This is a guest post by Peter Salonius, a Canadian soil microbiologist.

According to Peter, humanity has probably been in overshoot of the Earth's carrying capacity since it abandoned hunter gathering in favor of crop cultivation (~ 8,000 BCE). The problem is that soil needs tightly woven natural ecosystems to properly recycle nutrients and prevent soil erosion. Earth's inhabitants have devised a whole series of approaches to increase the amount of food that can produced, starting first with hand-cultivation and culminating in the last century with the widespread use of fossil fuels. These approaches strip the soil of its nutrients and cause soil erosion. Even Permaculture cannot be expected to overcome these problems. According to the paper, eventually, to reach sustainability, the world will need to reduce its population to that of the hunter-gathers, and go back to living on the resources the natural ecosystems can produce.

Peter's paper begins below the fold.