The article does a good job of setting out the challenge: as economies grow (as they have been doing in most places for decades now) people demand different kinds of food -- basically, more protein. One challenge is how we meet this growing demand while limiting possible environmental harms. A different challenge is how to produce food more cheaply so that poor consumers are better able to avoid hunger. One strategy for growing more food and keeping food prices low might be to cultivate more land, but this raises social, political, as well as environmental issues. Another strategy would be to increase yields on lands already under cultivation, but this will likely require use of controversial technologies like GM seeds. Trade offs, as ever.
Recognizing that many variables contribute increasing yields (geography, status of land tenure, access to good quality inputs, etc.) the authors offer a couple of ideas. First, they are cautiously optimistic about the use of GM products. Second, they advocate less waste -- waste less in the production process in the developing world and waste less when consuming in the developed world. Third, they think it might be useful if more of us were vegetarians (but for a counter argument see this story from the UK paper Telegraph). And finally, they think we need to raise and consume more fish.
These authors are relatively skeptical about the abilities of entrepreneurs, working in markets, to meet these challenges. I note that the ag sector is among the most heavily controlled in the global economy. I am surprised that in their discussion of challenges of feeding a growing population the authors largely sidestepped the politically difficult question of how to limit home-grown protectionism. This is another important strategy for feeding more of the world's poor.