BAUM – climate change and weather anomalies: assessment of agri-environmental measures | Umweltbundesamt

The regional observation data shows:
- the abrupt transition to 30-60-day monsoon activity
- the "period doubling" in midsummer, which alternately produces stronger and weaker cycles (and thus also heat waves)
- a period extension (slowdown) after the summer
- the variability and timing of the fall transition
For the project, an ensemble of 15 combinations of established global and regional climate models was used for the RCP4.5 and RCP 8.5 scenarios.

Water temperature

With regard to the erosivity of precipitation and soil erosion by water, it is still possible to bring about a slight decline to the current level outside of northern Brandenburg under moderate climate change until the middle of the century. In extreme climate change, a further increase of 40% by 2050 is conceivable. However, it is not only the change in daily totals that is decisive, but above all, whether the intensity peaks increase. If the trend towards more heat days continues, stronger thunderstorms are to be expected, which could lead to an underestimation of the future risk of erosion.
The effects of climate change on the regional water balance were investigated with the eco-hydrological model SWIM of the Potsdam Institute for Climate Impact Research. For the project regions, it emerged that
- in winter the runoff increases with precipitation
- the already low water levels in summer rather continue to decline
- the recharge in winter increases
- in the summer the trends are variable
- the drought stress on remote sites increases

To counteract the growing erosion risk, some measures are identified, e.g. field crops, cultivation of catch crops and under crops, conservation tillage, lower rollover frequency, subdivision of sloped beats by green strips and timely processing, at dry periods e.g. in the early morning. The goal of an intact, protective land cover in spring and summer is crucial, up to afforestation in high-risk locations. Less dense and not too finely worked soils are less slippery and reduce surface runoff. Conservation tillage is established in Brandenburg and is recommended from the point of view of soil protection against climatic challenges. The associated increased use of glyphosate is problematic.
For the level Havelberg, which covers the entire Havel catchment, was calculated by how much the nutrient input must be reduced in order to achieve good chemical status. The nutrient concentrations to be achieved are 1.2 mg N per liter or 0.8 mg P in the annual average. For this, the N-entry would have to increase by 34% (to 6700 tons per year) and the P-entry by 16% (to 580 tonnes). However, the climate scenarios showed an increase of 1-5%. The improvement of water quality therefore requires additional efforts.
Agricultural measures alone can not lead to a better water quality class by 2027. Only together with the optimization and expansion of sewage treatment plants, the orientation value for N would have to be created. For P, the orientation value can even be achieved by measures at sewage treatment plants alone. Because of the proximity to the reference level Havelberg the situation of the Havel in the district Havelland is very similar. For the Spree in the Beeskow region, the orientation values could be achieved by optimization (in the case of phosphorus) or expansion (in the case of nitrogen) of the sewage treatment plants.
The consequences of rising temperatures and increasing drought can be met locally by u.a. later sowing in autumn, early in spring, humus build-up on sandy soils, less humus-consuming plants, cultivation of heat- and dry-resistant species as well as mulch sowing, diversification, strategies against altered pest emergence.