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Delayed phenology and reduced fitness associated with climate change in a wild hibernator
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The most commonly reported ecological effects of climate change are shifts in phenologies, in particular of warmer spring temperatures leading to earlier timing of key events 1,2. Among animals, however, these reports have been heavily biased towards avian phenologies, whereas we still know comparatively little about other seasonal adaptations, such as mammalian hibernation. Here we show a significant delay (0.47 days per year, over a 20-year period) in the hibernation emergence date of adult females in a wild population of Columbian ground squirrels in Alberta, Canada. This finding was related to the climatic conditions at our study location: owing to within-individual phenotypic plasticity, females emerged later during years of lower spring temperature and delayed snowmelt. Although there has not been a significant annual trend in spring temperature, the date of snowmelt has become progressively later owing to an increasing prevalence of late-season snowstorms. Importantly, years of later emergence were also associated with decreased individual fitness. There has consequently been a decline in mean fitness (that is, population growth rate) across the past two decades. Our results show that plastic responses to climate change may be driven by climatic trends other than increasing temperature, and may be associated with declines in individual fitness and, hence, population viability.
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Dennis 1989.pdf
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CVA-DIM
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Density stratification in an estuary with complex geometry: Driving processes and relationship to hypoxia on monthly to inter-annual timescales
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The density field in Narragansett Bay (NB), a northeast U.S. estuary with complex geometry that suffers hypoxia, is described and related to driving factors using monthly means from time series observations at 9 sites during late spring to early fall 2001–2009. Stratification (deep-shallow density difference) is dominated by salinity and strongest (4–7 kg m␣3 in late spring) near rivers in the north and east. Shallow horizontal density gradients are about 0.2 kg m␣3 km␣1; deep densities have minor spatial and seasonal variations. Geographic structure in density, and its inter-annual anomalies, is weaker than expected based on the complex geometry and large size relative to the internal deformation radius. Inter-annual variability is primarily driven by river flow and weakly influenced by winds, contrasting nearby systems (Chesapeake Bay, Long Island Sound), likely due to reduced fetch and/or unfavorable alignment with prevailing winds. Stratification response to river flow follows 2/3 power scaling despite that the theory omits important NB attributes (complex geometry, depth-varying horizontal gradients). Contrasting other systems (Delaware Bay, San Francisco Bay), horizontal gradients are at least as responsive to river forcing as theoretical 1/3 power scaling; depth-dependent horizontal gradients or finite basin constraint of intrusion length may be responsible. Bay-wide inter-annual variations in seasonal hypoxia correlate with late spring stratification, though stratification peaks in the north and east with hypoxia most severe in the north and west. Long-term response of stratification, and thus its role in hypoxia, to climate-driven increases in river flow and temperatures will be dominated by the former.
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DenverNationalLCCInvite
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Department of the Interior Policy
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Department of the Interior Policy
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All official policy released by the Department of the Interior can be found in our Electronic Library of the Interior Policies. The list below only includes links to recent or frequently requested documents related to wildland fire.
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DeRolph, Chris
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Desert Thrashers Work Group (CWPRI)
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CWPRI members created this workgroup to generate sharing and innovative discussions. Leader of this group is Chris McCreedy..
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Desmond, Dennis
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Detection and Attribution of Streamflow Timing Changes to Climate Change in the Western United States
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This article applies formal detection and attribution techniques to investigate the nature of observed shifts in the timing of streamflow in the western United States. Previous studies have shown that the snow hy- drology of the western United States has changed in the second half of the twentieth century. Such changes manifest themselves in the form of more rain and less snow, in reductions in the snow water contents, and in earlier snowmelt and associated advances in streamflow ‘‘center’’ timing (the day in the ‘‘water-year’’ on average when half the water-year flow at a point has passed). However, with one exception over a more limited domain, no other study has attempted to formally attribute these changes to anthropogenic increases of greenhouse gases in the atmosphere. Using the observations together with a set of global climate model simulations and a hydrologic model (applied to three major hydrological regions of the western United States—the California region, the upper Colorado River basin, and the Columbia River basin), it is found that the observed trends toward earlier ‘‘center’’ timing of snowmelt-driven streamflows in the western United States since 1950 are detectably different from natural variability (significant at the p , 0.05 level). Furthermore, the nonnatural parts of these changes can be attributed confidently to climate changes induced by anthropogenic greenhouse gases, aerosols, ozone, and land use. The signal from the Columbia dominates the analysis, and it is the only basin that showed a detectable signal when the analysis was performed on individual basins. It should be noted that although climate change is an important signal, other climatic processes have also contributed to the hydrologic variability of large basins in the western United States.
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