Climate Change Impacts Water Movement in Grasslands

Research published in Science and co-led by the University of Maryland examines how drought and rising temperatures in a CO₂-rich environment impact how grasslands use and transport water.

The study is the first experimental evidence of the possible effects of climate change on water circulation across grassland ecosystems, which cover roughly 40 % of the Earth’s surface area and play an important part in the water cycle.

If we want to predict the effects of climate change on Earth’s water resources, we need data showing how the hydrologic cycle will respond at a small scale where we can define mechanisms, but that just hasn’t been available.

Jesse Radolinski, Study Corresponding Author and Post-Doctoral Research Associate, Department of Environmental Science & Technology, University of Maryland

Radolinski added, “Our experiments found that under summer drought conditions, and higher air temperatures that are expected under a future with elevated CO₂, two things change fundamentally. One, the structural properties of the soil in the root zone change so that water flows differently than we expected, and two, these altered climate conditions and soil properties cause the plants to access water differently.”

New rainfall typically mixes with existing soil water in the root zone before seeping into streams and rivers. This study suggests that under future climate conditions, heavy rainfall may pass through the soil more quickly, bypassing stored water and potentially carrying nutrients and contaminants into local water bodies.

Additionally, plants subjected to predicted drought conditions retain more water and release less into the atmosphere through transpiration. This reduced transpiration could lead to decreased atmospheric cooling, creating a feedback loop of intensified drought and warming.

Radolinski and his team conducted their experiment on grassland plots in Austria in collaboration with the University of Innsbruck. Using adjustable air temperature, elevated CO₂ levels, and repeated drought simulations with large, mechanically deployed shelters to block natural rainfall, they replicated six distinct climate scenarios. Deuterium-labeled water was used to simulate rainfall, and its movement through soil and plants was tracked.

The results showed that repeated droughts in plots with elevated CO₂ and warming altered soil pore structure. Older water became trapped in smaller pores, while newer water flowed more rapidly through larger pores, bypassing significant mixing with stored water.

Plants demonstrated an ability to access the most available soil moisture and reduce water loss through transpiration. While this adaptation may help plants cope with future water stress, further research is necessary to assess its impact on growth.

The study reveals that soil and plant water interactions are more intricate than previously understood, with significant implications for ecosystems’ resilience and recovery during droughts. These findings are critical for informing conservation strategies and ecosystem management in the context of a changing climate.

Journal Reference:

Radolinski, J., et. al. (2025) Drought in a warmer, CO₂-rich climate restricts grassland water use and soil water mixing. Science. doi.org/10.1126/science.ado0734