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The ranges of infectious diseases and vectors are changing in altitude, along with shifts in plant communities and the retreat of alpine glaciers. Additionally, extreme weather events create conditions conducive to clusters of insect-, rodent- and water-borne diseases. Accelerating climate change carries profound threats for public health and society.
Plants emit a substantial amount of biogenic volatile organic compounds (BVOCs) into the atmosphere. These BVOCs represent a large carbon loss and can be up to approximately 10% of that fixed by photosynthesis under stressful conditions and up to 100gCm(-2) per year in some tropical ecosystems. Among a variety of proven and unproven BVOC functions in plants and roles in atmospheric processes, recent data intriguingly link emission of these compounds to climate. Ongoing research demonstrates that BVOCs could protect plants against high temperatures. BVOC emissions are probably increasing with warming and with other factors associated to global change, including changes in land cover. These increases in BVOC emissions could contribute in a significant way (via negative and positive feedback) to the complex processes associated with global warming.
Peak expiratory flow (PEF) has been measured in 61 laryngectomees before and after a fortnight's stay on the Canary Islands during the Norwegian winter season. A statistically highly significant increase in the PEF-values has been shown. The warmer climate with a higher degree of humidity in the air on the Canary Islands is the most probable cause.
Monthly hospital admission rates (HA) for mania were classified by sex, type of admission (first, or re-admission) and by country (England and Wales or Scotland). Of the 8 classes thus created, all but one showed a statistically significant annual cycle with a peak in Summer and trough in Winter. There was no significant difference in phase or amplitude between male and female cycles. A linear increase in yearly re-admission rates was found during the 8 years of the English and the 11 years of the Scottish data. Current month's mean daily temperature (lag0) and last month's (lag1) mean day-length and mean daily hours of sunshine correlated better with admission rate than did the values for other months. In a multiple regression analysis temperature made the other 2 climatic variables redundant in accounting for variation in HA.
We review the literature dealing with mediterranean climate, vegetation, phenology and ecophysiology relevant to the understanding of tree-ring formation in mediterranean regions. Tree rings have been used extensively in temperate regions to reconstruct responses of forests to past environmental changes. In mediterranean regions, studies of tree rings are scarce, despite their potential for understanding and predicting the effects of global change on important ecological processes such as desertification. In mediterranean regions, due to the great spatio-temporal variability of mediterranean environmental conditions, tree rings are sometimes not formed. Often, clear seasonality is lacking, and vegetation activity is not always associated with regular dormancy periods. We present examples of tree-ring morphology of five species (Arbutus unedo, Fraxinus ornus, Quercus cerris, Q. ilex, Q. pubescens) sampled in Tuscany, Italy, focusing on the difficulties we encountered during the dating. We present an interpretation of anomalies found in the wood structure and, more generally, of cambial activity in such environments. Furthermore, we propose a classification of tree-ring formation in mediterranean environments. Mediterranean tree rings can be dated and used for dendrochronological purposes, but great care should be taken in selecting sampling sites, species and sample trees.
