Scientific American has a great article on the ability of the fern-like plant species Azolla to sequester carbon dioxide from the atmosphere. The most amazing stat from the article to me is that:
"Azolla bloomed and died like this in cycles for roughly 1 million years," over which period of time carbon dioxide level "dropped from between 25,000 and 35,000 [parts per million] to between 15,000 and 16,000 ppm."
Azolla. Source: Scientific American
What's so amazing about this?
- How much CO2 was in the atmosphere. Humans start to feel drowsiness and reduced cognitive function at about 1000 ppm CO2.
- How long it took to draw down these CO2 levels to the <600ppm levels of the past 2.5 million years. 50 million years is a long time -- especially given that scientists predict that only 50 years of unabated emissions will cause CO2 concentrations to rise above the 600 ppm levels not seen in recorded human history.
- The fact that the biological systems are capable of sequestering massive amounts of CO2: 1 pmm of CO2 weighs roughly 2 billion tons.