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projects > integrating monitoring and modeling of ecological responses to ecosystem in picayune strand and southwest florida: amphibian community component > work plan

Project Work Plan

Department of Interior USGS GE PES

Fiscal Year 2009 Study Work Plan

Project Title: Integrating monitoring and modeling of ecological responses to ecosystem in Picayune Strand and southwest Florida: Amphibian community component
Study Start Date: 2010
Study End Date: 2012
Web Sites:,
Location (Subregions, Counties, Park or Refuge): Picayune Strand State Forest, Fakahatchee Strand State Preserve and elsewhere in Collier County, southwest Florida
Funding Source: GE PES and CESI
Other Complementary Funding Sources: co-funded by CESI to University of Florida
Funding History: Proposed FY09
Principal Investigator: Susan C. Walls, Frank J. Mazzotti, Kristen M. Hart
Project Personnel: Melinda Schuman, Conservancy of Southwest Florida
Supporting Organizations: University of Florida, National Park Service
Associated/Linked Projects: CESI study of same name

Overview & Objective(s): Currently, one of the potentially most serious conservation problems is the synergistic effect of habitat alteration and climate change (Root and Schneider, 2006). Restoration efforts are traditionally designed to reinstate historical ecosystem services and functions to altered landscapes. The uncertainty in many climate-change projections makes it difficult, however, for conservation managers and planners to incorporate a response to climatic stresses in their restoration projects. For freshwater ecosystems, identifying the pathways through which a changing climate may impact the hydrology of a wetland (Figure 1) is a crucial first step to developing approaches to mitigating for climate change.

diagram showing conceptual model of the pathways through which climate change may impact amphibian reproductive success, population fluctuations, site occupancy and, thus, community species richness
Figure 1. Conceptual model of the pathways through which climate change may impact amphibian reproductive success, population fluctuations, site occupancy and, thus, community species richness. The hydroperiod of a breeding site is the principal factor influencing amphibian site occupancy. Climate change may modify several meteorological factors and their interplay with characteristics of the community–to influence site hydroperiod. [larger image]

Large scale efforts to restore hydrological processes in freshwater systems offer an opportunity to evaluate how climatic factors may interact with both local and landscape-level variables to influence restoration success across an ecological landscape. Implementation of the Comprehensive Everglades Restoration Plan (CERP), often described as the world’s largest ecosystem restoration effort (, offers such an opportunity. This plan provides overall guidance on the restoration of the ecosystems and water resources of central and southern Florida. However, it is not clear whether–and to what extent–the implications of climate change and climatic variability have been integrated into CERP. Because of CERP’s broad geographic coverage and planning and implementation phases that scale several decades, management decisions need to be consistent with and adapt to global climate change (RECOVER, 2006). Understanding how climate change is expected to affect key ecosystems and focal species is fundamental to this process.

One scenario of the potential effects of climate change on south Florida’s freshwater ecosystems (Mulholland et al., 1997) is summarized in Figure 2. These authors predict a 25% increase in summer precipitation for south Florida, which by itself, could partially restore the wetland area of this region (Mulholland et al., 1997). Although the resulting increases in water depth, hydrology and wetland surface area are predicted to be partially offset by increases in temperature and atmospheric CO2, these authors predict that the projected increase in precipitation will lead to the conversion of key community types (e.g., pine flatwoods and areas of sawgrass marsh; Figure 2). Moreover, the anticipated temperature and CO2 increases are anticipated to promote succession of systems with longer hydroperiods to ones with shorter hydroperiods that are more susceptible to fire and short-term drought (Mulholland et al., 1997; Figure 2). Under this scenario, the ecological restoration of habitats currently suffering from overdrainage in south Florida will likely be vital to preserving hydric pine flatwoods and other seasonal wetlands with longer hydroperiods. Wetlands with a hydroperiod that is sufficient for successful reproduction are essential to the long-term persistence of amphibians and many other wetland-associated taxa (Figure 1).

diagram showing redicted scenario of consequences of future climate change for freshwater ecosystems in south Florida
Figure 2. Predicted scenario of consequences of future climate change for freshwater ecosystems in south Florida. From Mulholland et al. (1997). [larger image]

