Illinois Wetlands Face Unprecedented Threats Following Landmark Supreme Court Ruling
Illinois, once endowed with over 8 million acres of wetlands, has witnessed a staggering contraction in wetland areas over the past century. By the 1980s, these vital ecosystems had dwindled to a mere 1.2 million acres due to extensive drainage for agriculture and urban development. The recent 2023 Supreme Court decision in Sackett v. Environmental Protection Agency has further imperiled approximately 72% of the remaining 981,000 wetland acres in Illinois by stripping away their federal protections under the Clean Water Act. This shift threatens to erode the critical ecosystem services wetlands provide, including flood mitigation, groundwater recharge, and habitat preservation, raising profound concerns among environmental scientists and policymakers alike.
The legal evolution of wetland protections under the Clean Water Act has been anything but static. Initially, a pivotal 1985 Supreme Court ruling affirmed that wetlands adjacent to traditionally navigable waters were “waters of the United States” (WOTUS) and thus enjoyed federal safeguards. This interpretation empowered agencies to curtail harmful activities, preserving millions of wetland acres nationwide. However, subsequent judicial decisions progressively narrowed this inclusive definition, culminating in the Sackett ruling. This decision mandates that protected wetlands must possess a continuous surface connection to relatively permanent waters, thereby excluding many wetlands that flood intermittently or are hydrologically isolated due to natural or artificial barriers.
Chelsea Peterson, a graduate student at the University of Illinois Urbana-Champaign who spearheaded the analysis, elucidates the technical implications of the Sackett criterion. She explains that wetlands lacking an unbroken surface water link to permanent water bodies—whether due to levees, dry land, or ephemeral flow—are now excluded from federal oversight. This redefinition severely curtails the scope of wetlands eligible for protection despite their ecological importance. The ruling fails to recognize subsurface hydrologic connections, which often sustain wetland function absent a visible surface linkage, as highlighted by co-author Jessica Monson, a research scientist with the Illinois State Geological Survey.
Apart from legal nuances, the ecological consequences of the Sackett ruling are profound. Wetlands have a dynamic hydrologic regime, often inundated intermittently rather than continuously saturated. This fluctuation plays a crucial role in mitigating flood surges by temporarily storing stormwater and reducing downstream flooding risks. The exclusion of wetlands lacking permanent surface connections from federal protection undermines these invaluable natural flood defenses. Economic assessments estimate that unprotected Illinois wetlands contribute approximately $419 million in residential flood control benefits annually, a figure now at risk should degradation or loss proceed unchecked.
Groundwater recharge is another critical ecosystem service imperiled by the ruling. Upstream wetlands in watersheds function as natural water purifiers, filtering contaminants and replenishing aquifers that supply drinking water. Geoffrey Pociask, a wetlands geologist involved in the study, emphasizes that these systems play a dual role: they enhance water quality and bolster water availability by intercepting and processing pollutants and nutrients before they enter groundwater reservoirs. The absence of federal protection may accelerate wetland loss, thereby diminishing these natural filtration and recharge mechanisms.
Biodiversity suffers significantly from wetland degradation. Many amphibian species, including salamanders, depend on the ephemeral nature of wetlands for breeding and survival, exploiting the reduced presence of aquatic predators like fish in intermittently flooded habitats. Peterson notes that nearly half of the United States’ threatened and endangered plant and animal species inhabit wetland ecosystems. The Sackett decision’s restriction threatens these vulnerable species by jeopardizing the habitats they depend upon, underscoring the ruling’s far-reaching ecological implications beyond hydrology alone.
To quantify the spatial and regulatory consequences of the Sackett decision at the state level, researchers adopted a multidimensional analytical approach. They examined variations in spatial distance, flood frequency, and stream flow permanence to interpret how different agency implementations might influence wetland classification and protection. Their data-driven scenarios converged on a startling conclusion: 72% of Illinois’ wetlands are no longer recognized as WOTUS and thus fall outside the purview of the Clean Water Act, exposing them to potential degradation.
