The Supreme Court recently decided to dramatically limit which wetlands are protected by the federal Clean Water Act. Not only is the Court’s decision out of touch with the realities of the water cycle, but it will also compromise one of our most important natural weapons in the fight against climate change.

While some may picture wetlands as nothing more than muddy swamps, they in fact provide services that benefit all of us every day. For one thing, wetlands store massive amounts of carbon. One recent study estimated that wetlands in the United States store the equivalent of four years of U.S. carbon emissions. When wetlands are degraded, this service is impaired; when wetlands are lost entirely, the carbon they’ve stored is released back into the atmosphere. And protecting this carbon storage function is all the more crucial at a time when we are far behind where climate science says we need to be in reducing greenhouse gas emissions.

Wetlands will only become more important as society adjusts to a warming world. They mitigate the impacts of rising sea levels and worsening storms and protect coastal infrastructure. And as droughts increase in frequency and intensity, wetlands’ capacity to capture and store freshwater will be critical. Wetlands even purify that water, acting as the “kidneys of the landscape”: A single acre of wetland can purify 7.3 million gallons of water per year.

In this context, the Supreme Court’s recent decision to limit federal protections for wetlands is all the more alarming, even though its language may seem technical or abstract. One key way the Clean Water Act protects wetlands is that—to prevent impacts on water quality and public welfare—the Act requires private landowners to seek a permit before they “dredge or fill” certain waters. The Act empowers the Environmental Protection Agency, the Army Corps of Engineers, and various state actors to police violations of the Act, including unauthorized efforts to fill in or dredge up sediment from these waters. Because the Act sets limits on the allowable uses of covered waters, the scope of the waters the Act applies to has been frequently litigated.

In general, the text of the Act only protects certain “navigable waters,” defined as “waters of the United States”: these are typically waters like rivers and lakes that one could conceivably swim or boat in. However, a separate part of the Act states that “waters of the United States” also “includ[e] wetlands adjacent” to traditionally navigable waters. This unambiguously means that some wetlands are covered, a fact which all of the Justices agreed on in Sackett. The question is which wetlands are covered and which are not.

The interpretation of the Act’s scope has repeatedly shifted due to regulatory changes and litigation, but in general, the relevant federal agencies previously applied two tests to determine whether a wetland fell within the scope of the Act, in keeping with prior Court decisions about its scope. If either test was satisfied, then a wetland would generally be covered. The first test was whether a wetland had a “continuous surface connection” to a traditional body of water like an ocean, stream, or river—a standard derived from the dictionary definition of the term “waters” in “waters of the United States.” The second test was whether a wetland had a “significant nexus” (in other words, a significant chemical, physical, or biological relationship) to one of those traditional bodies of water—a standard based on the purpose of the Act and the real-world interaction between the particular wetlands and waters in question.

In Sackett, the Court threw out the real-world test entirely. The majority opinion announced that the dictionary definition of the term “waters” restricts the scope of wetlands covered under the Act to those that have a “continuous surface connection” that makes them “indistinguishably part of” a traditional water body.¹ However, as Justice Kavanaugh—who has previously endorsed a limited view of the Clean Water Act’s scope—observed in his concurrence, this test has nothing to do with the actual behavior of water: pollution can travel between bodies of water even if they are only occasionally connected or are separated by natural or manmade barriers. The Sackett opinion’s requirement of a continuous connection is particularly at odds with the realities of the water cycle in drought-affected areas like much of the West, where the connection between a wetland and another body of water may be crucial despite being highly seasonal, intermittent, or infrequent. And as Justice Kavanaugh noted, the Court’s decision would eliminate federal protection under the Act for important wetlands like those adjacent to the Mississippi River levee system and the Chesapeake Bay.

There are many other approaches the Court could have taken that would have been more aligned with these realities. As an initial matter, the Court didn’t need to announce a new rule at all—it could have simply made a determination about the Sacketts’ particular set of circumstances. (The Court has aspired in the past to make its determinations as narrow as possible, a principle it strayed from in Sackett.) Or the Court could have clearly endorsed the “significant nexus” test, which works for the real world. Agencies, states, and private parties were familiar with this standard, which had been integrated into a variety of other regulatory schemes over the past 15 years. The Court instead created uncertainty by replacing this standard with an “indistinguishably part of” standard that is itself vague and difficult to understand: although the standard announced in Sackett is clearly more restrictive than prior interpretations, the question of what subset of wetlands are actually covered by the Act remains unclear and will continue to be litigated.

Moreover, the new test is at odds with the text, purpose, and history of the Act. The Clean Water Act was passed at a time of severe, widespread water pollution. And Congress responded to this situation appropriately, by giving the Environmental Protection Agency and Army Corps of Engineers latitude to prevent pollution across a wide range of waters, including water flowing through wetlands. Understanding this history is essential to understanding what elected officials did for the public when they wrote the Act into law. Instead, the Court chose to effectively replace the text of the Act with an imported definition, which—because it does not reflect this key historical context—limits the Act to a fraction of its proper scope.² And the opinion makes clear the Court’s reasons for doing so: the Court was concerned that the Act passed by Congress didn’t show sufficient deference to private property rights. In other words, the Court made a policy decision to rewrite the Act in a way that tips the scales in favor of property owners and against the public.

Unlike human laws, the physical laws that govern the water cycle and the climate are immutable. Our law should reflect this reality. When it fails to do so, as here, the public pays the price.

Amanda Zerbe joined the Climate and Energy Policy Program and Stanford Law School as an Early Career Climate Law Fellow in March 2023, where her work focuses on clean air and equitable decarbonization.

Eric Macomber joined the Climate and Energy Policy Program and Stanford Law School as a Wildfire Legal Fellow in September 2022. His work focuses on law and policy issues relating to wildfire and the wildland-urban interface, particularly in California and the West.

This post was originally shared on the Climate and Energy Policy Program‘s Substack.

¹ The majority reached this conclusion for two primary reasons: first, because “waters” is a plural term, and thus wetlands have to independently qualify as a “water”; and second, because the majority considers the section that incorporates wetlands relatively unimportant by comparison with the rest of the Act. Justice Kavanaugh and three other Justices disagreed, with Justice Kavanaugh noting that “adjacent” and “adjoining” mean different things, and if Congress had meant adjoining, that’s the word it would have used.

² In recent years, the Court has become increasingly willing to use this method of interpretation to limit the scope of statutory authority, particularly in the environmental context.