The resource crisis, with its attendant destruction of the biosphere (prominently due to greenhouse gas pollution affecting the climate), threatens to significantly reduce, if not eliminate, humanity’s population in this century. The amount of reduction and how fast it occurs depends on future trends in consumption and destruction of natural systems. In the worst case, humans could become extinct by the middle of the century; in the best case, the population could level off at some value higher than it is today. It is extremely unlikely that our numbers will continue to grow, at least on this planet.
There are other threats to our longevity. During the latter half of the twentieth century, our greatest fear was the use of weapons of mass destruction (WMD) by the world’s superpowers. With thousands of nuclear warheads aimed at each other, the United States and Soviet Union stood within minutes of killing many millions of people and plunging the rest of the world into a horrific winter that would cause starvation on an epic scale. In this century it is just as likely only a fraction of such weapons may be used, but recent research indicates that even a limited nuclear exchange would lead to devastating human and environmental consequences. This prospect has led a growing number of rational and caring people to conclude that the presence of ANY nuclear weapons is unacceptable. Unfortunately, not enough of the world’s leaders and their terrorist counterparts have adopted this point of view. Surely a critical step toward avoiding a decline in human longevity must be to ban all such weapons.