The National Park Service is mandated to preserve, protect, and manage biological resources to maintain ecosystem integrity. An essential component of this mission is vital signs monitoring, a national effort in cooperation with other federal and state agencies to determine trends in the condition of natural resources. The following resources are those for which we currently have information. They include rare and sensitive species and other resources of interest as well as landscape-scale indicators that tell us something about changes in the ecosystem beyond their individual status or trend. We also monitor stressors: agents of change, such as exotic species, that tend to reduce ecological integrity.