A few years ago, I explored the idea that people's behavior could be described in terms of personality traits interacting with associated environmental variables, directed by knowledge and enabled by power, with the goal of finding the best match that would manifest as maximum attainable happiness. Because, in aggregate, a population's happiness increases logarithmically with ecological footprint, the price of continually growing happiness is faster depletion of ecological "resources" – including other species that provide basic services that keep the planet habitable. Population size multiplies this effect, and exponentially increasing population accelerates our approach to a critical point where habitability can no longer be maintained.
My projections have shown that this point will likely be reached by 2030. As it approaches, the world will get harder to live in as resources become degraded and harder to find and use. But we will keep trying, because more happiness and life expectancy are what drives us. After that point, deaths will exceed births, and our population will drop to zero by 2075, which I now understand will likely be due to our ecological impact having grown due to self-sustained global warming. According to my calculations, the difference in global average temperature from pre-industrial times will climb past 3.3°C, and the world will be uninhabitable.
Using the Big Five personality traits (OCEAN: openness, conscientiousness, extraversion, agreeableness, and neuroticism), we can guess how groups of people will both perceive and want to act as this nightmare scenario unfolds. Power and knowledge can be expressed as efficiency in achieving total happiness, where efficiency is a fraction of the happiness someone doesn't have, which can be achieved in the amount of time it would ideally take to get from 0% to 100% happiness. Using efficiency, we can estimate change in happiness over time. Using the relationship between happiness and ecological footprint, we can tell how people's ecological impact will change over time. Assuming a statistical distribution of personalities among people, we can also estimate how many people will act in a given way.
I expect that the openness, conscientiousness, and extraversion traits correspond to variability in the environment. The more variable it is, the more a person with high openness prefers it. Because a rapidly changing environment can't be easily planned for, people with low conscientiousness will prefer it. Extraverts will like the excitement of rapid change, and be more inclined to be active parts of communities that must react to the change and share resources. I estimate that maybe 1% of the population would (initially) benefit from large variability.
The cooperation/competition dynamic inherent in the agreeableness trait would correspond to the distribution of resources among people, as well as the amount of social order and violence that accompanies its breakdown. People with high agreeableness (around 17%) would prefer to share resources and avoid conflict, while those with low agreeableness would do the opposite.
A high amount of neuroticism would translate into increased stress as deviation from preferred conditions for the other traits increases uncontrollably and inescapably. Stress leads to more disease and death, and ultimately may kill off the most people, even those with low neuroticism (17% of the population), before environmental conditions do.
Climate change due to global warming is perhaps the best example of how humanity's influence on the world's physical systems is changing the range of environmental conditions. In the case of temperature, the range has shifted significantly from what we depend on, and will continue to do so (such as in Australia this past summer). As some conditions become less likely, those people who are best adapted to them (and are happiest when experiencing them) will find it harder, and eventually next to impossible, to meet their desires and then their needs, mirroring what is already happening to other species whose ecological niches are disappearing. If the shift happened slow enough, our population (and those of other species) might be able to change its preferences through evolution so that more members would be adapted to the new conditions, or new species would do so in our place, but climate change in particular is happening far too fast.
Technology and social behavior have enabled people to adapt to different conditions, and can be expected to do so in the future – up to a point. My calculations indicate that they enabled our efficiency at achieving happiness to increase by several orders of magnitude until the 1950s, when it spiked due to immense technological progress. Efficiency achieved a minor peak in the late 1980s and has been declining since then. Notably, that last peak occurred less than a decade after the world's annual ecological impact exceeded what ecosystems could offset in production and processing our waste.
Using our highly complex civilization as a base, we can now support keeping small numbers of people reasonably comfortable in space for limited periods of time. With a moderate amount of additional development, artificial habitats might be able to support a dozen or more people over a lifetime on a planet like Mars. By my crude estimates based on personality, around 220,000 people would find our rapidly deteriorating world acceptable, and only 300 of them could have enough power to prepare for its physical consequences. It is conceivable that such a minority (curiously close to the actual number of extremely rich people) would attempt to outlast the rest of us just as Mars settlers would eventually be forced to do.