A modelling approach to simulating vegetation dynamics is described, incorporating critical processes of carbon sequestration, growth, mortality and distribution. The model has been developed to investigate the responses of vegetation to environmental change, at time scales from days to centuries and from the local to the global scale. The model is outlined and subsequent tests, against independent data sources, are relatively successful, from the small scale to the global scale. Tests against eddy covariance observations of carbon exchange by vegetation indicated significant differences between measured and simulated net ecosystem production (NEP). NEP is the net of large fluxes due to gross primary production and respiration, which are not directly measured and so there is some uncertainty in explaining differences between observations and simulations. In addition it was noted that closer agreement of fluxes was achieved for natural, or long-lived managed vegetation than for recently managed vegetation. The discrepancies appear to be most closely related to respiratory carbon losses from the soil, but this area needs further exploration. The differences do not scale up to the global scale, where simulated and measured global net biome production were similar, indicating that fluxes measured at the managed observed sites are not typical globally. The model (the Sheffield Dynamic Global Vegetation Model, SDGVM) has been applied to contemporary vegetation dynamics and indicates a significant CO2 fertilisation effect on the sequestration of atmospheric CO2. The terrestrial carbon sink for the 20th century is simulated to be widespread between latitudes 40 degrees S and 65 degrees N, but is greatest between 10 degrees S and 6 degrees N, excluding the effects of human deforestation. The mean maximum sink capacity over the 20th century is small, at 25 gC m(-2) year(-1), or approximately 1% of gross primary production. Simulations of vegetation dynamics under a scenario of future global warming indicate a gradual decline in the terrestrial carbon sink, with the capacity to absorb human emissions of CO2 being reduced from 20% in 2000 to approximately 2% between 2075 and 2100. The responses of carbon sequestration and vegetation structure and distribution to stabilisation of climate and CO2 may extend for up to 50 years after stabilisation has occurred.
Increased nitrate (NO3) concentrations in streamwaters draining forested catchments are reportedly an early indicator of nitrogen (N) saturation. Nitrate concentrations in streams draining 16 forested catchments in south central Ontario were monitored over a 16-year period, during which time N bulk deposition was relatively constant (approximately 9 kg ha(-1) yr(-1)). Mean annual NO3 concentrations in streams were both highly variable among catchments and among years, although patterns of annual concentration were similar among many catchments. Coherence analysis identified two stream groupings. Shallow soils, moderate slopes, low NO3 concentration, and a large wetland component characterized the first group. The second group had primarily upland characteristics including deeper soils, steeper slopes, higher NO3 concentrations, and a much smaller wetland component. Patterns in NO3 concentration in wetland-influenced streams appeared to be related to summer drought and cumulative frost depth, whereas NO3 concentrations in upland-draining streams appeared to be related to both mean annual air temperature and summer drought. Because a number of different climate parameters as well as the physical character of the catchments apparently influence NO3 export, NO3 concentrations in streams are not a good indicator of N saturation in this region.
In this study we have analyzed the hydrochemical effect of drought conditions during 311 hydrological episodes in nine headwater streams in central Ontario over the past 20 years. Acid Neutralization Capacity (ANC) was logarithmically correlated (p<0.05) to antecedent discharge in eight of the nine streams, with the largest decline in ANC occurring after low antecedent flow. In eight of the nine streams SO4(2-) was the most important driving mechanism of ANC decline, but dilution as well as organic acidity was important in several streams. No decrease in the SO4(2-) driven ANC decline was observed over the 20 year study period despite a approximately 40% reduction in SO4(2-) deposition. The strong correlation between ANC decline and low antecedent discharge demonstrates that episodic acidification during rain events is strongly associated with preceding drought conditions, especially in wetland-dominated catchments. The results have important implications for recoveryfrom acidification, especially in northern ecosystems where climate scenarios forecast that warmer and drier conditions will be more common.
Historical coliform measurements (n = 67,269; 32 years) in Newport Bay, a regionally important saltwater wetland and tidal embayment in southern California, have been compiled and analyzed. Coliform concentrations in Newport Bay decrease along an inland-to-ocean gradient, consistent with the hypothesis that this tidal embayment attenuates fecal pollution from inland sources. Nearly 70% of the variability in the coliform record can be attributed to seasonal and interannual variability in local rainfall, implying that stormwater runoff from the surrounding watershed is a primary source of coliform in Newport Bay. The storm loading rate of coliform from the San Diego Creek watershed--the largest watershed draining into Newport Bay--appears to be unaffected by the dramatic shift away from agricultural land-use that occurred in the watershed over the study period. Further, the peak loading of coliform during storms is larger than can be reasonably attributed to sources of human sewage, suggesting that nonhuman fecal pollution and/or bacterial regrowth contribute to the coliform load. Summer time measurements of coliform exhibit interannual trends, but these trends are site specific, apparently due to within-Bay variability in land-use, inputs of dry-weather runoff, and tidal mixing rates. Overall, these results suggest that efforts to improve water quality in Newport Bay will likely have greater efficacy during dry weather summer periods. Water quality during winter storms, on the other hand, appears to be dominated by factors outside of local management control; namely, virtually unlimited nonhuman sources of coliform in the watershed and global climate patterns, such as the El Nino Southern Oscillation, that modulate rainfall and stormwater runoff in southern California.
