A vast supermajority of the entire inhabited human planet is so far below replacement-level fertility that human extinction is now closer than the ice caps being completely 100% melted.
This has been the case for several years and is a trend that still accelerating. Fun fact: human fertility per person is shrinking faster than GHG emissions per person are growing.
Even with a handful of countries still breeding like rabbits with 6.0+ TFR, the world population is set to peak before 2100 before entering a prolonged decline.
Ecological overshoot is a bunk idea. From wikipedia: "Global ecological overshoot occurs when the demands made by humanity exceed what the biosphere of Earth can provide through its capacity for renewal."
Earth's capacity for natural resource renewal is routinely increased by human activity.
For instance, when humans switched from hunting and gathering to agriculture, earth's capacity for natural resource renewal rose rapidly as many new reccuringly-planted crops sprung up in places they never had before.
Another example, the invention of fertilizer. Food scarcity used to be a real problem for large swaths of the planet. It isn't a problem for most of the planet now, in spite of the fact that demand has grown, and demand growth accelerated by orders of magnitude relative to e.g. 1000 AD. In fact, human activity has made the renewal capacity for earth so much greater that we now have an entirely different problem: for the first time in human history, there are more people consuming too many calories than there are people consuming too few calories. Clearly, food isn't the problem.
The sun provides enough energy to desalinate every ocean on the planet hundreds of times over even with our current rudimentary PV technology with efficiency rates in the ballpark of just ~20%. Water isn't the problem.
While fusion may still eternally be 20+ years away, we've had fission for decades now. You can power the global electricity needs of twice the population of today's planet with reactors taking up less space than Rhode Island. The waste can be permanently and safely disposed of continuously by launching it into the sun for something like 0.000001% of the annual global GDP.
Of course, the sun is also blasting us with the product of nuclear fusion constantly, so we could just massively scale solar to humanity-sized installations. Imagine using a bullet train to get from one side of the humanity-scale PV installation because driving takes too long. So ultimately, electricity isn't the problem.
In order for humanity to be able to run, we need to not kill it right after it started crawling.
I must be missing something here because it seems like we have pretty straightforward roadmaps to meeting the water, electricity, and food needs of a population 2x the current global population - just what demands are being made by humanity that our solar system is incapable of meeting, when combined with human ingenuity giving us the stream of groundbreaking technological improvements that pretty much everyone on earth is not only accustomed to, but continuing to expect more of?