"I've been involved in social justice issues since I was very young and the biggest tool I had was the fact that people love their kids," she says in a phone interview from her home in Victoria. "I've met so many people who say, 'I wouldn't recycle if it weren't for my kid.' " Ms. Cullis-Suzuki's dad certainly seems in favour of human reproduction. Canada's father of environmentalism is also the father of five children - a number his daughter admits is high (consider him the mayor of a small town in Bangladesh).
"Growing up, we'd often tease him and say, 'Hey, Dad is overpopulating the world!' " she says. "But the truth is we're all human and we all have our hypocrisies. I'm not interested in judgment."
In fact, Ms. Cullis-Suzuki hopes to have children of her own one day. As she explains: "Our consumption habits are really the problem. But the point is, we have choices, so we can make a difference far more than someone who grows up in the developing world."
Of course not all "child-free" people choose to be that way for purely environmental reasons. For many environmentalists, the decision not to become a parent (just like the decision to become one) is based on a multitude of factors, including, but not limited to, their concern for the planet.
Nicola Ross, executive editor of Alternatives journal, an environmental magazine based in Waterloo, Ont., says her decision to remain childless was mainly a lifestyle choice - one that came with environmental fringe benefits.
"Now that I don't have any children, I think, on one level, who cares? As long as the planet's fine for the next 30 years, I'm fine, right?" she jokes. "What really gets me is people who have kids and still don't care."
Ms. Ross, 49, says that, while she doesn't believe in legislating biology (à la China's one-child law), she does find it "indulgent" when people have more than two children.
"Ultimately people have to be responsible for their own actions."
Personal responsibility, whether one has children or not, is at the heart of solving - or at least staving off - the current environmental catastrophe.
And as Prof. Rees points out, the triumph of consumer culture over human connection is what brought us to this juncture in the first place.
"Let's be really clear. The main reason for decline in birth rates in the Western world is people choosing not to have children because of the impact on their lifestyle. The choice they are making is materialism over motherhood. But you could equally have children and reduce your demands on the planet by reducing your footprint."
In other words, people are not just an environmental problem, we are also the only ones who can provide the solution. As Mr. Wackernagel asserts, "We need to have six billion heroes, because without that we won't find a solution."
And what proud parent doesn't like to think their child will be a part of that solution?
Jerry Steinberg, it goes without saying, doesn't share your unconditional love. "Everybody thinks that my child will cure cancer or end global warming, but guess what? The planet's overloaded and it hasn't happened yet."
Leah McLaren is a columnist and feature writer for The Globe and Mail.