Population decline is a good thing

While true, that ignores de-speciation and of course climate change. Greed accounts for some of that, but a lot of those billionaires come from meeting the needs of 8 billion humans on the planet.

We are recreating the conditions of the Permian-Triassic extinction, and while most of us will be long dead before that comes to fruition we absolutely could trigger cataclysmic change. We know how it works.

As to reduced population, that doesn't have to mean actively killing people off. It can very well mean not reproducing at replacement rate, which is already occurring in most advanced economies. China mandated it by law.

Of course, resources aren't endless, greed is real, we've already seen the first climate war in Syria, and we'll no doubt see quite a few more as we don't seem to have the will to make the alterations necessary.

So I expect violence, disease and famine to be doing a lot of work in the next 100 years. The Four Horsemen are becoming relevant again.