ABSTRACT
This chapter explores potential intersections between studies of subsurface microbiology and various studies of planetary-scale ecology. It outlines some important functional links between subsurface microorganisms and larger ecological processes. The chapter discusses how results in subsurface microbiology may contribute to resolving several intriguing questions about the evolution of the earth's biosphere. Subsurface microbiology provides an important model for exobiology. Findings in subsurface microbiology can contribute to the search for extraterrestrial life. One can paint an extremely speculative picture of the role of subsurface microbiology in the biosphere. The origin of life and the evolution of the biosphere is a fascinating multidisciplinary field of study to which subsurface science can make several contributions. Slow recolonization of the interfaces from the subsurface restarts surface biosphere processes. The biosphere extends from the lower atmosphere down into the earth's crust to the point at which local temperatures become too high for microbiological life.
