Which translates a tax break on each child into a tax penalty on each child after the first. Free family planning becomes free contraception and sterilisation for those who want it. Instead of advertising campaigns encouraging families a campaign discouraging larger families, and perhaps nudging it to be socially unacceptable. Make any fertility treatments an entirely private sector activity.
Population shrinkage will be a rounding error in the face of climate. We already had the AQ9 oil company document from 1980 on the front page today. That predicts the end of all economic growth by 2025. Sure they might be a out by a decade or so, but not a bad guess for 40 years ago! Growth has been trending down for decades. Think about that. Recession becomes the normal state of things. A downturn tips into a major depression if you start at recession.
There's another page for men... https://www.nhs.uk/conditions/contraception/female-sterilisa...
I'd hesitate to believe all economic growth will end by 2025. I just don't buy it; all but the UN low projections show continuing growth through at least 2100 [0]. How will we cope if that's true, any way? It will be tough when there are more old, retired people than young, working people to support them; I don't see the numbers adding. Recession being the normal state of things is not really a great outcome... if that happens, you will get a war, sure as shooting. Not just one, but lots. And a rise of authoritarianism. Liberty is good in good times, but most people are fair-weather patriots and will turn to a hitler-2.0 if things get bad enough. That ought to worry us all.
[0] https://ourworldindata.org/exports/comparison-of-world-popul...
Maybe not 2035 as the margin for error was wide, but I don't buy the idea of growth through to 2100. That doesn't feel at all credible. We're already spending billions cleaning up fires, floods, healthcare for problems of air pollution and often times not accounting them as the drains on productive activity they are, but as benefit.
The rest of your outcomes are exactly why I see climate and some of the other issues as pressing, as yes in depressions and austerity people do turn to more extreme places for answers, and reject the moderate. We're already seeing a huge rise of the far right, of right wing populists, of authoritarian populists, of racism and xenophobia, and migration across the world... Coincidence? I sure hope so.
I understand you don't buy the idea of growth continuing through 2100, but I don't buy the idea of it ending beforehand until I see a citation. I found at least one estimate that supports my position; I haven't seen significant evidence to support the idea of growth ending that soon. All the things you list keep people employed.
I wouldn't just point to the "right wing" as authoritarian; that seems like needlessly politicizing a social problem. Dictators have no values or political alignment but their own moral gain.
With respect to your earlier comments around advertising, I don't know about Europe, but America has never advertised having a large family or a small one. Not sure it's the role of government to try and shape social norms; that's generally referred to as brainwashing.
[0] https://www.brookings.edu/blog/the-avenue/2018/12/21/us-popu...
“Simply” is the most ironic formulation I can imagine, as I’m aware how many religions state as the explicit goal for their believers to have as many children as possible (and also avoid contraception). Moreover in most of the world, including developed, not having children translates in not having anybody to care for you once you’re old.
For countries that still have religion front and centre in their politics, sure it might be an issue... the consequences of ignoring an overpopulated world or country will still affect them, and sooner. Wars will start instead...