A 48-inch increase in the bay’s water level in coming decades could cause more than 100,000 Bay Area jobs to be relocated. Nearly 30,000 lower-income residents might be displaced, and 68,000 acres of ecologically valuable shoreline habitat could be lost.

These are among the findings in the most detailed study yet on how sea level rise could alter the Bay Area. The newly released, 700-page official report argues that without a far-sighted, nine-county response, the region’s economic and transportation systems could be undermined along with the environment.

The study by a consortium of state and local agencies concedes that “the findings in this report may cause some alarm.” But it argues that coordinated action is needed sooner rather than later — unlike how the Bay Area neglected its housing needs for decades, creating today’s high rents and mortgages that are driving lower-income residents out of the region.

“The Bay Area is at a tipping point, poised between a growing body of information ... and the beginnings of irreversible impacts,” the report states. “We know that rising sea levels are coming. And we know what the potential impacts will be.”

The study was led by the Bay Conservation and Development Commission, which released its first detailed look at sea level rise in 2007. But the autonomous state agency was joined in this effort by the Metropolitan Transportation Commission and the Bay Area Regional Collaborative. Caltrans funded most of the $1.2 million study, which bears the unwieldy title, “Adapting to Rising Tides Bay Area: Regional Sea Level Rise Vulnerability and Adaptation Study.”

This coordination signals that the impacts of climate change will go beyond ecological ones, say the creators.

“You can’t just focus on one piece,” said Zack Wasserman, who chairs the BCDC. “The challenges are huge — physically in terms of how we can adapt and governmentally in terms of whether the region can come together” to tackle a threat still seen as in the distance.

The full report analyzes scenarios for 10 different extremes of “total water levels,” a term that would apply to straightforward higher tides — day in and day out — as well as storm surges layered on top of higher tides. They range from 12 to 108 inches.

But much of the emphasis is on a raised water level of 48 inches, a number that corresponds to the “likely” amount of sea level rise forecast in the Bay Area for 2120 by the California Ocean Protection Council. More ominously, it’s an average level that could arrive as early as 2060 under the council’s “highest risk and least likely” model.

Each scenario is viewed through four filters: the impact on natural habitats, transportation networks, areas where new development is planned and “vulnerable communities” that, for instance, live in older, low-lying neighborhoods of Richmond and San Rafael.

The findings go beyond large-scale numbers to highlight specific aspects of the approaching threat to how the region functions.

• The access points to four major bridges would be affected, including the Bay Bridge in Oakland and both sides of the Dumbarton Bridge at the south end of the bay.

• Runways at San Francisco and Oakland airports would be largely under water.

• Nearly 31,000 jobs planned for north San Jose would need to be relocated.

• Cropland that now generates more than $15 million in annual revenue for local farmers could be lost.

• At least 78 miles of protected bicycle trails, most of them fairly new, would often be off-limits.

“All these different aspects of the region are interconnected,” said Dana Brechwald, who oversaw the study’s preparation. “The solutions aren’t going to be one size fits all.”

In a place with as many competing interest groups as the Bay Area — and a political process that allows those groups the opportunity to weigh in at multiple points along the way — there’s no guarantee that a guaranteed response will be easy.

The report acknowledges this, discreetly.

One example is the way that recreational treasures such as paths through restored marshes, or playing fields near the shore, must be balanced against the need to provide protected habitats for endangered and fragile species as waters rise: “Different stakeholders may have differing priorities,” it concedes, “for the management of natural shoreline areas that prioritize people, natural systems, or flood control ... over one another.”

Similarly, many low-lying areas along the bay have been defined in past regional planning as “priority development areas.” Nearly 30,000 housing units have been approved along San Francisco’s shoreline alone. These proposals include elevation of the existing sites by as much as 10 feet, but many environmental advocates say any new construction would be foolish.

The report, however, suggests that as the region moves forward to craft adaptation strategies for sea level rise, “We can’t let perfect solutions be the enemy of workable and fair ones,” that address other Bay Area needs.

The report has been in the works since 2017 and the original goal was to release it several months ago. Instead, it went online without fanfare last Thursday.

The reason for the muted release? The Bay Area’s shelter-in-place order that has been imposed through May 1 to try and contain the spread of the coronavirus — a fresh example of how present-day crises inevitably take precedence over long-term threats.

John King is The San Francisco Chronicle’s urban design critic. Email: jking@sfchronicle.com Twitter: @johnkingsfchron