Framing the Uncertain Future: Articulating IPCC-SRES Scenarios for European River Basins

Downscaled articulations of Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) have been outlined qualitatively for a hypothetical Southern, Central and Northern European river basin and a time horizon set at 2030. The purpose was to survey the sensitivity of ecosystem state indicators, to assess which drivers would be within the grasp of river basin management and to make a geographic comparison. Expert workshop debates were structured using a sequence of entries on drivers and the wider geographic setting, on the river basin and its hydrology, on pressures and on a range of ecosystem state indicators. The workshop elaborated IPCC-SRES scenarios A1 (global economy) and B2 (regional communities) only, since these are generally considered to be the two most divergent scenarios. Contrasts between these two scenarios in land, resource and energy use as well as in the orientation towards sustainability in governance were thought to lead to distinct contrasts in water and sediment delivery to stream networks, in contaminant loads and their remobilisation and in opportunities for riparian biota to populate available habitat. Also, these contrasts between A1 and B2 are probably most profound in the North and South. In contrast to other scenario assessments in the literature, the workshop found it highly plausible that agricultural land use would expand in the North, notably on deeper soils that had been afforested in previous decades. For the South, uncertainty on the direction of land use change was profound, leading to quite different, sketchy but plausible trajectories. Workshop participants remained cautious in the use of scenarios, because it was felt that adoption of altered lifestyles, transition to a carbon-neutral energy system or a nutrient-balanced, low-external-input agriculture can be charted as scenario elements, but their wholesale assimilation in real societies over the coming decades remains hard to predict. Notably discharge variability was foreseen to be highly responsive to the different scenarios but is considered to be under the influence of a river manager. Major drivers, such as the Common Agricultural Policy of the European Union and world market demand development for dairy or biofuel, will strongly affect land use and soil management. These appear to be largely outside the span of control of river basin authorities. The workshop hoped that risk preparedness in river management would include an identification of such major drivers outside their formal control and of the relevant institutions, both in different sectors and at different levels.