Allele Frequency Shifts in Response to Climate Change and Physiological Consequences of Allozyme Variation in a Montane Insect. Rank, Nathan E. & Elizabeth P. Dahlhoff.
http://dx.doi.org/10.1111/j.0014-3820.2002.tb00151.x DOI: 10.1111/j.0014-3820.2002.tb00151.x
Rapid changes in climate may impose strong selective pressures on organisms. Evolutionary responses to climate change have been observed in natural populations, yet no example has been documented for a metabolic enzyme locus. Furthermore, few studies have linked physiological responses to stress with allozyme genotypic variation. We quantified changes in allele frequency between 1988 and 1996 at three allozyme loci (isocitrate dehydrogenase, Idh; phosphoglucose isomerase, Pgi; and phosphoglucomutase, Pgm) for the leaf beetle Chrysomela aeneicollis in the Bishop Creek region of the Sierra Nevada of California (2900-3300 m). Beetles often experience high daytime (>32?C) and extremely low nighttime (<-5?C) temperatures during summer. Bishop Creek weather station data indicated that conditions were unusually dry before 1988, and that conditions were cool and wet during the years preceding the 1996 collection. We found directional changes in allele frequency at Pgi (11% increase in the Pgi-1 allele), but not at Id or Pgm. We also found that physiological response to thermal extremes depended on Pgi genotype. Pgi 1-1 individuals induced expression of a 70-kD heat shock protein (HSP) at lower temperatures than 1-4 or 4-4 individuals, and 1-1 individuals expressed higher levels of HSP70 after laboratory exposure to temperatures routinely experienced in nature. Survival after nighttime laboratory exposure to subzero temperatures depended on gender, previous exposure to cold, and Pgi genotype. Females expressed higher levels of HSP70 than males after exposure to heat, and recovery by female Pgi 1-1 homozygotes after exposure to cold (-5?C) was significantly better than 1-4 or 4-4 genotypes. These data suggest that the cooler climate of the mid-1990s may have caused an increase in frequency of the Pgi-1 allele, due to a more robust physiological response to cold by Pgi 1-1 and 1-4 genotypes.
A multi-century perspective of variability in the Pacific Decadal Oscillation: new insights from tree rings and coral. Gedalof, Ze'ev; Mantua, Nathan J & Peterson, David L.
Geophysical Research Letters:
http://dx.doi.org/10.1029/2002GL015824 DOI: 10.1029/2002GL015824
Annual growth increments from trees and coral heads provide an opportunity to develop proxy records of climatic variability that extend back in time well beyond the earliest instrumental records, and in regions where records have not been kept. Here we combine five published proxy records of North Pacific climatic variability in order to identify the extent to which these records provide a coherent picture of Pacific Basin climatic variability. This composite chronology is well correlated with the Pacific Decadal Oscillation (PDO) index, and provides a better record of PDO variability than any of the constituent chronologies back to 1840. A comparison of these records suggests that the PDO may not have been an important organizing structure in the North Pacific climate system over much of the 19th century, possibly indicating changes in the spatial pattern of sealevel pressure and consequent surface climate patterns of variability over the Americas.
A review of twentieth-century drought indices used in the United States. Richard R. Heim Jr..
Bulletin of the American Meteorological Society:
The monitoring and analysis of drought have long suffered from the lack of an adequate definition of the phenomenon. As a result, drought indices have slowly evolved during the last two centuries from simplistic approaches based on some measure of rainfall deficiency, to more complex problem-specific models. Indices developed in the late nineteenth and early twentieth century included such measures as percent of normal precipitation over some interval, consecutive days with rain below a given threshold, formulae involving a combination of temperature and precipitation, and models factoring in precipitation deficits over consecutive days. The incorporation of evapotranspiration as a measure of water demand by Thornthwaite led to the landmark development in 1965 by Palmer of a water budget-based drought index that is still widely used. Drought indices developed since the 1960s include the Surface Water Supply Index, which supplements the Palmer Index by integrating snowpack, reservoir storage, streamflow, and precipitation at high elevations; the Keetch-Byram Drought Index, which is used by fire control managers; the Standardized Precipitation Index; and the Vegetation Condition Index, which utilizes global satellite observations of vegetation condition. These models continue to evolve as new data sources become available. The twentieth century concluded with the development of the Drought Monitor tool, which incorporates Palmer's index and several other (post Palmer) indices to provide a universal assessment of drought conditions across the entire United States. By putting the development of these drought indices into a historical perspective, this paper provides a better understanding of the complex Palmer Index and of the nature of measuring drought in general.
