MR. KOJO NNAMDIFirst Alan Weisman imagined the world without us, finding out what would happen to Earth absent mankind. Now he's confronting a world with us, too many of us. The planet's population is around 7 billion strong at the moment, the number the UN projects will grow to nearly 10 billion by 2050. We're depleting resources and damaging the environment in ways our ancestors never did and in numbers so large, it's hard to get your head around them.

MR. KOJO NNAMDIHere to help us break them down and bring us to countries where the implications of outsize growth aren't hypothetical, they're happening, is Alan Weisman. He is a journalist and author of several books, the latest of which is "Countdown: Our Last Best Hope For a Future on Earth." Alan Weisman joins us in studio. Thank you for joining us.

MR. ALAN WEISMANHey, Kojo.

NNAMDIMany of our listeners have read your previous book "The World Without Us," but for those who have not, what was the premise of that book and how does it serve as a jumping off point of sorts for your latest book?

WEISMANWell, I really wrote that book because I would like a world with us. The idea was to theoretically remove us from the planet and to see, as I learned, that nature could recover from much of the damage that we've done with surprising swiftness, refill empty niches, start to flourish again. And my hopes was that readers would see that and say, isn't there some way that we can add ourselves back into this picture of a beautiful newly restored Earth, only in harmony as opposed to constant combat with the rest of nature?

WEISMANSo I talked about that in the epilogue but I ran into a disturbing fact. You know, to wrap my head around what we are doing right now, I looked at our population, did some long division on all those billions and found out that every four, four-and-a-half days we're adding a million people to the planet. So that did not seem like a sustainable figure.

WEISMANSo at the end of the book I did a little extra thought experiment asking theoretically, setting all social considerations aside, what if we all participated in the Chinese one-child policy? It turns out that by the end of this century we'd be down to 1.6 billion. And that was exactly the population in 1900 before the world suddenly doubled and then doubled again. We quadrupled in one century for reasons I'm sure we'll get into.

WEISMANNot everybody -- that most people don't like the Chinese one-child policy but so many people were interested in this disturbing figure of obviously too many people coming into the Earth constantly that finally I was impelled to take a look at it as a journalist. You know, it's a very explosive topic. But to see -- can we determine what would be a safe number? And if so, is there something acceptable and humane that we could do about it?

NNAMDIWell, population control is not a topic that it would appear a lot of people want to talk or even thing about. Were you at all reluctant to take on this topic?

WEISMANYou know, my agent said, don't touch it. But I couldn't really come up with anything else because it kept nagging at me. And then when I finally sat down to write an outline of what a population book would look like and two days later I had a 60-page book proposal that publishers started fighting over, I realized this is something that touches a nerve. Yes, it's very uncomfortable. And one of the things I had to do right away was to think about why it is so uncomfortable for us. And there's a whole lot of reasons.

WEISMANI mean, instinctively like every other organism on the planet, we're designed to make copies of ourselves. In fact, extra copies of ourselves because until our medical technologies suddenly improved around the beginning of the 19th century with a smallpox vaccine, you know, most of our young ones would die. Most babies were gone by their fifth birthday. So improving medicine suddenly helped jack up our numbers. And then in the 20th century we had some other technology. But even so, just the idea of not doing what comes naturally is kind of uncomfortable for people.

NNAMDIWell, given the fact that we have grown into this habit for such a long time, this notion of making not one but several copies of ourselves, how do you get people past the reluctance to talk about reducing our growth rate?

WEISMANWell, you know, another impediment that we have to that is that the one country that has really tried to do this with a policy, China, did something that everybody finds abhorrent. Most Chinese haven't liked it. But what I needed to find out for this book is that are there alternatives to it? And I found -- and I traveled to many countries...

NNAMDI...more than 20.

WEISMANYeah, I go to 21 countries in this book and I found several that without a coercive mandate from their government, have found ways to bring their population down simply by...

NNAMDIHold that thought for a second because I'd like to invite our callers to join the conversation at 800-433-8850. We're talking with Alan Weisman. He's a journalist and author of several books. The latest is called "Countdown: Our Last Best Hope For a Future on Earth." Do you think policy makers and average citizens alike should be more concerned about growing global population? What kind of role do you think the U.S. could or should take on this issue? Give us a call, 800-433-8850. You can send email to kojo@wamu.org or send us a Tweet on kojoshow.

