Marijuana boosters have declared war on booze.

The number of billboards and other advertisements aimed at converting drinkers into tokers or nibblers (of edible marijuana) has exploded over the past several years.

With California on Jan. 1 becoming the eighth state to legalize the recreational use of weed, the rhetoric has grown even louder.

“Hello Marijuana, Goodbye Hangover” declares one such billboard from cannabis tech company eaze.com in San Francisco.

Eaze.com also provides advice on ways to replace wine and other alcohol with marijuana “equivalents.”

“Marijuana,” blares a billboard in Arizona. “Less Toxic! Less Addictive! Less Scary Than Alcohol!”

Watching on the sidelines are bar and restaurant owners who are wondering whether they are the collateral damage in a cultural sea change. Among their concerns is the loss of both employees and customers to a burgeoning cannabis industry.

“We keep hearing that sales of alcohol seem to be impacted by the legalization of cannabis, but it’s still too early to know how it will impact sales and customer preferences,” said Jot Condie, chief executive of the California Restaurant Association.

Restaurants in Colorado, where recreational marijuana has been available since 2014, are already losing workers to higher-paying cannabis businesses.

“A lot of companies don’t even do drug testing anymore because it’s so difficult to find employees,” said Sonia Riggs, head of the Colorado Restaurant Association.

A growing body of research suggests that alcohol sales have plummeted in states where marijuana is legal.

According to Cowen and Co., 80 percent of consumers reduce their alcohol consumption with cannabis in the mix, while research from the University of Connecticut and Georgia State University shows that counties located in states that legalized medical marijuana — more than 25 states have done so — saw a 13 percent reduction in alcohol sales.

Even proponents of legal marijuana say consumers should not be told to choose between alcohol and weed.

“The marijuana industry is fostering this notion that it’s a zero-sum game,” Tony Magee, founder of Lagunitas Brewing Company, told The Post. “There’s a horse race that’s being created here.”

In Colorado, the cannabis industry is pushing for looser laws, including the right to consume marijuana in establishments with a liquor license.

Restaurant owners think that will make the situation worse.

“There are instances where tourists will come to a restaurant, order one drink and pass out 30 minutes later” because they had a marijuana edible earlier and ate more than they should have, said Riggs.

The liability issue is significant, said Tay Wilbanks, owner of the Greedy Hamster bar in Denver.

“We have had to turn people down [who are high] when they want to order drinks,” she said. “I don’t want people drinking and smoking in my establishment.”