Longtime conservationists Ron Brown and Seth Adams anxiously hovered over an office computer and prepared to type in bids quickly when the online auction began for a 5-acre slice of Brentwood grasslands they hoped to get for a bargain.

The Save Mount Diablo leaders usually had months or years to make land deals. This time, though, they figured to have 60 to 90 seconds to buy or lose the foreclosed property on this Internet auction of distressed properties.

Adams tapped in a $5,000 raise. Someone in cyberspace upped the bid. Adams raised his bid again. Within a minute, Save Mount Diablo won out, paying $84,000 for a property once assessed at more than $500,000.

"We were juiced with adrenaline," Adams recalled later. "For conservation groups, this is a once-in-a-lifetime opportunity to get bargains on land."

From Brentwood grasslands to ridges above Pleasanton to Franklin Canyon east of Hercules, park and conservation land buying is booming in Contra Costa and Alameda counties like no time in recent memory.

Depressed real estate values and tight credit markets, a source of pain and loss for many property owners, has created a golden opportunity for open space groups. The agencies also are benefiting from an abundance of land on the market as would-be developers throw in the towel on their housing plans.

By the end of the year, the East Bay Regional Park District will have bought 9,274 acres during 2009 and 2010 for about $45 million, park officials said. That amounts to 14.5 square miles, nearly a third the size of San Francisco.

The shopping spree has increased park district holdings by about 10 percent, to 108,000 acres.

"This is an extraordinary time for us," said Nancy Wenninger, a park district assistant general manager.

The park district isn't the only group snapping up land:

  • The Contra Costa Water District this year bought the first 600 acres of the thousands of acres it plans to acquire for open space to offset the environmental effects of expanding Los Vaqueros Reservoir.

  • Save Mount Diablo, a nonprofit land preservation group based in Walnut Creek, is buying six small parcels along Marsh Creek and elsewhere on the east side of Mount Diablo this year. It usually buys a one property every year or two.

  • The Muir Heritage Land Trust has acquired 506 acres in areas east of Hercules and in Lafayette in the past two years.

    While the state parks system and many other open space organizations in California are short of land-buying funds, that's not the case in Contra Costa and Alameda counties.

    The East Bay Regional Park District is tapping the $500 million bond Measure WW that voters in the two counties passed in 2008 to buy and develop regional and local parks.

    Another large new source of money is the East Contra Costa Habitat Conservancy, a joint powers agreement of Contra Costa County and four cities.

    In just 18 months, the conservancy has secured $40 million in grants -- mostly federal money -- and spent about $20 million to buy and protect habitat for protected species such as the California tiger salamander and California red-legged frog. Other agencies will own and operate the land.

    The habitat conservancy could not have secured so much money unless the regional park district, foundations and conservation groups had not provided matching funds, said John Kopchik, the group's executive director.

    The buying spree is not without critics, however. Buying so much public land takes property off the two counties' property tax rolls and reduces the availability of land for homes in a region with high housing prices.

    Park supporters, however, say the purchases preserve scenery, protect wildlife habitat and travel corridors, and provide public recreation lands.

    "They increase property values in our area by making it a desirable place to live," said Brown, Save Mount Diablo's executive director.

    His group, aided by increased donations and grants, focuses on buying small rural parcels where large-lot luxury home sites would fragment open space or put development next to a park.

    The Dry Creek property purchased in the auction this summer is an example. A property owner planned to build a house on the lot adjacent to a yet-to-open 3,600-acre state park on the old Cowell Ranch. Before a bank foreclosed on the property, the landowner dug a well and put a shed over it, a forlorn reminder of the abandoned dreams.

    "You can have one home on 5 acres next to a 3,600-acre state park, or you can preserve this scenic area in a valley that is rich habitat for rare plants and animals like the burrowing owl and San Joaquin kit fox," Adams said during a recent trip to the property on Briones Valley Road, a half-mile from Brentwood's urban limit line.

    Save Mount Diablo for years bought land and turned it over to park agencies, but lately it has had to keep and care for land the state cannot afford to accept.

    The East Bay Regional Park District often buys much larger parcels from third- or fourth-generation ranch families to expand parks such as Black Diamond Mines near Antioch, Pleasanton Ridge and Vasco Caves near Byron.

    In September, the regional park board approved an agreement to pay $6.4 million for the first 640 acres of a new park to open in Dublin's Doolan Canyon.

    Not everyone is happy with the land dealing.

    Bill Tharp, of San Ramon, read a news story about the Doolan Canyon deal and complained about it to the regional park board directors.

    You overpaid for grazing land with no trees, he told them.

    "I think $10,000 an acre is too much to pay for land in the middle of nowhere," he told Bay Area News Group.

    Tharp said the district's land-purchase process shuts out the public because land prices negotiated in closed sessions are not publicly disclosed until shortly before the park board votes on them.

    He said the park district lacks transparency because it will not release the appraisal for the Doolan Canyon purchase until after the park district finishes buying land in the area. Without the appraisal, Tharp said the public has no way of knowing if the district is using taxpayer money wisely.

    Wenninger defended the price, saying other land in the Doolan Canyon area has sold for comparable prices.

    Even though the land is used for grazing, its value is influenced by being near Dublin subdivisions and other lands with development potential, she said.

    To arrive at its land price offers, the park district commissions outside appraisals, which three land experts on the park district staff review, she said.

    Wenninger said that disclosing an appraisal before a new park is assembled could tip the district's hand in negotiations with landowners and also disclose personal information about landowners the district is bargaining with.

    "There often is a long dialogue with the landowners before we reach an agreement," she said.

    Contact Denis Cuff at 925-943-8267.

    Follow him at Twitter.com/deniscuff.