Suchergebnisse

Includes bibliographical references. ; 2015 Summer. ; This thesis explores the ways contemporary children's ABC books can politically shape or frame the way audiences interpret and conceptualize content within the books. Using the children's ABC books A is for Activist (2013) and America: A Patriotic Primer (2002), I examine how children's texts can construct audiences, create a unique site of focalization--known as a focalized dialogue--for those audiences, and utilize phenomenological metaphors to politically shape the focalized dialogues that occur between readers of the books. In doing so, contemporary children's ABC books can wield social and political power that can function to characterize contemporary understandings of cultural artifacts and even children themselves.

Since amphibian declines were first proposed as a global phenomenon over a quarter century ago, the conservation community has made little progress in halting or reversing these trends. The early search for a "smoking gun" was replaced with the expectation that declines are caused by multiple drivers. While field observations and experiments have identified factors leading to increased local extinction risk, evidence for effects of these drivers is lacking at large spatial scales. Here, we use observations of 389 time-series of 83 species and complexes from 61 study areas across North America to test the effects of 4 of the major hypothesized drivers of declines. While we find that local amphibian populations are being lost from metapopulations at an average rate of 3.79% per year, these declines are not related to any particular threat at the continental scale; likewise the effect of each stressor is variable at regional scales. This result - that exposure to threats varies spatially, and populations vary in their response - provides little generality in the development of conservation strategies. Greater emphasis on local solutions to this globally shared phenomenon is needed. ; US Geological Survey ; This work was conducted as part of the Amphibian Decline Working Group supported by the John Wesley Powell Center for Analysis and Synthesis, funded by the US Geological Survey. Data deposited at the US Geological Survey's John Wesley Powell Center for Analysis and Synthesis. The authors declare no competing financial interests. This manuscript is contribution #541 of the USGS Amphibian Research and Monitoring Initiative. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Comments from D. Hocking, P. Toschik and three anonymous reviewers improved the manuscript.

Changing climate will impact species' ranges only when environmental variability directly impacts the demography of local populations. However, measurement of demographic responses to climate change has largely been limited to single species and locations. Here we show that amphibian communities are responsive to climatic variability, using >500,000 time-series observations for 81 species across 86 North American study areas. The effect of climate on local colonization and persistence probabilities varies among eco-regions and depends on local climate, species life-histories, and taxonomic classification. We found that local species richness is most sensitive to changes in water availability during breeding and changes in winter conditions. Based on the relationships we measure, recent changes in climate cannot explain why local species richness of North American amphibians has rapidly declined. However, changing climate does explain why some populations are declining faster than others. Our results provide important insights into how amphibians respond to climate and a general framework for measuring climate impacts on species richness. ; John Wesley Powell Center for Analysis and Synthesis - US Geological Survey ; U.S. Geological Survey-Amphibian Research and Monitoring Initiative (ARMI) ; U.S. Fish and Wildlife Service ; National Park Service ; U.S. Forest Service ; National Science Foundation [DEB-0841758, DEB-1149308] ; National Institutes of Health [R01GM109499] ; National Geographic Society ; Morris Animal Foundation ; David and Lucille Packard Foundation ; This work was conducted as part of the Amphibian Decline Working Group supported by the John Wesley Powell Center for Analysis and Synthesis, funded by the US Geological Survey. Funding and logistical support for field data collection came from a range of sources including the U.S. Geological Survey-Amphibian Research and Monitoring Initiative (ARMI), U.S. Fish and Wildlife Service, National Park Service, U.S. Forest Service, National Science Foundation (DEB-0841758, DEB-1149308), National Institutes of Health (R01GM109499), National Geographic Society, Morris Animal Foundation, and David and Lucille Packard Foundation. Data are deposited at the U.S. Geological Survey's John Wesley Powell Center for Analysis and Synthesis. This manuscript is contribution 654 of USGS ARMI. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.