An index of biological integrity (IBI), also called an index of biotic integrity, is a scientific tool typically used to identify and classify water pollution problems, although there have been some efforts to apply the idea to terrestrial environments. An IBI associates anthropogenic influences on a water body with biological activity in the water body, and is formulated using data developed from biosurveys. 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. Biological integrity is built on the assumption that a decline in the values of an ecosystem's functions are primarily caused by human activity or alterations. The more an environment and its original processes are altered, then by definition, the less biological integrity it holds for the community as a whole. If these processes were to change over time naturally, without human influence, the integrity of the ecosystem would remain intact. Similar to the concept of ecosystem health, the integrity of the ecosystem relies heavily on the processes that occur within it because those determine which organisms can inhabit an area and the complexities of their interactions. Deciding which of the many possible states or conditions of an ecosystem is appropriate or desirable is a political or policy decision.
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. Often IBIs are region-specific and require experienced professionals to provide sufficient quality data to correctly assess a score. 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.
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Évaluation de la qualité d'une rivière en utilisant des méthodes d'observation ainsi que des méthodes physico-chimiques et biologiques. Collecte d'échantillons sur le terrain et analyses de laboratoir