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Background: Climate change is safe to be one of the biggest challenges of mankind. Human activities, especially the combustion of fossil fuels, contribute to the increase of greenhouse gases in the atmosphere and thus to the pace of climate change. The effects of climate change are already being felt, and the resulting damage will most likely be enormous worldwide. Because global impacts vary widely and will lead to very different national vulnerability to climate impacts, each country, depending on its economic background, has different options to ward off negative impacts. Decisions have to be made to mitigate climate consequences according to the preparedness and the vulnerability of countries against the presumed impacts. This requires a profound scientific basis. To provide sound background information, a bibliometric study was conducted to present global research on climate change using established and specific parameters. Bibliometric standard parameters, established socioeconomic values, and climate change specific indices were used for the analyses. This allowed us to provide an overall picture of the global research pattern not only in terms of general aspects, but also in terms of climate change impacts, its effects and regional differences. For this purpose, we choose representative indices, such as the CO2 emissions for the responsibility of countries, the global climate risk index as a combination value for the different types of damage that countries can expect, the increase in sea level as a specific parameter as a measure of the huge global environmental impacts, and the readiness and vulnerability index for the different circumstances of individual countries under which climate change will take place. We hope to have thus made a comprehensive and representative selection of specific parameters that is sufficient to map the global research landscape. We have supplemented the methodology accordingly.
Results: In terms of absolute publication numbers, the USA was the leading country, followed by the UK, and China in 3rd place. The steep rise in Chinese publication numbers over time came into view, while their citation numbers are relatively low. Scandinavian countries were leading regarding their publication numbers related to CO2 emission and socioeconomic indices. Only three developing countries stand out in all analyses: Costa Rica, the Fiji Atoll, and Zimbabwe, although it is here that the climate impact will be greatest. A positive correlation between countries’ preparedness for the impacts of climate change and their publication numbers could be shown, while the correlation between countries’ vulnerability and their publication numbers was negative.
Conclusions: We could show that there exists an inequity between national research efforts according to the publication output and the demands and necessities of countries related to their socioeconomic status. This inequity calls for a rethink, a different approach, and a different policy to improve countries' preparedness and mitigation capacity, which requires the inclusion of the most affected regions of the world in a strengthened international cooperation network.
Detailed information on species temperature preferences are needed to measure the effects of global warming on species and communities in European rivers. However, information currently available in the literature on taxon-specific temperature preferences or temperature tolerances is very heterogeneous and therefore not well suited for forecasting purposes. To close this gap, we derived so-called ’central temperature tendencies’ (CTTt values) for benthic invertebrate species. For this end, 547 species and temperature data from regional monitoring programmes in Germany collected at 4249 sites were analysed. Due to the vulnerability of species to high
temperatures, CTTt values were calculated for mean summer temperatures, following a robust approach of calculating a weighted average based on temperature classes. Derived CTTt values correspond well to species temperature preferences as reported in literature as long as the latter were homogeneous in terms of how they were derived and which temperature reference was at focus. Based on taxon-specific CTTt values, a community value, CTTCom, was calculated for each benthic invertebrate sample. CTTCom values were validated by correlation with mean summer water temperatures. As the slope a of the linear regression model between CTTCom values and measured summer temperatures was comparatively low (a = 0.49), a correction function was derived in order to optimise the relation between both. This was crucial, because it is assumed that although CTTt was derived solely from taxa abundances within summer temperature classes, CTTCom not only reflects the effect of (summer) water temperature itself, but also corresponds to a temperature equivalent value, which describes the overall quality of all respiration-relevant aquatic summer habitat conditions that determine the metabolism of respective benthic invertebrates. By comparing this equivalent value with water temperatures measured in the year previous of sampling, statements can be made about the influence of flow conditions and other factors determining oxygen availability.
Thus, CTTCom reflects the mean aerobic scope of the overall benthic invertebrate fauna: the better the respiration conditions for rheophilic species with high oxygen demand, the larger the aerobic scope and the lower CTTCom.
The approach taken in our study is promising and provides a tool to track and even project past, present, and future impacts of global warming on benthic invertebrates in rivers based on measured values of respiratory relevant environmental variables. We encourage all stakeholders in the field of freshwater ecology to test this
Small-scale phenotypic differentiation along complex stream gradients in a non-native amphipod
(2019)
Background: Selective landscapes in rivers are made up by an array of selective forces that vary from source to downstream regions or between seasons, and local/temporal variation in fitness maxima can result in gradual spatio-temporal variation of phenotypic traits. This study aimed at establishing freshwater amphipods as future model organisms to study adaptive phenotypic diversification (evolutionary divergence and/or adaptive plasticity) along stream gradients.
Methods: We collected Gammarus roeselii from 16 sampling sites in the Rhine catchment during two consecutive seasons (summer and winter). Altogether, we dissected n = 1648 individuals and quantified key parameters related to morphological and life-history diversification, including naturally selected (e.g., gill surface areas) as well as primarily sexually selected traits (e.g., male antennae). Acknowledging the complexity of selective regimes in streams and the interrelated nature of selection factors, we assessed several abiotic (e.g., temperature, flow velocity) and biotic ecological parameters (e.g., conspecific densities, sex ratios) and condensed them into four principal components (PCs).
Results: Generalized least squares models revealed pronounced phenotypic differentiation in most of the traits investigated herein, and components of the stream gradient (PCs) explained parts of the observed differences. Depending on the trait under investigation, phenotypic differentiation could be ascribed to variation in abiotic conditions, anthropogenic disturbance (influx of thermally polluted water), or population parameters. For example, female fecundity showed altitudinal variation and decreased with increasing conspecific densities, while sexual dimorphism in the length of male antennae—used for mate finding and assessment—increased with increasing population densities and towards female-biased sex ratios.
Conclusions: We provide a comprehensive protocol for comparative analyses of intraspecific variation in life history traits in amphipods. Whether the observed phenotypic differentiation over small geographical distances reflects evolutionary divergence or plasticity (or both) remains to be investigated in future studies. Independent of the mechanisms involved, variation in several traits is likely to have consequences for ecosystem functions. For example, leaf-shredding in G. roeselii strongly depends on body size, which varied in dependence of several ecological parameters.