NNAMDII wanted to get back to the fact that you visited these 21 countries. How did you decide where to go?

WEISMANWell, there are several countries that have come up with different strategies to persuade their constituents, their citizens that it's probably to their advantage to have fewer children. So those are some of the ones that I had to go to. There are also some countries whose population is waxing way beyond control. And I had to see, you know, what the worse side of this is like.

WEISMANI also obviously had to go to China because they have tried to deal with it. And some good things came out of the one-child policy. There are 400 million fewer Chinese now than there would've been otherwise. And the ecologists from the Chinese Academy of Sciences I was traveling with say that there's no way that the ecosystem could possible survive had all of those people come to be born.

WEISMANBut we also learned some of the pitfalls about trying to control population. And that's why I ultimately conclude in this book that control isn't what we want. What we want is choice. We want to give people the means to decide how many babies they want and to give them some pointers as to what might be most affordable.

NNAMDIEverywhere you went you asked four basic questions. What were they and who did you ask those questions of?

WEISMANWell, number one is, what would be the optimum number of people on this planet or how many people can the planet hold without capsizing? And then there's sort of a converse of that. How much nature do we need to guarantee our own survival? You know, we're part of an ecosystem and can we identify which species are essential to us before we obliterate anymore? Since the one-child policy wasn't -- isn't that palatable, I needed to go to lots of different countries to see, is there anything in their histories or there liturgies or their culture that would allow for, so to speak, refraining from embracing so much in times of need? And I did discover that. I spoke to many religious figures all over the world.

WEISMANAnd the fourth, how could we, in a shrinking world or a world that was at a stable sustainable size, develop an economy that could prosper without constantly growing, as we constantly hear that that's the definition of health for an economy.

NNAMDIAnd of course, I guess we can embrace without procreating all the time, but I'd like to go to the telephones and start with Steven in Silver Spring, Md. Steve, you're on the air. Go ahead, please.

STEVEHi. My question is, it seems that many of the points made around the notion of population and its demands relative to the finite capacity of Earth are based around a number of assumptions about how that population functions. And I'm wondering about how much of what we're assuming due to population numbers is really a matter of consumption and the degree to which consumption can change might change what we think about population and where we place those numbers as ideal.

WEISMANWell, if you could change consumption, I'd be all for it. But the fact is, we have condoms to control population but we don't have one to control consumption. I really don't know how. I mean, you and I are speaking to each other through electricity. And as a result some carbon atoms are going up into the atmosphere. The impact of humanity is our numbers multiplied by our consumption. And the one thing that I know that we do have the technology for is bringing down the number of consumers. How we cure consumption, I think if we finally raise everybody's consciousness to really do that, the Earth might be long trashed beforehand.

NNAMDII think adding to that issue -- and thank you for your call, Steven -- is David in Hedgesville, W.V. David, you're on the air. Go ahead, please.

DAVIDGood afternoon, Kojo. I just want to make a comment that the United States' impact on the global problem of global warming and all is well higher than any other country. And we need to stabilize our population to decrease our continuing increasing impact. And what we can do to help the other countries is get the political will to provide assistance in family planning around the world. And also to stop our promotion of large families by limiting deductions to one per individual, so two per family.

NNAMDIWhat do you feel about those suggestions, Alan Weisman?

WEISMANWell, I think I agree with the listener on all accounts. If we multiply our numbers by our consumptive habits, the United States is the most overpopulated country on Earth. The population has to come down everywhere, but even in poorer countries -- and I go to some of the poorest places, rural and urban, on this planet. Poor people still need shelter. They need firewood or fuel and they need food. Forty percent of the planet's non-frozen terrestrial surface now is devoted to feeding just this one species, homosapiens. And that's way out of whack. Nature is not going to let that continue forever.

WEISMANIf poor people go to urban areas -- I was in some of the worst slums on the planet and somehow they still manage to get cell phones now. And even if that electricity's pirated, they're plugging in their chargers every night just like you and me.

