There is little doubt that life on Earth, including human life, has a significant impact on the contemporary composition of the planet's atmosphere. All the major "greenhouse" trace gases, CO₂, CH₄, N₂O, O₃, have important interactions with biospheric processes that vary in a fairly predictable manner, both seasonally and inter-annually. Our general understanding of the physical and chemical controls over global biosphere-atmosphere exchange of trace gases has increased dramatically over the past several years, owing in part to advances in the coupling of remote sensing technology and simulation modeling of ecosystem processes. We can now develop reliable global images that characterize optimal physical conditions for major life forms on Earth and their associated exchange of biogenic trace gases with the atmosphere. For example, using computer models developed at NASA Ames we have deduced that production of oxygen by terrestrial plant-life appears to optimize over a fairly narrow range of 5-35^o C, whereas production of CO₂ by soil microbes is severely limited by rainfall rates less than about 2 cm per month. Although characterization of optimal conditions for planet-wide colonization by Earth-like species may prove useful for identification of favorable conditions (habitable zones) for life on distant bodies, numerous questions remain as to whether even a globally significant pattern of biosphere-atmosphere exchange of trace gases will be detectable over great distances. Can a potential seasonal pattern of biogenic gas exchange be separated from other sources of signal variation in multi-temporal observations of distant planets? Can hemispheric or continental differences in gas dynamics be resolved with near-term technology? If such discrimination becomes feasible, what unique combination(s) of trace gas cycles should we be searching for, in order to characterize life as we know it? Recent advances in remote sensing Earth observations should soon provide answers to at least the third question posed here.