How much do you think the respective arguments come down in the end to whether one is an optimist or a pessimist? The instant I start spouting out my own beliefs I become just another guy on the internet. I can contribute something as a reporter. And I thought that was a more valuable service. 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. It was difficult to some extent as I have – like anyone else – a full kit of knee-jerk prejudices and unexamined beliefs.

You examine each argument on its strengths and weaknesses without necessarily expressing an opinion. 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. 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. 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. It really started the night my daughter was born 19 years ago. What made you frame this story of humanity’s future in terms of these two individuals? One believed in scientific ingenuity as the answer to our problems, the other was convinced that it only deepened the crisis.

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. Borlaug (1914-2009) was instrumental in the green revolution that vastly expanded the amount of food humanity has been able to cultivate. 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). His books 14, looking at the Americas before and after Columbus, were widely acclaimed. Charles C Mann is a science journalist, author and historian.

Mann charles c