Also, the patterns revealed in their models are useful for understanding patterns in nature and human interaction with it.
I know it is always appealing to tell a story with a grand unifying narrative. But sound research must prop it up with empirical evidence. Could there be limits to growth? Probably. But a highly simplistic model not informed by appropriate data or economic understanding is not the way to tell such limits.
that's what an economist would answer. ask a physicist.
for best results, get an economist and a physicist in the same room and ask them both.
Space migration doesn’t change the equation much on Earth unless you start mining and manufacturing off world and importing product, and that is pretty far off.
Why? Many civilizations have come and gone through the collapse cycle already. Why do you suspect we're any different? What makes you think the ecosystem can even tolerate 9-10 billion of us?
As for a specific carrying capacity for the Earth, it should be obvious how impossible such a number is to give without a lot more detail in the question. But if we were to assume 10B global population, it could be done with a population density roughly equivalent to precolumbian California. This is not to suggest that indigenous californians lived in perfect natural harmony, but rather to illustrate how low the numbers actually are. I suspect there's probably many reasonable (though utterly alien) ways of life where that density could be "sustainable". Equally, I suspect there are many ways of life where those numbers are not "sustainable".
But we got away with it long enough to a large number of people now believe that this is normal. It isn't. The wake up call will be a very harsh one.
Agreed. Nothing about this is normal. Not the way we live, not the way we work, not the way we take a hot shower every morning. It's highly un-normal. But because we're relative creatures and define the 'normal' by what we experience and not by what has been the normal for hundreds of millennia, we tend to misunderstand the reality of our situation.
The wake up call will be a very harsh one.
(Not to mention that we probably have neither the abilities nor the ecosystem to revert to hunter-gatherer subsistence.)
No, I don't expect a collapse back to the stone-age in the short run. But to every human living in "modern" conditions, a reversion back 100 or even 200 years in terms of comfort and luxury will be quite staggering.
The wake up call will be a very harsh one, nonetheless.
Just in case, here is another empirical data comparison for world3 predictions, this time from 2020.
I agree that decreasing population is desirable from an environmental POV, to the extent that population is more or less directly proportional to consumption. But, capitalism as we know it can't survive it. Here's a good explanation: https://www.axios.com/the-new-threat-to-capitalism-73ff54bd-...
"starting to" is a prerequisite, but a reduction in birth rate doesn't necessarily lead to a population collapse, and you don't seem to present any evidence that this is one of the cases where it does.
Again, I will remind you, the comment says we are "starting to see evidence," of population collapse, not that population collapse is happening or is inevitable. Globally declining birth rates is certainly evidence that it may be happening.
The inputs are the number of people of childbearing age over that time period and the number of births per adult. We know the maximum number of people (since new people don't get born at ages above zero). The number of births per adult tends to change very very slowly and pretty predictably.
A population collapse would be caused by one or both of these things changing dramatically.
There's no evidence of this. Instead there is evidence of a slow decline in population as the birthrate (especially in Africa) slowly decreases.
> What evidence would you consider sufficient, besides globally falling birthrates?
Something that indicates that the current models showing a slow decline are wrong.