ILLINOIS (WCIA) — After a 2023 Supreme Court ruling narrowed Clean Water Act (CWA) protections for wetlands, researchers at the University of Illinois set out to learn more about the ruling’s implications for Illinois. Their research indicated that about 72% of Illinois wetlands are no longer protected.

Illinois used to be home to more than 8 million acres of wetlands. But by the 1980s, there were only about 1.2 million acres left. Fast-forward to 2023, and the US Supreme Court’s decision in Sackett v. EPA narrowed Clean Water Act protection for wetlands by requiring a “continuous surface connection” to “Waters of the United States” (WOTUS).

“That removes protections from wetlands that flood infrequently, have surface connections to nonpermanent streams or are spatially isolated from permanent streams, which could be due to levees or dry land,” Chelsea Peterson, one of the leaders on the project and a U of I graduate student, told the U of I News Bureau.

Jessica Monson, a study co-author and research scientist at the Illinois State Geological Survey, said requiring a connection to relatively permanent waters could lead to issues.

“The concern is that it’s not really addressing the hydrologic connections that occur below the land surface,” Monson said.

Wetlands provide habitats for threatened and endangered species, recreation activities and flood mitigation. In Illinois, researchers estimate that the unprotected wetlands are worth up to $418.9 million in prevented flood damage.

To understand how the Supreme Court’s ruling might impact wetlands, first the researchers needed to identify non-WOTUS wetlands. Once they concluded which wetlands might qualify — versus which ones might not — the researchers worked to compare wetland protection levels, and to evaluate the impacts on vulnerable communities.

From their research, the team estimated that about 72% of Illinois’ remaining wetlands is non-WOTUS — meaning that it is not protected by the Clean Water Act. 79.5% of non-WOTUS wetlands have no alternate protections from county, state or federal regulations, the researchers added.

Losing wetlands in Illinois could mean ecological, recreational and aesthetic threats but it could also mean higher chances of flood and crop damage in the future. The researchers said their findings indicate the importance of municipal and county-level ordinances, aimed at protecting wetlands.

INHS research scientists, Julie Nieset, Brian Wilm and Paul Marcum; U of I natural resources and environmental sciences professor, Jeffrey Matthews; and wetlands geologist at the ISGS, Geoffrey Pociask, also contributed to the study.

Click here to find the full study.