Sonoma County has the third-highest tally of protected open space in the nine-county Bay Area.
But more land in the county also remains threatened by development than in any other part of the bay region, according to a new report from the Greenbelt Alliance, an open space preservation group.
About 115,000 acres — an area more than four times the size of Santa Rosa — could be transformed by development within the next three decades, the group said.
That's more than a third of the 322,000 acres across the Bay Area likely to be threatened by development over the next 30 years, the report said.
The environmental group, which has produced the report every six years since the late 1980s, said it provides a snapshot of the mix of building pressure and open space protection throughout the 4.5-million-acre Bay Area.
Open space advocates and government officials said it serves as a useful report card for growth and land-use issues.
"It reminds everybody what's at risk and what we need to do," said Ralph Benson, executive director of the Sonoma Land Trust, a private nonprofit organizations that has protected about 25,000 acres in Sonoma County.
A local building industry leader, however, said it appears to overstate development pressure that has hardly existed since the recession.
That dropoff, combined with the county's low population growth in the past decade, government zoning and subdivision restrictions and public and private land protection efforts, have stemmed any risk of overdevelopment, said Keith Woods, chief executive officer of the North Coast Builders Exchange.
"The threat doesn't seem real to me," Woods said.