Long-term data are now recognized as crucial to our understanding of environmental change and management. Historically, these studies have been difficult to maintain because of the dominance of short term funding programs, a misconception that long-term studies are merely monitoring, and emphasis on short term experimentation or hypothesis testing of specific interactions or processes under the assumption of equilibrium conditions. The complexity of the environment and the dynamic nature of environmental conditions require additional research efforts that are not only long-term, but also address questions of scale dependency, complex assemblages of species and their interactions, and the role of humans in the environment. Long Term Ecological Research (LTER) sites offer this important complement to the more traditional types of ecological research. These sites also provide the opportunities for interdisciplinary research that is fundamental to understanding the environment. Such collaborations are essential for the development of sustainable management of our natural resources.