Mr. Swindells learned about the nonprofit two years ago, when he was looking for something to do with a large piece of property he had bought a decade earlier, a parcel known as Bohemia Ranch. The land had been used for a cattle ranch, for logging and for mining, but for years before Mr. Swindells’s purchase it had been held by real estate developers who had done little to maintain it. As a result, it was a popular party spot. On summer days, it rang with the whine of motorcycles and the crack of gunfire. A meadow known as the “shooting gallery” offered a scenic setting for target practice.

“There was garbage everywhere, especially old cars and shotgun shells, so I was advised to get an environmental impact report when I bought it,” Mr. Swindells remembers. “They basically said there was nothing to worry about, but they also didn’t see one living thing — no animals, no birds, not even any lizards. I think the people who’d been hanging out up there had been getting drunk and shooting anything that moved.”

Mr. Swindells, who hails from an Oregon logging family, bought the property in part to create a weekend retreat and in part to get some hands-on experience in conservation practices. But despite considerable investment, he and his family never ended up spending much time there. In 2009, he decided he wanted to sell, preferably to keep the property available for public use.

Years earlier, he had established a conservation easement that restricted the ways he or any future owners could develop the land. The nonprofit to which he had donated the easement, Sonoma Land Trust, tried to structure a deal with state and local agencies. But Mr. Swindells began to doubt that the state could effectively manage the property; it had its hands full trying to stave off closings and cutbacks in the hundreds of parks it was already operating.

LandPaths was a different story. “That’s what they do,” says Liz Burko, the state’s superintendent of the Russian River and Mendocino park districts. “They know how to inspire people to want to take responsibility for the stewardship of public lands.”

When an acquaintance told Mr. Swindells about the organization, he quickly decided its participation was crucial to the deal. “Craig had the right model for a changing environment,” Mr. Swindells says. “The parks are in trouble because they have so many properties they can’t afford to manage any more. But you can’t just let people run around in parks wherever they want. There are liability issues. Land management issues. All that stuff, you have to do it with volunteers now. That’s where everything’s headed, and Craig had already been doing it for years.”

In the end, Mr. Swindells sold an even more restrictive conservation easement to Sonoma Land Trust for $1.45 million. Then, he donated 554 acres of Bohemia Ranch to LandPaths.