Overshoot - the road we couldn't take, and the road we did.



Population growth in the animal kingdom tends to follow a logistic curve: an s-shaped curve that starts off low when the species is first introduced to an ecosystem, then at some later point rises very fast as the population becomes established, then levels out as the population saturates its niche.



Humans have been on the front end of our logistic curve for our entire history. Our population has risen very slowly over the last couple of hundred thousand years, as we (very) gradually developed the adaptive skills we needed in order to deal with our varied and changeable environment (language, writing and arithmetic). As we developed and disseminated those skills our ability to modify our environment grew, and so did our growth rate.



If we had not discovered the stored energy resource of fossil fuels, we would probably be following the green curve in the chart below, and would be well on our way to achieving balance with the energy flows in the world around us, with our numbers settling down somewhere aroud two billion. This is the road not taken.



The road we have taken is the one in red, on which our numbers and consumption have been driven well past the world's long-term carrying capacity, deep into overshoot territory. As we partied hearty since 1900, we have degraded the flow-based carrying capacity of the biosphere by messing up the earth, air and water. As a result, when the party ends, the resulting correction will take us back well below a carrying capacity of 2-billion, since that no longer exists - we have already "eaten" much of it.



The inertia of the correction will carry us even below the remaining carrying capacity, which I currently estimate to be enough for about 1.25 billion people.







I don't think we can do anything to prevent the correction. We may have been in overshoot since 1920 or so, based on our usage of fossil fuels shown here:







Of course we've learned an awful lot since 1920. If we'd been on the green curve all along we wouldn't have developed wind or solar power, or large-scale hydro. We need to leverage as much of this knowledge as we can - not to prevent the Big Red Spike (we can't, it's already been happening for a hundred years) but to try and slow down the descent a bit, and maybe prevent the Dead Cat Bounce a century from now.



Oh, where did I pluck the carrying capacity of 2 billion from? It was the population of the planet in 1925, when we were already using some coal but had just begun to exploit the other two phases of carbon: liquid oil and natural gas. It seems as good a place as any to drive in my picket pin.



The details are all speculative, and open to change based on what assumptions you choose to make. The overall shape of the curve, though, will define the human operating environment over the next century or two. I posted about carrying capacity yesterday, and that got me interested in revisiting my assessment of the human situation, taking the influence of fossil fuels into account.Population growth in the animal kingdom tends to follow a: an s-shaped curve that starts off low when the species is first introduced to an ecosystem, then at some later point rises very fast as the population becomes established, then levels out as the population saturates its niche.Humans have been on the front end of our logistic curve for our entire history. Our population has risen very slowly over the last couple of hundred thousand years, as we (very) gradually developed the adaptive skills we needed in order to deal with our varied and changeable environment (language, writing and arithmetic). As we developed and disseminated those skills our ability to modify our environment grew, and so did our growth rate.If we had not discovered the stored energy resource of fossil fuels, we would probably be following the green curve in the chart below, and would be well on our way to achieving balance with the energy flows in the world around us, with our numbers settling down somewhere aroud two billion. This is the road not taken.The road we have taken is the one in red, on which our numbers and consumption have been driven well past the world's long-term carrying capacity, deep into overshoot territory. As we partied hearty since 1900, we have degraded the flow-based carrying capacity of the biosphere by messing up the earth, air and water. As a result, when the party ends, the resulting correction will take us back well below a carrying capacity of 2-billion, since that no longer exists - we have already "eaten" much of it.The inertia of the correction will carry us even below the remaining carrying capacity, which I currently estimate to be enough for about 1.25 billion people.I don't think we can do anything to prevent the correction. We may have been in overshoot since 1920 or so, based on our usage of fossil fuels shown here:Of course we've learned an awful lot since 1920. If we'd been on the green curve all along we wouldn't have developed wind or solar power, or large-scale hydro. We need to leverage as much of this knowledge as we can - not to prevent the Big Red Spike (we can't, it's already been happening for a hundred years) but to try and slow down the descent a bit, and maybe prevent the Dead Cat Bounce a century from now.Oh, where did I pluck the carrying capacity of 2 billion from? It was the population of the planet in 1925, when we were already using some coal but had just begun to exploit the other two phases of carbon: liquid oil and natural gas. It seems as good a place as any to drive in my picket pin.The details are all speculative, and open to change based on what assumptions you choose to make. The overall shape of the curve, though, will define the human operating environment over the next century or two. 3 Tweet