Climate change has an impact on the seasonal weather patterns and this in turn influences the development of agricultural crops. Temperatures are expected to rise in spring whilst summers are expected to be drier and hotter, winters warmer and more humid. This poses new challenges for agricultural management planning.
Rising temperatures have a variety of effects on agriculture: The vegetation period is extended and higher temperatures can increase yields. However, an early start of vegetation also increases the risk of late frosts and thus the risk of yield losses, especially for fruit growers.
Agriculture is affected by climate change, whilst also being a source of greenhouse gases itself. Depending on the type of cultivation, more carbon can be released from the soil. In addition, excessive nitrogen input from fertilizers can cause nitrous oxide to escape into the atmosphere, which is particularly harmful to the climate.
At the same time, higher concentrations of CO2 in the atmosphere can stimulate photosynthesis and plant growth.
Field experiments show, however, that this so-called "CO2 fertilization effect" often has no or only a temporary effect on growth, since the negative effects such as heat and drought predominate in open land. In addition, the gain in biomass growth is often not reflected in the harvested products: for example, a higher grain biomass is not always associated with a higher mass of harvested grain.
As a result of rising temperatures, a spread of plant diseases and pests, which previously were only found in warmer areas, is to be expected.
Other pests, on the other hand, which are dependent on longer periods of humidity, for example, could decline. As a result of climate change, shifts in the species spectrum of plant pests are to be expected in the coming years. Damage caused by fungal diseases is expected to decrease in many areas, with the exception of diseases caused by thermophilic fungi such as mildew.
On average, higher temperatures and milder winters lead to a shift of cultivation areas towards the north and to altered vegetation and growth periods of plants. Especially fewer days of frost in spring could lead to an earlier start of growth. The cultivation of new varieties, especially of heat-loving species such as corn, soy or millet, becomes possible. Cultivation areas in northern Germany, in low mountain ranges and in eastern Bavaria, which today are comparatively cool and humid, can profit from these developments. A moderate rise in temperature and an adequate water supply can be expected to increase the yield potential for many fruit species there.
However, some plant species could also be disturbed in their growth by climate change. For example, some cereal plants such as wheat are extremely sensitive to heat during flowering. Temperatures above 30 degrees Celsius during this period can lead to a sharp drop in yield.
For winter wheat, on the other hand, the decrease in the number of frost days is problematic, since a cold stimulus is required in a certain growth phase (the "shooting"). If this is missing, the harvests suffer.
The productivity of animal husbandry and animal health in Germany are increasingly endangered by so-called vector-transmitted diseases. These are diseases that are transmitted by pests or parasites. These can develop new habitats with rising temperatures and fewer days of frost. This is how the diseases they transmit spread.
Heat stress is also increasing for livestock with climate change. Especially dairy cows are sensitive to temperature changes. Increasing heat could therefore lead to yield losses in the dairy industry. A reduced quality of animal feed due to climatic effects reinforces this trend.
In the course of climate change, both the quantity and the distribution of precipitation in Germany are changing. This has a direct effect on the temporal and regional availability of water. Fluctuations in the soil water and groundwater balance affect the soil quality and productivity of agricultural land. If temperatures rise at the same time, the consequences for agricultural production will increase.
Especially in southwestern Germany and parts of the former East Germany, decreasing precipitation in the summer and more consecutive dry days can be observed as a result of climate change. In these already comparatively warm or dry regions, climate change is becoming increasingly problematic for agriculture.
Due to decreasing precipitation in spring and summer, the availability of water in the soil also decreases during the vegetation period. According to data from the Deutscher Wetterdienst, the number of days with low soil moisture has already increased significantly since 1961. After the dry years of 2018 and 2019, the drought monitor by Helmholtz Centre for Environmental Research in Leipzig shows that in 2020, the total soil down to an average depth of 1.80 meters will experience the third dry year in a row during the growing season. The effects of drought on soil are described in more detail in the Field of Action: Soils.
This development has an impact on agriculture. For example, the droughts of recent years have led to significant regional crop losses - for example, in the 2018 drought year, grain yields were 18% below average, with Schleswig-Holstein (-31%), Brandenburg (-27%) and Saxony-Anhalt (-26%) being the hardest hit. The extent of the damage is estimated at €770 million.
Persistent drought can also lead to an increased need for irrigation in agriculture and cause conflicts over the use of water as a resource.
Excessive rainfall due to climate change can also have negative consequences for agriculture as too much moisture has a negative effect on plant growth. Wetness also hinders sowing, care and harvesting of plants on the areas of arable land or the grazing of meadows.
Extreme weather events
Experts assume that weather extremes such as dry spells and droughts, heavy precipitation, hail and thunderstorms will increase in Germany in the next three decades with high to very high probability. Only an increase in storms is less certain. Extreme heat and persistent dryness as well as excessive wetness due to increasing heavy rainfall events lead to considerable yield losses. The effects are particularly strong when temperature or water stress occurs during sensitive growth phases of plants, such as during leaf formation.
Heavy rainfall is also associated with increased surface runoff and therefore with soil erosion or flood damage to agricultural infrastructure.
The increasing variability of weather conditions and more frequent extreme weather events can lead to greater fluctuations in yield and make adaptation more difficult.