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Supporting wild, self-sustaining populations is a fundamental goal in conservation biology. On-the-ground management work is typically designed to improve habitat or reduce the negative impacts of stressors on wildlife populations. Responses of wildlife populations to such management actions can be difficult to monitor in practice, especially for herpetofauna. Furthermore, future changes can challenge the success of ongoing conservation programs by introducing new threats or shifting baseline environmental conditions. Using long-term monitoring data to better understand how populations respond to current management and potential future changes can be an effective strategy for guiding conservation decisions.
This article highlights how long-term monitoring of Reticulated Flatwoods Salamander (Ambystoma bishopi) populations on Eglin Air Force Base led to the development of population models that were applied to estimate viability under future climate changes. This work was part of my dissertation research and was conducted with collaborators at Virginia Tech.
Amphibian Declines and Climate Change
Climate change has been linked to well-publicized global amphibian declines for over three decades (Pounds and Crump 1994, Carey and Alexander 2003). Amphibian life-history characteristics and physiology make them broadly susceptible to changes in environmental conditions, particularly temperature and precipitation patterns. Such changes can impact growth rates and body sizes, alter behavior, increase sensitivity to disease and parasites, create long-term changes to habitat characteristics, and alter reproductive success. The impacts from changing environmental conditions can interact with other environmental stressors, creating complex conservation challenges. Identifying and preparing for the impacts of climate change on population dynamics is a critical aspect of recovery planning for imperiled amphibian species.
For species with complex life cycles, it can be challenging to assess how changing environmental conditions may impact populations. A complex life cycle in amphibians is generally characterized by an aquatic larval stage followed by metamorphosis into a terrestrial adult. The environmental conditions experienced in both the aquatic larval habitat and in surrounding upland environments used by terrestrial adults both play key roles in determining individual- and population-level success. Thus, researchers must effectively quantify processes that span environmental gradients to understand population dynamics.
In the southeastern U.S., many species with complex life cycles breed in ephemeral wetlands that experience regular cycles of wetting and drying. Many species rely on specific environmental cues to trigger breeding movements into wetland habitats, but changing temperature and precipitation patterns can shift the timing of these events (i.e., changes in phenology; Todd et al. 2011). This can ultimately impact individual fitness and reproductive success. Altered climate regimes can also directly impact wetland hydrology, which can lead to population declines (McMenamin et al. 2008). Overall, climate change can have multifaceted effects on amphibians breeding in ephemeral wetlands, altering both demographic processes and the underlying environmental conditions. Responding to these changes is a key need in amphibian conservation.
Long-term Flatwoods Salamander Monitoring
Reticulated Flatwoods Salamanders exemplify many of the challenges faced by amphibians with complex life cycles. Adult salamanders migrate to breeding wetlands in the fall, where they deposit eggs in dry wetland basins. Breeding migrations are triggered by fall and winter rains, and eggs must be deposited such that they are inundated by rising water levels as wetlands fill. After hatching, aquatic larvae remain in the breeding wetlands for 3–5 months before undergoing metamorphosis. This process is often a race against time as wetlands begin to dry during the spring. In some years, wetland drying can lead to complete reproductive failure in flatwoods salamander populations.
Reticulated Flatwoods Salamander populations on Eglin Air Force Base have been the focus of a long-term conservation program led by Dr. Carola Haas at Virginia Tech for over two decades. As part of this work, two small breeding wetlands were completely encircled with a drift fence from 2010–2020 (10 breeding seasons). Adult salamanders were captured entering wetlands, and newly metamorphosed juveniles were captured leaving wetlands. All salamanders were measured and marked to better understand population dynamics at these breeding sites. In addition to salamander data, we also collected water level data using monitoring wells, which allowed us to quantify the hydrologic characteristics of these sites. Salamander monitoring and research has been complemented by active habitat management, which has increased the prevalence of flatwoods salamander populations across this landscape (Martin et al. 2025).
Creating a Population Model
There is a long history of using population models to make inferences in conservation biology. While always challenging and generally somewhat of a best guess, these techniques often provide the best available data for making informed management decisions. For flatwoods salamanders, development of a population model was initiated by Dr. George Brooks as part of his dissertation research.
