Today, the causes, results, and time scale(s) of climate change, past and potential, are the focus of much research, news coverage, and pundit speculation. Many of the US government scientific agencies have some funds earmarked for research into past and (or) future climate change (National Science and Technology Council, 1997). The Mississippi Basin Carbon Project (MBCP) is part of the U.S. Geological Survey (USGS) effort in global change research . The project is motivated by the need to increase our understanding of the role of terrestrial carbon in the global carbon cycle, particularly in the temperate latitudes of North America. The global land area between 30 O and 60 O N is thought to be a large sink for atmospheric CO2 (IPCC, 1996). The identity of this sink is unknown, but is in part the soil and sediment that makes up the upper several meters of the Earth's surface. The MBCP focuses on the Mississippi River basin, the third largest river system in the world (fig. 1), that drains an area of 3.3 x 10 6 km 2 (1.27 x 10 6 mi 2 ). The Mississippi River basin includes more than 40 percent of the land surface, and is the home of more than one-third of the population, of the conterminous United States. Because climate, vegetation, and land use vary greatly within the Mississippi River basin, the primary terrestrial sinks for carbon need to be identified and quantified for representative parts of the basin. The primary goal of the MBCP is to quantify the interactive effects of land-use, erosion, sedimentation, and soil development on carbon storage and nutrient cycles within the Mississippi River basin. The project includes spatial analysis of a wide variety of geographic data, estimation of whole-basin and sub-basin carbon and sediment budgets, development and implementation of terrestrial carbon-cycle models, and site-specific field studies of relevant processes. Areas can be studied and compared, and estimates can be made for whole-basin carbon storage and flux.