Biological integrity is associated with how "pristine" an environment is and its function relative to the potential or original state of an ecosystem before human alterations were imposed.
[2] To quantitatively assess changes in the composition of biologic communities, IBIs are developed to accurately reflect the ecological complexity from statistical analysis.
There is no one universal IBI, and developing metrics that consistently give accurate assessment of the monitored population requires rigorous testing to confirm its validity for a given subject.
Because communities naturally vary as do samples collected from a larger population, identifying robust statistics with acceptable variance is an area of active and important research.
A case in point is the phenomenon that stream IBI scores indicate significant impairment, or partial ecological collapse where more than 10 to 15 percent of the immediately surrounding watershed is impervious due to urbanization.
[8] Identifying reasons for such impairments, and possible exceptions to these trends, are major research challenges for academics studying cumulative watershed effects, and the use of low-impact development techniques to mitigate the impacts of stormwater runoff pollution.