The world’s population is nearing 7 billion and will perhaps hit 9 billion by 2050. In a previous post, I estimated that the earth could feed up to 15 billion based on the amount of arable land and current farm yields. Ever since Thomas Malthus, people have predicted that we would eventually reach saturation resulting in massive famine and global unrest. However, technology keeps coming along to make farming more and more efficient, pushing off the Malthusian crisis into the future. The green revolution led by Norman Borlaug, saved over a billion people from starvation in the mid-twentieth century. In fact, food production is so efficient now that it has led to an obesity epidemic in the developed world (e.g. see here).
The question then is what is a sustainable population. Currently, food production requires a lot of fossil fuels, which comes with its own set of issues. Scientific American recently published an article arguing that phosphorous, one of the three components of fertilizer, with nitrogen and potassium, may run out by the end of this century. Obviously, our current means of food production is not sustainable indefinitely. I think our situation is like the person walking across a railroad bridge with a train bearing down on her. She can either run towards the train or away from it to get off the bridge. Depending on the speed of the train and how fast she can run, there is a critical point on the bridge where running in one of the directions is optimal. For us, going backwards away from the train is to try to reduce population growth and try to find a sustainable level. Running towards the train is to rely on technological progress to increase food production. Given that good ideas seem to grow linearly with the population and possibly slower (e.g. see here), going towards the train actually means we should keep growing as fast as we can and hope that another Norman Borlaug comes along. Where we are on that bridge is anybody’s guess.