Slide 66 of 75
Notes:
Studies by DeVivo, et al. and Couch have shown that as human population densities increase, the Index of Biological Integrity for fish, which measures the quality of the fish community, also decreases.
This data from a study conducted by Couch and DeVivo in the Atlanta areas shows the stream Index of Biological Integrity (IBI) as a function of the population density, which is a surrogate for impervious cover. The forest stream scored very high, as did the agricultural streams. But as more people were added to the watershed along with more impervious surfaces, fish diversity declined in a regular manner. Similar relationships have been developed for Illinois, Ohio and streams of the Puget Sound.