Systematic observation and anecdotal information indicate connections between the geologic characteristics of an area and ecology. Plants and animals adapt to the landscape in response to soil texture and acidity/alkalinity, rock hardness and fracture networks, trace element chemistry, water retention/drainage, and other geologic features. When geologic map characteristics such as map units and structures are carefully organized in a database, biological data sources can be analyzed to evaluate the connections among all segments of an ecosystem. We are implementing a pilot geologic map database project for the Greater Yellowstone Area (GYA) a large region surrounding Yellowstone National Park. This is a part of the National Geologic Database activities of the National Cooperative Geologic Mapping Program and the multidisciplinary USGS studies of habitat, ecosystems, and land management in the GYA. We use geologic map data at 1:100,000 scale (and state coverages at smaller scales) in combination with a variety of biological, topographical, and hydrological data layers. Some of the analysis employs Weight of Evidence statistical techniques and artificial intelligence methods to determine the relationships between the flora and fauna of an ecosystem and the attributes of the land on and in which they live. Investigators have studied, for example, the distribution of optimal habitat for certain varieties of fish, the likelihood of cave habitat for bats, and the distribution of preferred packrat habitat relative to roadways. Geologic factors have been shown to be important for the distribution and abundance of certain moths in the Absaroka Mountains that are an important food source for grizzly bears. White bark pine trees, also an important food source for grizzlies, are associated with certain geologic conditions and geologic aspects of the landscape that seem to have influenced whether those trees survived or perished in the 1988 wildfires. Elk herds that winter over near the hot springs areas at Yellowstone ingest plants and water that are affected by the hydrothermal geochemistry, which impacts both dental health and longevity.