NNAMDIIn talking with experts from various backgrounds, environmentalists, demographers, economists and so about this issue, where did you find the most likely to be at odds?

WEISMANWell, you know, there are some traditional religions that the extreme thereof are against population control because every religion begin with a mandate to be fruitful and multiply. And that was a strategy to have a lot of babies to become the most, you know, powerful nation or group or tribe in the neighborhood. In fact, I begin this book in Israel and Palestine where you've got two peoples who've been trying to out-populate each other to be the majority in a land much of which is a sandbox.

WEISMANAnd as a result they're running out of water. You know, those Israeli settlements in the West Bank are there because there are wells underneath it. There's an aquifer underneath them and Israel doesn't want to give that up. So, you know, the Catholic church of course is very famous and I go to the Vatican at one point in this book and have some rather spirited conversations with Cardinals there. But the Vatican is this country of 1,000 people, most of them male. And it's surrounded by a large Catholic country called Italy which has one of the lowest fertility rates on the planet. And one of the big reasons for that is that Italy also has one of the highest per capita rates of female education. Rich country or poor country, wherever I went, it turns out that female education is the best contraceptive of all.

WEISMANA girl who's studying will defer her childbearing until she's out of school and then she's got something interesting and useful, hopeful to her family's economy to do, but it's hard to do that with seven kids so most educated women, on the average, have two children or fewer.

NNAMDILet me go to Tesfa (sp?) who is in Arlington, Virginia. Tesfa, you're on the air. Go ahead, please.

TESFAGood afternoon. It should come -- procreation control should come from individual citizens and this happens only when the individual citizen of each country has a right and is responsible because he has the right in his country and he knows his resources as to how many children he can have. That happens only when there are stable countries and democracy and human rights.

TESFAAnd also, when there is an economy being built that doesn't take the money from loaned -- from outside and make a u-turn back to the countries it was borrowed from. This happens in countries corrupt, like the Ethiopian government and other undemocratic governments. This can happen only...

NNAMDIYou raise several very important questions, Tesfa, one of them I'd like to address or I'd like Alan Weisman address is because Tesfa was talking about what goes on in the minds of the average adult in these situations. In addition to seeking out experts, you also spoke with local adults everywhere you went, average residents living the reality of these challenges.

NNAMDIDid you find that they perhaps grasped these challenges in a way that experts did not?

WEISMANWell, oftentimes I was in countries where people wanted to use contraception if it was available to them. I'll give an example, a country we're all thinking about a lot these days is the Philippines. This is one of the few countries where the Catholic Church is really powerful and yet the Philippines which depends on the sea for 90 percent of its protein is ringed with fishing villages where family planning is starting to spread all over on a local level because fishermen have figured out that you have to keep the number of fishermen in balance with the fish stocks.

WEISMANSo this is an occasion where, you know, despite government, people are making these decisions for themselves. But the caller is quite -- is right in that we want all of those things to happen. We want an end to corruption. But in the meantime, I've got a couple of interesting examples in this book where family planning turned out to be the path to a more equitable society and to better economic development because some smart economists in the government realized that there was no way that they were going to be able to develop when they had every village and province overrun with teeming hordes of people.

NNAMDIYou seem to be saying in response to Tesfa that you don't have to have, necessarily, high levels of democracy, high levels of literacy, high levels of economic opportunity or necessarily high levels of education in order for individual families to be able to have access to the information they need to organize their own families properly.

WEISMANWell, you want all those things, but you can start. Let me give an example that will surprise a lot of people in this country. The most successful family planning program on Earth took place in a country that we consider part of the axis of evil here, that's Iran. After the 1979 Islamic Revolution, the Ayatollah actually asked every fertile woman in Iran to get pregnant, do her patriotic duty because they had been invaded by Saddam Hussein and he wanted to fight off the invading Iraqis with a 20 million man army.

WEISMANWell, they held them to a stalemate for eight years and then, after the truce, the economist who was head of planning and budget realized that there were going to have a terrible problem within about 10, 15 years 'cause all these kids would grow up and how would they possibly employ them all? In a country with all these unemployed or underemployed young people becomes -- they are frustrated. They are angry and they become destabilized, destabilizes the whole country.

