Paris, France (CNN) -- Joy Monroe, a tourist from Montana, has come to Paris's Pont des Arts bridge on a mission of love.
To celebrate her marriage of 28 years, she attaches a padlock to the bridge's rail then throws the key into the river below.
"Our love is locked forever," she says.
It's an act that's been repeated thousands of times, barnacling the Pont des Arts with a dense mass of "love locks."
But its popularity is now straining both the bridge and Paris's relationship with its romantic visitors, prompting a campaign that seeks to outlaw the trend.
American Lisa Anselmo and French-American Lisa Taylor Huff say they co-founded No Love Locks because the padlocks are endangering historic landmarks and have become a threat to safety.
"I understand that this is a modern expression of love and it's cool, but history should not be compromised," says Anselmo.
"It's almost painful to watch this vandalism."
She and Taylor Huff say the Pont des Arts, built in the 1800s under Napoleon and damaged in a 1979 barge collision, might not survive much longer unless authorities act.
The bridge currently carries about 700,000 locks with an estimated combined weight of 93 metric tons -- roughly the same as 20 elephants standing on a bridge designed for pedestrian traffic.
Sections of fencing have already fallen out under the weight only to be replaced by unsightly wooden panels.
No Love Locks has created a petition that's collected more than 2,200 signatures.
"We just want to give back to the city we love and protect its heritage and beauty," says Anselmo.
"One lock is a poem; hundreds of thousands are a conundrum."
According to the official Paris website, the padlock trend started in 2008 and was initially seen as charming.
But the practice quickly got out of hand, with padlocks spreading to other bridges and reappearing as quickly as authorities removed them.
There are concerns that the keys thrown in the Seine will add to the river's existing pollution.
Graffiti, pickpockets and vendors selling cheap padlocks have also become a problem, prompting many locals to avoid the once picturesque promenade.
"Parisians feel helpless because we don't want to appear unwelcoming to tourists," Anselmo says. "But people need to understand that what you're doing is impacting the residents of the city you love."
She points out that a lock is an inappropriate symbol for love in France, a country where the main annual holiday celebrates an historic assault on a prison -- the storming of the Bastille.
Olivier Passelecq, the deputy mayor of the Parisian neighborhood that includes the Pont des Arts, agrees that the locks have become invasive.
"The public has to know that a public monument is not there just for lovers," he says.
"[The bridge] has an historical perspective as one of the most beautiful spots in Paris between the French Institute and the Louvre."
Both Passelecq and No Love Locks want to find another place for the locks, mirroring similar schemes in Moscow and Rome.
"Travelers want to leave their mark on Paris -- it's touching and we understand that," Anselmo says.
"But show love to the history, to the beauty first, and maybe not putting a lock is the most loving thing you can do."