The seas are rising. Are actual property builders Boston’s greatest hope for fending them off?

But will it be enough to ward off disaster?

Waterfront advocates aren’t so sure. They’re glad developers are taking the matter seriously. But they worry a project-by-project approach could leave swaths of Boston’s waterfront and low-lying inland neighborhoods vulnerable. Then there’s the question of equity: What if flood protection gets built first for luxury housing and pricey offices, while defenses elsewhere are put off?

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“In moments of despair, I say, ‘Oh my God, how are we going to get this done?’ ” said Bud Ris, a former chief executive of the New England Aquarium, who champions waterfront resiliency efforts. “The water rises everywhere. We have to plan for it. The more essential question is not where to start but: Who is going to pay for it, and who benefits?”

A group of athletes from Inside Out Fitness Concepts train on the field at Moakley Park, which is due for a $250 million overhaul over the next decade, in part to prevent flooding in neighborhoods behind it.Craig F. Walker/Globe Staff

City officials say they’re working hard to climate-proof key public parks and the city-owned Raymond L. Flynn Marine Park in the Seaport. But several of the biggest resiliency proposals depend on private-sector developments. It’s an approach that began under former mayor Marty Walsh, and new mayor Michelle Wu has made it clear that new waterfront development must keep climate change top of mind

The stakes are enormous. The 2016 “Climate Ready Boston” report projected up to three feet of sea level rise in Boston Harbor by 2070, from 2000 levels, and possibly seven feet by 2100. And by the end of this decade, there’ll be at least a 1 percent chance each year of a severe flood that could inundate up to 2,100 buildings and cause $2 billion or more in damage. The citywide report and several related neighborhood-specific plans offer dozens of solutions, but the collective price tag could easily exceed $1 billion to $2 billion.

So far, Boston has dodged the sort of disaster that hit New York with Superstorm Sandy in 2012. But a storm in the winter of 2018 underscored the city’s precariousness, with rivers of seawater coursing through Seaport streets, and a viral video of a Dumpster bobbing past the brick-and-beam buildings of Fort Point.

Something else happened that year that received less attention but was no less important: Researchers at UMass Boston, led by professor Paul Kirshen of the School for the Environment, determined a massive flood barrier across Boston Harbor wouldn’t be worth the cost. The barrier, Kirshen said, would require a public works project the scale of the Big Dig, and likely wouldn’t be completed until 2050. Boston needs protection long before then. Plus a huge barrier, while helpful in storms with big surges, would do little to prevent high-tide-related flooding. The researchers urged public officials to focus now on more natural solutions that could provide ecological benefits as well as reduce flood risk.

Enter the Boston Planning & Development Authority. Last year, the BPDA issued new zoning rules for the waterfront and roughly 5,000 acres of the city — including most of the South End and some of the Back Bay — believed to be at risk from coastal flooding. The agency established a base elevation point for new construction that assumes the potential for 40 inches of sea level rise in a severe storm and required occupiable space in residential buildings to be at least 2 feet above that point. (Commercial buildings could be lower with flood-proofing measures.) This would essentially result in new construction getting built nearly 22 feet above the low-tide mark.

City agencies are also directly targeting some high-risk spots.

A man fishes off the shore of Dorchester Bay along the former Bayside Expo Center property. Nearly half of DBC’s 36 acres will be open space, much of it elevated nearly 22 feet above the low-water mark.Craig F. Walker/Globe Staff

The BPDA is securing a $10 million federal grant to help fund a $20 million berm along the east side of Fort Point Channel, where a string of new buildings is going up on parking lots previously part of the Gillette campus. Meanwhile, at the Flynn industrial park, the BPDA is starting to pump money from long-term land leases into a new fund for a significant seawall.

The city is also shoring up waterfront parks as they come up for renovation — such as the North End’s Langone Park, and Ryan Playground in Charlestown — designing them to double as barriers during storms. The biggest will be Moakley Park in South Boston, which is due for a $250 million overhaul over the next decade, in part to prevent flooding in neighborhoods behind it. The park’s elevation would rise from the beach, but gradually so it is barely perceptible.

Next door to Moakley, Accordia Partners and Ares Management plan six million square feet of development for their Dorchester Bay City project, primarily on the site of the old Bayside Expo Center. Nearly half of DBC’s 36 acres will be open space, much of it elevated nearly 22 feet above the low-water mark. A new stormwater management system will be built, and portions of the existing harbor-walk will be elevated along the Harbor Point residential complex next door. All told, Accordia estimates, the development’s contribution to this resiliency work will cost about $70 million.

“The private sector is going to not only be part of the solution, but driving the solution,” Accordia principal Dick Galvin said.

In Charlestown, developer Flatley Co. has similar plans to shore up a vulnerable part of the coastline behind the Schrafft Center, as part of a 25.5-acre redevelopment it’s planning there. They’ll augment the work next door at Ryan Playground with a half-mile resiliency project that includes a waterfront walkway and steps leading down to the Mystic, building up a protective barrier against seawater that could otherwise reach low-lying neighborhoods as far away as eastern Cambridge and Somerville. It would obviously be less expensive to simply build a floodwall to protect Flatley’s own site, said chief executive John Roche; instead, the more extensive landscaping work will add tens of millions of dollars to the development cost.

But developers have an important incentive to think broadly about resiliency: It endears them with city and state regulators who ultimately decide what they can build.

While advocates say these projects represent a promising start, they point out that there’s still so much left to be protected.

“You have a bunch of properties that are on islands of resilience,” said Deanna Moran at the Conservation Law Foundation. “That doesn’t help anybody if we get hit by a huge storm.”

Richard Rose and his dog Cooper pass through the parking lot at the former Bayside Expo Center. Accordia Partners and Ares Management plan six million square feet of development around here.Craig F. Walker/Globe Staff

Moran said she would rather see more public dollars pumped into broader efforts, particularly if the building boom slows and new projects stall. Funding could come from an increase in the deeds excise tax, or a property tax for all significant properties within a particular waterfront area, much like how business improvement districts work today.

“I get nervous about the idea that we’re seeing redevelopment as the No. 1 source of funding for climate resilience,” Moran said.

Boston Harbor Now president Kathy Abbott agrees.

“The majority of developers that we talk to and hear from are taking it very seriously,” Abbott said of sea level rise. “(But) we can’t just rely on the private sector.”

As growth continues, Abbott hopes to avoid the shortcomings of the Seaport, where projections indicate billions of dollars in new development could face routine flooding. Policy makers, she said, need to have hard discussions about the waterfront parcels that should be developed, the ones that should not, and how to make all of it more resilient.

“Now, it’s obvious we didn’t do enough,” Abbott said. “We didn’t raise enough of it up. We didn’t protect the edges well enough. We haven’t begun to limit where you can build and where you can’t.”

Kirshen, the UMass Boston expert, said there are some advantages to a neighborhood-by-neighborhood approach, especially in a city like Boston with an existing blueprint for the areas that need protection.

“The city knows what has to be done and when it has to be done by,” Kirshen said. “The challenge the city is facing now is how to finance it. … Where’s that money going to come from? It’s going to come from these public-private partnerships.”

Jon Chesto can be reached at [email protected]. Follow him on Twitter @jonchesto.