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Amphibians and Reptiles and Climate Change
Preparer: Amy J. Lind, Sierra Nevada Research Center, Pacific Southwest Research Station, Davis, CA.
Newer (2011) version of this paper is available here.
For amphibians and reptiles, responses to climate change will be influenced by the following primary factors: (1) expected changes and variability in local environmental and habitat conditions; (2) the phenology (timing) of life-requisite activities; (3) interactions with emerging pathogens and invasive species; and (4) interactions with other environmental stressors (e.g., chemicals). Over the short term (e.g., annually), the interaction of these factors will determine reproductive success rates and survival to metamorphosis. Over the long term, the frequency and duration of extreme temperature and precipitation events will likely influence the persistence of local populations, dispersal capabilities and consequently the structure of metapopulations on the landscape. Synergisms among a variety of environmental stressors have been documented to adversely affect native amphibians and reptiles and climatic changes are likely to exacerbate these effects.
Although amphibians and reptiles are typically grouped together in assessments such as this one, it should be noted that these two groups represent a great variety of species that are adapted to diverse ecosystems and environments throughout the world. Amphibians have recently been documented to be experiencing global population declines (Stuart et al. 2004) and similar signs of decline may be emerging for reptiles (Gibbons et al. 2000).
Global and regional climate models predict climate warming and increased variability in the timing and type of precipitation (rain or snow). As a consequence of these changes, fire regimes are likely to be altered; in the Western United States this may result in increased fire frequency and intensity. In general, particular ecological communities are expected to move upward in both elevation and latitude (Walther et al. 2002). As with other species, montane and higher-latitude populations of amphibians and reptiles are most at risk (Root et al. 2003).
Amphibian and reptile populations are sensitive to and respond strongly to changes and variability in air and water temperature, precipitation, and the hydroperiod (length of time and seasonality of water presence) of their environments (Carey and Alexander 2003). This is partly because they are ectothermic; their body temperatures and activity cycles are dependent on the presence of optimal environmental conditions. Also, many amphibians require aquatic habitats for egg laying and larval development and moist environments for post-metamorphic life stages (Deullman and Trueb 1986, Wells 2007). As temperatures warm, and the availability of water in aquatic habitats becomes more variable, amphibians are likely to experience lower rates of survival to metamorphosis. Species associated with ephemeral waters, such as shallow ponds and intermittent streams, may be particularly vulnerable to altered precipitation patterns. Temperatures outside of their thermal optima will also cause physiological stresses. Some reptile species exhibit temperature-dependent sex determination during egg incubation that could be influenced by changes and variability in global climates (Gibbons et al. 2000, Hawkes et al. 2007). Increases in frequency or intensity of wildfires is predicted for many areas, especially the Western United States. These changes may directly affect animals during the fire event or degrade habitat conditions necessary for their survival postfire.
Because of their affinities to aquatic habitats and their small size, amphibians typically have relatively small home ranges and low dispersal rates, although there are some exceptions (Deullman and Trueb 1986, Wells 2007). Reptiles are somewhat more mobile and have a greater ability to withstand the expected dryer and warmer conditions (Pough et al. 2001). However, because key habitats and species ranges have already been altered and fragmented by human use and development, the physical pathways to connect animals with suitable habitats (e.g., upwards in latitude or elevation) may not exist. Although some near-term benefits to climate warming may be seen for some reptile species owing to increases in preferred temperatures and activity periods (e.g., Chamaillé-Jammes et al. 2006), over the long term, expected variability and temperature extremes will likely not be beneficial to these taxa.
For amphibians and reptiles, the timing of key ecological events is influenced by environmental conditions, such as air and water temperature and precipitation patterns. The timing of reproduction (breeding/egg laying), metamorphosis, dispersal, and migration may shift in response to higher temperatures and changes in rainfall (Beebee 1995). If such shifts in amphibian and reptile activities occur inconsistently with other ecological events (e.g., emergence of their insect prey), growth and survival rates would be affected.
