I think it's going to be incredibly challenging to avoid potentially catastrophic harm to the environment due to politics and incentive structures. As far as food goes, beef and pistachios stand out to me as particularly environmentally harmful/wasteful, due to methane from cows and enormous water requirements for nuts, and it's not clear that anyone can change incentive structures to sufficiently change peoples' habits regarding these foods. (though in the grand scheme of things my understanding is beef and pistachios pale in comparison to habits such as flying for climate change.) I usually see people who think about this topic discourage the idea of technological development as a magic bullet, but I'm biased in this direction (it's also fitting for people who read hacker news) -- advances like impossible foods are inspiring to me. They've created "fake meat" aimed at traditional meat-eaters, allowing people like me to keep our luxurious food preferences in a manner that's much more environmentally friendly. They've had an impressive amount of success so far, with deals with chains like Burger King. If they can convert a sizable fraction of meat-eaters, they will have made an enormous impact on climate change.
You're putting it mildly. The second scenario is a delusional fantasy, I don't understand how it can be mentioned seriously.
We may end up closer to the first scenario thanks to the prospects of the third one. I hope we do.
(Can't link to the specific stat, but take a look here for raw data and projections https://population.un.org/wpp/DataQuery/)
the authors discuss & model different interventions & policies that could be put in place to try to prevent the "overshoot and collapse" type scenario where human population peaks and then crashes.
some academics argue that things are tracking somewhat consistently with projections of the modelling from 50 years ago: https://www.theguardian.com/commentisfree/2014/sep/02/limits...
a lot of the critique of the "limits to growth" modelling is of the form "a crash in global population was predicted by time T, but that didn't happen", but the modelling doesn't really try to make predictions in terms of specific events happening at specific timescales, it's focused on understanding the underlying behaviour based on the structure of the system.
I think theres a 4th future, which is that natural selection and evolution ultimately control population on a global scale and is the single biggest factor influencing the world today.
1) Humanities general inability to foresee the future.
2) The surprising resistance of political bodies to trying new things when the current method 'seems to be working'.
I've come around to the idea that China's 1 Child Policy was a a very responsible idea. It was probably executed with the characteristic horrors of an authoritarian government - but the idea that population is just going to sort itself out is imprudent.
There are 3 futures. One where population naturally levels off and finds a sustainable level, one where growth turns out to be truly exponential in defiance of physical limits and one where a lot of people discover they can't be supported by what is on offer and die of starvation or violence.
The good news is that is 2 happy endings to 1 bad one. But humanity has a very long history of need-resource-access-driven violence and evolutionary factors will push us back there if it isn't politically resisted at a grand scale.