This study estimates potential energy and peak demand savings from energy-efficiency measures in California. In contrast to energy conservation, which often involves short-term behavioral changes, energy-efficiency opportunities are typically physical, long-lasting changes to buildings and equipment that result in decreased energy use while maintaining constant levels of energy service. It was recently estimated that roughly 70 percent of California's peak demand reduction in the summer of 2001 is attributable to short-term conservation behavior rather than long-lasting efficiency improvements (Goldman et al. 2002). Our study shows that significant additional and long-lasting energy-efficiency potential exists.
Chapter 10: The transboundary setting of California's water and hydropower systems linkages between the Sierra Nevada, Columbia, and Colorado hydroclimates in Climate and Water: Transboundary Challenges in the Americas. Daniel R. Cayan, Michael D. Dettinger, Kelly T. Redmond, Gregory J.
McCabe, Noah Knowles and David H. Peterson.
Climate fluctuations are an environmental stress that must be factored into our designs for water resources, power, and other societal and environmental concerns. Under California's Mediterranean setting, winter and summer climate fluctuations both have important consequences. Winter climatic conditions determine the rates of water delivery to the state, and summer conditions determine most demands for water and energy. Both are dictated by spatially and temporally structured climate patterns over the Pacific and North America. Winter climatic conditions have particularly strong impacts on hydropower production and on San Francisco Bay/Delta water quality. It is thus noteworthy that precipitation from winter storms in California is more variable than in neighboring regions. For example, annual discharge from the Sacramento-San Joaquin system has a coefficient of variation (standard deviation/mean) of 44% compared to 19% in the Columbia Basin and 33% in the Colorado Basin. Also, in California, multiyear droughts occur more often than would be expected by chance, but wet years do not exhibit such persistence. A crucial aspect of California's climate stresses is that they influence conditions over broad spatial scales. Climate patterns that cause the state's climatic fluctuations typically reach well beyond its boundaries. This breadth affects California because much of the energy and water used here is supplied by distant parts of the state as well as from the Northwest and Southwest. When dry winters occur in the Sierra Nevada, they also tend to occur in the Columbia and Colorado Basins.
This study integrates information on current distributions of major vegetation community types in California with projections of climate change and future urbanization patterns. The goal of this analysis was to identify how the future distribution and spatial extent of these community types might be altered. The main results of our work follow. We estimate that climate change will substantially change the distribution and spatial extent of many community types in California. We project that the extent of many community types will be reduced (e.g., alpine tundra, boreal conifer forest, C3 grassland, and subtropical shrub desert), and that the extent of others (e.g., C4 grassland and warm temperate mixed forest) will increase. Urbanization in California is estimated to increase as a result of population growth. This would reduce the spatial extent of community types as undeveloped areas become developed (although some development will take place on lands that are currently used for agriculture). We project that urbanization will most affect Mediterranean shrubland (e.g., southern coastal scrub), temperate mixed xeromorphic woodlands (e.g., oak and juniper woodlands), and maritime temperate forests (e.g., redwoods). Climate change would have a much larger impact on the extent of the major vegetation community types studied (e.g., Mediterranean shrubland and C3 grassland) than would urbanization. In a landscape context, habitat heterogeneity in California may be reduced if climate change results in lowered soil moisture (from a combination of higher temperatures and no change in precipitation) or substantially higher temperatures (i.e., approximately 5°C). We expect that diversity will increase slightly if climate change results in wetter conditions with smaller increases in temperature (i.e., 3°C or less). Coastal sage scrub (CSS) is particularly threatened by future urbanization, with more than a 20% loss of existing habitat expected by 2100. Furthermore, climate change could result in three times greater loss of coastal sage habitat. Potential refugia for CSS have been preliminarily identified. These, and areas where urbanization ' but not climate change ' threatens CSS, could be the focus of future conservation efforts. Some results of this study should be treated with caution. In particular, there is substantial uncertainty about exactly where, if anywhere, CSS would survive climate change. In addition, there are many uncertainties about future development patterns. Conducting more detailed and site-specific analyses on CSS and development in the areas identified in this study as those where CSS would survive (but could be threatened by development) would reduce uncertainty.
