Extreme weather events, dry soils, and concerns about the water supply: The consequences of climate change are already being felt in some parts of the world, such as Spain. At the 7th Organic Vegetables and Potatoes Expert Forum in Visselhövede, representatives of the German Weather Service and the Lower Saxony Chamber of Agriculture presented their findings on the consequences of climate change for German agriculture.
Mathias Herbst from the Centre for Agricultural Meteorological Research Braunschweig (ZAMF) of the German Weather Service gave a presentation on the development of the water balance as a result of climate change. "By climate change, we don't mean that temperatures and precipitation are merely shifting by a certain amount, but that the distribution is changing. It also means that more extreme weather events will occur in the coming years. We need to adapt to more variable conditions," says Herbst.
2-degree target difficult to achieve
Climate projections relating to the coming decades depend heavily on whether and how political measures to limit emissions take effect. "In the so-called climate protection scenario, it is assumed that we will achieve a maximum global warming of +1.7 degrees by the end of the century. However, we are already at a warming of +1.4 degrees. In the business-as-usual scenario, i.e., the high-emissions scenario, we will be dealing with temperature increases of a completely different order of magnitude. If we want to achieve the 2-degree scenario, this can hardly be achieved by limiting emissions. Instead, we would have to pull even more CO₂ out of the atmosphere." The German Weather Service uses the term "climate" to refer to a period of 30 years.
"What is comforting for our region is that the entire area north of the Alps has become wetter overall and receives more precipitation. In the Mediterranean region, it has tended to become drier. Over the course of the year as a whole, the projections show that annual precipitation in Germany will hardly change, even in the pessimistic scenario. In winter, however, there will be more precipitation, while in summer, it will decrease somewhat or remain largely the same."
The old reference period from 1991 to 2020 shows that Lower Saxony, for example, is already experiencing a negative water balance in contrast to the period from 1961 to 1990. "It has also become significantly drier in Lower and Middle Franconia, the Rhine-Main region, and the Cologne Bay area. The deficits in the affected regions will remain dry for the foreseeable future, which means that full production can no longer be guaranteed. The plants will always be affected by water stress, meaning that yields can only be maximized through the additional use of water."
The high temperatures would result in increased evaporation and consumption, which would also increase the need for water. In recent years, soil moisture has also fallen below 30 percent of the usable field capacity in large areas, which leads to water stress, especially for carrots. "Since 2011, there has been a sustained trend towards drier soils."
Premature change in vegetation
The premature change in vegetation also extends the period in which the plants evaporate water or in which they need water. However, you can't always be sure that the period will last that long or that frosts won't occur again in April/May." Therefore, a complete switch of crops is only of limited benefit.
"A change in the climatic water balance can be observed, which shows higher evaporation, with hardly any change in precipitation. Another effect that we have to take into account is the change in phenology, i.e., plant development. We can see that vegetation is developing earlier overall, meaning that dormancy is three weeks shorter than in the previous 30 years." This winter, there is at least a recharge of the groundwater in sight.
Herbst's conclusion: "Precipitation is increasing in winter, but not in summer. Water availability will be very variable. After all, it cannot be assumed that groundwater can be recharged every winter. The cultivation of catch crops can at least be an approach to counteracting climate change in the future. In Germany, we will continue to remain in a favored region. However, we must adapt to the changed conditions, as certain weather conditions and periods of weather will last longer."
Deteriorating water balance in many regions
Ekkehard Fricke from the Lower Saxony Chamber of Agriculture presented his findings on the upcoming challenges and adaptation options. "According to the Federal Statistical Office, 16.6 million hectares of land are used for agriculture in Germany. Of this, 770,000 hectares are irrigated, which corresponds to around five percent. Lower Saxony is the most irrigated federal state with a total share of 14 percent." With regard to the water balance, however, a deterioration can be observed in regions of Germany. "The introduction of irrigation is the most effective measure for agriculture to adapt to climate change."