Chapter 19, The Second Cloud Summary and Analysis

Humanity faces two imminent risks to survival - nuclear holocaust and environmental holocaust. Nearly everyone realizes the risk of planetary destruction posed by massive nuclear stockpiles but the greater and more certain risk posed by environmental holocaust is argued and all-too-frequently dismissed.

The author suggests that perhaps 30 million species currently exist on earth, though only about 2 million have been scientifically enumerated. Extinction rates are alarming though exact numbers are probably impossible to calculate in most cases. It is relatively certain that 1 percent of North American birds have become extinct since 1600; archaeological evidence suggests that pre-historic humans were directly responsible for 80 percent of large-mammal extinctions in North and South America. Thus, human-caused extinction rates vary tremendously and can be exceptionally high.

Extinction is caused by four primary things: over-hunting and over-utilization; damage caused by human-introduced foreign...