The future fate of groundwater-dependent wetlands globally driven by groundwater dynamics and land cover change
This study projects that global groundwater-dependent wetlands will decline by mid-century under all climate and land-use scenarios, with the magnitude and primary drivers of loss (groundwater dynamics versus land conversion) varying significantly across different socioeconomic pathways.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Wetlands are among the most vital ecosystems on Earth, acting as nature's sponges that filter water, store carbon, and provide a home for countless species. While many people think of wetlands as places defined by surface water—swamps, marshes, and floodplains visible to the eye—a significant portion of these ecosystems relies on something hidden: groundwater. These are groundwater-dependent wetlands, areas where the soil stays saturated because the water table, the underground layer of water, sits just below the surface. If that underground water level drops too low, the wetland dries out, even if the rain above looks normal. As the planet warms and human demand for water grows, scientists are increasingly concerned about how these invisible water reserves will change and what that means for the wetlands that depend on them.
A new study led by researchers at Utrecht University and Radboud University in the Netherlands takes a comprehensive look at the future of these hidden wetlands. Using a sophisticated computer model that simulates groundwater movement across the entire globe, the team projected how these ecosystems will fare from the late 20th century through the middle of this century. They ran their simulations under three different future scenarios, each representing a distinct path humanity might take regarding economic development, population growth, and greenhouse gas emissions. The goal was not just to see if wetlands would disappear, but to understand exactly why: is it because the climate is changing the water cycle, or is it because people are converting wetland land into farms and cities?
The researchers started by establishing a baseline, estimating that between 2005 and 2014, the world contained roughly 3.43 million square kilometers of groundwater-dependent wetlands. This vast area is spread across every major region of the planet. When they looked ahead to the period between 2041 and 2050, the simulations showed a consistent trend: under all three future scenarios, the total global area of these wetlands is expected to shrink. The decline is not uniform, however, and the reasons for the loss shift depending on the path humanity chooses. In the scenario where the world becomes fragmented, with high competition between regions and extensive agricultural expansion, the loss of wetlands is most severe. In this specific future, the conversion of natural land into farmland and urban areas is the primary driver of wetland disappearance, accounting for the largest share of the decline.
Yet, the story changes when looking at other futures. In the scenarios representing either a sustainable, low-emission world or a high-emission world driven by fossil fuels, the main culprit for wetland loss shifts away from land conversion and toward the water itself. In these cases, changes in groundwater dynamics—such as shifts in rainfall patterns, increased evaporation, and the pumping of water for irrigation—become the dominant force pushing wetlands to dry out. This finding is crucial because it suggests that even if we stop converting wetland land into cities or farms, the wetlands could still vanish if the underground water levels drop too low. Conversely, the simulations also showed that in some regions, particularly in the northern high latitudes and parts of Africa, rising water tables could actually create new wetland areas. However, the researchers caution that these potential gains are often offset by losses elsewhere, and the creation of new wetlands depends heavily on local land management decisions that are not fully captured in global models.
The study also highlighted that the impact is not felt equally across the globe. The Neotropical realm, which includes much of South America, faces the most significant absolute losses across all scenarios. Here, the combination of changing groundwater levels and the expansion of agriculture creates a double threat. In contrast, the Indo-Malayan realm shows a stark difference depending on the future path taken; under one scenario, wetlands shrink due to agricultural expansion, while under another, they actually expand because farming becomes more efficient and requires less land. This suggests that the choices societies make about how they grow food and manage their economies may be just as important as the level of carbon emissions in determining the fate of these ecosystems.
Ultimately, the research indicates that protecting these vital ecosystems will require a dual approach. In regions where land conversion is the main threat, strict conservation of wetland areas remains essential. But in many other parts of the world, where the water table itself is the fragile link, managing groundwater use becomes just as critical as protecting the land surface. The study concludes that a successful strategy for the future must integrate groundwater management with land-use planning. We cannot simply save the wetlands by fencing them off; we must also ensure the invisible water beneath them remains available, recognizing that the health of these ecosystems depends on a balance between what happens in the soil and what happens in the fields and cities above.
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