Prior to extensive drainage, wetlands historically covered approximately 50% of Florida (Mulholland et al., 1997). The present-day landscape of southwest Florida still contains a matrix of diverse wetland types that vary in hydroperiod, ranging from permanent to seasonally ephemeral, isolated sites. The latter are important breeding sites for many amphibians, although ephemeral wetlands have received little or no mention in most summaries of the expected effects of climate change on freshwater systems (e.g., Mulholland et al., 1997; Meyer et al., 1999; Allan et al., 2005; Bates et al., 2008). Amphibians are important "bioindicators" of habitat suitability and ecosystem restoration success (Waddle, 2006): they are sensitive to changes in the environment, especially those having to do with water quantity and quality. Because amphibian reproduction is so tightly tied with the aquatic habitat, changes in hydrology are perhaps the biggest threat to most species. Indeed, freshwater wetlands of varying types are considered "optimal" habitat for 95% of the species of anurans and 64% of the species of salamanders found in the southeast U.S. (Bailey et al., 2006). Amphibians are also abundant and readily sampled with established methods. When several species of amphibians are evaluated together, the species composition is a good indicator of habitat quality.

The DOI Science Plan for CERP and the research areas outlined by the BAA request for proposals described a need for scientific research that will develop models that can be used as tools to evaluate restoration alternatives and assess restoration outcomes. Because hydrology is a major driving factor in Everglades habitats, our focus in prior funding was to create a model of amphibian occupancy in relation to hydrology and habitat, to be used as a restoration evaluation tool. We collected data on amphibian distributions by habitat and hydrology in Everglades National Park, Big Cypress National Preserve, Florida Panther National Wildlife Refuge, Fakahatchee Strand State Reserve and Picayune Strand State Forest. These data were collected for analysis, along with hydrological data, to produce an ecological model of occupancy of amphibian communities. The goal was for this community level occupancy rate to serve as an index, a target for restoration assessment and, in a spatial framework, as a tool for evaluation of alternatives.

This community index model of amphibians throughout southwest Florida, called the Stressor Response Model for Southwest Florida Amphibians, is currently being finalized. Estimates of the proportion of sites occupied by amphibian species in various habitats under different hydrologic conditions will elucidate patterns and lead to the creation of an amphibian community index. This index can then be used to predict the effects of various water management scenarios on the amphibian community.

This model also serves as a promising tool for assessing the potential impact of climate change on amphibians occupying a hydrologically modified/restored landscape. Climate change may influence the hydrology of freshwater wetlands by altering patterns of precipitation, groundwater levels, evapotranspiration, and the frequency and intensity of fires (Figure 1). Variation in these factors may interact with various community characteristics (e.g., community type, canopy cover) to further influence site hydroperiod. For instance, Mulholland et al. (1997) predicted that large increases in summer precipitation during the wet season in south Florida may lead to extensive pine flatwoods/cypress swamp areas becoming dominated by pond cypress, and extensive areas of sawgrass marsh being converted to open water (Figure 2). Modification of wetland hydroperiod ultimately affects the presence of fish and invertebrate predators on larval amphibians, larval growth, survival and, ultimately, the species richness of amphibians at a site (Figure 1). The Stressor Response Model can potentially be used to predict how amphibians may respond under different climate change scenarios.

Our long-term objective in the present study is to validate this newly-developed model with respect to predicted responses of an amphibian community to hydrologic and habitat restoration at a focal site. Two objectives in prior funding were (1) to define amphibian communities appropriate for evaluating restoration success and (2) to develop restoration targets for the amphibian community of southwest Florida. With that funding, we identified two anuran species (the Pinewoods treefrog, Hyla femoralis and the Barking treefrog, Hyla gratiosa) that are particularly sensitive as indicators of suitable pine flatwoods habitat. This habitat is important because it is the most extensive terrestrial ecosystem in Florida, covering approximately 50% of Florida’s land area ( However, with encroaching climate change, the hydric pine flatwoods of south Florida are specifically predicted to be converted to sites dominated by pond cypress (Mulholland et al., 1997). Moreover, only approximately 12% of the historic (ca. 1940) pinelands in some regions of southwest Florida remains (Mazotti et al., 1992, sensu Pearlstine et al., 1995). During our prior effort we also identified the habitat targeted in CERP’s Picayune Strand Hydrologic Restoration project (see work plan, below) as being well suited for testing the predictions of our model with regards to the potential responses of H. femoralis and H. gratiosa to restoration of the hydrologically degraded habitat in Picayune Strand State Forest. Our specific objectives are to:

Specific Relevance to Major Unanswered Questions and Information Needs Identified:

