Restoring nature, it turns out, is not as simple as letting wild vegetation take over. A team had to hunt for signs in the peat deposits far below ground for clues about where water used to move through the site. For a year, heavy equipment was used to reconstruct the stream, remove dams, break up the bog mat and create divots and mounds in the ground, called micro-topography, where water pools and birds alight.

“The big story of change here — it’s going from dry to wet, essentially,” Mr. Hackman said, adding, “We like to remove the limiting factors and let nature heal herself over time.”

Over all, Mr. Hackman said, the restoration cost more than $3 million, much of which came from federal programs like the United States Department of Agriculture’s Wetlands Reserve Program. The state and the landowners also put in hundreds of thousands of dollars. A conservation organization called Mass Audubon plans to buy much of the property; the town of Plymouth purchased another section, which still holds part of the disused bog, and said it would restore that, too.

There is a push and pull between old and new on Tidmarsh, between nascent plants and those that are dying. The land is dotted with newly planted Atlantic white cedars, a native species that has become increasingly rare in this part of the state because so much of it was logged.

Meanwhile, pitch pines — small trees common in drier environments like Cape Cod that sprang up here when the bog was full of sand — are struggling. The scientists said that was a sign that the restoration was working.