<<---PRESENT Day is on the left side!!! This chart shows the CO2 levels for the past 500million years.
The two major ways that plants use CO2 are called C3 and C4 photosynthesis. The C3 process evolved first when CO2 levels were at least double today's, from 100M-500+M years ago, and is used by 99% of plants now. About 30Million years ago, the increasing SCARCITY of CO2 gave rise to the C4 process. Even though the C4 plants are only 1% of species, they are much more efficient in this scarce CO2 environment, and yet represent over 5% of plant mass since that 1% of species is 30% better at using CO2 in this rarefied CO2 environment.
As CO2 rises, the C3 process, used by so many plants including many of the "endangered" species, becomes more competitive. No surprise! It was evolved in a MUCH higher CO2 environment!
C4 plants are much better in extreme hot temperatures and drought (read deserts). In normal damp tropical environments nowadays (tropical jungles) they overwhelm the C3s now.
A true ecologist would be cheering for HIGHER CO2 to help the all those endangered C3 species grow better!