Correct, when there is very little, life on earth would die out. If we were back in the 3000-8000 ppm range, life would likely explode again. This is actually the sort of thing I'm talking about, you feel the need to have some caveat here, when there is absolutely no evidence that CO2 is bad for anything in any levels that are even practically achievable or have ever existed since there has been life on the planet at all. Every reasonable piece of evidence we have says that more CO2 means more life.

Guy Swann

Quite to the contrary to this bizarre belief, life exploded inexplicably, the literal "Cambrian explosion," when CO2 levels ranged in the 3,000-8,0...

Significant moves in either direction could have a huge impact on human life. Like ok you may have had events in the past at very high levels of co2 that resulted in an increase of life on the planet, but going back to those levels may not be good for humanity specifically. Increasing global temperatures 5C+ or whatever the number is would be extremely risky for us. To me it seems desirable to limit the amount to what it has been when humanity has been healthiest.

It’s less about total amounts and much more about rate of change. The actual issue is the rate of change acceleration that the industrial era has seen. The rate of change is the fastest in recorded human history. Obviously the screeching freak outs over this issue are absurd, but that doesn’t change the fact that accelerating rate of change of most systems is generally hard to manage for biological entities.