A 491-acre Chileno Valley ranch will forever be agricultural land after a $2.23 million easement ensured that a large swath of Petaluma’s southern gateway will remain free from development.

The Marin Agricultural Land Trust announced last week that it had purchased the easement on the Wilson Hill Road ranch, nestled among the amber hills between Petaluma and Nicasio just south of the Sonoma-Marin county line. The ranch joins 16 other properties that MALT has protected in a corridor flanking western Petaluma, a traditional agricultural belt.

Petaluma natives Walt and Arleen Jacobsen, who have owned the ranch since 1950, are in their 90s and wanted to ensure that their land would not be subdivided and converted to estate homes, according to a press release. They were driven in part by the development on the east side of Petaluma that the two have witnessed in the past generation.

“East Petaluma, that was all farmland and ranches in our day, and now it’s just houses,” Arleen Jacobsen said in a statement. “We love our ranch and open space, and we want to keep it this way — always agriculture.”

Though the Jacobsens are retired, they lease their land to a neighbor who grazes dairy cows, and they plan to keep the ranch in the family. The easement, which was purchased for half the property’s assessed value, protects the land from future development in perpetuity, said Marisa Walker, marketing and communications manager for MALT.

“The most significant thing about this ranch was it’s proximity to Petaluma,” she said. “With easy road access about 10 minutes from Petaluma, there would have been significant pressure to develop the land in the future.”

The latest purchase brings the total area of protected ag land in the Chileno and Hicks valleys to 12,981 acres, Walker said. MALT has been working on piecing together properties to form a contiguous area of protected land, which is key to creating a habitat for migrating wildlife.

“A larger protected block helps to maintain the landscape as it looked for generations,” Walker said. “We’re beginning to fill in those gaps.”

MALT, a nonprofit formed in 1980 as the nation’s first land trust dedicated solely to preserving ag land, operates exclusively in Marin County, though it has an outsize influence on Petaluma. Many of the protected properties have Petaluma addresses, and the property owners identify with Petaluma as their closest commercial hub.

In total the organization has protected 78 family farms and ranches in west Marin in an area totaling 48,000 acres.

“Strategic protection of large blocks of farmland and wildlife habitat is the surest way to counter the threats of loss and fragmentation,” Jamison Watts, MALT’s executive director, said in a statement. “By protecting the Jacobsen’s beautiful ranch, we’re allowing both farming and wildlife to continue to thrive in our region.”

(Contact Matt Brown at matt.brown@arguscourier.com.)