What happens when land that has been farmed or built upon for more than 300 years, and hunted and fished for thousands of years before that, becomes open water? What happens when nuisance flooding becomes prevalent and undermines roads to such an extent that the cost of fixing them cannot be justified by local government? What happens when one of the most popular national wildlife refuges in the country turns from marsh and upland — beneficial to migratory birds and many native species — to open water with barren bottom?

High Tide in Dorchester, a new Bay Journal documentary film about the cultural and ecological effects of rising sea level in Chesapeake Bay, will seek to answer these and other questions in an area already subject to the vagaries of a changing climate.

Bay Journal writer Tom Horton and photographer Dave Harp are again teaming up with filmmaker Sandy Cannon Brown to make the film. Their first collaboration, Beautiful Swimmers Revisited, was produced by the Bay Journal in 2016. A rough-cut preview of this latest film will be shown at the Chesapeake Film Festival in Easton, MD, on Oct. 28, with a full premiere to follow at the Environmental Film Festival in the District of Columbia in March 2018.

Set in Maryland’s lowest-lying county, High Tide in Dorchester is a hyper-local view of the effects of sea level rise in one of the Bay’s prime locations for frequent tidal flooding. Home to the Blackwater National Wildlife Refuge — which is already being affected by climate change — Dorchester County has approximately 1,700 miles of Chesapeake shoreline. More than 55 percent of the county is in the 100-year floodplain.

Erosion, exacerbated by rising water levels and greater nuisance flooding, plus scientists’ warnings of these forces’ increased strength and frequency — make Dorchester ground zero for climate change. In 50 years, the county will most likely be smaller, with much of the vast marshland turned into open water. Between 1938 and 2006, 5,000 acres of wetlands were lost. Water levels in the mid-Atlantic are rising at three times the global pace.

The film features interviews with biologists, oceanographers and climate scientists, ornithologists, political leaders and residents who are fighting more frequent higher tides and may have to flee in the future.

It shows cemeteries being washed into the Bay by accelerated erosion, erasing the histories of those who lived in Dorchester in the 18th and 19th centuries. The effects of drowning parts of the Blackwater refuge are also highlighted.

The film will pair sound science with the fragile beauty of a place once called “the Everglades of the North,” and tell the stories of those people and creatures most affected by the rising waters. Its creators hope High Tide in Dorchester will spark a conversation about how we might live with more water, less land and a changing climate.

For information, visit hightidedorchester.org.