For millennia there have been predictions about the end of the world. But between climate change, global pandemics, and the possibility of nuclear war, humankind faces an unprecedented number of existential threats today. Will any of these bring an end to life on Earth, or even to the existence of Earth itself? This volume explains and assesses some of the factors that scientists have identified as major threats to human life to give readers a clearer sense of the dangers they pose. It also, more optimistically, offers suggestions on ways that these threats can be eliminated or at least mitigated.