[UCANSEE2]

Flowering plants first appeared about 130 mya at a time when CO2 levels were about 1,700 ppm. Seems like such a major change in plant physiology, which now makes up approx. 80% of all plant species, would have occurred when conditions were optimal for plants in general.

All life forms adapt to the environment, or go extinct. Small changes over long periods of time are just what 'life forms on Earth' are good at adapting to. The Earth's 'environment' has changed many, many times over the eons. Yet... life still exists on this planet. If some minor change in the mix of gases of our lower atmosphere could kill off all life, or cause the Temperature to raise so high it killed off all life, we wouldn't be here talking about it.

[Clutch Martin]

“All life forms adapt to the environment, or go extinct.”

I do not know how accurate the following quote is but for some reason it has always stuck in the back of my mind:

Carl Sagan — ‘Extinction is the rule. Survival is the exception.’

[TigersEye]

I don’t know if a change from 1,700 ppm CO2 to 380 ppm is a “minor” change. Further back, in the Cambrian period CO2 was 7,000 ppm. As someone else pointed out, if CO2 drops below 150 ppm all plant life dies.