Dot Earth blog, New York Times

#8. July 11th, 2008, 12:17 p.m.

Wilson’s Law sounds an awful lot like James Lovelock’s Gaia Hypothesis, i.e., that the entire planet, physical and biological, is a functioning entity that regulates itself.

After the major mass extinctions in the course of Earth’s history, the geologic record typically shows a period of several million years passing before fossils record a resurgence of speciation and biodiversity. This is probably because the level of environmental collapse that occurs in a mass extinction leaves an impoverished biosphere in its wake, and time is needed for it to right itself. Ecosystems are built from the bottom up -- microorganisms and producers provide the resources and nutrient cycling necessary for the complex iterations that come later. As fossils preserve large vertebrate life forms preferentially, several million years may be what is required for sufficient recovery to occur for these to begin to evolve and radiate again.

Also, the biosphere provides important feedbacks to the physical earth system, such as control of erosion, moisture transport, etc. When the biosphere collapses, the physical Earth function is affected as well.

Herein lies a warning, we must protect the physical abiotic factors as well and the biotic factors that make up the environment if we are to succeed as a species. If we damage enough of the parts, the biosphere can collapse. What is left may not be sufficient to support us.

Food for thought: at the end of the Permian period, about 250 million years ago, approximately 90% of life in the seas and 70% of land dwelling organisms went extinct. The geologic record records that temperatures were higher, carbon dioxide was higher, and oxygen levels in the atmosphere may have fallen to 15% or so. I am not suggesting a parallel to today, only that when the biosphere collapses, as it has at least six times in the past, it is possible for even the physical environment we take for granted to change beyond our tolerance. We are forcing the environment of this planet with unknown consequences.

— Posted by Scott Wahlstrom on Dot Earth, 11 July 2008