The U.S. National Assessment of the Potential Consequences of Climate Variability and Change was a federally coordinated nationwide effort that involved thousands of experts and stakeholders. To draw lessons from this effort, the 10 authors of this paper, half of whom were not involved in the Assessment, developed and administered an extensive survey, prepared a series of working papers, and conducted an invitational workshop in Washington, DC, on April 29, 2004. Considering all these sources, the authors conclude that the Assessment was largely successful in implementing its basic design of distributed stakeholder involvement and in achieving its basic objectives. Future assessments could be significantly improved if greater attention were devoted to developing a collective understanding of objectives, preparing guidance materials and providing training for assessment participants, developing a budgeting mechanism which would allow greater freedom in allocating resources across various assessment activities, and creating an environment in which assessments were part of an ongoing process.
Embodied greenhouse gas (GHG) emissions and their structure of inducement by the supply-chain networks of 480 goods and services in the United States are analyzed for 44 GHGs. Producing a dollar of a product or service generates an average of 0.36 kg of CO2 equivalent GHGs onsite, increasing to 0.83 kg when supply-chain-induced emissions are taken into account. Services produce less than 5% of total U.S. GHG emissions directly, and their direct GHG emission intensities per dollar output are much less (0.04 kg C02 equiv/dollars) than those of physical products, even when supply-chain-induced emissions are included (0.47 kg C02 equiv/dollars). When both supply-chain effects and the volume of household expenditures are taken into account, however, household consumption of services excluding electric utilities and transportation services proves to be responsible for 37.6% of total industrial GHG emissions in the United States, almost twice the amount due to household consumption of electric utility and transportation services. Given the current structure of GHG emissions, a shift to a service-oriented economy is shown to entail a decrease in GHG emission intensity per unit GDP but an increase, by necessity, in overall GHG emissions in absolute terms. The results are discussed in the context of U.S. climate change policy.
Measurements of the ratios of stable isotopes in the martian atmosphere and crust provide fundamental information about the evolution of the martian volatile and climate system. Current best estimates of the isotope ratios indicate that there has been substantial loss of gases to space and exchange of gases between the atmosphere and the crust throughout geologic time; exchange may have occurred through circulation of water in hydrothermal systems. Processes of volatile evolution and exchange will fractionate the isotopes in a manner that complicates the possible interpretation of isotopic data in terms of any fractionation that may have been caused by martian biota, and must be understood first. Key measurements are suggested that will enhance our understanding of the non-biological fractionation of the isotopes and of the evolution of the martian volatile system.
