"Energy has been fundamental to our story of growth. The various hockey stick curves over the last century or so are a reflection of energy and population. What’s more, human population itself is a reflection of energy, as mechanized, fertilized agriculture was made possible by fossil fuels. Since energy per capita has also increased like a hockey stick, the ecological impact (and many other metrics like GDP) takes on the shape of a super-exponential (still resembling a hockey stick on a logarithmic plot)."