Before building a population model, there were several important demographic processes that needed to be quantified using the long-term monitoring data. This included adult survival (Brooks et al. 2024a), size at first reproduction, and growth during both the larval and adult phase (Brooks et al. 2020). We also quantified reproductive output using previously published data and data collected from preserved specimens housed in the Georgia Southern University – Savannah Science Museum Herpetology Collection (Chandler and Brooks 2023). Other parameters had to be estimated from values available in the literature. For example, the number of eggs that hatch and survive through the larval period to reach metamorphosis is incredibly difficult to quantify in practice, but there are a few previous studies that have attempted this for some southeastern amphibians.
We then used the available data to construct an Integral Projection Model for flatwoods salamanders (Brooks et al. 2024b). I will spare you the details, but the important part of this framework is that the model estimates demographic rates (survival, reproduction) using body size. The impacts of body size are apparent in model outputs. For example, our data have shown that longer periods of inundation result in larger metamorphs, which reach reproductive size faster than smaller metamorphs. Increasing larval size had a noticeable positive effect on population growth rate when keeping other factors constant. Furthermore, the model consistently indicated that survival of juveniles (1–2 years post-metamorphosis) had important impacts on population growth rate (i.e., as animals reach the body size of first reproduction). The percentage of eggs reaching metamorphosis had weaker impacts on overall population growth.
While amphibian populations are adapted to persist through periods of drought, frequent reproductive failure can lead to population declines and ultimately local extinction events. This effect was highlighted in the model results. For example, increasing the rate of reproductive failure from 50% to 67% increased the extinction probability from approximately 8% to 59% after 70 years. On average, successful recruitment is required every other year for flatwoods salamander populations to have low extinction probabilities over long time periods. Finally, changes in adult survival rates also had strong impacts on the extinction probability in these populations. Shifting from low to high adult survival led to an approximately 4-fold decrease in extinction probability. Importantly, we have a poor understanding of the factors that impact adult survival in flatwoods salamanders, despite evidence that it is variable across years (Brooks et al. 2024a). This is a critical research need.
Viability Under Future Climate Change
One of the major goals of my dissertation research was to apply this existing demographic model to understand how flatwoods salamander populations may respond to future climate changes. This work is possible because there are a variety of simulations that predict future climate (temperature and precipitation) patterns based on current trends and different emission scenarios. For this work, we selected three global climate models, each with two emission scenarios (RCP 4.5 [low] vs. RCP 8.5 [high] on the figures below).
This project was conducted in three parts. First, we used long-term hydrologic data and the climate projections to predict water levels in focal flatwoods salamander breeding wetlands (Chandler et al. 2023). Second, we combined data describing salamander movements (i.e., phenology) with the hydrologic and climate data to characterize the quality of each flatwoods salamander breeding season from 2030–2100 (Chandler et al. 2024). This allowed us to predict whether salamanders would reproduce in each breeding season and, if reproduction was successful, the size and number of metamorphs produced. Third, we combined the breeding season projections with the existing population model to simulate population trajectories using the available climate projections (Chandler et al. 2025).
Across all scenarios, flatwoods salamander populations fluctuated through time, experiencing relatively predictable declines during periods of poor breeding conditions. Including the potential negative interactions between salamander phenology and climate had strong effects on long-term population viability in some scenarios. At the two breeding sites, simulations considering only hydrology led to a high probability of extinction in one and two scenarios, while simulations considering both hydrology and phenology increased the extinction probability in four scenarios at both sites. This highlights how the impacts of climate change can be multifaceted and affect multiple aspects of the amphibian life cycle.
Finally, the results of this work were primarily driven by the individual climate model rather than being consistent across emission scenarios. Most increases in extinction probability were directly tied to specific points in time where models predict many consecutive years of no or poor recruitment. This suggests that management can potentially be enacted to lower long-term extinction probabilities during specific periods where environmental conditions are poor.