Recent research on amphibian declines has documented the role of emerging pathogens and in some cases epidemic outbreaks of particular infections and diseases (Daszak et al. 2003). Changes in climatic regimes are likely to increase pathogen virulence and amphibian and reptile susceptibility to pathogens. Similarly, warm water invasive species (e.g., bullfrogs, some fishes in the western United States) are a concern to native species and may expand their ranges given warming trends.
Options for Management
Reduce the effects of other factors that have negative influences on amphibians and reptiles (e.g., habitat alteration, pollutants, and toxins) to decrease stresses on individuals and populations.
Plan nature reserves that span elevational and altitudinal boundaries, so that species can disperse into environments with suitable temperatures and aquatic hydroperiods.
Lannoo, M., ed. 2005. Amphibian declines: the conservation status of United States species. Berkeley, CA: University of California Press. See especially Reaser and Blaustein, Chapter 11, “Repercussions of Global Change.”
Schneider, S.H.; Root, T.L. 2002. Wildlife responses to climate change: North American case studies. Washington, DC: Island Press. 461 p.
Walther, G-R.; Post, E.; Convey, P.; Menzel, A.; Parmesan, C.; Beebee, T.J.C.; Fromentin, J-M.; Hoegh-Guidberg, O.; Bairlein, F. 2002. Ecological responses to recent climate change. Nature. 416: 389-395.
- Amphibian Data Clearinghouse with short papers on causes of amphibian decline.
- IUCN–Amphibian Conservation Plan.
- Partners and Reptile and Amphibian Conservation.
Beebee, T.J.C. 1995. Amphibian breeding and climate change. Nature. 374: 219-220.
Cary, C.; Alexander, M.A. 2003. Climate change and amphibian declines: Is there a link? Diversity and Distributions. 9: 111-121.
Chamaillé-Jammes, S.; Massott, M.; Aragon, P.; Clobert, J. 2006, Global warming and positive fitness response in mountain populations of common lizards, Lacerta vivipara. Global Change Biology. 12: 392–402.
Daszak, P.; Cunningham, A.A.; Hyatt, A.D. 2003. Infectious disease and amphibian population declines. Diversity and Distributions. 9: 141-150.
Deullman, W.E.; Trueb, L. 1986. Biology of amphibians. New York: McGraw-Hill. 670 p.
Gibbons, J.W.; Scott, D.E.; Ryan, T.J.; Buhlmann, K.A.; Tuberville, T.D.; Metts, B.S.; Greene, J.L.; Mills, T.; Leiden, Y.; Poppy, S.; and Winne, C.T. 2000. The global decline of reptiles, déjà vu amphibians. BioScience. 50: 653-666.
Hawkes, L.A.; Broderick, A.C.; Godfrey, M.H.; Godley. B.J. 2007. Investigating the potential impacts of climate change on a marine turtle population. Global Change Biology. 13: 923-932.
Pough, F.H.; Andrews, R.M.; Cadle, J.E.; Crump, M.L.; Savitzky, A.H.; Wells, K.D. 2001. Herpetology. Upper Saddle River, NJ: Prentice-Hall, Inc. 736 p.
Root, T.L.; Price, J.T.; Hall, K.R.; Schneider, S.H.; Rosenzweig, C.; Pounds, J.A. 2003. Fingerprints of global warming on wild animals and plants. Nature. 421: 57-60.
Stuart, S.N.; Chanson, J.S.; Cox, N.A.; Young, B.E.; Rodrigues, A.S.L.; Fischman, D.L.; Waller, R.W. 2004. Status and trends of amphibian declines and extinctions world-wide. Science. 306: 1783-1786.
Walther, G-R., Post, E.; Convey, P.; Menzel, A.; Parmesan, C.; Beebee, T.J.C.; Fromentin, J-M.; Hoegh-Guidberg, O.; Bairlein, F. 2002. Ecological responses to recent climate change. Nature. 416: 389-395.
Wells, K.D. 2007. The ecology and behavior of amphibians. Chicago, IL: University of Chicago Press. 1400 p.
How do climate-related factors interact with other factors (such as habitat alteration and environmental toxins) to influence amphibian and reptile populations and long-term persistence?
Will reducing the impacts and stresses of these other factors lead to increased resiliency of amphibian and reptile populations?
To what degree will carefully planned land reserves provide protection from expected climatic changes?
