The SSP5 appears to be presupposing everything else just works out in a high-trust, globally-integrated economy. The basic problems expected to surface in this

The SSP5 appears to be presupposing everything else just works out in a high-trust, globally-integrated economy. The basic problems expected to surface in this century are largely ravaging of coastal communities and at least a few places that can currently support human life no longer being able to, largely near the equator. As far as balance of global land mass versus human population, there should still be enough, but significant migration will need to occur, including across national boundaries. I'm not all that confident, given the way strong nationalism, isolationism, and anti-immigrant sentiment seem to have made major comebacks in rich nations far from the equator, that this would really happen. But the bulk of the more serious ecosystem collapse scenarios probably don't happen until the next century. You can certainly make the argument that more people, more money, and significant investment into basic research and geoengineering stands a better chance of addressing this than stomping on emissions to prevent it. Higher GDP is probably a prerequisite to this happening, but political will and strong, trusted governments are another. We can't just have that GDP going toward bigger houses, faster cars, smarter targeted advertising, and even better-funded attacks on public services, science, and expertise.