As with our previously funded work, this project continues to address several science objectives in the USGS Science Plan in Support of Everglades Restoration. Primarily, this work is concentrated under the second main goal: "Activities to restore, protect, and manage natural resources on DOI lands in south Florida." The tasks directly address four science objectives:

This project applies to the following research areas designated by the BAA RFP:

The need for monitoring and modeling amphibian populations during CERP is specifically mentioned in the DOI Science Plan in Support of Everglades Restoration under several projects such as the Picayune Strand (Southern Golden Gate Estates) Hydrologic Restoration Project. In the DOI Science Plan, the need for monitoring and simulation projects for indicator species is listed in at least the Ten Mile Creek Reservoir Assisted Stormwater Treatment Area, Henderson Creek/Belle Meade Restoration, Southwest Florida Feasibility Study, Florida Bay and Florida Keys Feasibility Study, Landscape-Scale Modeling, and Everglades National Park Fire Ecology Science Action Plan projects. The need to develop models simulating response of species sensitive to change in hydrology, especially those of threatened and endangered species; and determine response of key indicators to changes in water management is described as a research area/restoration goal of the South Florida Ecosystem Restoration Task Force (SFERTF).

Planned Products: In FY09, we plan to submit manuscripts on the development of the model and other results from previous funding. Currently, at least one manuscript from FY08 funding is in preparation, tentatively titled "Use of amphibians to establish a baseline for measuring restoration success at a hydrologically degraded site in southwest Florida, USA", with the goal of submitting it to the journal Restoration Ecology.

We will present results of our study at national and international meetings during FY09. We will also provide results of model simulations on the web.


Title of Task 1: Validation of amphibian models for use in the Southwest Florida Feasibility Study: Evaluation of prerestoration communities and potential impacts of climate change
Task Funding: GE PES
Task Leaders: Susan C. Walls, Frank J. Mazzotti and Kenneth G. Rice
Phone: 352-264-3507
FAX: 352-378-4956
Task Status (proposed or active): Active
Task priority: High
Time Frame for Task 1: 2009–2011
Task Personnel: Melinda Schuman, Conservancy of Southwest Florida
Task Summary and Objectives: This is the only task and will accomplish the objectives stated above.

Work to be undertaken during the proposal year and a description of the methods and procedures: We propose to conduct surveys for anuran amphibians at sites in Fakahatchee Strand State Preserve and Picayune Strand State Forest. These data will be used to generate unbiased estimates of site occupancy for all species detected, but our primary focus will be on the Pinewoods and Barking treefrogs. In years one and two of our work, we will conduct two types of surveys: (1) visual and aural (auditory) surveys for adult anuran amphibians and (2) dipnet and trapping surveys for tadpoles and the presence of predatory fish and invertebrates. Detection of adults at a site indicates the presence of a species at a given site, but it does not provide information about the reproductive success or persistence of a species at a site. Thus, the results of our dipnet and trapping efforts will be used to evaluate various components of our conceptual model (Figure 1), such as the impact of site hydroperiod on the presence of predatory invertebrates and fishes, and the reproductive success (larval growth, metamorphosis and survival) of amphibians. These components, in turn, influence site occupancy and overall species richness of the community at a site (Figure 1).

Study area: Picayune Strand State Forest is targeted for hydrological restoration through the Picayune Strand Restoration Project (PSRP), one of 60+ planned projects to be implemented under CERP. The goal of the PSRP is to counteract the overdrainage that resulted from a failed real estate development project (the Southern Golden Gates Estates) of the 1960s. The development of this area (by the Gulf American Corporation) involved dredging 48 miles of canals and building 290 miles of shell-rock roads. Restoration plans for this area include the installation of a combination of spreader channels, canal plugs, road removal and pump stations in the Western Basin and Big Cypress of Collier County. Thusfar, by 2006 the northern seven miles of the Prairie Canal (the easternmost of four large canals originally constructed to provide drainage and flood protection for the planned residential development) were plugged. Most roads adjacent to the canal have also been removed and exotic plant species were removed from the canal banks. The effort completed thusfar is expected to be especially beneficial in terms of reducing drainage of the adjacent Fakahatchee Strand State Preserve.