Ongoing Research at PSW
Amphibian and reptile research at the Pacific Southwest Research Station in California includes work on high-elevation species that may be especially vulnerable to predicted climate warming, such as mountain yellow-legged frogs (Rana mucosa) and Yosemite toads (Bufo canorus). Species like the foothill yellow-legged frog (Rana boylii) and western pond turtle (Clemmys marmorata) that inhabit riverine environments, especially in regulated (dammed) systems are also vulnerable to projected variability in the timing and amount of precipitation. Research on amphibians includes development of restoration techniques that could be used to enhance populations in areas that may be less impacted by climate change [the following bullets each link to an existing FS-PSW Web site http://www.fs.fed.us/psw/topics/climate_change/ecosystem/ see herpetology section].
- Impacts of year-to-year variations of precipitation
(snowpack and rainfall) on amphibian recruitment and survival.
- Seasonal habitat use and site fidelity of
the mountain yellow-legged frog in Sierra Nevada high-elevation
- Multiscale environmental relationships and
population status of lentic-associated amphibians in the Lake
- Amphibian assemblages and introduced fishes
in the wilderness areas of the Klamath-Siskiyou bioregion
- Aseasonal pulsed-flow effects on the foothill
yellow-legged frog (Rana boylii): integration of empirical, experimental
and hydrodynamic modeling approaches
- Effects of damming on two herpetofaunal species
- Reproductive ecology of the foothill yellow-legged
frog (Rana boylii) in Hurdygurdy Creek, northwestern California:
implications for species conservation and management
- Reintroduction of declining amphibians: a
case study for the foothill yellow-legged frog (Rana boylii)
and development of a quantitative database
This section was Prepared by Dede Olson, Pacific Northwest Research Station, Corvallis, OR
Ongoing Research at PNW
Herpetological research at the Pacific Northwest Research Station includes work on several species that may be particularly vulnerable to changing conditions in response to altered patterns of temperature, precipitation, snowpack or snowmelt. These species include both regional sensitive species with restricted ranges and species living in habitats that are patchy in distribution and susceptible to change. Due to their reliance on temperature and moisture regimes, several amphibian species are of key interest. Categories of amphibians of heightened concern relative to climate change scenarios include (1) forest-dependent amphibians such as woodland salamanders (Plethodon spp.) which are typically found in cool, moist microhabitats away from standing and flowing water; (2) forest-dependent species breeding in cool streams, some of which are associated with intermittent streams that may change with variable rain/snowfalls; and (3) species that rely on ephemeral ponds or shallow lake shores for breeding. Species in any of these three categories that are restricted to either mid or high elevations are of special interest, because their habitats may be greatly altered. Furthermore, examining how climatic factors may interact with other known stressors (timber harvest, disease) on these animals is a new research direction in the region. Understanding scenarios of change from climate change and other potential disturbances, and then designing land management activities to provide habitats and habitat connectivity for populations in the face of change can help provide some resiliency for these species.
Related PNW studies include:
- Climate change modeling of amphibian habitats in the Oregon Cascade Range.
- Long-term monitoring of amphibians in high-elevation lakes of the Cascade Range.
- Managing forested landscapes for biodiversity.
- Landscape-scale habitat suitability modeling and risk assessments for the Siskiyou Mountains salamander (Plethodon stormi) in the Applegate Watershed of southwest Oregon, Oregon slender salamander (Batrachoseps wrighti) in forests of the Cascade Range west of the crest in Oregon, and the foothill yellow-legged frog in streams of western Oregon. http://www.fs.fed.us/r6/sfpnw/issssp/species-index/fauna-amphibians.shtml
- Examining the effects of thinning and riparian buffers on species occurring in headwater systems in western Oregon, and development of forest management designs to retain fauna. http://ocid.nacse.org/nbii/density/
- Understanding amphibian disease distributions. http://www.parcplace.org/bdmap2008update.html
Lind, Amy J. 2008. Amphibians and Reptiles and Climate Change. (May 20, 2008). U.S. Department of Agriculture, Forest Service, Climate Change Resource Center. http://www.fs.fed.us/ccrc/topics/amphibians-reptiles.shtml