On the premise that today's complex environmental challenges require innovative long-term study over many types of habitat and over large areas of the landscape, the National Science Foundation established the Long Term Ecological Research (LTER) Network. The LTER Network consists of 24 sites located throughout the climates and habitats of North America and Antarctica. Although the scale of research and specific research foci differ across sites, the LTER sites share a commitment to the long-term perspective and to measurements that extend over decades. Researchers at these sites study many species and environmental variables, from bacteria to bison and from air temperatures to soil moisture. Synthetic results include an analysis of the relationship between diversity and productivity in multiple ecosystems; a model of the workings of an entire ecosystem at one site; and a compilation of regional effects of changes in temperature, precipitation, and nitrogen deposition. Sites are funded for 6 years at a time, with the expectation that continued high-quality research will lead to a decades-long project.