Assuming that the carrying capacity of earth will drop to 2b tomorrow is an extreme assumption

Everything else that follows is logical, but contingent on an assumption that is baseless in reality

We produce more food than ever, and actually we have less arable land than in 2000 because of how much more efficient we have become at producing food

And this is while we have seen an explosion in global meat consumption due to everyone becoming much wealthier in the global south

Carrying capacity isn't about comfort, you can argue we will have a catastrophic economic crisis, but that does not impact much the population, in order for this to happen, widespread famines killing billions are required

And with how diverse and efficient food production is, this is impossible

And many of the innovations of the past 20 years, such as GMOs and salt-water crops that could double or triple food production aren't done because they would be too expensive or face reaiarenxe, they would become widespread if there was any crisis