Hiking equipment
According to Tom Brown, the basic plan for survival is in the order of shelter (including clothing), water, fire, and food. Cody Lundin writes about the "Rule of 3s"; this relates to human survival without basics: three minutes without air, three hours without shelter, three days without water, or three weeks without food.
Feeding Everyone No Matter What
As a backup plan, it is even possible that humans could eat this predigested biomass. In a sun-obscuring crisis, stored food would last the human population less than one year. The book shows how many of these solutions can be ramped up in less than one year.