The problem with the headline about vegetarianism is that it suggests that the world is one unit, and that somehow resource constraints would affect the world in a more or less uniform way. Barring the emergence of some centralized global government, this won’t happen. Some people will always be able to afford meat and will consume it. In 50 years, some people will probably still eat as much as modern Americans. The question is how are we going to create a world that is food secure for billions. I’m very confident that we will go through multiple advances in crop science, etc. that will allow us to feasibly grow more than enough food for 9 billion people. Imagine 6-10 tonnes of harvest per hectare. I’m 100% a techno-optimist in that regard. I’m not, however, optimistic that we are guaranteed to sort out how to ensure that people are food secure, meaning that the food that is produced can reach people who have the purchasing power to acquire it. Ultimately, “food security of billions” will boil down to the ability of those billions to purchase what they can’t grow themselves, and that is a complicated issue that was addressed by Malin Falkenmark in her talk(s), but by very few others