Grasslands cover nearly 40% of the Earth’s land area and play a critical role in the planet’s water cycle. These ecosystems, which are essential for agriculture, wildlife, and atmospheric processes, are increasingly threatened by climate change. New research co-led by the University of Maryland sheds light on how climate change, specifically drought conditions combined with elevated temperatures and higher CO2 levels, could drastically alter how grasslands use and move water. The findings, published in the prestigious journal Science, provide the first experimental evidence of how climate change will impact water movement in grasslands, revealing far-reaching implications for both ecological systems and water resources.
The Research Experiment: Investigating Future Climate Conditions
The study, which began as a collaborative effort with the University of Innsbruck, used a real-world experiment to simulate climate conditions expected in the future, specifically focusing on how grasslands would respond to drought, warming, and elevated CO2 concentrations. Researchers carried out their work in open plots in an Austrian grassland, where they simulated six different climate conditions by adjusting air temperature, CO2 levels, and introducing recurring drought conditions. To simulate drought, large shelters were deployed to prevent natural rainfall from reaching certain experimental plots.
To track how water behaved under these experimental conditions, researchers utilized deuterium, a stable isotope of hydrogen, mixed into water. The isotope allowed the scientists to trace the movement of water through the soil and plants with much greater precision, revealing the paths water took after simulated rainfall.
This research is crucial for our understanding of how water, an essential resource for all life, will move through ecosystems under future climate conditions. Grasslands depend on a predictable and stable exchange of water between the soil, plants, and atmosphere. This exchange is vital for maintaining ecological balance, but changing temperatures, drought frequency, and elevated levels of atmospheric CO2 could alter this delicate process.
Fundamental Changes to Water Movement
The study’s results indicate that under future climate conditions — where drought, heat, and elevated CO2 levels are commonplace — two fundamental shifts in water dynamics occur. First, the structural properties of the soil change, affecting how water moves through it. Second, plant behavior changes, especially in how they use available soil moisture.
One of the most important findings of this study is how changes in soil structure during droughts affect the way water is retained and moved through the grassland ecosystem. During the experiment, the team observed that recurring drought conditions caused the pores in the soil within the root zone to change in size and structure. Older water, left behind by previous rainfalls, was trapped in smaller pores, while newer water would flow quickly into larger pores that drained more rapidly.
This altered structure of the soil means that water from heavy rainfall events may not remain within the soil long enough to interact with the deeper, older water supplies as it usually would. Instead, it may quickly flow into nearby water bodies such as streams and rivers without adequately interacting with the plants and soil it would typically nourish. This faster runoff could also carry away vital nutrients, pollutants, and contaminants with it, degrading local water quality in a way that could affect entire ecosystems, including agriculture.
How Plants Adapt: Water Conservation Strategies
Another critical discovery from this research is how plants respond to these new, more water-stressed conditions. In an environment where water is scarce and rainfall is irregular, plants are under immense pressure to conserve moisture. As temperatures rise and the frequency of droughts increases, the plants in these grasslands have adapted by reducing the amount of water they release back into the atmosphere through the process known as transpiration.
By releasing less water through transpiration, plants help conserve moisture during drought conditions, which can be seen as a survival strategy to prevent further dehydration. However, this change could have negative long-term effects. When plants conserve water by lowering transpiration, there is less atmospheric cooling, which in turn leads to a rise in local temperatures. This forms a feedback loop in which more intense droughts can trigger further warming, exacerbating the situation and making recovery even more challenging.
This finding suggests that grasslands may become more resilient to water stress in the short term, as plants conserve available water. However, the long-term consequences for plant growth are uncertain. Reduced water loss through transpiration could impair the plant’s ability to flourish, potentially stunting growth or changing the composition of species in the ecosystem over time.
The Implications of Altered Water Dynamics
The interaction between plants, soil, and water in grassland ecosystems may be much more complex than initially thought, according to the study’s authors. Their work reveals that while plants can access water more efficiently, altered soil properties may cause other unintended consequences. One of the greatest challenges lies in predicting how ecosystems that depend on these intricate water interactions will respond to combined changes in climate, temperature, CO2 levels, and precipitation patterns.
These findings have important implications for the conservation and management of ecosystems, especially in the face of escalating climate change. The delicate balance between water conservation by plants, soil structural integrity, and runoff could result in unpredictable changes that could make ecosystems less able to recover from drought conditions. The study’s conclusions point to a more fragile future for grasslands as water distribution becomes more unpredictable and intense, and these shifts could have ripple effects through other interconnected ecosystems.
In particular, the fact that runoff could increase under these climate conditions emphasizes the importance of watershed management and conservation efforts that focus not only on drought resilience but also on water quality and the prevention of nutrient and pollutant transport through water systems.
Preparing for Future Climate Challenges
Understanding how ecosystems, especially vital grasslands, will adapt to climate change is not just of academic importance. Grasslands contribute significantly to carbon sequestration, support biodiversity, and serve as a food source for livestock and other organisms. The effects of climate change on these ecosystems may thus have far-reaching consequences for both human and environmental health.
As researchers, conservationists, and policymakers prepare for a future in which extreme drought and elevated temperatures are more common, the data presented in this study will become crucial for developing strategies to manage these delicate ecosystems. Water resource management in regions with large grassland areas will have to account for the new challenges associated with soil structure and water movement, ensuring that both natural and agricultural systems can continue to thrive despite changing climate patterns.
Jesse Radolinski, corresponding author of the study and postdoctoral research associate in the Department of Environmental Science & Technology at the University of Maryland, notes the importance of this experiment: “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.” The hope is that this kind of research will be the foundation for developing more accurate predictive models and conservation strategies in the future.
Conclusion
This ground-breaking study, co-led by the University of Maryland and published in Science, reveals that climate change is already beginning to alter how grasslands use and distribute water. The results of this study indicate that future drought conditions combined with higher temperatures and elevated CO2 could radically alter not just water dynamics in grassland ecosystems but also have profound impacts on water availability, plant health, and the wider ecosystem’s resilience to environmental stresses. The intricate relationships between soil structure, plant water use, and water movement point to a more complicated and unpredictable future for many of the Earth’s most important ecosystems.
Understanding these new dynamics and how they affect water distribution is critical to preparing for climate change’s widespread consequences. As researchers continue to explore these changes, the insights gained will play a pivotal role in shaping strategies to safeguard both natural ecosystems and human water resources in an increasingly unpredictable climate.
Reference: Jesse Radolinski, Drought in a warmer, CO2-rich climate restricts grassland water use and soil water mixing, Science (2025). DOI: 10.1126/science.ado0734. www.science.org/doi/10.1126/science.ado0734