On a windy, overcast October day, Gedan, from George Washington University, and her colleague Kate Tully, an agroecologist from the University of Maryland, are checking salinity levels at several of their seven test sites in the region, farmlands only a few feet above sea level. “We knew this was an area where we were likely to see impacts,” says Gedan.

Sea-level rise near the Chesapeake Bay, the largest estuary in the United States, is twice as high as the global average. It’s not solely the result of atmospheric warming, melting ice, and expanding waters. The ground is also subsiding. This is happening for a variety of reasons, most notably aquifer withdrawals and the continued settling of land that had been pushed up by ice sheets to the north during the last Ice Age. “We are sinking and the water is rising,” says Michael Scott, a geographer at Salisbury University in Maryland.

The result of this slow-motion catastrophe is that saltwater is threatening America’s first colonial farms.

Salt is a notorious land degrader. On several occasions between 2,400 B.C. and 1,200 A.D., Mesopotamians fled once-productive agricultural regions when salt accumulated in the soil following excessive irrigation. Today, salt may be slithering onto the lower eastern shore’s farmlands by any number of routes—chronic flooding from an increasing number of high tides, saltwater intrusion into aquifers, and even wicking upward through the soil from shallow water tables.

We don’t know the true extent of the Chesapeake Bay area’s salt problem because state and federal agencies have just put resources toward investigations. The Maryland Department of Natural Resources’ most recent regional report on chloride levels in lower-eastern-shore aquifers was produced almost 30 years ago. The 1990 report predicted it would take 50 years for groundwater with a perceptibly salty taste to reach a future Princess Anne well—but this was based on projected pumping increases. Thirty years ago, climate change and sea-level rise were not on the radar. The area’s chief concern has been preventing agricultural runoff into the bay—a problem that will likely be made worse by salt.

With little existing ability to predict where salt will move, it will be difficult to adapt, much less preserve, farmland and the cultural heritage that goes with it. Gedan and Tully cobbled together funding to document the salt damage in the area. New funding from the U.S. Department of Agriculture will help them expand their efforts. “The whole region is a window in the future,” says Gedan.

“We are not treating this like the crisis that it is,” Scott adds. “If we don’t start operating as a collective effort soon, suddenly the problems will get much more expensive.”

Not far from Almodington, Bob Fitzgerald farms land that has been in his family since 1666. His father, born in 1884, farmed this land with mules. Fitzgerald and his brother tromped through the nearby marsh as boys. Now, at 79, Fitzgerald says the marsh is rotten and the salt is seeping onto their soybean fields. The tide gate he installed helps, but high tides are getting higher and more frequent each year.