It’s far from a sure thing that depopulation can be reversed, that fertility rates can be increased, or that demographic winter can be avoided. I recommend watching the movie for a least a summary of the problem. Even if demographic winter is avoided, the falling fertility rates portend decades of no growth economies and falling prosperity.
A much more interesting question is if depopulation
should be reversed. As far as ecosystem stress and resource exhaution are concerned, depopulation is a good thing.
Paradoxically, depopulation should be causing an
increase in prosperity. Think about it in this way. If there is a fixed amount of resources, then decreasing the number of persons to share these makes the amount of resources available per person go up.
The main reason depopulation is a problem is that the world currently uses an economic system which is based on credit. Since credit needs to be repaid with interest,
the system requires a perpetual growth to support itself. Once the growth stops, the debts cannot be repaid, and the system crashes.
This is particularly apparent in social security systems. A social security system is a Ponzi scheme where a future generation finances a current generation. The system can operate only as long as a tax base increases – i.e. as long as each new generation is more numerous than the previous one,
or there are productivity improvements increasing GDP (i.e. tax revenue) in a manner which offsets population decrease.
However, I’m dubious if such productivity improvements will happen, because the West has been busy dismantling its education system and cutting R&D spending for the last several decades.