Carbon calculations for a bond portfolio

For half of the Earth’s existence, there was virtually no oxygen. Then two billion years ago, just one type of bacteria – cyanobacteria (or blue-green algae) – stumbled upon photosynthesis of which oxygen is a bi-product. This was a true evolutionary one-off: no other lifeform, before or since, has pulled off the same trick. Indeed, trees and plants rely on cyanobacteria for photosynthesis1 and it’s the reason trees are green.