Congaree National Park, in South Carolina Congaree National Park

South Carolina’s Congaree National Park is a small swamp off the beaten track, but like so many wetlands, it’s well connected—like a capillary within the country’s freshwater ecosystem. The swamp feeds the veins of the Congaree and Santee Rivers before its waters eventually join the pulsing Atlantic. According to a 1990 report by the U.S. Environmental Protection Agency, the Congaree Swamp removes as much pollution annually as a $5 million wastewater treatment facility.

Nevertheless, President Trump’s recent executive order to roll back the Clean Water Rule (also called the Waters of the United States Rule) threatens the Congaree, along with the rest of the nation’s wetlands and rivers and as much as 59 percent of all stream miles. The consequences for drinking water, flooding, and coastal protection are huge.

“Laws are in place to prevent oil companies, fly-by-night dumpers of hazardous waste, and coal companies from just dumping crap in rivers and little streams,” says Jan Goldman-Carter, the director of wetlands and water resources for the National Wildlife Federation (NWF). (On top of contaminating drinking water and destroying favorite fishing spots, Goldman-Carter notes, this type of the pollution threatens the production of craft beer.)

But since the Clean Water Act was passed in 1972, polluting industries have fought to limit which waterways are worthy of protection. They’ve particularly challenged the inclusion of source waters—the waterways that flow into rivers, lakes, and oceans. Supreme Court decisions during the George W. Bush presidency created uncertainty about which waters qualify; then the Obama administration restored protections for many vulnerable waters with the Clean Water Rule.

When the EPA and the Army Corps of Engineers finalized the rule in 2015, they did so recognizing that stopping polluters on, say, the banks of the Mississippi River is not enough. You also have to stop them from contaminating the small tributaries and streams that feed into the Mississippi.

That all waterways are connected, however, isn’t a concept President Trump seems to grasp. His executive order, issued earlier this year, asks Scott Pruitt, the new EPA chief, to exclude isolated wetlands and many rivers and streams from protection, falsely claiming the Clean Water Rule will hurt the agriculture industry and regulate “every puddle.” (The EPA has repeatedly assured farmers that the rule does not create new requirements for the agriculture industry.)

“People like to pit the health of the environment and the economy against each other,” says Megan Desrosiers, executive director of One Hundred Miles, a coastal advocacy group based in Brunswick, Georgia. “But that’s not how it works.”

The concern is that carrying out the executive order will kill the existing rule and replace it with one that not only reverses protections for streams and wetlands, but also interprets the Clean Water Act in ways it wasn’t intended, says Jon Devine, senior attorney in NRDC’s Water program.

Here’s what all that would mean for the South.

Not only is natural filtration at risk. So too is natural flood control. Sometimes, wetlands have two safety nets—federal laws and state laws. But not all states, Georgia for one, have wetlands protections. So, if the EPA nixes the Clean Water Rule, it would be open season on many wetlands that developers could buy, fill, and pave over at will. Of course, more concrete would create more runoff, which leads to more flooding. The region’s intensified rains associated with climate change would then only further exacerbate the problem.

While wetlands right on the coast are not in jeopardy, those farther from the shore but still in the coastal plain are. Disrupting those wetlands would weaken the land’s defenses against sea-level rise. The sediments the wetlands receive from upstream help build resilience. As seas rise, that sediment gets pushed back, allowing the marsh to slowly creep inland. Should parts of South Carolina and Georgia’s coastal plain become hardened or drained by development, they will lose the ability to move with the rising tide and instead will slowly disappear into the sea—along with all their buffering benefits.

Great Blue Heron looking over the murky waters of Okefenokee Swamp Warren Price/Shutterstock

Last but not least, the drinking water of 20 million southerners (including five million Georgians and two million South Carolinians) is in jeopardy. “In these streams and creeks you have water intakes for drinking water, and if the feeder streams get piped or destroyed in some way, then essentially you are jeopardizing the drinking water for a lot of people,” says Bill Sapp, an attorney at the Southern Environmental Law Center (SELC) who focuses on wetlands and coastal issues and says his group is going to fight like crazy to combat the executive order.

That battle has already begun. NRDC, NWF, and SELC, on behalf of One Hundred Miles and the Coastal Conservation League, have asked the Supreme Court to prevent the Trump administration from indefinitely obstructing the implementation of the Clean Water Rule. The Supreme Court agreed, but the legal war is not nearly over, and Pruitt is inviting state leaders to Washington this week to discuss his plans for the Clean Water Rule’s undoing.

“It’s a mess,” says Sapp. “And as long as Trump’s in the White House, it’s going to be a mess.” But a mess he and his partners are dedicated to cleaning up.