For Marjorie Mayfield-Jackson of Norfolk’s Elizabeth River Project, signing a groundbreaking agreement to tear down the organization’s new $9 million headquarters when waters rise too high was bittersweet.

“It’s hard to not even have had the grand opening yet and we’re talking about celebrating taking it down,” she said.

When, decades from now, time and tide can no longer be denied, the nonprofit will surrender the 6,500-square-foot Pru and Louis Ryan Resilience Lab in a final act of adaptation to the climate crisis, making way for the rise of wetlands on Knitting Mill Creek, a slender offshoot of the Lafayette River. The lab will be torn down, what can be recycled will be recycled, connections to utilities like water, sewer and electrical will be removed, and the site will be transferred to a land trust, never to be developed again.

The Elizabeth River Project, which Mayfield-Jackson helped found 33 years ago, signed what’s called a rolling conservation easement on Tuesday. Mayfield-Jackson and Mary-Carson Stiff, the executive director of Wetlands Watch, a nonprofit that drew up the agreement, say it is the nation’s first privately held rolling easement, a legal restriction triggered by a change in circumstances — in this case, rising tides — that requires whoever owns the property at the time to return it to nature.

Monitoring for the easement to take effect will begin when the mean higher high-water average reaches an average over 10 years of 4.5 feet above what it is now, a level estimates say will occur around 2065. Deconstruction of the building will be required when it reaches an average over three years of 6.5 feet, something projected to happen in 2085, and the property will be transferred to the Coastal Virginia Conservancy.