"You know what else isn't likely to cause human extinction? Weaning ourselves off fossil fuels."

You might want to look into where the fertilizer that grows the world's food crops comes from, and exactly how that food gets distributed around the globe.

Extinction? Probably not. Mass deaths? Yeah, that would be very likely.

Caveat: assuming that the fossil fuels aren't replaced with nuclear power, but in general those who hate fossil fuels are even more vehemently opposed to nukes.