For 51 ficus trees lining 24th Street in the Mission District, the end is near.

Despite their impressive canopies, the trees have been condemned by San Francisco Department of Public Works as too hazardous to safely leave standing.

For Susan Cervantes and many other residents of this bustling stretch from Mission to Potrero streets, the trees are an integral part of the neighborhood.

“It’s sort of a mass-deforestation,” said Cervantes, whose office at Precita Eyes Muralists Association overlooks the trees. “It would completely the change the look of our corridor that we’ve been used to for several decades.”

Major tree removals like the one planned in the Mission will become more common now that the Street Tree SF program has gained momentum. The initiative began after San Francisco voters overwhelmingly approved Proposition E in 2016. The measure shifted responsibility for caring for the city’s roughly 125,000 street trees to Public Works — overturning the widely unpopular and often confusing policy that forced tree maintenance and removal onto property owners.

The measure also set aside $19 million annually for maintenance work, including tree removal. None of that money, however can be used for planting or caring for new trees or for the intensive watering that saplings require during their first few years in the ground.

Public Works’ budget for planting new trees lags far behind the money available for maintenance and removal — hobbling San Francisco’s ability to grow its urban canopy.

City officials are aware of the problem and have more than doubled the money available for tree planting this year, to around $5.3 million.

By the numbers $19 million Amount spent annually on tree maintenance and removal $5.3 million Amount allocated for planting this year $2.5 million Amount allocated for planting last year 2,650 Number of trees that can be planted this year with the $5.3 million budget 7,000 Number of trees expected to be removed in the next 2½ years

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“It will not be a great result if what comes out of the city taking responsibility for our urban forest is simply the removal of a bunch of old trees. We want to plant new ones and expand the canopy, not shrink it,” said Supervisor Rafael Mandelman, a member of the budget committee.

District 11 Supervisor Ahsha Safaí introduced legislation last week that would require Public Works to replace any trees they remove within 120 days. That legislation and the new funding, he said, “will allow us to increase the canopy by thousands of trees. That’s a good thing for San Francisco and it’s a good thing for the environment.”

But as the city works to eliminate its greenhouse gas emissions to confront climate change, some critics of the city’s tree management practices say San Francisco needs more substantial investments in urban forest expansion.

“Why on earth are we not dumping money into planting trees? That’s literally what they do — they eat carbon for breakfast,” said Joshua Klipp, an attorney and urban forest advocate.

San Francisco has one of the smallest tree canopies of any major U.S. city, at just 13.7% of its area, according to Public Works officials. Los Angeles, by comparison, has 21% canopy coverage; New York has 24%.

Each tree the city plants costs around $2,000. That includes up to $500 for planting and another $500 annually for three years of watering costs.

“That sounds like so much money, but really it’s two cups of coffee a week,” said Carla Short, superintendent of the Public Works Urban Forestry Bureau.

Partly because of budget constraints, tree planting has been glacially slow. The Urban Forest Plan set a goal of adding 2,500 new trees annually through 2034. Last fiscal year, the city came up 2,499 trees short of that goal — as the number of trees planted exceeded the number of trees removed by a single tree, according to the annual urban forest report from the Department of the Environment.

The $5.3 million for this year’s planting is enough to put about 2,650 trees in the ground. But over the next 2½ years, roughly 7,000 trees will likely come down, Short said. That’s largely because the city is only now catching up on long-delayed maintenance work funded by Prop. E.

Over the past decade, 41 major limbs or full-trees have failed along that bustling 24th Street stretch of the Mission, according to Public Works. Like so many ficus in San Francisco, the trees were growing in ways that weaken their tangled limbs, making them vulnerable to cracking off. In some cases, deeper root problems made them susceptible to toppling over.

The most recent failure happened in late February, when a ficus tree fell across 24th Street between Bryant and Florida streets, smashing three parked cars. In 2014, Public Works Director Mohammed Nuru made it easier to remove the trees, which have been illegal to plant in the city since the 1990s, after a rash of limb failures.

“There’s deferred maintenance all around the city,” Short said. “Some of the trees we recently inspected and posted for removal were the property owners’ responsibility, but now we’re responsible for them and we’re finding major concerns we have to address.”

After addressing the worst-off trees, removals will begin to level off, allowing more focus on planting new trees — not just replacing them, Short said.

“All we’re doing is playing catch-up right now. We have so many trees to remove because of 30 years worth of deferred maintenance,” said Dan Flanagan, executive director of Friends of the Urban Forest, who lobbied for more planting funds. “The most important thing is for the city to start understanding that trees are a part of our green infrastructure. We need to grow that infrastructure to maximize the benefits in light of climate change.”

Dominic Fracassa is a San Francisco Chronicle staff writer. Email: dfracassa@sfchronicle.com Twitter: @dominicfracassa