by Terry Schulze

I was fascinated by Patrick Moore’s comment about CO2 at 150 ppm and how the plants would die. I went and did some research and sure enough he’s right. Here’s a bit from my research –

Atmospheric CO2 is not alarmingly high, it is too low for optimal plant growth and alarmingly low for the survival of carbon-based terrestrial life. The real danger is not too much CO2 – it is CO2 starvation. Over geologic time, CO2 is ~permanently sequestered in carbonate rocks.

Plants evolved at atmospheric CO2 concentrations of 2000 ppm and greater, and many grow best at about 1200 ppm CO2 – about 3 times current levels. That is why greenhouse operators maintain 1000-1200 ppm CO2 in their greenhouses.

Major food crops (except corn) use the C3 photosynthetic pathway, and die at about 150 ppm from CO2 starvation – that is just 30 ppm below the minimum levels during the last Ice Age, which ended just 10,000 years ago – “the blink of an eye” in geologic time. Earth came that close to a major extinction event.

During one of the next Ice Ages, unless there is massive human intervention, atmospheric CO2 will decline to below 150 ppm and that will be the next major extinction event – not just for a few species but for ~all complex terrestrial carbon-based life forms.