19 - Crises and catastrophes

Summary

The most remarkable events in the history of life are the brief, great contractions, sometimes nearly collapses, that for a while sharply reduce the diversity and sometimes also the abundance of life. Each time in the past, a complete recovery brought a new and different flowering.

It has lately become fashionable to feel guilty about the damage we are inflicting on nature, so guilty that we regard the damage as without counterpart in the history of the earth. But nature, capable of great havoc without our help, is also capable of repair. Time and again tropical rainforests and coastal wetlands have recovered from glacial climatic setbacks and sea level changes so severe that, were they to repeat themselves today, we would despair of the future.

The great dyings stir the imagination and it is easy to see them as catastrophes that demand extraordinary causes. It were well to resist this temptation until we have examined just how catastrophic these events really were and how unusual the causes need to have been. So let us learn from the record what we can.

DEATH AND RENEWAL

During the early Paleozoic the diversity of shallow marine life continued to increase as specialization and new adaptations gave access to an everwidening range of environments (Figure 19.1).