My latest simulation of the future, which integrates personal priority-setting like that discussed in "Groups, Goals, and Actions" with the potential futures described in "Shutdown Scenarios," indicates that the best way to reduce major casualties over the next few years is to have everyone in the world immediately stop increasing both population and consumption of ecological resources (ecological footprint).
The urgency is a consequence of the possibility that humanity will breach a critical environmental limit in less than a year, killing off species needed to sustain those species we directly depend upon for our own survival. With global warming getting worse and threatening to push us over the limit anyway, we need to also work on decreasing our footprint with an emphasis on greenhouse gas emissions. This is the equivalent of slamming on a car's brakes before it flies into a ditch, and then backing up to escape collapse of the eroding ground under it.
Changes to personal behavior have an effect on the global whole that is inversely proportional to the size of the population and therefore extremely small (currently one in 7.26 billion). The best way to have a significant effect is to therefore convince many other people to make the same changes. For the expected ("combined case") scenario, I estimate that about nine times as many people can be saved as are convinced per year to stop growth in population and consumption, with the potential for billions of lives to be saved over the next 16 years.
In the worst case, higher population growth is projected before we make changes, and this results in higher speed toward the limit. To avoid hitting the limit and to minimize casualties we would have to now be decreasing our personal consumption by twice the rate we increased it last year, and stop at no more than 88% (and no less than 60%) of the current global average by the end of the century. Ideally, we should be following this approach anyway, following the sound advice of preparing for the worst case and hoping for the best case.
That "best case" is not, of course, my best case – it is the "limitless case" that seems to be the main planning scenario for the world. For that, there is no need to consider changing anyone's way of life, except to convince them to help increase our own happiness, population, and longevity. Given that our influence over our lives and those of our friends and family is much greater than any influence we might have over the rest of the population, it makes sense under this scenario to focus only on these groups. Doing so inevitably results in more consumption and a growing population, which a lack of limits allows so long as the corresponding complexity can be managed.
If I am wrong about the nearby limit my models indicate we are about to hit, there is another limit behind that: the effective depopulation of other species that includes those we directly depend upon. If we can proceed along the trajectory of the limitless case, I estimate we will hit that final limit by 2029 with a population of 8.5 billion people. If growth continues after that, then we are indeed on a world without limits, and I will stand corrected. There is, however, the very real threat of climate change that is expected by scientists to get much worse in the near future, as well as verifiable increases in pollution and species extinction that are a source of justifiable worry for the foreseeable future.
We already know, or should know, that as biological entities our fates are intricately tied to the fates of our fellow creatures, and that we are collectively responsible for their fates taking a catastrophic turn for the worst. If our species follows them, then our personal and familial priorities will be forced to include the "others," and it may be too late to stop the worst from happening to us.