While some wetlands retain partial protection through a complex mosaic of state and county regulations, these frameworks are uneven and often insufficient. For example, eight counties in the Chicago metropolitan region enforce stormwater management ordinances that regulate wetland activities, and Illinois state law mandates compensation for wetland area lost due to state-funded developments. Nonetheless, these measures leave up to 563,000 acres unprotected at any governmental level, representing roughly 80% of the wetlands stripped of federal protection post-Sackett.
The unprotected wetlands frequently overlap with regions facing heightened climate-related risks. Through layered spatial analysis, the research team identified multiple Illinois locales vulnerable to floods and other hazards, including metropolitan areas such as Moline-Rock Island-Burlington near the lower Rock River and Grafton-Alton-East St. Louis at the confluence of major rivers. The loss of wetlands in these high-risk zones could exacerbate flood severity, inflict infrastructural damage, and impose significant socioeconomic costs on communities.
Importantly, wetlands act as natural insurance against environmental disasters. Apart from ecological benefits, they safeguard human lives, properties, and livelihoods by attenuating floodwaters, stabilizing soil, and supporting agriculture. Pociask references complementary studies estimating each wetland acre’s flood-protection value at approximately $750 annually, quantifying the substantial economic benefits wetlands confer. The erosion of legal protections threatens this security net, potentially escalating disaster losses and hampering climate resilience efforts.
Reflecting on Illinois’ wetland trajectory over time, Paul Marcum of the Illinois Natural History Survey contextualizes the current crisis. From an initial 22% landscape coverage, wetlands have dwindled to just 2.6% by 2023. The Sackett decision jeopardizes what remains, risking further fragmentation and loss. This backdrop highlights the urgency for robust local ordinances and preservation initiatives, which serve as critical bulwarks against the erosion of wetland ecosystems amid shifting federal policies.
The study underscores the need for a more comprehensive and scientifically informed regulatory framework that embraces the complex hydrologic and ecological realities of wetlands. While federal policy retrenchment poses a challenge, coordinated state and local governance, coupled with community engagement and conservation science, may present a viable path forward. These efforts are imperative to sustain the multifunctional benefits wetlands provide in an era of escalating environmental stressors.
This investigation was conducted by a multidisciplinary team from the University of Illinois Urbana-Champaign, Illinois State Geological Survey, and Illinois Natural History Survey, supported by funding from the U.S. Environmental Protection Agency. The full research article, “A national policy with local consequences: Quantifying the downstream effects of Sackett on Illinois wetlands and communities,” was published in the Journal of Environmental Management on August 11, 2025, and offers detailed methodologies and data analyses for further examination.
Subject of Research: Not applicable
Article Title: A national policy with local consequences: Quantifying the downstream effects of Sackett on Illinois wetlands and communities
News Publication Date: 11-Aug-2025
Web References:
- Full article DOI: https://doi.org/10.1016/j.jenvman.2025.126931
- University of Illinois Natural Resources and Environmental Sciences: https://nres.illinois.edu/
- Jeffrey Matthews Laboratory: https://matthewslab.nres.illinois.edu/people/
- Illinois State Geological Survey: https://isgs.illinois.edu/
- Illinois Natural History Survey: https://inhs.illinois.edu/
- Prairie Research Institute: https://prairie.illinois.edu/
References:
- Sackett v. Environmental Protection Agency, U.S. Supreme Court, 2023
- Additional referenced studies on wetland flood protection benefits: https://www.rff.org/publications/working-papers/wetlands-flooding-and-the-clean-water-act/
Image Credits: Photo by Fred Zwicky
Keywords: Illinois wetlands, Clean Water Act, Sackett decision, wetland protection, hydrologic connection, flood control, groundwater recharge, wetland habitat, environmental policy, flood-risk mitigation, ecological conservation, state and county regulations
