The current human population is between 7.5 billion and 7.6 billion. The growth is continuing, but is expected to reach a maximum of 10 billion to 12 billion by 2100. Unfortunately, there are only sufficient resources to provide the standard of living available to most in the United States to about 1.5 billion. We’re already five times higher than the planet can sustainably support. As they said in The Matrix Reloaded;
“There are levels of survival we are prepared to accept.” – IMDB.com
The movie was talking about robots, but evidently the same applies to humans because somehow there are fives times more people alive, at least for now. The two main solutions seem equally difficult: rapid reduction in birth rates, or rapid development of off-planet resources like asteroid mining. Debates about sustainability can sound like trying to avoid a future event; but the sustainability limit was passed sometime between 1800 when there were 1 billion humans and 1927 when there were two billion humans. Without replacements for non-renewable resources and with the growth in population, we will be accepting other levels of survival.