Charles C Mann is a science journalist, author and historian. His books 1491 and 1493, looking at the Americas before and after Columbus, were widely acclaimed. His new book, The Wizard and the Prophet, examines the highly influential and starkly contrasting environmental visions of Norman Borlaug (the Wizard) and William Vogt (the Prophet). Borlaug (1914-2009) was instrumental in the green revolution that vastly expanded the amount of food humanity has been able to cultivate. Vogt (1902-1968) was a pioneering ecologist who argued that humans had exceeded the Earth’s “carrying capacity” and were heading for cataclysm unless consumption was drastically reduced. One believed in scientific ingenuity as the answer to our problems, the other was convinced that it only deepened the crisis.

What made you frame this story of humanity’s future in terms of these two individuals?

It really started the night my daughter was born 19 years ago. I was standing in the parking lot at three in the morning and it suddenly popped into my head that when Amelia, my daughter, became my age there would be almost 10 billion people in the world. And I believe that centuries from now, when historians look back at the time when you and I have been alive, the big thing that they’ll say happened is that hundreds of millions of people in Asia and Latin America and Africa lifted themselves from destitution to something like the middle class. So not only will there be 10 billion people but all those people will want the same things you and I want – nice homes, nice car, nice clothes, the odd chunk of Toblerone, right? And so I stood there in the parking lot and thought to myself: how are we meant to do this? I’m a science journalist, so when I was talking to researchers, I’d say: “How are we going to feed everybody, how are we going to get water for everybody, house everybody? What are we going to do about climate change?” After a while I realised that the answers I was getting fell into two broad categories, each of which had a name that kept being associated with it: one was Borlaug, the other Vogt.

You examine each argument on its strengths and weaknesses without necessarily expressing an opinion. Was that difficult?

It was difficult to some extent as I have – like anyone else – a full kit of knee-jerk prejudices and unexamined beliefs. So I thought, let’s be fair here. Partly because I think this is what a journalist should do, and partly because in the age of the internet there are all too many people who are willing to tell you what to think and not nearly enough trying to report what’s going on. And I thought that was a more valuable service. I can contribute something as a reporter. The instant I start spouting out my own beliefs I become just another guy on the internet.

How much do you think the respective arguments come down in the end to whether one is an optimist or a pessimist?

I think that in the end it has to do with people’s fundamental perceptions of what the good life is like, what the world is like and what people are like. I don’t know where those come from, but people have them. I have them. Once you understand that, you realise there’s a certain type of person who sees people as endlessly inventive, these wily managers and thinkers and doers that can expand endlessly. And other people who see us as fundamentally embedded in the community, as part of something larger, and we shouldn’t wreck that larger thing.

Younger people are considerably less enthusiastic about limiting the reproduction of poor people and brown people Charles Mann

You write about how in the past in the ecology movement there was a fascistic desire to control human reproduction. Do you think there is a deep-lying seam of misanthropy among ecologists?

It’s certainly a big streak historically. The environmental movement originally came from the upper-crust types who were the same people involved in eugenics. They saw it as a cleaning up and purifying of nature, and that unless human reproduction was governed by wise people, very bad things would result. You do still find that attitude. When I give talks, there’s almost always a guy in the audience, usually a silver-haired, distinguished-looking gent, who says: “The real problem is population and we’ve got to control it.” Then they say we have to reduce the population of the Earth by 50% or something. So it’s still present. Younger people who are involved in the movement are considerably less enthusiastic about limiting the reproduction of poor people and brown people.

Do you think it’s possible to make effective international laws governing the environment?

Well, there’s a couple of examples of them. The big one is the Montreal protocol, which is the law that limits the production of gases that deplete the ozone layer, and it’s been extraordinarily successful. I’m much more sceptical about things like the Paris agreement. Not because it was badly intended, but conditions in countries are so unlike one another that it’s very hard to come up with a blanket approach that fits everything.

Norman Borlaug is known in scientific circles, but he’s not a household name in the way that Albert Einstein is. Giving the profound effect of his work, should he better known?

Yes. If you look at it, the average person needs something in the order of 2,200 calories a day to be moderately active. Some time in the 1980s, the average person in the world had that necessary level of calories for the first time in human history and, for the first time, most people on the planet had a regular supply of food. Borlaug and the people he inspired had a huge impact on that. If I were teaching history to teenagers I would say there were two big events in the 20th century. The first was the development of antibiotics and the second was the green revolution, and they have changed our lives unimaginably. Throw in the emancipation of women and you have a really remarkable century.

Given that the Earth must have limits, is there a danger of the boy who cried wolf in the continual warnings of impending environmental disaster?

I would say that there are two dangers. The first is that while it’s obviously true on some level that the world is finite, and there are only a certain number of molecules, it’s very unclear exactly where that limit lies. And it’s very difficult to find out. The second is that there’s this terrible trap that people fall victim to again and again, the idea that the relationship between consumption and population is simple and straightforward. That’s simply not the case.

Having done such extensive research, do you now feel more or less reassured by what the future holds?

One of the arguments of the book is that both Vogt and Borlaug essentially had a biological view of our species and our planet. And there’s much to be gained from that – but they were both almost totally ignorant of the human sciences, economics, sociology, psychology, political science. And the conclusion I came to was that you could successfully follow either the Wizard’s or the Prophet’s path and people who feel one way or the other could be quite happy. But the human part of the equation is the real issue. I think that we can succeed, but it’s not at all clear to me that we will succeed. In the United States we’re experiencing a time when the national government is really quite dysfunctional but local governments are doing all kinds of very interesting things. And I don’t know which of those different paths will prevail in the end. If our future depends on our national government, we’re really in trouble.

• The Wizard and the Prophet by Charles Mann is published by Picador (£25). To order a copy for £21.25 go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99