Sulfur pollution suppression of the wetland methane source in the 20th and 21st centuries.
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Natural wetlands form the largest source of methane (CH(4)) to the atmosphere. Emission of this powerful greenhouse gas from wetlands is known to depend on climate, with increasing temperature and rainfall both expected to increase methane emissions. This study, combining our field and controlled environment manipulation studies in Europe and North America, reveals an additional control: an emergent pattern of increasing suppression of methane (CH(4)) emission from peatlands with increasing sulfate (SO(4)(2-)-S) deposition, within the range of global acid deposition. We apply a model of this relationship to demonstrate the potential effect of changes in global sulfate deposition from 1960 to 2080 on both northern peatland and global wetland CH(4) emissions. We estimate that sulfur pollution may currently counteract climate-induced growth in the wetland source, reducing CH(4) emissions by approximately 15 Tg or 8% smaller than it would be in the absence of global acid deposition. Our findings suggest that by 2030 sulfur pollution may be sufficient to reduce CH(4) emissions by 26 Tg or 15% of the total wetland source, a proportion as large as other components of the CH(4) budget that have until now received far greater attention. We conclude that documented increases in atmospheric CH(4) concentration since the late 19th century are likely due to factors other than the global warming of wetlands. (+info)
Environmental impacts of the Japanese beef-fattening system with different feeding lengths as evaluated by a life-cycle assessment method.
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The objectives of this study were to evaluate the environmental impacts of a beef-fattening system using the life-cycle assessment (LCA) method and to investigate the effects of feeding length on the LCA results. The functional unit was defined as one animal, and the stages associated with the beef-fattening life cycle, such as feed (concentrate and rough-age) production, feed transport, animal management, animal body (i.e., biological activity of cattle), and the treatment of cattle wastes, were included in the system boundary. Our results suggest that enteric or gut CH4 emissions of cattle were the major source in the impact category of global warming (2,851 kg of CO2 equivalents), whereas NH3 emissions from cattle waste were the major source in the impact categories of acidification (35.1 kg of SO2 equivalents) and eutrophication (6.16 kg of PO4 equivalents). Feed production also contributed a great deal to all categories. A shorter feeding length resulted in lower environmental impacts in all the environmental impact categories examined in the current study, such as global warming and acidification, although there was a difference in effect of reducing environmental impacts among the categories. (+info)
Emissions pathways, climate change, and impacts on California.
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The magnitude of future climate change depends substantially on the greenhouse gas emission pathways we choose. Here we explore the implications of the highest and lowest Intergovernmental Panel on Climate Change emissions pathways for climate change and associated impacts in California. Based on climate projections from two state-of-the-art climate models with low and medium sensitivity (Parallel Climate Model and Hadley Centre Climate Model, version 3, respectively), we find that annual temperature increases nearly double from the lower B1 to the higher A1fi emissions scenario before 2100. Three of four simulations also show greater increases in summer temperatures as compared with winter. Extreme heat and the associated impacts on a range of temperature-sensitive sectors are substantially greater under the higher emissions scenario, with some interscenario differences apparent before midcentury. By the end of the century under the B1 scenario, heatwaves and extreme heat in Los Angeles quadruple in frequency while heat-related mortality increases two to three times; alpine/subalpine forests are reduced by 50-75%; and Sierra snowpack is reduced 30-70%. Under A1fi, heatwaves in Los Angeles are six to eight times more frequent, with heat-related excess mortality increasing five to seven times; alpine/subalpine forests are reduced by 75-90%; and snowpack declines 73-90%, with cascading impacts on runoff and streamflow that, combined with projected modest declines in winter precipitation, could fundamentally disrupt California's water rights system. Although interscenario differences in climate impacts and costs of adaptation emerge mainly in the second half of the century, they are strongly dependent on emissions from preceding decades. (+info)
Climate impact on plankton ecosystems in the Northeast Atlantic.
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It is now widely accepted that global warming is occurring, yet its effects on the world's largest ecosystem, the marine pelagic realm, are largely unknown. We show that sea surface warming in the Northeast Atlantic is accompanied by increasing phytoplankton abundance in cooler regions and decreasing phytoplankton abundance in warmer regions. This impact propagates up the food web (bottom-up control) through copepod herbivores to zooplankton carnivores because of tight trophic coupling. Future warming is therefore likely to alter the spatial distribution of primary and secondary pelagic production, affecting ecosystem services and placing additional stress on already-depleted fish and mammal populations. (+info)
Genetic response to climatic change: insights from ancient DNA and phylochronology.
