment rate is high
– Eradication costs are high
– Damage costs are high
– Sample sensitivity is low
– Costs of sampling are low
– Population growth rates are moderate
Application: Gypsy moth (Lymantria
dispar) eradication in California
- Detected with pheremone traps
- We parameterize model based on existing
data, literature review, and expert opinion
http://hyg.ipm.illinois.edu/article.php?id=66
Optimal pheromone trap density by
county
Conclusion
• Developed a bioeconomic approach that can
optimize surveillance for eradication of plants,
pests, or pathogens