Effects of extreme drought are underestimated worldwide

Grassland and open land cover more than 40% of the Earth's land area. Grassland is an important carbon sink. Researchers from all over the world have therefore joined forces in an international Drought-Net Experiment (IDE) to investigate the consequences of increasing drought due to climate change on different ecosystems. Prof. Dr. Anke Jentsch, holder of the Chair of Disturbance Ecology and Vegetation Dynamics at the University of Bayreuth, is involved.

By reducing precipitation by up to 50% at 100 research sites on six continents using experimental roof constructions, the scientists found that a single year of drought can reduce vegetation growth by more than 80%. This significantly reduces the ability of ecosystems to absorb carbon dioxide. Overall, plant growth in grasslands artificially exposed to drought declined by an average of 36%, which is far higher than previous estimates. The special feature: "In contrast to the globally observed effects, the simulated drought had no significant impact on biomass production at around 20% of the study sites, including a species-rich grassland site in Germany," says disturbance ecologist Anke Jentsch. The climate at German sites was more humid, the number of plant species higher and the drought less severe than on the prairie. Overall, species-rich meadows in the wetter zone of Central Europe survived the drought better than those in drier climate zones.

The research results can help ecologists predict which ecosystems are most at risk during periods of drought and what the wider ecological impact will be. Less plant material can mean less food for grazing animals or even lower harvests. Anke Jentsch points out that during the last summer drought in Europe, intensively managed grassland with relatively few species, such as pure farm meadows or sown clover-grass mixtures, was severely affected. "By maintaining species-rich hay meadows or sowing and reseeding a more diverse species mix, such grasslands could continue to maintain vegetation dynamics and provide the desired ecosystem services even during severe drought," she says. "Biodiversity promotes resilience to extreme events and faster recovery: In changing extreme weather situations, meadows are particularly stable due to the diversity of functional properties of their 'members', i.e. herbs and grasses. Promoting biodiversity in grassland is therefore an effective protection against crop failure during droughts."

The coordination of the International Drought Experiment (IDE) is funded by the US National Science Foundation (NSF). Since 2013, the University of Bayreuth has been involved in the study with Prof. Dr. Anke Jentsch and her international team - including Alexander von Humboldt Fellow Dr. Yujie Niu, postdocs Dr. Tyson Terry and Dr. Andreas von Heßberg, as well as doctoral students Svenja Wanke, Thomas Deola and Peter Wolff. The Bayreuth field experiments are being conducted as part of the SUSALPS "Sustainable use of grassland in the Alps and Alpine foothills under climate change" supported by the Federal Ministry of Education and Research.