Developers in the 1980s and ’90s had big plans to build sprawling campuses for Apple, Cisco Systems and other tech firms in Coyote Valley, a pastoral expanse of farmland and ranches on San Jose’s southern edges.

But now a new plan for the valley is being rolled out that doesn’t involve bulldozers.

Working to preserve key corridors for deer, mountain lions and other wildlife so they can roam and expand as Silicon Valley’s population continues to grow, the Santa Clara Valley Open Space Authority and the Peninsula Open Space Trust on Thursday will unveil a long-range blueprint to link 1.1 million acres of open space in the Diablo Range and the Santa Cruz Mountains.

The plan focuses on Coyote Valley as a key connection between the two vast mountain ranges. It proposes spending $80 million over the next decade to preserve at least 1,000 acres, mostly in North Coyote Valley, where much of the land is zoned for tech campuses.

It’s a switch in strategy for environmentalists, who will now try to play offense with big money in Coyote Valley rather than reacting to development proposals.

The plan aims to allow wildlife to hunt and breed between the Diablo Range and the Santa Cruz Mountains without being hit by cars or blocked by development. It also includes building tunnels for animals — from bobcats to badgers — under highway lanes; restoring streams and wetlands to protect endangered species; recharging groundwater; and purchasing open space and development rights in Coyote Valley.

“Where else do you find open space, recreation, farmland and wildlife habitat right next to the 10th largest city in the United States?” said Andrea Mackenzie, general manager of the open space authority, a government agency based in San Jose. “The fact that it is still here is a miracle. It’s our number one priority.”

But purchasing all the land won’t be cheap. The Peninsula Open Space Trust, a nonprofit environmental group based in Palo Alto, recently closed a deal to buy 30 acres for $5.8 million in North Coyote Valley from Panattoni Development Company, based in Newport Beach.

Two years ago, the company submitted a proposal to San Jose planners to build a 414,000-square-foot warehouse and distribution center at Blanchard Road and Monterey Highway. The project, which would have had 196 parking spaces and 72 truck docks, was intended to create a massive facility for a company like Amazon to sort and ship orders.

But the idea ran into controversy when neighbors and environmental groups raised concerns about traffic, noise and loss of the area’s rural character.

Walter Moore, a real estate attorney who is president of the Peninsula Open Space Trust, said his group’s purchase of the property will help develop a wildlife crossing — perhaps a tunnel under Monterey Highway. The four-lane road has a four-foot high concrete median with a two-foot fence on top, and only one culvert underneath. Dozens of animals are killed every year trying to cross it — a major risk for motorists.

In a wider sense, the purchase — at land rates 10 times as high as the trust usually pays to preserve ranches and other open space — also lays down a marker, Moore said.

“This is a statement to the other landowners that we will pay full fair market value for your land,” Moore said.

Since 1977, the trust has preserved more than 75,000 acres of parkland, open space and farms in San Mateo, Santa Clara and Santa Cruz counties by raising tens of millions of dollars from private foundations and wealthy Silicon Valley donors.

Moore said that the latest purchase is the first in Coyote Valley for his organization, but it is part of sustained commitment to work with willing sellers to buy land and development rights.

Of the $80 million estimate to buy the necessary land, Moore said, he expects half to come from individual donors, a quarter to come from private foundations and a quarter to come from public sources such as Measure Q, a $24 annual parcel tax that voters approved in 2014 to fund the Santa Clara Valley Open Space Authority.

Although some of Silicon Valley’s biggest and most influential developers own hundreds of acres in Coyote Valley, including the Sobrato Organization in Cupertino and Brandenburg Properties of San Jose, political pressure in recent years has pushed large tech companies more toward urban areas.

San Jose Mayor Sam Liccardo said in an interview this week he is not ruling out some development in Coyote Valley. But he said his main priority is to bring major Silicon Valley employers to downtown San Jose and North San Jose. So he has not been recruiting tech companies to come to Coyote Valley.

Earlier this month, Liccardo announced San Jose is in talks with Google to build a massive new campus downtown, near the SAP Center and Diridon Station, for up to 20,000 Google employees.

“We see all around us the sprawling nature of development over the last half century,” Liccardo said. “Our freeways are in gridlock. Housing is increasingly expensive. And now we are trying to revitalize the core of our city that was neglected in the 1960s and 1970s.”

Historically, the roughly 7,100-acre Coyote Valley was a mix of oak woodlands, streams, wetlands and other landscapes. Much of that land was converted over generations to orchards, ranches and farmland.

Biologists say that despite some development along Bailey Avenue, such as IBM’s campus and a satellite campus of Gavilan College, key areas can still be restored. They include Fisher Creek, an important corridor for birds and wildlife, and Laguna Seca, a large wetlands complex that is rich with ducks and other migrating waterfowl, as well as endangered species such as the California tiger salamander. Restoring the land could also absorb flood waters before they head to nearby Coyote Creek.

“There are definitely modifications, but a lot of this landscape hasn’t changed,” said Robin Grossinger, a historical ecologist with the nonprofit San Francisco Estuary Institute, as he looked last week at an 1847 map of Coyote Valley.

“In the South Bay, we’ve done a great job preserving the hills,” he said. “And we’re bringing back the bay’s salt marshes. This is the last piece.”