Einfluss erhöhter atmosphärischer CO2-Konzentrationen auf die globale Vegetationsentwicklung sowie den Ertrag und die Produktqualität im landwirtschaftlichen Pflanzenbau

The relationships between increased CO₂ supply on the one hand and vegetation development, plant growth, yield and quality of different crop species on the other hand were examined on the basis of observations and experiments (meta studies) available worldwide. Special attention was paid to FACE experiments (Free-air CO₂ enrichment method), but satellite surveys and chamber fumigation systems were also included. The results are: (1) The increase of the atmospheric CO₂ concentration by about 100 ppm during the last 100 years led to increased plant growth worldwide. The global vegetation cover increased by 11–14%, which is attributed by 70% to the increased atmospheric CO₂ content. Since 1982 the global tree population has increased by 7.1%. (2) The increase of the CO₂ content in the air (typically from 350 to 550 ppm) resulted in the yield increases of selected crops from 10 to more than 30%. (3) In Germany, from 1990 to 2015 the yields of wheat, barley, maize and potatoes increased by more than 30% which was partly due to the increased CO₂ content in the air. Across all crop species, the annual net CO₂ fixation in Germany is 96.3 million tons. (4) The CO₂-related yield increases are based on an increase in photosynthesis performance. They were subject to large fluctuations depending on plant species, water supply and nutrient supply (especially N and P). (5) In the case of poor nutrient availability in the soil and insufficient fertilization, the CO₂ induced yield increase can be associated with a reduction in plant nutrient and protein concentrations (mainly due to "dilution effects") and thus with a reduction in quality. N (to a lesser extent also P) obviously plays a key role in this process. This can be compensated by adapted fertilization management and by breeding of drought-tolerant "low-input" varieties with high nutrient utilization efficiency. (6) The CO₂ induced yield increases should be used to secure the world's food supply and improve the income situation in poorer countries.