Our ability to conduct detailed studies of our environment and civil infrastructure will be transformed radically by developing and deploying sensor networks supported by a wireless infrastructure, producing--for the first time--a continuously updated set of "state variables" from the field. This, in turn, will enable us to better detect and forecast climate variability, manage natural resources preserve and restore ecosystems and carry out crisis management. The challenge is that we must place sensors in remote locations not convenient for landline or commercial wireless access.