The timing of life-history events in a changing climate.
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Although empirical and theoretical studies suggest that climate influences the timing of life-history events in animals and plants, correlations between climate and the timing of events such as egg-laying, migration or flowering do not reveal the mechanisms by which natural selection operates on life-history events. We present a general autoregressive model of the timing of life-history events in relation to variation in global climate that, like autoregressive models of population dynamics, allows for a more mechanistic understanding of the roles of climate, resources and competition. We applied the model to data on 50 years of annual dates of first flowering by three species of plants in 26 populations covering 4 degrees of latitude in Norway. In agreement with earlier studies, plants in most populations and all three species bloomed earlier following warmer winters. Moreover, our model revealed that earlier blooming reflected increasing influences of resources and density-dependent population limitation under climatic warming. The insights available from the application of this model to phenological data in other taxa will contribute to our understanding of the roles of endogenous versus exogenous processes in the evolution of the timing of life-history events in a changing climate. (+info)
Microbial production in anoxic wetland rice soils is a major source of atmospheric CH4 the most important non-CO2 greenhouse gas. Much higher CH4 emissions from well managed irrigated rice fields in the wet than in the dry season could not be explained by seasonal differences in temperature. We hypothesized that high CH4 emissions in the wet season are caused by low grain to biomass ratios. In a screenhouse experiment, removing spikelets to reduce the plants' capacity to store photosynthetically fixed C in grains increased CH4 emissions, presumably via extra C inputs to the soil. Unfavorable conditions for spikelet formation in the wet season may similarly explain high methane emissions. The observed relationship between reduced grain filling and CH4 emission provides opportunities to mitigate CH4 emissions by optimizing rice productivity. (+info)
The melting ice cellar: what native traditional knowledge is teaching us about global warming and environmental change.
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Environmental problems have often been observed by Alaska Native communities decades before they have been confirmed by scientific research. (+info)
Fragile transmission cycles of tick-borne encephalitis virus may be disrupted by predicted climate change.
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Repeated predictions that vector-borne disease prevalence will increase with global warming are usually based on univariate models. To accommodate the full range of constraints, the present-day distribution of tick-borne encephalitis virus (TBEv) was matched statistically to current climatic variables, to provide a multivariate description of present-day areas of disease risk. This was then applied to outputs of a general circulation model that predicts how climatic variables may change in the future, and future distributions of TBEv were predicted for them. The expected summer rise in temperature and decrease in moisture appears to drive the distribution of TBEv into higher-latitude and higher-altitude regions progressively through the 2020s, 2050s and 2080s. The final toe-hold in the 2080s may be confined to a small part of Scandinavia, including new foci in southern Finland. The reason for this apparent contraction of the range of TBEv is that its transmission cycles depend on a particular pattern of tick seasonal dynamics, which may be disrupted by climate change. The observed marked increase in incidence of tick-borne encephalitis in most parts of Europe since 1993 may be due to non-biological causes, such as political and sociological changes. (+info)
Predicting the effects of climate change on avian life-history traits.
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Across North America, tree swallows have advanced their mean date of clutch initiation (lay date) by approximately 9 days over the past 30 years, apparently in response to climate change. In a sample of 2,881 nest records collected by the lay public from 1959 to 1991, we examined whether clutch size has also responded to climate change. We found that clutch size is strongly related to lay date, both within and among years, and there has been no significant temporal variation in the slopes or intercepts of the clutch-size/lay-date regressions. As a consequence, we expected increases in clutch size with advancement in lay date; however, we detected no such trend over time. The distributions of egg-laying dates were more constricted in the warmest (and earliest) years, suggesting that changes in mean clutch size might be constrained by changes in the distribution of laying dates. If spring temperatures continue to increase, we predict further reductions of variance in laying dates and relatively small increases in clutch size. Such constraints on life-history variation probably are common and need to be considered when modeling the effects of climate change on reproduction in natural populations. Predicting the long-term effects of constraints and interpreting changes in life-history traits require a better understanding of both adaptive and demographic effects of climate change. (+info)
Interactions of climate change with biological invasions and land use in the Hawaiian Islands: Modeling the fate of endemic birds using a geographic information system.
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The Hawaiian honeycreepers (Drepanidae) represent a superb illustration of evolutionary radiation, with a single colonization event giving rise to 19 extant and at least 10 extinct species [Curnutt, J. & Pimm, S. (2001) Stud. Avian Biol. 22, 15-30]. They also represent a dramatic example of anthropogenic extinction. Crop and pasture land has replaced their forest habitat, and human introductions of predators and diseases, particularly of mosquitoes and avian malaria, has eliminated them from the remaining low- and mid-elevation forests. Landscape analyses of three high-elevation forest refuges show that anthropogenic climate change is likely to combine with past land-use changes and biological invasions to drive several of the remaining species to extinction, especially on the islands of Kauai and Hawaii. (+info)
Climatic change: possible impacts on human health.
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This paper addresses a number of problems relating to climatic change and human health. Following an introduction outlining the overarching issues, a short summary is given on climatic change and its anthropogenic causes. The rest of the paper then focuses on the direct and indirect impacts of global climatic change on health. Direct effects comprise changes in the hygrothermal stress response of humans, atmospheric pollution, water quality and availability; indirect effects include the potential for the spread of vector-borne diseases outside their current range. The paper concludes with some comments on possible response strategies aimed at alleviating the adverse effects of climatic change on human health. (+info)
Hot topic or hot air? Climate change and malaria resurgence in East African highlands.
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Climate has a significant impact on malaria incidence and we have predicted that forecast climate changes might cause some modifications to the present global distribution of malaria close to its present boundaries. However, it is quite another matter to attribute recent resurgences of malaria in the highlands of East Africa to climate change. Analyses of malaria time-series at such sites have shown that malaria incidence has increased in the absence of co-varying changes in climate. We find the widespread increase in resistance of the malaria parasite to drugs and the decrease in vector control activities to be more likely driving forces behind the malaria resurgence. (+info)