Guest post by Indur M. Goklany
This illustration from a recent article in Science magazine shows that CO2 is plant food. It is based on both empirical data and model results (not “data”). I know that looking at empirical data might seem like a novel idea to some people, but for some perverse reason, I find it more compelling.
On the right: Empirical Data. Growth of 21-day-old rice and S. viridis seedlings at different ambient CO2 concentrations ranging from 30 to 800 parts per million. NOTE: The very last set of pots on the extreme right is out of sequence. They are for 390 ppm, while the next to last pots are for 800 ppm.
On the left, Modeled Data:
A comment from The Chiefio:
Most plant species evolved during times of much higher CO2 concentration. At the historical level of 280 ppm, they were near starvation. ( At about 100 ppm some species die).
C4 type metabolism is a relatively recent invention and lets plants survive in lowering CO2 levels.
As a result, C3 plants respond more to increases in CO2 than do C4 plants.
In general, the increase in yields and growth continues to about 1000 ppm / 2000 ppm range (which is about where it was when the c3 plants were dominant).
The planet has been sequestering CO2 to excess as carbonates for so long that the plants were on the verge of dying. Their breathing a sigh of relief and getting back to normal (higher) growth rates as CO2 rises is clear evidence of that.
A forest or a bamboo plot will clear 100% of the CO2 above it in short order if allowed to grow.
So world plant growth “limits” on CO2 as the limiting nutrient unless someone puts a lot more into the air or forest fires burn…