Conservation Outlook
This project was the culmination of many years of on-the-ground salamander and environmental monitoring. It would not have been possible without this long-term investment of time and resources. The work highlights how long-term monitoring data can be used to inform ongoing conservation efforts both now and in the future. Given the relatively high risk of extinction under certain scenarios, conservation efforts for flatwoods salamanders should focus on restoring clusters of breeding wetlands that can undergo natural processes of extinction and colonization. This is especially valuable if hydroperiods in some restored wetlands are consistently long enough to support flatwoods salamander recruitment. Hydrology must be monitored over time to make such inferences.
Furthermore, the work discussed here focuses on small populations inhabiting relatively small breeding wetlands. Larger wetlands that support larger salamander populations are likely more resilient to environmental change and should be a target of future restoration work, despite the challenges associated with restoring such wetlands. Large wetlands may also support populations in smaller wetlands through movement of animals across the landscape.
Ultimately, flatwoods salamanders will continue to face an uncertain future in the face of a changing climate. The species has declined to the point where there is little room for error in the management of remaining populations. Continued vegetation and fire management (both within wetlands and surrounding uplands) will have long-term benefits to salamander reproduction and increase overall resiliency. Landscapes with multiple, connected breeding wetlands will have the highest likelihood of persisting through uncertain conditions in the coming decades and beyond.
Literature Cited
Brooks, G. C., T. A. Gorman, and C. A. Haas. 2024a. Variation in flatwoods salamander survival is unrelated to temperature and rainfall. Ichthyology & Herpetology 112:31–40.
Brooks, G. C., H. C. Chandler, Y. Jiao, D. Z. Childs, and C. A. Haas. 2024b. Predicting the population viability of an endangered amphibian under environmental and demographic uncertainty. Population Ecology 66:184–195.
Brooks, G. C., T. A. Gorman, Y. Jiao, and C. A. Haas. 2020. Reconciling larval and adult sampling methods to model growth across life‐stages. PLoS ONE 15:e0237737.
Carey, C., and M. A. Alexander. 2003. Climate change and amphibian declines: Is there a link? Diversity and Distributions 9:111–121.
Chandler, H. C., and G. C. Brooks. 2023. The relationship between female body size and clutch size in Frosted Flatwoods Salamanders (Ambystoma cingulatum). Southeastern Naturalist 22:588–594.
Chandler, H. C., N. M. Caruso, D. L. McLaughlin, Y. Jiao, G. C. Brooks, and C. A. Haas. 2023. Forecasting the flooding dynamics of flatwoods salamander breeding wetlands under future climate change scenarios. PeerJ 11:e16050.
Chandler, H. C., N. M. Caruso, G. C. Brooks, and C. A. Haas. 2024. Wetland hydrology, not altered phenology, challenges Reticulated Flatwoods Salamander (Ambystoma bishopi) management under future climate change. Ichthyology & Herpetology 112:531–543.
Chandler, H. C., G. C. Brooks, Y. Jiao, and C. A. Haas. 2025. Predicting long-term population viability for an imperiled salamander under future climate changes. The Journal of Wildlife Management 90:e70158.
Martin, A. K., G. C. Brooks, H. C. Chandler, K. C. Jones, B. K. Rincon, and C. A. Haas. 2025. Tracking Reticulated Flatwoods Salamander (Ambystoma bishopi) recovery in response to habitat restoration and assisted translocations. Conservation Science and Practice 7:e70144.
McMenamin, S. K., E. A. Hadly, and C. K. Wright. 2008. Climatic change and wetland desiccation cause amphibian decline in Yellowstone National Park. Proceedings of the National Academy of Sciences of the United States of America 105:16988–16993.
Pounds, J. A., and M. L. Crump. 1994. Amphibian declines and climate disturbance: The case of the Golden Toad and the Harlequin Frog. Conservation Biology 8:72–85.
Todd, B. D., D. E. Scott, J. H. K. Pechmann, and J. W. Gibbons. 2011. Climate change correlates with rapid delays and advancements in reproductive timing in an amphibian community. Proceedings of the Royal Society B 278:2191–2197.
