“There is nothing new about prophecies to the effect that the end of the world is near if we do not repent. What is new is that such a prophecy is now true, for two obvious reasons. First, nuclear weapons give us the means to wipe ourselves out quickly: no humans possessed this means before. Second, we already appropriate about forty per cent of the Earth’s net productivity (that is, the net energy captured from sunlight). With the world’s human population now doubling every forty-one years, we will soon have reached the biological limit to growth, at which point we will have to start fighting each other in deadly earnest for a slice of the world’s fixed pie of resources. In addition, given the present rate at which we are exterminating species, most of the world’s species will become extinct or endangered within the next century, but we depend on many species for our own life support.”