Natural mycoflora associated with fumonisins were analyzed in 150 samples of freshly harvested corn from Central-Southern, Central-Western and Northern regions of the State of Paraná, Brazil and correlated to climatic conditions. The corn samples were frequently contaminated with Fusarium sp. (98.7 to 100%) and Penicillium sp. (93 to 100%), when compared to Aspergillus sp. (not detected to 27.7%). The highest contamination with potentially mycotoxigenic fungi occurred in corn harvested in the Central-Western region, where total mould and yeast counts ranged from 5.5 x 10(3) to 5.2 x 10(6) CFU/g, with 98.7% contaminated by Fusarium sp. and 93% by Penicillium sp. In this region F. moniliforme (F. verticillioides) was the predominant Fusarium sp., and was isolated in 85.9% of the samples. Aspergillus sp. was isolated from 27.7% samples. FB1 was detected in 100% of the samples (mean of 2.39 micrograms/g) and FB2 in 97.7% (mean of 1.09 micrograms/g). Fumonisins were also detected in all samples from Northern region, with mean of 4.56 micrograms/g (FB1) and 2.20 micrograms/g (FB2). Considering 1.0 microgram/g as the threshold, 72% of the corn samples from the Central-West and 92% from the North were contaminated with concentrations above this value, in contrast to a 18.5% contamination rate from Central-Southern samples. Between corn planting to harvesting season, the average maximum temperature and relative humidity were 26 degrees C and 77.1% (Central-Southern), 27 degrees C and 69% (Northern) and 29.9 degrees C and 89.1% (Central-Western). Therefore, the higher fumonisins contamination of corn from Northern region when compared to the Central-South were due to the differences in rainfall levels (92.8 mm in Central-Southern, 202 mm in Northern) during the month preceding harvest.
A simple coupled ecosystem-climate model is described that can predict levels of atmospheric CH4, CO2, and H2 during the Late Archean, given observed constraints on Earth's surface temperature. We find that methanogenic bacteria should have converted most of the available atmospheric H2 into CH4, and that CH4 may have been equal in importance to CO2 as a greenhouse gas. Photolysis of this CH4 may have produced a hydrocarbon smog layer that would have shielded the surface from solar UV radiation. Methanotrophic bacteria would have consumed some of the atmospheric CH4, but they would have been incapable of reducing CH4 to modern levels. The rise of O2 around 2.3 Ga would have drastically reduced the atmospheric CH4 concentration and may thereby have triggered the Huronian glaciation.
Abstract. At three study sites, representing Mediterranean, semi-arid and mildly-arid climatic conditions, the effect of shrubs on the spatial patterns of soil moisture was studied. At each site soil moisture was measured, on hillslopes, at the vicinity of 8 shrubs. For each shrub the measurements have been taken at 3 microenvironments, i.e. under the shrub (US), at the margins of shrub (MS) and between shrubs (BS). At the microenvironments US and MS the measurements were taken at 3 directions: upslope, downslope and sideslope of the shrubs. At all sampling points soil samples were taken from 3 depths: 0-2, 2-5 and 5-10 cm. In addition, rock fragments cover percentage near the shrubs was determined. A soil moisture pattern was found, around each shrub, which is composed of a radial gradient and a downslope gradient. The radial gradient is expressed by soil moisture decreasing from the US microenvironment, in all directions, through the MS towards the BS microenvironment. The US microenvironment has a 'spatial advantage' of higher soil moisture content due to (1) relatively higher infiltration rate, (2) capture overland flow from the BS area upslope that shrub and (3) low evaporation rate because of the shading effect. The downslope gradient is expressed by decreasing soil moisture from the upslope direction of each shrub (MS and US microenvironments) towards the downslope direction of that shrub (MS and US microenvironments, respectively). This gradient is controlled by the relatively high content of rock fragments near the shrubs at their upslope direction. Such rock fragments spatial distribution is attributed to (1) the detachment and transport of rock fragments by sheep and goats trampling and (2) the effect of shrub on the continuity of overland flow and sediment transport. The effect of rock fragments is similar to that of shrubs regarding increasing infiltration and decreasing evaporation rate. The relatively high soil moisture at the upslope direction of each shrub enhances annuals growth producing a positive feedback loop: soil moisture--annuals growth--trampling. This sequence maintains the typical rock fragments spatial organization and contributes to the sustainability of the grazing system. At all the study sites at the US microenvironment there is a trend of decreasing soil moisture with increasing soil depth. At microenvironments MS and BS soil moisture increases with soil depth. The results are of great relevance for rehabilitation strategies as they suggest that in order to combat desertification in degraded semi-arid and mildly-arid areas, where the main land use is grazing, both shrubs and rock fragment should be kept at their present spatial distribution.
