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Amphibian Research and Monitoring Initiative

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Climate Change

Ground truthing
Robert Fisher and Stacey Hathaway (ARMI) ground-truthing potential desert-frog breeding sites selected using remote sensing of soil characteristics derived from known breeding site. Photo by: C. Schwalbe.

Freshwater wetlands provide critical habitat for a diverse array of organisms including many amphibians. Yet, under the continued impacts of water diversions and the newer threats of climate change, these habitats are among the most imperiled ecosystems on Earth. Climate change has the potential to alter many sources of water critical to the habitats amphibians need, especially those associated with breeding and development. Potential changes include: change in timing and availability of water from glacier melt, snow and rain timing and amount; persistence of vernal pools and seasonal wetlands; altered evapotranspiration rates; and reduced stream flows and groundwater recharge rates.

Other ecosystem components likely to change in response to climate change include the timing and frequency of fires, the spread of invasive plants and animals, and microclimates in which the animals live.

ARMI Products on Climate Change

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Elizabeth Gallegos, USGS  
This is an ARMI Product. Chapter D. Summary and conclusions.
Authors: Schroeder RA, Gallegos EA, Smith GA, Martin P, Fisher RN | Date: 2015 | Outlet: U.S. Geological Survey Scientific Investigations Report pp 97-106
Hydrological and biological investigations were done during 2005 and 2006 in cooperation with the U.S. National Park Service at Darwin Falls in Death Valley National Park, Piute Spring in Mojave National Preserve, and Fortynine Palms Oasis in Joshua Tree National Park where discharge from springs or groundwater seeps sustains rare perennial streams in the otherwise arid environment of the Mojave Desert in which surface water is scarce and usually ephemeral. The study collected data on water quantity (discharge), temperature, water quality, and endemic anuran (frog and toad) populations and their health. In addition, a single survey of endemic anuran populations and their health was completed at Rattlesnake Canyon in the Joshua Tree National Park. Results from this study were compared to historical data, and can provide a baseline for future hydrological and biological investigations to evaluate health and sustainability of the resource as well as its response to changing climate and increases in human use.

T. Garner  
This is an ARMI Product. Heterogeneous responses of temperate-zone amphibian populations to climate change complicates conservation planning
Authors: Muths E, Chambert T, Schmidt BR, Miller DAW, Hossack BR, Joly P, Grolet O, Green DM, Pilliod DS, Cheylan M, Fisher RN, McCaffery RM, Adams MJ, Palen WJ, Arntzen JW, Garwood J, Fellers G, Thirion J-M, Besnard A, Grant EHC | Date: 2017-12 | Outlet: Scientific Reports. DOI:10.1038/s41598-017-17105-7 | Format: .PDF
The pervasive and unabated nature of global amphibian declines suggests common demographic responses to a given driver, and quantification of major drivers and responses could inform broad-scale conservation actions. We explored the influence of climate on demographic parameters (i.e., changes in the probabilities of survival and recruitment) using 31 datasets from temperate zone amphibian populations (North America and Europe) with more than a decade of observations each. There was evidence for an influence of climate on population demographic rates, but the direction and magnitude of responses to climate drivers was highly variable among taxa and among populations within taxa. These results reveal that climate drivers interact with variation in life-history traits and population-specific attributes resulting in a diversity of responses. This heterogeneity complicates the identification of conservation ?rules of thumb? for these taxa, and supports the notion of local focus as the most effective approach to overcome global-scale conservation challenges.

Cheryl Brehme, USGS  
This is an ARMI Product. Longevity and population age structure of the arroyo southwestern toad (Anaxyrus californicus) with drought implications
Authors: Fisher RN, Brehme CS, Hathaway SA, Hovey TE, Warburton ML, Stokes DC | Outlet: Ecology and Evolution | Format: .PDF
The arroyo southwestern toad is a specialized and federally endangered amphibian endemic to the coastal plains and mountains of central and southern California and northwestern Baja California. It is largely unknown how long these toads live in natural systems, how their population demographics vary across occupied drainages, and how hydrology affects age structure. We used skeletochronology to estimate the ages of adult arroyo toads in seven occupied drainages with varying surface water hydrology in southern California. We processed 179 adult toads with age estimates between one and six years. Comparisons between skeletochronological ages and known ages of PIT tagged toads showed that skeletochronology likely underestimated toad age by up to two years, indicating they may live to seven or eight years, but nonetheless major patterns were evident. Arroyo toads showed sexual size dimorphism with adult females reaching a maximum size of 12mm greater than males. Population age structure also varied among the sites. Age structure at sites with seasonally predictable surface water was biased toward younger individuals, which indicated stable recruitment for these populations. In contrast, age structures at the ephemeral sites were biased toward older individuals with cohorts roughly corresponding to higher rainfall years. These populations are driven by surface water availability, a stochastic process, and are thus more unstable. Based on our estimates of toad ages, climate predictions of extreme and prolonged drought events could mean that the number of consecutive dry years could surpass the maximum life span of toads making them vulnerable to extirpation, especially in ephemeral freshwater systems. Understanding the relationship between population demographics and hydrology is essential for predicting species resilience to projected changes in weather and rainfall patterns. The arroyo toad serves as a model for understanding potential species responses to long term climatic and hydrologic changes in Mediterranean stream systems. We recommend development of adaptive management strategies to address these threats.

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