Klimawandel in der Region Havelland-Fläming
A. Lüttger, F.-W. Gerstengarbe, M. Gutsch, F. Hattermann, P. Lasch, A. Murawski, J. Petraschek, F. Suckow, P. C. Werner (Januar 2011)
The project region MORO ‚Havelland-Fläming’ is part of the East-German Lowland in the transitional zone between a maritime and continental climate. The rainfall in the relatively warm summer is higher than during the mild to moderately cold winter. In future the rising temperature will lead to decreasing rainfall from May to October, but precipitation will increase slightly in winter. A temperature rise between 2 K and 3 K could reduce the average rainfall in the south-eastern part of the project area. Overall, however, changes precipitation will not be significant. Yet rising temperatures in combination with unchanging rainfall will lead to more pronounced negative water balances, especially in summer, due to increasing evaporation. Another impact in summer will be the dramatic increase of heat load. On the other hand the number of cold days will decline over the next decades.
The project region is part of the Elbe catchment. Changes in the runoff characteristics of the Elbe River and its tributaries as well as changes in groundwater recharge are already visible today. Rising precipitation in winter and more rainfall in spring will lead to a shift of the peak runoff to the early spring season. In addition, less rainfall with higher evaporation in summer will lead to declining runoff. Increased temperatures will result in lower groundwater level on the plateaus.
The vast majority of the project region is part of the East-German Lowland. The higher yearly mean temperature and global radiation (compared to the small part of the project area belonging to the Northeast German Lowland), the lower rainfall and site conditions were the reasons for higher yield variability in the past. In future, rising temperature will contribute to rising yields in winter wheat, rye and maize. The gain will be greatest under a temperature increase of 2 K. If temperatures rise further, this may lead to yield losses, especially in maize on locations with low groundwater tables. On the other hand higher CO2 concentrations in the atmosphere could contribute to higher yields and might compensate yield losses.
Lower water availability during the main vegetation period raises the threat of droughts and increases the risk of forest fires. Vegetation periods will lengthen, bringing higher productivity of pine and oak under a temperature rise of up to 2 K. A temperature rise of 3 K up to 2050 would reduce the productivity again. In areas with low groundwater tables and low water storage capacity beech productivity will decline. Rising risk of drought could be a threat to reforestation with planting of beech on such areas. Planting of oaks seems to be more suitable. Short rotation coppice plantations of the drought-tolerant European aspen could be an option for the region's agriculture.