WEISMANThat kind of describes Pakistan, another place where I went. So they convinced the Ayatollah, and particularly the current Ayatollah, that family planning was in order. So they did four easy things. First, they issued a fatwa saying there's nothing in the Koran that says that if wisdom dictates you've got the number of children that you can responsibly care for, that you can't have a vasectomy or tubal ligation, as well as use any other form of birth control pills -- birth control.

WEISMANAnd they only required people to attend premarital classes, which is, frankly, a good idea for anybody. And in these classes, among other things, they talked about how much does it cost to feed, educate, clothe a child. They made all this contraception available throughout the country. I talked to an ob/gyn, a very devout Muslim woman in Tehran, who talked about the horseback brigades with surgical teams going everywhere to offer these services.

WEISMANBut most important, they convinced women to stay in school. And at the time, there was only one-third literacy among Iranian women. Today, 60 percent of university students are female in Iran and they came down to replacement rate, that's two people having two children, a year faster than China and it was totally voluntary.

NNAMDIGot to take a short break. When we come back, we'll continue our conversation with Alan Weisman. His latest book is called "Countdown: Our Last Best Hope For A Future On Earth." We're still taking your calls at 800-433-8850. Have you tried to reduce your impact on the environment to ease demand for resources? Is there anything else you think individuals can do? I'm Kojo Nnamdi.

NNAMDIWelcome back to our conversation with Alan Weisman. He's a journalist and author of several books, the latest of which is "Countdown: Our Last Best Hope For A Future On Earth." If you'd like to join the conversation, give us a call at 800-433-8850. Have concerns about overpopulation influenced your own approach to family planning? Tell us why or how? 800-433-8850. Here is Sam in Ashburn, Virginia. Sam, you're on the air. Go ahead, please.

SAMYes, Mr. Kojo. What I realized is that there exists the (unintelligible) describing the people that it's about procreation, which is the problem. I'll give you an example. In Africa, the whole Africa put together, you have the total carbon dioxide emission being around 3.2 percentage of the world global emissions. A country like Canada with the tar sand oil, you have (unintelligible) 4 million people, which has got, of course, (unintelligible) children per family, has got contribution of about twice as much of the whole of Africa put together.

SAMThis is not about the children, because in fact as I point out, most of these high fertility families in Africa, they have the least pollution. You cannot equate the percent of the (unintelligible) with the number of children.

NNAMDIOkay, sure. Allow me to have Alan Weisman respond.

SAMI mean, that is a joke.

WEISMANWell, you know, I went to Africa twice for this book and I've been there on other occasions for previous books and the countries I went to this time, Niger and Uganda, you know, the caller is right, they may not be putting as much carbon dioxide up the chimney, but that doesn't mean that overpopulation doesn't make them suffer. In Niger, every village I went to had 150, 200 children dying of nutrition.

WEISMANPeople would...

NNAMDILack of nutrition.

WEISMANYeah, lack of nutrition. People would constantly say, you know, if you'd been here 25 years ago, you couldn't have seen that house 100 meters off because of all the trees that we had here. What happened to the trees? Well, they had to cut them for firewood. And their lands have been divided so many times between sons that now, particularly with climate change, in Niger, they used to have 10-year drought cycle, then it became a 5-year drought cycle.

WEISMANBy the time I was there, it was a three-year drought cycle that hadn't ended in four years. So everyone is dealing with a situation now where there are just too much of a good thing, too many people.

NNAMDIIn the Philippines, you found a nation closely linked to the sea on your visit, a nation now struggling with the aftermath of a monster typhoon, what do you think we can learn from that event?

WEISMANWell, what we know now is that we're having extreme weather event much more often. I mean, every place I go, the 500-year flood or the 500-year hurricane is coming twice in a decade, sometimes twice in a year. When I was in the Philippines, it was right after a typhoon. I had been on Hainan Island in China and barely escaped the typhoon that came and 135,000 people had to be evacuated the following day.