The area targeted in the Picayune Strand Restoration Project (the former Southern Golden Gates Estates) is bordered to the east by Fakahatchee Strand State Preserve (FSSP) and, to the west, by the Belle Meade Conservation and Recreation Lands (CARL) area. Belle Meade, together with the former Southern Golden Gates Estates, now comprise the Picayune Strand State Forest (PSSF). Both Belle Meade and FSSP are reservoirs of natural habitat that, in Belle Meade, is largely hydrologically intact. The FSSP is threatened by unnatural patterns of water flow and unrestricted use in the private ownerships of the area. Belle Meade includes some of the most extensive examples of remaining old-growth wet flatwoods in southwest Florida, along with high quality, undisturbed subtropical dwarf cypress savanna communities. Fakahatchee Strand is the best example of a strand swamp in the United States, and contains the largest concentration and the greatest diversity of native orchids in North America. These two areas are therefore vital refugia of native flora and fauna that can recolonize the Picayune Strand following its restoration. The results of our field surveys in 2008 revealed that both Belle Meade and FSSP had significantly higher species richness of amphibians than did Picayune Strand (Figure 3). Moreover, 80% of the sites at which Pinewoods treefrogs were detected were within the boundaries of the Bell Meade area. Thus, because of their proximity to Picayune Strand, along with their high species richness of amphibians, Belle Meade and FSSP will likely play a crucial role in the recovery of anuran amphibians in this ecosystem.

bar chart showing mean species richness of anuran amphibians in 2008 across the three proposed study areas
Figure 3. Mean species richness of anuran amphibians in 2008 across the three proposed study areas. Mean richness was significantly lower in Picayune Strand State Forest, the site targeted for hydrological restoration. Species richness in the two reference areas (the Belle Meade Conservation and Recreation Lands (CARL) area and the Fakahatchee Strand State Preserve) was statistically similar. [larger image]

Proportion of area occupied by a species: One problem with many of the methods used to sample amphibians is the lack of any control of myriad environmental factors that affect behavior and activity of animals. Abiotic factors like temperature, humidity and hydrology as well as biotic factors like presence of predators or conspecifics can affect observability of amphibians. The observability of a species’ population is a function of the population size, the behavior of individuals, and the ability of observers to locate animals in particular habitats. Many monitoring programs simply count animals and do not control for this observability or capture probability (p). Therefore, comparisons over time or space are limited. If the monitoring program can assume costs of marking individual animals, then p can be determined and population size or density determined (standard mark-recapture methods, see Williams et al., 2002). However, this would be cost prohibitive in a monitoring program for all amphibian species throughout the Everglades. MacKenzie et al. (2002) have developed a novel approach to this problem. Rather than marking individuals, we "mark" species. Therefore, presence/absence data from several plots within a habitat provides an estimate of p and allows estimation of the proportion of a habitat stratum occupied by a given species at a given time (proportion of area occupied or PAO). Strata will be defined by habitat and hydrology.

Our standardized sampling unit will be a circular plot of 20-m radius. Plots will be sampled after dark to increase the probability of observing nocturnal amphibians. At each plot a two person crew will begin by listening for anuran vocalizations for 10 minutes. The abundance of each species will be categorized as: no frogs calling, one frog calling, 2-5 calling, 6-10 calling, >10 calling, or large chorus. The intensity of the vocalizations will be categorized as: no frogs calling, occasional, frequent, or continuous. After the vocalization survey, we will perform a 30-minute visual encounter survey (VES) in each plot. During this time, all individual amphibians observed will be identified to species and captured if possible. We will record the species, categorize the age (egg, larvae, juvenile, subadult, or adult), measure and record the snout-to-vent length and record the sex if it can be determined. The animal will then be released at the original capture site. We also will record the substrate and perch height of the animal. A University of Florida Institutional Animal Care and Use Committee approval will be obtained for animal capture. In addition to VES, in plots that are completely flooded, we will use dipnets and funnel traps to attempt to capture aquatic amphibians, fishes and invertebrates. All amphibians captured will be counted, identified to species and stage of development and measured for body size (total lenth). We also will record several environmental variables at each plot (air temperature, relative humidity, presence of water, water temperature, wind speed, cloud cover).

Individual species capture histories (matrix of detections/nondetections of each species at each sampling occasion of each plot) and corresponding covariates (e.g. habitat, hydrological parameters, temperature, relative humidity, etc.) will be assembled. We will then estimate the proportion of each stratum occupied by a species and the capture probability using maximum likelihood estimation (MLE) with logistic regression for covariates in program PRESENCE (MacKenzie et al., 2002). Information-theoretic methods for model selection based on Akaike’s Information Criterion (AIC) will be employed (Burnham and Anderson, 1998). The best model will minimize AIC and adequately estimate the parameters in the model (the candidate model list will be developed a priori based on ecological knowledge and will not include all possible combinations).

