Hello phred! Nice to meet you here!
You bring up a very important topic:
In the most crisis-scenarios is not the too little number of people the problem, but the too big number of people wich is not possible to get feeded and supplied with all the ressources they need.
So there will be hard conflicts - and women with little children will be most vulnerable by hunger, violence and slavery.
Surely the rhytm method is better than nothing -
but it needs a secure environment and a good nutrition for to work.
In crisis the cyclus may come out of rythm and will no longer be calculable -
and in the case of sexual abuse and the necessarity to prostitute for getting ressources to survive,
there is no possibility to take care about the rythm.
So it is important to
- spread and conserve the knowledge about all birth control methods as wide as possible
- storing big stocks of birth control tools (preservatives, antibaby-pills, pessars, spirals,abortion-pills...) decentral in all regions
- spreading the knowledge how to produce this tools in the industrie of every region and making this industrie as crisis-resistant as possible
- fighting against every enemies of sexual and reproductive self-responsibility