WEISMANI was sloshing around ankle-deep water in Manila and that was just a small typhoon compared to the one that it just suffered right now. We're going to be having more of these weather events and, frankly, we don't know how to control carbon dioxide. I mean, we know theoretically renewable resources would be a great way to go for energy, but the uptick on them is extremely slow.

WEISMANThere are many forces that are trying to impede it and last year, our carbon dioxide contribution in the atmosphere increased, rather than going down. If we want to remain within safe levels by the year 2020, that's only seven years away, we have to get back to 1990 levels and then, cut them in half and then keep diminishing. Now how are we going to do that? The one thing that we can do is start diminishing the numbers by simply making contraception available to people.

WEISMANIf every family had between one and two kids for the next couple of generations, we'd really start making a serious dent in our environmental impact.

NNAMDIOnto Jessica in Fredericksburg, Virginia. Jessica, you're on the air. Go ahead, please.

JESSICAHi, Kojo and Alan. One objection that I've heard raised by some against population control is the assertion that human beings have some kind of right to have children. And my response to that would be that rights are not inherently -- you're not born with rights. Rights are granted to you by society and when the global society being beyond just humans, all animals, all life, the planet itself, our ecosystem, when this society demands that humans cut back on population growth, that should take precedence over humans' natural drive to procreate and have children of their own and to create little copies of themselves so that they may continue on.

NNAMDIWell, Alan Weisman can tell you, as he's said before on this broadcast, forcing people to do that is not apparently acceptable in most of the world. It certainly wasn't very popular in China. But he's talking about there are other ways family planning and contraception that works in other countries.

WEISMANWell, I think that we have as much of a right as any other species to procreate, otherwise we're going to go extinct and I'm not ready for my species to go extinct. But we now have to become a limiting factor on ourselves and not have as many children. Look, for most of human history, 99 percent, our population growth was almost a flatline, barely any more people survived than died.

WEISMANAnd then, with medical technology, but then with food technology, basically artificial nitrogen fertilizer, without it, 40 percent of us wouldn't be here. And then, a green revolution, our numbers quadrupled in the 20th century and it's so abnormal, you know. Suddenly, the graph shot skyward and you and me and all of us, we were born in the middle of that graph so this looks normal to us, but it actually -- this is far more than nature ever intended and eventually, nature will knock us back unless we manage it gracefully and humanely and do it ourselves.

NNAMDIJessica, you're calling from Virginia so you should know that state officials estimate that Virginia sterilized 7,325 people under a 1924 state law that remained on the books until 1979 and the Commonwealth is currently under renewed pressure to compensate people sterilized without their knowledge from the '20s to the '70s so trying to enforce that on people gets a very huge pushback.

NNAMDIYou know, Alan Weisman, "The World Without Us" imagined Earth without people. "Countdown" considers the toll of too many on nature. What kind of balance do you think we could reasonably strive for or strike?

WEISMANWell, you know, I suggested before that if we could hold ourself to two children or fewer per family, we would bring our population down over the next century into a much more sustainable level. There'd be much more room on the planet for other species. We wouldn't be hogging most of the planet to feed ourselves. There would be, you know, room for us to move around in instead of being stuck in endless traffic.

WEISMANAnd that, to me, seems like a really attractive thing to do. By the way, people can have big families if they really, really treasure them. You know, one resource that we've never run out of on this planet is children who need a home. So adoption is a wonderful way to go after you've had your one or two biological children yourself.

NNAMDII'm afraid we're almost out of time, but you did arrive at an idea of an ideal standard of living that would sustain what you describe as the optimum population. In 30 seconds or so, what might that look like?

WEISMANWell, you know, we were about 2 billion of us before artificial nitrogen was commercialized and suddenly kicked up our numbers. And if we could bring ourselves back to between 2 and 3 billion, I think that we'd have a much happier nation, a much happier world. As we brought our population down, economies would adjust, demands would be fewer, but earnings per capita would still remain just as high and productivity would remain high.

WEISMANWe'd just have to work less. We'd have more leisure time. That's not a bad future.

NNAMDIAlan Weisman, I'm for more leisure time. Alan Weisman is a journalist and author of several books, the latest of which is "Countdown: Our Last Best Hope For A Future On Earth." Thank you very much for joining us.

WEISMANThank you, Kojo.