The authors’ central claim is that global groundwater modelling has delivered an impressive diagnostic picture of depletion but a limited understanding of sustainable use. Over the past decade, large-scale hydrological models have mapped where water tables are falling fastest, from the High Plains aquifer in the United States to the Indo-Gangetic plain and the North China Plain. Studies such as the 2019 analysis led by de Graaf in Nature demonstrated that groundwater depletion is not a local curiosity but a global phenomenon, with falling water tables affecting streamflow and ecosystems across entire river basins. Complementary work by researchers including Bridget Scanlon and Carole Dalin has quantified the dependence of food systems on non-renewable aquifer storage, linking over-pumping to national food security and international food trade. Yet, as the Nature Water perspective points out, these efforts largely stop at the diagnosis.

The gap, according to the authors, lies in how the models are built. Most global assessments treat groundwater as a reservoir to be withdrawn, tracking the volume of water removed from storage. What they rarely capture is the full set of processes that connect pumping to the things society actually cares about: the yield of a wheat field under a given irrigation schedule, the baseflow that keeps a river alive through a dry summer, the depth at which a wetland’s vegetation can no longer reach the water table, or the feedback between soil moisture, evapotranspiration and crop physiology. Without those process-based links, a model can say that an aquifer is being depleted, but it cannot say what will happen to food production or to ecosystems if pumping is reduced by ten, twenty or fifty percent, nor where a given reduction would do the most good or the most harm.

To close this gap, de Graaf and her co-authors, including Anton Urfels of the International Rice Research Institute and Cornell University, Fatemeh Karandish, Sida Liu and Iwan Supit of Wageningen, propose a shift towards integrated, process-based frameworks that support decision-making across scales. In practical terms, this means coupling global groundwater models with crop growth models, ecohydrological representations of surface-water dependency, and the socio-economic realities of farming decisions. Crop models of the kind represented in the literature by work such as that of Joost Kroes on agrohydrology and Joseph Amthor on crop physiology simulate how plants respond to water stress, allowing researchers to translate a change in water availability directly into a change in yield. Ecohydrological theory, advanced by researchers such as Tom Gleeson, Mark Cuthbert and Donald Perrone, describes how aquifers exchange water with rivers and groundwater-dependent ecosystems, and how slowly those connections recover once disturbed.

The perspective also stresses that scale matters in ways current approaches handle poorly. A pumping decision is made by an individual farmer, in a specific field, in a particular season, often in response to rainfall that arrived or failed to arrive weeks earlier. Global models, by contrast, operate on grid cells of tens to hundreds of kilometres and on annual or monthly time steps. Between those two extremes lies the entire chain of cause and effect that determines whether groundwater use is sustainable. The authors argue that frameworks capable of moving information across these scales, from field-level agronomy up to basin-level water allocation and back down again in the form of policy-relevant guidance, are essential if groundwater governance is to be based on evidence rather than on crisis response.

Climate change sharpens the urgency of this argument. The Intergovernmental Panel on Climate Change has documented intensifying droughts and shifting precipitation patterns, and groundwater is increasingly treated as the buffer that will carry agriculture through a more volatile climate. But the perspective warns that treating aquifers as a climate insurance policy without understanding the environmental consequences risks simply transferring one crisis into another. When water tables fall, streams that depend on groundwater discharge lose flow, groundwater-dependent ecosystems degrade, and in coastal regions the void left by fresh water can be invaded by salt. Recent work by de Graaf and colleagues published in Environmental Research Letters in 2024, and by Cuthbert and colleagues in Nature Climate Change in 2019, has shown how slowly these systems respond to changes in pumping, with time lags that can span decades or centuries. Decisions made today may lock in environmental damage long after the agricultural benefits have been realised.

The food security dimension is equally stark. The Food and Agriculture Organization’s State of Food and Agriculture reports, along with analyses by Matti Kummu and colleagues on global food security, highlight how much of the world’s food production depends on water supplies that are under stress. In regions such as Iran, where Karandish and colleagues have published detailed analyses in the Journal of Hydrology in 2025, agriculture draws heavily on groundwater in semi-arid conditions where surface water is unreliable. In such settings, the trade-off between pumping for crops and preserving environmental flows is not an abstraction; it plays out every growing season in the choices farmers make about how much to irrigate and where. The authors argue that integrated frameworks can make these trade-offs explicit, quantifying the yield gained per unit of environmental harm and identifying management options, such as adjusted cropping patterns, deficit irrigation or targeted aquifer recharge, that shift the balance.

What distinguishes this perspective from a simple call for more modelling is its emphasis on decision support. The authors are explicit that the goal is not a bigger or more detailed simulation, but a framework that produces information usable by the people who allocate water: basin authorities designing pumping quotas, agricultural agencies advising on crop choices, and international bodies assessing food security risks. That requires models that represent adaptation itself, the ways farmers and water managers respond to scarcity, as part of the system rather than as an afterthought. It also requires honest treatment of uncertainty, since projections of future recharge, crop demand and ecosystem response all carry substantial error bars that decision-makers need to understand rather than ignore.

The work is grounded in a broader research programme. De Graaf leads a project funded by the European Research Council under the European Union’s Horizon Europe programme, an ERC Starting Grant that supports the development of the integrated ideas presented in the paper. The perspective draws on a body of literature spanning hydrology, agronomy, environmental science and sustainability studies, from Konikow’s foundational estimates of global groundwater depletion to the recent syntheses of the field’s state of the art. In pulling these threads together, the authors are effectively issuing a roadmap for the next generation of groundwater science: less emphasis on measuring the hole we are digging, more emphasis on understanding the machinery that connects that hole to our food supply and our ecosystems.

