The population in most western countries is already on the decline, since fertility rates are below replacement rates as documented by the CIA:
https://www.cia.gov/library/publications/the-world-factbook/rankorder/2127rank.html
So your message of telling people to stop having children is in my opinion is wrong.
With an aging population who will look after you when you are old... Most western countries need more children... Without children a society dies...
Gods plan for mankind from the beginning was to be fruitful and multiply. The act of reproduction can be considered a sacred duty.
Telling people to stop having children goes against nature and God's laws.
The problem is not too many children, there is enough in the world to supply every single need, but there is not enough to supply all the greed.
Can we feed everyone in the world? YES! If we choose to. There hasn't been a year in recent history in which the world has produced less food than it needed. Food is a basic human right, yet some 800 million people globally suffer hunger or malnutrition. The causes of hunger are complex, but the problem lies more in the control, distribution and access to food than in production levels.
Ending hunger is possible. Nutrition and basic healthcare for everyone in the world would cost just US$13 billion a year extra. Here in Australia, were I live. US$61 billion is spent each year on gambling.
This Christmas I recommend supporting one of the charities that help the needy rather than spending money on stuff people don't really need!
The cost of living in most western countries is the problem, people spend a large chunk of their earnings on housing, ie rent or paying of a mortgage... why is housing so expensive? Because of greed.
Rather than preach against having babies, how about preach against greed... The real problem with the world.