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Project Work Plan

Department of Interior USGS GE PES
Fiscal Year 2014 Study Work Plan

Study Title: Optimal Control Strategies for Invasive Exotics in South Florida
Current Study Start Date: October 1, 2013 Current Study End Date: September 30, 2014
Location (Subregions, Counties, Park, or Refuge): South Florida and Loxahatchee National Wildlife Refuge
Funding Source: GEPES
Funding History: Funded by GEPES in 2012 and 2013 for literature review and conceptual formulation
FY14 USGS Funding:
Principal Investigator: Dr. Fred Johnson
USGS Project Officer: Dr. Fred Johnson
USGS Technical Officer:
Supporting Organizations: Florida Cooperative Fish & Wildlife Research Unit, Loxahatchee National Wildlife Refuge

Overview & Objective(s): The establishment and proliferation of exotic plants and animals can interfere with native ecological processes and can cause severe stress to sensitive ecosystems. Perhaps nowhere in the contiguous U.S. is this more evident than in South Florida, where millions of dollars are spent annually to monitor and control the spread of exotics such as Brazilian pepper (Schinus terebinthifolius), melaleuca (Melaleuca quinquenervia), the Mexican bromeliad weevil (Metamasius callizona), and Burmese python (Python molurus bivittatus), just to name a few. With the number of established exotic species now numbering well into the hundreds in South Florida, the potential impact of invasives has emerged as a high-priority issue in planning the restoration and conservation of the Greater Everglades (South Florida Environmental Report, 2011, South Florida Water Management District). However, agencies with responsibility for protecting native ecosystems in South Florida have limited resources with which to control the spread of invasive exotics. Therefore, there is a pressing need to develop cost-effective monitoring programs, new control methods, and decision-support tools.

This study has the following objectives:

Specific Relevance to Major Unanswered Questions and Information Needs Identified:

Within the constraints of their budgets, responsible agencies must routinely make tradeoffs inherent in controlling the spread of invasives; e.g., monitoring abundance in well-established areas vs. monitoring potential sites for colonization, eradicating large infestations vs. eradicating newly colonized sites, and monitoring populations vs. implementing control measures. There are also temporal tradeoffs that must be considered because decisions made now produce a legacy for the future (e.g., how long to wait before implementing controls). These tradeoffs can be investigated formally within the context of a decision-theoretic framework, which can identify optimal actions based on management goals and constraints, available budgets, and the demography of the invasive population. A key advantage of a decision-theoretic framework is the ability to make optimal decisions in the face of various sources and degrees of uncertainty, such as the rate at which an invasive will colonize new areas or the variable effectiveness of control measures. The product of this approach is a state-dependent management strategy that prescribes an optimal action for each time period for each possible state of the system. In this case, the state of the system would be characterized by extant knowledge of the spatial distribution and abundance of the target invasive. The state-dependent strategy can also be adaptive, as predicted and observed system responses are compared over time.

Planned Products for FY14: (1) A review article describing the development of systematic screening tools and decision analyses for potentially invasive pets in South Florida; and (2) Workshop on controlling damage by Burmese pythons at Loxahatchee NWR, to be held at the National Conservation Training Center

Work Plan

Task Leaders: Dr. Mathieu Bonneau
Phone: 352.264.3504
FAX: 352.378.4956
Task priority: Medium
Task Personnel: Dr. Fred Johnson
Task Summary and Objective(s): There are multiple steps in the invasion process: to become invasive, a species must survive transport to be introduced, it must then begin reproducing to become established and finally must spread and cause harm to be considered invasive. A quantitative risk assessment approach considers that success at any time step is a function of species traits (e.g. biological traits, invasion history, etc.) and that patterns in those traits can be used to explain success or failure. The risk assessment model can take into account more general information like climate matching or community information. Note that at this step success can relate to introduction, establishment or invasion. The risk assessment tool can then been used by decision makers to allow or deny the importation of a given species. This choice is based on: (a) the possible net benefits of allowing the species to be imported and (b) the possible net cost if the species becomes invasive and then needing management. Our objective is to review the literature on risk assessment and decision analyses regarding importation of animal pets and to prepare a manuscript for publication in a peer-reviewed journal.

Work to be undertaken during the proposal year and a description of the methods and procedures: The result of allowing the species or not to enter the country is not known in advance because the invasive potential of the species is generally unknown, but it can be predict by a stochastic model f. Formally, the decision maker has to choose between two actions, a∈{0,1}, allowing or rejecting the importation, which is a=0 or a=1, respectively. Let ua,I and ua,B be the net benefit of a screening action a, given the species will become invasive or is benign. Then the decision problem can be formulated as a maximization of the expected net benefits:

maximum of the expected net benefits equation

Then it can be shown that it is optimal to reject a species (a = 1) when the probability of establishment is greater than a cutoff, c:

probability of establishment is greater than a cutoff equation

During this fiscal year, we will: (a) conduct a literature review regarding screening processes for invasive species; (b) develop a general analytical framework that can be used for importation decisions; and (c) prepare a draft manuscript for publication.

Specific Task Products:

Product manuscript
Delivery Date July 1, 2014

Task Leaders: Dr. Fred Johnson
Phone: 352.264.3488
FAX: 352.378.4956
Task priority: High
Task Personnel: Dr. Mathieu Bonneau
Task Summary and Objective(s): Burmese pythons have become widespread in the southern portion of the Everglades, where their presence is causing extensive ecological damage. Pythons are spreading northward, but so far have not become established at Arthur R. Marshall Loxahatchee National Wildlife Refuge in the northern portion of the Everglades. The refuge wishes to determine how to allocate resources between surveillance and control activities in and around the refuge to minimize ecological damage resulting from the establishment of pythons. This allocation decision must be made over both space and time, and is subject to budgetary constraints. Management actions involve the allocation of efforts for detection and for control once the presence of pythons is detected. The objective of the refuge is to minimize the ecological impacts of python invasion, as well as the costs of detection and control. Because of the difficulty in detecting pythons, surveillance might involve the use of indirect methods such as small-mammal monitoring or python eDNA. Control activities might involve the use of radio-collared prey or "judas" snakes to locate pythons for removal.

Work to be undertaken during the proposal year and a description of the methods and procedures: Refuge and USGS staff will participate in a Structured Decision Making Workshop at the National Conservation Training Center in June 2014. Rebekah Gibble, Senior Refuge Biologist, will serve as project coordinator. She recently coordinated a SDM workshop for invasive plants at the refuge and therefore has knowledge of the process. We envision needing some additional refuge support, as well as one or more representatives from the relevant state management agencies. It will also be necessary to have a thorough understanding of python ecology and current control efforts in the southern Everglades; fortunately, there is a large pool of federal and state expertise to draw upon. Finally, there will be a need for expertise in invasive-species modeling and in spatial and dynamic optimization methods.

Specific Task Products:

Product Workshop Report
Delivery Date July 31, 2014

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