The world's population is forecast to rise to 10 billion by 2050... so where is the food for these extra 2.5 billion people going to come from?
Science and technology might help us out, up to a point. And we could continue breeding hardier, more productive crops that can grow on marginal agricultural land.
People having eaten insects and their eggs and grubs for millennia and now there's a growing interest in breeding and consuming bugs as a more eco-friendly and sustainable protein source than farmed meat.
Malcolm Diack is a locust farmer breeding what he calls "sky prawns" in his garden shed in Dunedin.