According to the experts one has read, there are are three species-level risks that humans face. The first is entirely man-made and it is that of nuclear weapons. When I was a high school student for a year in the United States in 1986-87, one of my classmates was doing a paper on the theory of mutual assured destruction, the prime theory of deterrence between the Soviet Union and the US.
Today, it is fair to say that there is not as large or at least as visible a threat from the world nuking itself into oblivion. This is mainly because