Recently, I interviewed John Briscoe, a Harvard professor and development expert who has spent decades thinking about how poor countries get richer, with a particular focus on water. He has come to believe that large-scale dams and genetically engineered foods can be good for poor countries.

These are controversial views. See, for example, the website of a nonprofit group called International Rivers, which says:

Africa's dams have done considerable social, environmental and economic damage, often with complete disregard for the human rights of dam-affected communities, and have left a trail of "development-induced poverty" in their wake.

Friends of the Earth, meanwhile, says that it "opposes the introduction of GMOs as it will constitute a threat to African biodiversity and the continent's food sovereignty, and will make nothing to help Africa tackling poverty and hunger."

For his part, John, who was trained as a civil and environmental engineer, has worked as an engineer in the water agencies of South Africa and Mozambique; as an epidemiologist at the Cholera Research Laboratory in Bangladesh; as a professor of water resources at the University of North Carolina; and, for the past 20 years in a variety of policy and operational positions in the World Bank. Most recently he has served as the Bank's Senior Water Advisor and the Country Director for Brazil. John now a professor of environmental engineering at Harvard.

Here's an edited version of our interview:

Marc Gunther: John, let's begin by talking about water. You've called water scarcity "a massive and growing problem in the developing world." What do you mean by that? Are you talking about drinking water and sanitation? Or water more generally? And if it's the latter, why is it that we are experiencing scarcity since there is, essentially, a finite amount of water in the world? We don't deplete our supply of water like we do, say, our supply of oil.

John Briscoe: I think it's useful to think about water as you suggest: There's the resource itself and then the services that are derived from that resource. So, when it comes to drinking water and sanitation as a service, in my view, there is a large but not a growing problem. In fact, the number of people who do not have adequate water and sanitation services is shrinking. Lots of people who never had services are getting services, because of economic growth in the developing world in general and China and India in particular. Of course, one person without these services is one person too many, but the situation is improving. You see this improvement reflected in the rapid decline of infant mortality rates in many countries. There are important financing and institutional issues for delivering these services, but for societies at large, I do not consider that a huge, massive, existential challenge.

The greater challenge in countries like India, Pakistan and China is that the resource itself, as you said, is finite, and the demands on it are ever-increasing. We need more agriculture to grow our food. We need more energy. We need more industry. We need more water and sanitation. It's essentially a Malthusian problem of a limited resource and the ever-growing demands on it. And that is a massive problem.

MG: For the west, or just for the developing world?

JB: Water is always a local issue. So you can't call it a problem throughout the developing world. But it's a massive problem in many places, particularly in the large parts of the developing world which the God-given endowment (of water) was relatively small; so a great swath across the Middle East, North Africa, into India and in China, where you have limited resources and a very large number of claimants.

Details matter a lot, but typically agriculture is the biggest user of water, and so in China, India, Jordan and Morocco, among other places, agriculture and its use of water is absolutely at the heart of this problem.