The first peak oil shock is over but the world economy is still ploughing ahead with little to stop it in

First you could soften the citizens up a bit with an advertising campaign like ‘Do you want your children to die in a global warming disaster—Only Have One Child' or ‘Do you want your children to starve in a global warming drought—Only Have One Child.’ Have advertisements like these or something similar for about 6 months so most people know about what is going to happen in the future. 

Now you could bring out the big one. 

To save the children of the future the government will pay any women between the ages of 15 and 35 who already has one or more children say $5000 tax free to get their tubes tied, so they can’t have any more children. You could offer a bonus of $5000 to women with one child so they receive $10000 all up. That might inspire them to get their tubes tied. 

If the economy is in recession and people are hurting for cash then this should catch on. 

There will be the debunkers but that is to be expected. After this policy has be in effect for 6 months say it will end in 6 months time and put a date on it. Three months later bring on the future policy and that is: Any family that needs government assistance for anything - that is they go on social welfare - the mother in the family must have her tubes tied before they can receive assistance. 

Now all the women that have been putting off getting their tubes tied will rethink the situation. They have three months to make up their minds. After the one year is up I think the government should still pay women with only one child the $5000 bonus only to get their tubes tied. I think there should be some pay off between the government paying out social welfare and the people receiving it.