Is limiting population growth the key to a sustainable future?

First aired on Quirks & Quarks (28/09/13)

The planet isn't getting any larger, we're running out of cheap energy and arable soil, and despoiling our oceans and atmosphere. But every four-and-a-half days, we're adding a million more people. It's predicted that by the middle of the century, the Earth's population will be between nine and 10 billion. But how many people can the planet sustain, with proper food, housing and energy for each of us? And how do we persuade the world to limit our population growth, or even reverse it? The award-winning science writer Alan Weisman addresses these provocative questions in his latest book, Countdown: Our Last Best Hope for a Future on Earth? He talked to Quirks & Quarks about the challenges of overpopulation in a recent interview.


"We're no longer growing exponentially, but we're going to have two-and-a-half billion more people on this planet. And we're already having trouble feeding at least a billion of us," Weisman told host Bob McDonald, adding that food isn't the only factor to consider. "There are many pressures that each one of us puts on this planet. And the next two billion are going to put even more pressures on it than the last two billion."

In Paul and Anne Ehrlich's famous book The Population Bomb, they predicted that in the 1970s, hundreds of millions would starve to death. That didn't happen, but Weisman pointed out that the authors added the caveat "unless there is an agricultural miracle, those famines are going to take place." And that miracle did take place, in the form of the Green Revolution. "So people who might have otherwise died of starvation not only lived, but they lived to beget more people."

Weisman went on to say that "in 50 years, we're going to have to produce more food than has been consumed by human beings in all of human history."

In his book, Weisman poses four questions, starting with: How many people can the Earth reasonably sustain? He acknowledged that it's difficult to come up with a precise number, but several scientists have looked at various indicators and "they all seem to come up with numbers somewhere between two and three billion as being optimum."

We're already well beyond that, so how do we reduce our birth rate, especially when there are cultures and religions, such as the Catholic Church and the Mormons, "who believe in large families." Weisman set out to discover if there was "anything in the histories of all these peoples, in their liturgies, that might make it acceptable, in times of urgent need, to have fewer children, " and he found that indeed there are.

Another factor affecting population growth is that "in most of the world not enough women are having access to contraception," Weisman said. "I've spent a lot of time in really poor countries, like Niger, like Uganda, parts of the Philippines, where there have been cultural or religious pressures against letting women have contraception," he said.

Though we need to reduce the world's population, this poses a problem when economic prosperity depends on growth. "We kind of accept that growth is a good thing, and yet this is all taking place on a planet that isn't growing," Weisman said. "And all of our economic system is based on our physical environment. Ultimately it depends on resource, and also on the other end, it depends on the waste stream that comes out of the economic products that we use. And there's more and more of us contributing to it all the time."

Weisman admits it's not realistic to suggest having a one-child policy everywhere. "Like any other species, we're designed to make copies of ourselves, and we don't want to be told that we should have just one." But he added that if we have just one or two children, the population will come down gradually, and our economy and agriculture can adjust. "I didn't say that this was going to be easy, but it's probably going to be less complicated than doing some of the things that we're trying to do, like finding zero-emission energy. That may be defying the laws of physics, frankly."

It's not a problem that we can ignore. "Every organism that exceeds its resource base ultimately suffers a population crash," Weisman said. Thanks to technology, "we've managed to stretch ours some, but you can't do it forever."

Listen to the whole interview in the audio player above.

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