That's the topic of a thoughtful essay by Nathanael Johnson on the Grist website. He gives a reasonable summary of my argument that many hoped-for improvements either involve tradeoffs (some of them acceptable) or radical enough changes that their effects will be hard to predict.
He also cites my colleague Jonathan Foley's suggestion that "we" should "Reduce food waste, eat less meat, and make fertilizer and irrigation available to the farmers that need it."
OK, but who's "we"? Any "solution" that requires billions of people to change what they're doing -- because they read Foley's article in Science? -- will be a long time coming. For example, a few million rich consumers eating less meat -- this would lower the demand for meat so that meat prices decrease so that slightly-less-rich consumers eat more meat, but let's pretend total meat consumption goes down a few percent -- would not have much effect on global greenhouse gas production or food security for the billion or two in greatest need. Similarly, if a couple billion consumers wasted less food, that would free up some resources. But if you and a few friends reduce your waste, it's a drop in the ocean.
Reducing pre-consumer food waste has more potential. Because reducing pre-consumer waste could mean larger profits for farmers, food companies, etc., near-universal adoption of practical waste-reducing methods is at least conceivable. Motivation linked to higher profits also means, however, that the obvious improvements have already been made. Less-obvious improvements are already a major research focus, but more likely to be invented by engineers than ecologists.
Expanding access to irrigation might greatly increase food security, but it would be a big project, perhaps costing a significant fraction of what we spend on war or video games. So I'm not holding my breath.
Increasing access to fertilizer can start small and scale up -- avoiding over-fertilization -- so that's an area where contributions from a few million people (or a handful of rich people) could really make a difference. But I worry about solutions that require on-going subsidies.
And then there's plant breeding. Develop a cultivar that out-performs what's available now, and watch it spread.