(CNN) -

Destructive graffiti wars are being waged by anonymous vandals, deliberately defacing many of the meticulously painted murals that vividly illustrate San Francisco's streets.

The attacks have sparked calls by outraged professional artists and their supporters demanding everything from public humiliation to experimental collaboration with the hostile graffiti "taggers" to avoid violence and more lost art.

If you're going to San Francisco, keep in mind that the outdoor murals you see are ephemeral, so appreciate them -- and take lots of photos -- before they disappear.

Countless gorgeous, larger-than-life murals illustrate this city's weathered exteriors, bestowing visual intrigue to homes, shops, parking lots, recreational facilities, derelict buildings and alleys.

Artistic themes include anarchy, surrealism, science fiction, eroticism and other fantasies and realities.

Some gigantic paintings include political slogans or poetry for the public to ponder.

Now, however, a rolling population of taggers has been wreaking havoc on many of the best murals, by hurriedly spray-painting initials, names, words, acronyms and other lettering across the majestic urban displays.

Gang intimidation at work

Some victimized artists worry that the taggers may include criminal gangs marking their neighborhoods, making it unwise to confront them or remove their destructive scrawls.

"There is always that possibility of violence, if you approach someone tagging a mural," said Carlos Daniel Perez-Boza, 26, who teaches art at San Francisco's Cultural Arts Division of the Recreation and Parks.

"Some taggers come in large numbers, some are gang related. Their intention is to mess things up and possibly look for a fight," he said in an interview.

"I can only hope taggers would appreciate the street arts, and truly see what are the possibilities that we are building, for artists to showcase their talents in public space," said Perez-Boza, who is also a muralist, painter, street and studio artist.

Mission District art targeted

Clarion Alley, the Mission District neighborhood's prestigious, free, open-air gallery, isn't immune from desecration.

Since 1992, Clarion Alley's urban lane has allowed artists to voluntarily adorn its outdoor walls, fences, residences, gutters and every other available space with fanciful and often profound murals.

The public alley runs parallel between 17th and 18th streets, linking Mission and Valencia streets -- you can visit anytime day or night for free.

Prominent artist Mats Stromberg completed his 12-foot-tall, 15-foot-wide, ant-infested "Giant Selfie" Clarion Alley mural in 2013.

His mural portrays a man's huge turquoise head -- resembling himself -- laying on the ground, "with two factions of ants battling it out in front of his very eyes, representing the sort of narcissism associated with all the latest social media gadgets, as well as the individual's helplessness in the face of conflicts either nearby or globally," he said in an interview.

Stromberg wasn't amused when his masterpiece was defaced in July.

Big, bold blobs of silver-colored letters, outlined in red -- spelling the name "Blake" -- suddenly smothered much of the mural.

Asked what punishment anti-mural taggers should suffer, Stromberg suggested perhaps the person should be "tarred and feathered, and tied to the defaced wall for a few days and nights? Spray-paint their faces?"

Compromising with taggers?

Stromberg, whose signature "Mats?!" includes double punctuation, has seen his art attacked by other taggers in the past.

His previous response was to painstakingly paint over the graffiti, and restore his mural.

This time, however, Stromberg painted fresh chaotic designs over parts of the silvery letters, rendering "Blake" unrecognizable under blossoming, newly evolved weird images.