VANCOUVER -- An ad at a downtown Vancouver bus stop is raising eyebrows, encouraging couples to restrict their family size to just one child in order to help curb the world’s population.

The U.S. group behind the ad calls itself World Population Balance, and it believes there are too many people on earth, leading to serious negative consequences for the planet.

“It’s really a sensitive subject. People are reluctant to talk about it. So I fully expect a range of reactions,” said Dave Gardner, executive director of World Population Balance.

The poster is on the southbound bus stop on Granville Street in the block immediately south of Robson Street.

“I think that’s a great initiative. The planet is overpopulated as it is,” said Karmina Lake when she heard about the ad.

Others felt discussions around family planning are sensitive.

“It’s a personal decision, at the end, what you do,” said Maryam Sadeghi. “And there are so many factors that will have an impact on what you do and how you decide.”

Gardner says the campaign is about starting a conversation about how individuals can make a choice to help the planet.

“We want couples around the world to be able to make free decisions but fully informed,” he said. “And right now, it’s surprising how many people are not aware of overpopulation and not aware how easy it is to solve it because we’ve been afraid to talk about it.”

As the earth’s population approaches eight billion, World Population Growth believes it could be cut nearly in half in the next 100 years if people only had one child, but they say they are not advocating for laws restricting family size.

“I think it can be a slippery slope towards that,” said Vancouver resident Kristin Gabriel. “I tend to think everything should be left up to the individual, but on a personal level, I definitely think that is beneficial to society to have a little bit of a depletion in the population growth.”

World Population Growth began its ad campaign in a handful of American cities and says now that it has started advertising in Vancouver, the campaign could spread to other Canadian cities.