Supervisor Scott Wiener introduced legislation on Tuesday that — if approved by the Board of Supervisors — would close the parks from midnight to 5 a.m., putting San Francisco in line with Los Angeles, New York and about a dozen other U.S. cities.
Wiener said the closure could help curb rampant vandalism, metal theft and illegal dumping at the city's roughly 200 parks.
Wiener said sleeping in parks is already illegal, and his proposal is not directed at homeless people.
However, Lisa Marie Alatorre of the Coalition on Homelessness in San Francisco said hundreds of people live in city parks, especially Golden Gate Park, which covers more than 1,000 acres.
"I do think that it is going to have a huge effect, even if Supervisor Wiener is saying it's not the intention," Alatorre said. "They'll do huge sweeps where it will be massively enforced, but those people have nowhere to go so they'll come back the next night."
Wiener said about 80 of the city's parks already have a "mishmash" of closing rules set by the recreation and park commission. The inconsistency makes the rules tough to enforce, he said.
Currently, city laws only allow people to be cited for failing to obey a park sign. But many signs indicating when a park closes are hard to see because they get obscured by foliage or face the wrong direction. Supporters say an across-the-board rule would better allow law enforcement to cite violators.
Under Wiener's proposal, anybody violating the rule would be ticketed or face misdemeanor charges.
"These kinds of laws, as common sense as they are and as consistent as they are with the best practices of the country, will always spark a debate in San Francisco," he said.
The board was expected to take up the proposed legislation in September.
Park officials said illegal dumping and vandalism occur largely at night and cost the city about $1 million annually. Earlier this year, vandals snapped the top off of saplings in Golden Gate Park, making the trees vulnerable to disease and rot.
Sarah Ballard, director of policy for the city recreation and park department, said in recent weeks toilets have been smashed by sledgehammers, trees have been lit on fire, and people have stolen benches from parks.
Alatorre argued that keeping people from parks at night will not reduce vandalism and theft, which she believes are happening because the perpetrators are facing tough economic times.
"It doesn't solve the problem because the problem is so much bigger," she said. "Get at the root cause, then maybe we would see a decrease."