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Understanding how climatic change impacts biological diversity is critical to conservation. Yet despite demonstrated effects of climatic perturbation on geographic ranges and population persistence, surprisingly little is known of the genetic response of species. Even less is known over ecologically long time scales pertinent to understanding the interplay between microevolution and environmental change. Here, we present a study of population variation by directly tracking genetic change and population size in two geographically widespread mammal species (Microtus montanus and Thomomys talpoides) during late-Holocene climatic change. We use ancient DNA to compare two independent estimates of population size (ecological and genetic) and corroborate our results with gene diversity and serial coalescent simulations. Our data and analyses indicate that, with population size decreasing at times of climatic change, some species will exhibit declining gene diversity as expected from simple population genetic models, whereas others will not. While our results could be consistent with selection, independent lines of evidence implicate differences in gene flow, which depends on the life history strategy of species. (+info)
Topical humidified carbon dioxide to keep the open surgical wound warm: the greenhouse effect revisited.
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BACKGROUND: Perioperative hypothermia is common in open surgery and is associated with increased rates of wound infection. This is a result of decreased wound tissue oxygenation, which can be normalized by local warming. Recently, a technique has been developed to establish a carbon dioxide atmosphere in an open surgical wound. Therefore, the authors studied the possible "greenhouse effect" of carbon dioxide insufflation and operation lamps on wound temperature. METHODS: In a fully ventilated operating room surface temperature was measured at steady state in a model of an open surgical wound containing blood agar. The wound model was randomized to either no insufflation or insufflation of dry and humidified carbon dioxide or air, respectively, at a flow of 5 l/min via a gas diffuser. The surface temperature was measured with operation lamps switched on and off, respectively. Evaporation rates were also measured. RESULTS: With the operation light off, the surface temperature in the control was 31.8 degrees C, and with the operation light on, the temperature increased by 1.5 degrees C (P < 0.001). Additional insufflation of dry carbon dioxide increased the surface temperature another 1.9 degrees C (P < 0.001). When the carbon dioxide was humidified, the evaporation rate was lowest and the surface temperature increased further to 35.6 degrees C (P = 0.002). In contrast, insufflation of dry and humidified air did not have a significant effect on the evaporation rate and only marginally increased the wound temperature in comparison with the control. CONCLUSIONS: Insufflation of humidified carbon dioxide in combination with light from the operation lamps may help to keep the open wound warm during surgery. (+info)
Ammonia-oxidizing bacteria respond to multifactorial global change.
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Recent studies have demonstrated that multiple co-occurring global changes can alter the abundance, diversity, and productivity of plant communities. Below ground processes, often mediated by soil microorganisms, are central to the response of these communities to global change. Very little is known, however, about the effects of multiple global changes on microbial communities. We examined the response of ammonia-oxidizing bacteria (AOB), microorganisms that mediate the transformation of ammonium into nitrite, to simultaneous increases in atmospheric CO2, precipitation, temperature, and nitrogen deposition, manipulated on the ecosystem level in a California grassland. Both the community structure and abundance of AOB responded to these simulated global changes. Increased nitrogen deposition significantly altered the structure of the ammonia-oxidizing community, consistently shifting the community toward dominance by bacteria most closely related to Nitrosospira sp. 2. This shift was most pronounced when temperature and precipitation were not increased. Total abundance of AOB significantly decreased in response to increased atmospheric CO2. This decrease was most pronounced when precipitation was also increased. Shifts in community composition were associated with increases in nitrification, but changes in abundance were not. These results demonstrate that microbial communities can be consistently altered by global changes and that these changes can have implications for ecosystem function. (+info)
Curbing the U.S. carbon deficit.
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The U.S. emitted approximately 1.58 petagrams (Pg) of fossil fuel carbon in 2001, approximately one-quarter of global CO(2) production. With climate change increasingly likely, strategies to reduce carbon emissions and stabilize climate are needed, including greater energy efficiency, renewable energy sources, geoengineering, decarbonization, and geological and biological sequestration. Two of the most commonly proposed biological strategies are restoring organic carbon in agricultural soils and using plantations to sequester carbon in soils and wood. Here, we compare scenarios of land-based sequestration to emissions reductions arising from increased fuel efficiency in transportation, targeting ways to reduce net U.S. emissions by 10% ( approximately 0.16 Pg of carbon per year). Based on mean sequestration rates, converting all U.S. croplands to no-till agriculture or retiring them completely could sequester approximately 0.059 Pg of carbon per year for several decades. Summary data across a range of plantations reveal an average rate of carbon storage an order of magnitude larger than in agricultural soils; in consequence, one-third of U.S. croplands or 44 million hectares would be needed for plantations to reach the target of approximately 0.16 Pg of carbon per year. For fossil fuel reductions, cars and light trucks generated approximately 0.31 Pg of carbon in U.S. emissions in 2001. To reduce net emissions by 0.16 Pg of carbon per year, a doubling of fuel efficiency for cars and light trucks is needed, a change feasible with current technology. Issues of permanence, leakage, and economic potentials are discussed briefly, as is the recognition that such scenarios are only a first step in addressing total U.S. emissions. (+info)