Archaeologists at Jamestown, Virginia, have unearthed over 5 million artifacts since 1994, including glass bottles, pottery, tools, beads, and human remains that have reshaped historians' understanding of the first permanent English settlement in North America. But the site is now under siege from rising seas, which have climbed about 1.6 feet over the last century and are projected to rise another three feet or more by 2075. The James River is eating away at one side of the island while wetlands encroach from the other, forcing archaeologists to prioritize excavations based on flood risk.

Sean Romo, director of archaeology for Jamestown Rediscovery, says, "We always have to be meticulous, but we do need to pick the pace up because we are under severe threat from climate change. And the real big one for us is flooding." Ground-penetrating radar helps researchers identify what lies beneath before they dig, allowing them to focus on areas most at risk. Every excavation has become an exercise in triage to decide which pieces of history can be saved before the water reaches them.

Jamestown is among the most visible examples of a problem unfolding along America's coastlines. By 2050, an estimated 2.5 million Americans and many historic sites could face severe coastal flooding, according to Climate Central. Coastal geologist Rob Young of Western Carolina University, whose team is assessing climate risks at all 107 coastal units of the national park system, says, "The map is changing, and climate change and rising sea levels are making that map change more quickly than it was 100 years ago."

Flooded roads and parking lots increasingly restrict visitor access to national parks. Historic forts experience more frequent inundation. Barrier islands along the southeast are eroding so rapidly that some landscapes are becoming almost unrecognizable. In 1999, engineers moved the Cape Hatteras Lighthouse nearly a quarter mile inland to protect it from the encroaching sea. But some landmarks, like Fort Sumter, cannot be relocated. Young argues the country will have to decide which places can be defended and which may have to be surrendered to a changing coastline. "So no, it's not gonna look like what it looks like now for your kids or for your grandkids," he says. "The trick for us as a society is to care enough to admit that and have a good national conversation about what we do about it and what we can save and what we can't."

Jamestown's sea wall, dating to 1902, was recently reinforced with giant boulders to prevent erosion. Romo knows this is not a permanent solution. "If we do nothing, we're gonna go from Jamestown Island to Jamestown Islands in the next 50 years," he warns. "The time to act is now to protect this space and to make sure future generations can still learn about and experience the place where American history was made."