Specific Task Product(s):
Anticipated Results: The ultimate goal of this project is to validate a modeling tool that has been developed for decision support for managers interested in the effects of hydrologic restoration on amphibians in the Everglades system. We will test this model using estimates of amphibian occupancy in a site planned for hydrological restoration and its surrounding natural habitat on adjacent conservation lands. This model will be used to forecast future expected amphibian occupancy, based on hydrology and habitat, in the restored areas.

Using information on the predicted responses of amphibians to hydrology and habitat, we will refine the model to allow consideration of the potential effects of future climate change, manifested as changes in hydrology, will impact the amphibian fauna of southwest Florida and the greater Everglades ecosystem.

Reporting schedule is described below. Semiannual report is due six months after contract initiation, and final report is due 12 months after contract start. Milestones and deliverables are described below.




1 Semiannual Progress report (sampling progress)
1 Annual Final report (model description and output)

Funded projects will adhere to research data reporting and data custody requirements of the South Florida Natural Resources Center, Everglades National Park, and those of the USGS.

Literature Cited:

Allan, J.D., M. Palmer, and N.L. Poff. 2005. Climate Change and Freshwater Ecosystems. Pp. 274-290 in Climate Change and Biodiversity (T.E. Lovejoy and L. Hannah, eds.). Yale Univ. Press, New Haven, CT, USA.

Bailey, M.A., J.N. Holmes, K.A. Buhlmann, and J.C. Mitchell. 2006. Habitat Management Guidelines for Amphibians and Reptiles of the Southeastern United States. Partners in Amphibian and Reptile Conservation Technical Publication HMG-2, Montgomery, Alabama. 88 pp.

Bates, B.C., Z.W. Kundzewicz, S. Wu, and J.P. Palutikof (eds.). 2008. Climate Change and Water. Technical Paper of the Intergovernmental Panel on Climate Change, IPCC Secretariat, Geneva, 210 pp.

Burnham, K.P. and D. R. Anderson. 1998. Model selection and multi-model inference: A practical information-theoretic approach. Springer-Verlag, New York.

MacKenzie, D.I., J.D. Nichols, G.B. Lachman, S. Droege, J.A. Royle, and C.A. Langtimm. 2002. Estimating site occupancy rates when detection probabilities are less than one, Ecology. 83:2248-2256.

Mazzotti, F.J., L.A. Brandt, L.G. Pearlstine, W.M. Kitchens, T.A. Obreza, F.C. Depkin, N.E. Morris and C.E. Arnold. 1992. An evaluation of the regional effects of new citrus development on the ecological integrity of wildlife resource in southwest Florida. Final report. South Florida Water Management District, West Palm Beach, Florida.

Meyer, J.L., M.J. Sale, P.J. Mulholland, and N.L Poff. 1999. Impacts of climate change on aquatic ecosystem functioning and health. Journal of the American Water Resources Association 35:1373-1386.

Mulholland, P.J., G.R. Best, C.C. Coutant, G.M. Hornberger, J.L. Meyer, P.J. Robinson, J.R. Stenberg, R.E. Turner, F. Vera-Herrera, and R.G. Wetzel. 1997. Effects of climate change on freshwater ecosystems of the South-Eastern United States and the Gulf Coast of Mexico. Hydrological Processes 11:949-970.

Pearlstine, L.G., L.A. Brandt, W.M. Kitchens, and F.J. Mazzotti. 1995. Impacts of citrus development on habitats of Southwest Florida. Conservation Biology 9:1020-1032.

RECOVER. 2006. Monitoring and Assessment Plan (MAP), Part 2, 2006 Assessment Strategy for the MAP, Final Draft. Restoration Coordination and Verification Program, c/o United States Army Corps of Engineers, Jacksonville District, Jacksonville, FL, and South Florida Water Management District, West Palm Beach, FL. December 2006.

Root, T.L. and S.H. Schneider. 2006. Conservation and climate change: the challenges ahead. Conservation Biology 20:706-708.

Waddle, J.H. 2006. Use of amphibians as ecosystem indicator species. Unpubl. Ph.D. Dissertation, University of Florida, Gainesville, FL, USA.

Williams, B.K., J.D. Nichols, and M.J. Conroy. 2002. Analysis and management of animal populations. Academic Press, London.