A catchy TV commercial in 1977 claimed all 200 million people in the U.S. could agree on one thing: That we all liked Burger King hamburgers, as long as we could get them our own way.

A little more than a generation away from humming that jingle, Burger King now has a whopping 309 million Americans to market to, with one additional person every 12 seconds. Births outpace deaths here nearly 2-to-1. By 2050, the Census Bureau predicts, Burger King will be able to sell to 400 million Americans.

The worldwide population now is climbing above 7 billion people (up from 4 billion when that TV commercial ran) and is growing by 8,640 people every hour. There are about 40 more people on Earth now than when you started reading this story.

Forecasts say the world population will climb to somewhere between 8 billion and 11 billion people by 2050, about the same time many scientists say the amount of carbon in the atmosphere could hit an irrevocable tipping point toward global warming.

“Eight billion would be better than 11 billion, for human beings and the natural systems that sustain us,” said Laurie Mazur, director of the Population Justice Project, on the release of her new book “A Pivotal Moment: Population, Justice and the Environmental Challenge.”

Mazur will be in Duluth on Saturday to talk about the book that includes essays by leading demographers, environmentalists and reproductive health advocates.

Every new person means more fossil fuel is burned for energy, agriculture and travel. More carbon-eating trees are cut. More wetlands filled. More land disturbed and carbon released. More water used.

“It’s time to put population back on the environmental agenda,” she said.

More directly, Mazur will be exploring the value of women’s rights and easily accessible birth control options for women worldwide as a step toward slowing population growth and climate change.

But even supporters say the effort needs to stress education, access and economics while treading carefully with cultures and religions that have historically not allowed women to make those choices.

“These issues do reverberate within the Izaak Walton League and (other environmental groups). There’s quite a bit of discussion on it and not everyone agrees,” said Brent Gurtkek, president of the Duluth-based McCabe Chapter of the League. “But the Ike’s approach is pretty straightforward. If we can uplift women’s status and rights, not just in undeveloped nations but among some populations in our country, so they have access to family planning, we can do a lot of good … for social justice, women’s rights and the environment.”

Gurtek said there’s ample evidence that women who are educated, out of poverty and empowered to make their own family choices inherently choose to have two or less children.

“We’re not talking about forcing people to stop at two. We’re talking about people who are in a position to make that choice,” he said.

Promoting gender equality and expanding access to voluntary reproductive health services leads to smaller, healthier families and can play an important role in helping communities adapt to climate change, Mazur says. She said world leaders must work to ensure access to family planning and reproductive health services, empower women and promote sustainable, equitable development. She urges investment in education and job opportunity for the young men and women of the current generation, the largest in history, who will make the child birth decisions that determine how high the population is at mid-century.

Social justice and human rights, she said, must be at the center of population policy.

Mazur said the consequences of unabated climate change — droughts, rising sea levels, disruptions to agriculture, water shortages — will be felt by communities across the globe, but especially in places where women have less freedom.

“Talking about population growth as an environmental problem might seem to be blaming the victim, especially when they (women without access to birth control) probably have had the least to do with our environmental problems,” Mazur said. “But in fact it’s the people of Bangladesh who will be under water if we don’t do something on climate change. And it will be the people of sub-Saharan Africa who won’t have food or water. So it really becomes a social justice issue.”