[Porterville]

That’s right the Pre Cambrian period had 33-36% oxygen levels... about 250-500million years ago.

The high oxygen levels allowed for giant insects and lush fern forest. However, there were giant flash fires in the atmosphere.

I watch Discovery.

[Fichori]

“The high oxygen levels allowed for giant insects and lush fern forest.” [excerpt]

Plants are carbon based.

High oxygen levels does not make plants grow at high rates.

Plants need CO2 to grow. (CO2 is plant food)

Somewhere here on FR I recall something about the earth being at its greenest in a long time.

High CO2 levels mean plants grow fast.