impaired due to habitat degradation (Figure 2). Twenty-five of 58 states and territories that report such statistics claimed that zero miles of rivers and streams had been negatively affected by the modification of habitat. Of the states that did report such impairment, only 15 reported an effect on more than 100 miles. These statistics are difficult to believe given the pervasive nature of well-documented practices that modify habitat, such as flood control, impoundments, agriculture and forestry, resource extraction, and urban development (Benke, 1990; Judy et al., 1984). The wide variation in state statistics is probably due to the use of different indicators and programmatic biases toward the control of toxic chemicals and point-source discharges (Ohio Environmental Protection Agency, 1990; Rankin and Yoder, 1990a).