What's the biggest challenge in the world? Climate change? Economic disparity? Species extinction? A Western billionaire -- maybe a member of the one per cent the Occupy protesters are talking about -- will likely say population growth. A lot of well-off people in North America and Europe would agree. But is it true?

It's worth considering, especially in light of the fact that, somewhere in the world, the seven billionth person was just born. In my lifetime, the human population has more than tripled. (I know I'm guilty of contributing to the boom.) But is overpopulation really the problem it's being made out to be? And if so, what can we do about it?

First, supporting more people on a finite planet with finite resources is a serious challenge. But in a world where hunger and obesity are both epidemics, reproduction rates can't be the main problem. And when we look at issues that are often blamed on overpopulation, we see that overconsumption by the most privileged is a greater factor in rampant environmental destruction and resource depletion.

I once asked the great ecologist E.O. Wilson how many people the planet could sustain indefinitely. He responded, "If you want to live like North Americans, 200 million." North Americans, Europeans, Japanese, and Australians, who make up 20 per cent of the world's population, are consuming more than 80 per cent of the world's resources. We are the major predators and despoilers of the planet, and so we blame the problem on overpopulation. Keep in mind, though, that most environmental devastation is not directly caused by individuals or households, but by corporations driven more by profits than human needs.

The nonprofit organization Global Footprint Network calculated the area of land and water the world's human population needs to produce the resources it consumes and to absorb carbon dioxide emissions. If it takes a year or less for nature to regenerate the amount we use in a year, that's sustainable. But they found it takes 1.5 years to replace what we take in a year. That means we are using up our basic biological capital rather than living on the interest, and this has been going on since the 1980s.

As people in developing countries demand more of the bounty and products we take for granted, environmental impacts are bound to increase. The best way to confront these problems is to reduce waste and consumption, find cleaner energy sources, and support other countries in finding ways to develop that are more sustainable than the ways we've employed -- to learn from our mistakes. Stabilizing or bringing down population growth will help, but research shows it's not the biggest factor. A United Nations report, The State of World Population 2011, concludes that even zero population growth won't have a huge impact on global warming.

But, just as it's absurd to rely on economies based on constant growth on a finite planet, it can't be sustainable to have a human population that continues to increase exponentially. So, is there any good news? Well, population growth is coming down. According to the UN report, the average number of children per woman has gone from six to 2.5 over the past 60 years. Research shows the best way to stabilize and reduce population growth is through greater protection and respect for women's rights, better access to birth control, widespread education about sex and reproduction, and redistribution of wealth.

But wealthy conservatives who overwhelmingly identify population growth as the biggest problem are often the same people who oppose measures that may slow the rate of growth. This has been especially true in the U.S., where corporate honchos and the politicians who support them fight against environmental protection and against sex education and better access to birth control, not to mention redistribution of wealth.

Population, environmental, and social-justice issues are inextricably linked. Giving women more rights over their own bodies, providing equal opportunity for them to participate in society, and making education and contraception widely available will help stabilize population growth and create numerous other benefits. Reducing economic disparity -- between rich and poor individuals and nations -- will lead to better allocation of resources. But it also shows that confronting serious environmental problems will take more than just slowing population growth.

Dr. David Suzuki is a scientist, broadcaster, author, and co-founder of the David Suzuki Foundation. Written with contributions from David Suzuki Foundation editorial and communications specialist Ian Hanington.

Learn more at www.davidsuzuki.org.