The stakes could hardly be higher. Groundwater depletion is already reducing crop yields in some of the world’s most productive agricultural regions, and the ecosystems that depend on aquifers are among the fastest-disappearing on Earth. If the authors are right, the tools that revealed the problem are not, in their current form, the tools that will solve it. Building integrated, process-based frameworks that link the water table to the wheat field and the wetland, and that work at the scales where decisions are actually made, is presented as the necessary next step. Whether the research community and the policy world can build and apply such frameworks fast enough may help determine how much of the world’s hidden water, and the food and ecosystems it sustains, survives the coming decades.

Subject of Research: Integrated process-based groundwater modelling for balancing agricultural irrigation with environmental sustainability

Article Title: Balancing groundwater for crop production and a healthy environment

Article References: de Graaf, I., Urfels, A., Karandish, F., Liu, S., & Supit, I. (2026). Balancing groundwater for crop production and a healthy environment. Nature Water. https://doi.org/10.1038/s44221-026-00720-y

Image Credits: AI Generated

DOI: 10.1038/s44221-026-00720-y

Keywords: groundwater, depletion, irrigation, crop production, food security, hydrology, ecosystems, water management, global modelling, climate change, aquifers, sustainability

It doesn’t require a degree in ornithology, a lab test or even an app for most growers to determine whether bird poop near their crops presents a food safety risk. They just need to ask themselves a simple question: How big is it? 

That’s according to a study from the University of California, Davis, published today in the Journal of Applied Ecology. The study said an informed, nuanced view of food-safety risks and wild birds could help growers avoid crop losses and manage farms for food safety, biodiversity conservation and crop production.

Since 2006, when an E. coli outbreak devastated the U.S. leafy greens industry, growers have been pressured to remove natural habitat to keep wildlife — and the foodborne pathogens they sometimes carry — from visiting crops. Growers are often advised not to harvest crops within a roughly three-foot radius of any wildlife feces, lest they risk failing a food safety audit or losing a buyer contract. Growers often cite such concerns as a barrier to implementing conservation actions they would otherwise consider taking on their farms. 

“We wanted to find out the true risk of wild birds to food safety,” said lead author Austin Spence, a postdoctoral researcher in the UC Davis Department of Wildlife, Fish and Conservation Biology. “Which birds have pathogens, which birds are spending time on farms, and if a bird has a pathogen, does that pathogen survive long in bird poop? Our findings indicate that we can co-manage our areas for both agriculture and conservation.”

Where pathogens persist

Through field and greenhouse experiments, bird surveys, point counts and fecal transects, the authors assessed food-safety risks from nearly 10,000 birds across 29 lettuce farms on California’s Central Coast. They spent hours following turkeys, bluebirds and other wild birds at the UC Davis Student Farm and nearby Putah Creek, collecting hundreds of fecal samples. They compared E. coli survival in bird droppings on lettuce, soil and plastic mulch to measure pathogen persistence.

After all of these efforts, they landed on a simple finding: Smaller poops from smaller birds carry very low risk of foodborne pathogens, which were rare in birds overall. If a bird were to become infected, pathogen survival depends heavily on the bird’s size. 

“Birds that are large produce really big feces, and that’s where pathogens are more likely to survive,” said Spence. “Birds that are small have tiny feces, and the pathogens die off quickly. So farmers don’t have to know the species of bird it came from. They just need to know the size. If it’s the size of a quarter, don’t harvest near that. If it’s a tiny white speck, it’s very low risk and probably fine.”

Balancing conservation, crop yields, and food safety

Beyond fecal size, what the birds pooped on — be it the crop, soil or plastic — made a difference for pathogen survival. In the study, E. coli survived longer on lettuce itself than on soil or plastic mulch. 

Fortunately, about 90% of birds observed on the farms were small and tended to poop mostly on soil, where pathogens perish quickly. By avoiding no-harvest buffers when food-safety risks are low, growers of leafy greens could harvest about 10% more of their fields. 

“Birds generally present really low food-safety risks,” said senior author Daniel Karp, a UC Davis professor in the Department of Wildlife, Fish, and Conservation Biology. “The industry has been concerned about birds for a while. But pathogenic E. coli and Salmonella are vanishingly rare in wild, farmland birds. And we now know E. coli tends to die off quickly in most bird poop.”

The study opens up new strategies for growers to better balance conservation and food-safety risks. For example, growers could erect nest boxes to attract small, beneficial insect-eating birds, like bluebirds and swallows, that help control pests without risking food safety. 

The work also contributes to a growing body of research that suggests growers do not need to remove habitat to improve food safety. 

“There have been no studies to date that suggest habitat removal improves food safety,” Karp said. “Habitat around farms is actually likely to favor the small, insect-eating birds that are unlikely to carry pathogens. Studies like ours are giving farmers science-based permission to conserve habitat — and many species of wild birds — on their farms again.”

The study’s additional coauthors are Jeffery McGarvey and SangIn Lee at the USDA Agricultural Research Service, Olivia Smith at Michigan State University, Elissa Olimpi at Conservation Science Partners, and undergraduates Wentao Yang and Meirun Zhang at UC Davis. 

The study was funded through the Center for Produce Safety, the California Department of Food and Agriculture and the U.S. Department of Agriculture.