There was scraggly grass in one sand trap and wooden blocks and a toy castle in another, evidence of children at play. People were walking their dogs on the fairway, which was looking rather ragged and unkempt. This was only to be expected.

Nowadays, these grounds are mowed just twice a year, and haven’t been doused with pesticides or rodenticides since 2018, which was when this 157-acre stretch of land stopped being the San Geronimo Golf Course, and began a journey toward becoming wild, or at least wilder, once again.

A small number of shuttered golf courses around the country have been bought by land trusts, municipalities and nonprofit groups and transformed into nature preserves, parks and wetlands. Among them are sites in Detroit, Pennsylvania, Colorado, the Finger Lakes of upstate New York, and at least four in California.

“We quickly recognized the high restoration value, the conservation value, and the public access recreational value,” said Guillermo Rodriguez, California state director with the nonprofit Trust for Public Land, which bought the San Geronimo course in Marin County for $8.9 million in 2018 and renamed it San Geronimo Commons.