Abstract
Recent research has demonstrated that temperature and precipitation conditions correlate with successful reproduction in some insectivorous bat species that live in arid and semiarid regions, and that hot and dry conditions correlate with reduced lactation and reproductive output by females of some species. However, the potential long-term impacts of climate-induced reproductive declines on bat populations in western North America are not well understood. We combined results from long-term field monitoring and experiments in our study area with information on vital rates to develop stochastic age-structured population dynamics models and analyzed how simulated fringed myotis (Myotis thysanodes) populations changed under projected future climate conditions in our study area near Boulder, Colorado (Boulder Models) and throughout western North America (General Models). Each simulation consisted of an initial population of 2,000 females and an approximately stable age distribution at the beginning of the simulation. We allowed each population to be influenced by the mean annual temperature and annual precipitation for our study area and a generalized range-wide model projected through year 2086, for each of four carbon emission scenarios (representative concentration pathways RCP2.6, RCP4.5, RCP6.0, RCP8.5). Each population simulation was repeated 10,000 times. Of the 8 Boulder Model simulations, 1 increased (+29.10%), 3 stayed approximately stable (+2.45%, +0.05%, -0.03%), and 4 simulations decreased substantially (-44.10%, -44.70%, -44.95%, -78.85%). All General Model simulations for western North America decreased by >90% (-93.75%, -96.70%, -96.70%, -98.75%). These results suggest that a changing climate in western North America has the potential to quickly erode some forest bat populations including species of conservation concern, such as fringed myotis.
Highlights
The NCAR-UCAR future climate models project that the temperature in our study area will increase over historic values, with the lower emission scenario (RCP2.6) predicting relatively stable mean annual temperature increase of ~1.2 ̊C after about year 2020, but with the other emission scenarios (RCP4.5, RCP6.0, and RCP8.5) all predicting increases in temperature through 2086 (e.g., > 4.0 ̊C increase for the RCP8.5 scenario)
All of the range-wide General Models eroded substantially over the 77 year simulations, with all representative concentration pathways (RCP2.6, RCP4.5, RCP6.0, RCP8.5) resulting in >90% reduction in simulated fringed myotis populations (Table 3). This result suggests that fringed myotis populations in some parts of western North America have the potential to be substantially impacted by a changing climate
Our results suggest that fringed myotis populations may be susceptible to the impacts of a changing climate in the southwestern U.S (e.g., Arizona and New Mexico) and in northern Mexico (Fig 3)
Summary
The potential impacts of a changing climate on bat populations is of increasing concern [1,2,3,4], in part because bats represent a large contribution to mammalian species diversity [5] and ecosystem processes [6], including important economic impacts to agricultural systems [7,8,9]. Bat populations and climate change supporting the field research described in this paper. The City of Boulder Open Space and Mountain Parks department was generous in funding, support, and access to their properties. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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