1 / 20

Integrating Prevention and Control of Invasive Species: The Case of the Brown Treesnake

Integrating Prevention and Control of Invasive Species: The Case of the Brown Treesnake. Kimberly Burnett, Brooks Kaiser, Basharat A. Pitafi, James Roumasset University of Hawaii, Manoa, HI Gettysburg College, Gettysburg, PA. Objectives.

richard_edik
Télécharger la présentation

Integrating Prevention and Control of Invasive Species: The Case of the Brown Treesnake

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Integrating Prevention and Control of Invasive Species: The Case of the Brown Treesnake Kimberly Burnett, Brooks Kaiser, Basharat A. Pitafi, James Roumasset University of Hawaii, Manoa, HI Gettysburg College, Gettysburg, PA

  2. Objectives • Illustrate dynamic policy options for a highly likely invader that has not established in Hawaii • Find optimal mix of prevention and control activities to minimize expected impact from snake

  3. Boiga irregularis

  4. Methodology • First consider optimal control given N0 (minimized PV of costs and damages) =>Nc* • We define prevention to be necessary if the population falls below Nmin (i.e., Nc*< Nmin) • Determine optimal prevention expenditures (to decrease probability of arrival) conditional on the minimized PV from Nc*

  5. N0 ≥Nmin Nc* = Best stationary N without prevention Nc* Nmin Nc*<Nmin We have a winner! N* = Nc* Choose y to min cost of removal/prevention cycle Z(Nc*) V(Nmin) N* = Min (Z,V)

  6. Algorithm to minimize cost + damage => V* => Nc*

  7. PV costs + damage ifNc* < Nmin • If N*c <Nmin, we must then consider the costs of preventing re-entry. Z =

  8. Prevention/eradication cycle • Expected present value of prevention and eradication: • p(y): probability of successful introduction with prevention expenditures y. Minimizing Z wrt y results in the following condition for optimal spending y:

  9. N0 ≥Nmin Nc* = Best stationary N without prevention Nc* Nmin Nc*<Nmin We have a winner! N* = Nc* Choose y to min cost of removal/prevention cycle Z(Nc*) V(Nmin) N* = Min (Z,V)

  10. Choose optimal population • If N* Nmin, same as existing invader case • Control only • If N* < Nmin, • Iterative prevention/removal cycle

  11. Case study: Hawaii • Approximately how many snakes currently reside in Hawaii? • Conversations with expert scientists: between 0-100

  12. Growth • Logistic: b=0.6, K=38,850,000

  13. Damage • Power outage costs: $121.11 /snake • Snakebite costs: $0.07 /snake • Biodiversity: $0.32 – $1.93 /snake • Total expected damages:

  14. BiodiversityLosses

  15. Control cost • Catching 1 out of 1: $1 million • Catching 1 out of 28: $76,000 • Catching 1 out of 39m: $7

  16. Probability of arrival a function of spending

  17. Results • Aside from prevention, eradicate to zero and stay there. • Since prevention is costly, reduce population from 28 to 1 and maintain at 1

  18. First period cost Annual cost PV costs Annual damages NPV damages PV losses Status quo $2.676 m $2.676 m $133.8 m $4.5 b $145.9 b $146.1 b Opt. policy $2.532 m $227,107 $13.88 m $121 $9,400 $13.89 m Snake policy: status quo vs. optimal (win-win) NPV of no further action: $147.3 billion

  19. Summary • Re-allocation between prevention and control may play large role in approaching optimal policy even at low populations • Eradication costs increased by need for prevention, which must be considered a priori • Catastrophic damages from continuation of status quo policies can be avoided at costs much lower than current spending trajectory

  20. Uncertainties • Range of snakes currently present (0-100?) • 8 captured • More may’ve gotten away • Not much effort looking • Probability of reproduction given any pop’n level • Don’t know, need to look at range of possibilities • Here all control • If N*<Nmin, prevention makes sense • Need to find optimal mix

More Related