In 1998, two cases of silica urolithiasis occurred in castrated male dromedaries on an intensive camel farm in the Canary Islands. The immediate attributable cause was the ingestion of large amounts of silica in the feed, estimated as 84.44 g/day. An associated cause was the low level of salt in the diet. Daily ingestion of salt from feed and water was estimated to be 21.8 g (8.6 g of sodium). Seventy-six castrated males from the same farm were divided into four groups: group A received 30 g of salt daily; group B received 40 g; group C received 60 g; and group D received no added salt in the diet (control). The animals were maintained on these dietary regimes for 2 years. No animals from groups A, B or C suffered overt urinary retention. One animal from group D had an obstructive urinary retention 10 months after the study commenced. Thus, 52 g of salt daily appears to be sufficient to prevent urinary retention in dromedaries raised in a subtropical climate.
BACKGROUND: The role of Tetranychus urticae (TU) as an occupational allergen has thus far been investigated only in selected farmer samples. METHODS: The prevalence of TU-induced sensitization and occupational diseases in a randomized sample of farmers living in a temperate climate area was investigated. Occupational/nonoccupational symptoms, skin prick test (SPT) results with common allergens and TU, specific occupational test results, and greenhouse or open-field sources of TU exposure were assessed. The study design was cross-sectional. RESULTS: The prevalence of positive SPT to TU was 6%. TU-induced allergic/nonallergic complaints accounted for 65% of farmers with challenge-confirmed occupational disease. In all farmers, sensitization to common allergens was a risk factor for both current occupational and nonoccupational complaints, while TU sensitization was a prominent risk factor for occupational complaints. Furthermore, in SPT-positive farmers, only the presence of seasonal occupational complaints was significantly associated with TU sensitization. Common allergen sensitization was a risk factor for development of TU sensitization, which was more frequent in greenhouse than in open-field workers. CONCLUSIONS: TU was a common nontraumatic, allergic occupational hazard for farmers. Since occupational seasonal symptoms could be directly related to the presence of TU sensitization, allergy to this mite should be routinely investigated in farmers.
BACKGROUND: The aim of this study was to evaluate the difference between the mite fauna in the inland and coastal Croatia. METHODS: Ninety-nine floor house dust samples were collected: 28 from the coastal area, 31 from the inland rural and 40 from the inland urban area. Data on basic household characteristics were collected for 81 of 99 households. The mites were separated from the dust using the floatation method and then microscopically identified. The levels of Dermatophagoides pteronyssinus (Der p) 1, Dermatophagoides farinae (Der f) 1 and Der 2 were measured using the Dustscreen test. Ordinal descriptive statistics and nonparametric tests were used for data analysis, assuming statistical significance at P < 0.05. RESULTS: More than 70% of mites identified in all areas were pyroglyphids. Nonpyroglyphid mites accounted for 20-25% of all identified mites in the coastal areas (Blomia, Lepidoglyphus and Glycyphagus) and with 15% in the inland areas (Lepidoglyphus and Acarus). The highest Der p 1 median levels were found in the coastal area, with significantly lower levels in the inland rural and inland urban areas (4.5; 2; 0.85 microg/g of dust; P = 0.0001). The highest Der f 1 median levels were found in the inland urban area, with significantly lower levels in the inland rural and coastal areas (0.88; 0.75; 0 microg/g of dust; P = 0.0013). The levels of Der f 1 were significantly higher in samples taken from households with central heating than from those with traditional heating (1; 0.25 microg/g of dust; P < 0.01). CONCLUSIONS: Separate diagnostic dust mite lists for the coastal and inland areas because of climatic and dwelling differences required to be implemented. Compared with traditional heating, central heating significantly increases the risk of exposure to Der f 1 levels >2 microg/g of dust (odds ratio, 7.35; 95% confidence interval, 1.43-37.87; P = 0.01).