Increasing temperatures are likely to affect flood control operations in the Sacramento Valley. Snowpack storage will decrease and the fraction of rain in storm events will increase. Reservoirs with flood control objectives manage floods using static rule curves that define how much water can be stored and the rate at which it can be released from the dam. Studying the effect of climate change, and, in particular, increasing temperatures, on the Shasta, Oroville and New Bullards Bar dams' flood control operations illustrates that static flood control curves perform poorly in changing climates. Two reservoirs, Shasta and Oroville, have dynamic curves that improve each dam's flood control and storage abilities. The existing flood control rule curves are based on historic data from the first half of the 20th century and should be updated to account for past and projected changes to the hydrologic regime.
Climate change is expected to alter the distribution and abundance of many species. Predictions of climate-induced population extinctions are supported by geographic range shifts that correspond to climatic warming, but few extinctions have been linked mechanistically to climate change. Here we show that extinctions of two populations of a checkerspot butterfly were hastened by increasing variability in precipitation, a phenomenon predicted by global climate models. We model checkerspot populations to show that changes in precipitation amplified population fluctuations, leading to rapid extinctions. As populations of checkerspots and other species become further isolated by habitat loss, climate change is likely to cause more extinctions, threatening both species diversity and critical ecosystem services.
Climate responses to a doubling of atmospheric carbon dioxide for a climatically vulnerable region. Snyder, Mark A; Bell, Jason L & Sloan, Lisa C.
Geophysical Research Letters:
Global modeling studies of future climate change predict large scale climatic responses to increased atmospheric carbon dioxide (CO2). While there have been several regional climate modeling studies that produced results at spatial and temporal scales relevant for climate change impact analysis, few have employed statistical significance testing of results. In a sensitivity study that focused on mean climate states, we use a regional climate model to generate ensembles of climate scenarios under atmospheric conditions of 280 and 560 ppm CO2, for a domain centered over California. We find statistically significant responses by mean annual and monthly temperature, precipitation, and snow to CO2 doubling. Relative to the 280 ppm results, 560 ppm results show temperature increasing everywhere in the region annually (up to 3.8°C), and in every month, with the greatest monthly surface warming at high elevations. Snow accumulation decreased everywhere, and precipitation increased in northern regions by up to 23%, on a mean annual basis.
Decadal and shorter period variability of surf zone water quality at Huntington Beach, California. Boehm, A. B.; Grant, S. B.; Kim, J. H.; Mowbray, S. L.; McGee, C. D.; Clark, C. D.; Foley, D. M. & Wellman, D. E..
Environmental Science & Technology:
http://dx.doi.org/10.1021/es020524u DOI: 10.1021/es020524u
The concentration of fecal indicator bacteria in the surf zone at Huntington Beach, CA, varies over time scales that span at least 7 orders of magnitude, from minutes to decades. Sources of this variability include historical changes in the treatment and disposal of wastewater and dry weather runoff, El Nino events, seasonal variations in rainfall, spring-neap tidal cycles, sunlight-induced mortality of bacteria, and nearshore mixing. On average, total coliform concentrations have decreased over the past 43 years, although point sources of shoreline contamination (storm drains, river outlets, and submarine outfalls) continue to cause transiently poor water quality. These transient point sources typically persist for 5-8 yr and are modulated by the phase of the moon, reflecting the influence of tides on the sourcing and transport of pollutants in the coastal ocean, Indicator bacteria are very sensitive to sunlight; therefore, the time of day when samples are collected can influence the outcome of water quality testing. These results demonstrate that coastal water quality is forced by a complex combination of local and external processes and raise questions about the efficacy of existing marine bathing water monitoring and reporting programs.