Présentations Colloques

    Oral Presentation
    Session 5.01: Groundwater resources in a world facing climate change
    Klöve Björn
    Climate-induced warming imposes a threat to North European spring ecosystems
    This study reports a long-term water temperature trends in northern European cold-water springs. The study rely on a good set of data from 66 springs in Finland and Sweden and bryophyte and macroinvertebrate species data from s subset of Finnish springs. Mean spring temperatures were closely related to regional air temperature and global radiative forcing of the corresponding year. Most springs (82%) in our data responded rapidly to changes in local climatic conditions during 1968-2012. This is due likely to the fact that the aquifers were mostly unconfined glaciofluvial deposits, being relatively small and shallow. The few karst springs in Sweden showed no or weak response to climate. Moreover, our results suggest that springs fed by aquifers with a small recharge area and low storage volume are more prone to climate-induced warming than those associated with larger aquifers. Based on the three alternative climate scenarios representing low (RCP2.6), intermediate (RCP6) and high emission scenarios (RCP8.5), we estimate that increase of mean spring temperature in the region is likely to range from 0.67 °C (RCP2.6) to 5.94 °C (RCP8.5) by 2086. According to the worst case scenario, the water temperature of these originally cold-water ecosystems (regional mean in late 1970’s 4.7 °C) may exceed 12 °C by the end of this century. Our results show that several degrees shift in the thermal regime of springs will have substantial biodiversity impacts and result in regional extinction of native, cold-stenothermal spring specialists, whereas, in contrast, species diversity of generalist taxa is likely to increase in future. Even a slight (by 1 °C) increase of water temperature is likely to eliminate rare and sensitive spring-preferring species thus altering bryophyte and macroinvertebrate assemblages in spring-fed streams but much less so in streams with lower groundwater input. Our results provides the first empirical evidence that climate change is warming groundwater and associated ecosystems in the northern hemisphere.


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